MODERN TRENDS IN AGRONOMY

By Dr. A. Ramachandran

Assistant Professor, Department of Agronomy, Mother Terasa College of Agriculture, Mettusalai, Illuppur (Po), Pudukkottai - 622102. Tamil Nadu, India E-mail : [email protected]

Dr. M. Mohana Keerthi

Assistant Professor, Department of Agronomy Mother Terasa College of Agriculture, Mettusalai, Illuppur (Po), Pudukkottai - 622102. Tamil Nadu, India E-mail : [email protected]

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Title: MODERN TRENDS IN AGRONOMY

Author(s): Dr. A. Ramachandran, Dr. M. Mohana Keerthi

Edition: First

Volume: I

© Copyright Reserved 2019

All rights reserved. No part of this publication may be reproduced, stored, in a retrieval system or transmitted, in any form or by any means, electronic, mechanical, photocopying, reordering or otherwise, without the prior permission of the publisher.

ISBN: 978-93-86675-86-6 MODERN TRENDS IN AGRONOMY iii

Preface The field of agricultural science in general and agronomy in particular has achieved many milestones worldwide in 21st century. Our country is no exception in development of crop production science keeping in pace with technological developments in other branches of science. There is continuous change in technology i.e. from local varieties to high yielding varieties, hybrids and genetically modified crops and varieties; simple fertilizers to complex fertilizers and nano fertilizers; mono cropping to cropping system and farming system approach etc. There are many discussions on conservation agriculture, organic farming, sustainable development, climate change, etc in these days. Crop production is primarily dependent on soil and climate besides various crop management practices. Therefore, understanding their interrelationship will give a sound knowledge of agronomy. As an agronomist we must have sound knowledge on soil, climate, crops and varieties, water management, weed management, nutrient management, dryland farming, cropping and farming system, statistics etc. In the present scenario we will have to focus not only on productivity enhancement but also sustainability, soil health improvement, resource recycling, increasing water use efficiency, climate change mitigation and adaptation techniques etc. Therefore, an attempt has been made to cover all fields of agronomy with up to date information from various reliable sources. This book will help the undergraduate and post graduate students in preparation of PG and Ph.D., and who are preparing for competitive examinations like ARS, UPSC exanimation others in agriculture and allied fields. Considering the need of the students at large, this book is prepared to give current aspects in modern agriculture. The different chapters in the book are compiled after analyzing the information available in various sources such as textbooks, review articles, popular articles and research articles from different journals . Finally, I have belief and hope that this book will fulfill the requirement of our student of agronomy stream for appearing in different competitive examinations.

Dr.A.RAMACHANDRAN

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CONTENTS Chapter Particulars Page No. 1. Climate change and mitigation 1-16 2. Conservation agriculture in India 17-29 3. Precision Agriculture 30-35 4. Soil and Soil quality 36-48 5 Tillage and Modern concept of tillage 49-54 6 Integrated Nutrient management 55-62 7 Integrated Weed Management 63-75 8 Soil- plant water relationships 76-100 9 Cropping System and IFS 101-107 10 Crop residue management in multiple cropping systems 108-114 11 Organic farming 115-126 12 Latest developments in crop management 127-131 13 Allelopathy 132-138 14 Genetically Modified (GM) Crops 139-145 15 Dryland farming 146-161 16 Sustainable Agriculture 162-170 17 Nanotechnology in crop production 171-178 18 Crop modeling: A tool for agricultural research 179-189 19 Research methodology in Agronomy 190-194 20 References 195

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Chapter 1: Climate change and Mitigation 1. Environmental factors affecting plant growth Plant growth and geographic distribution are greatly affected by the environment. If any environmental factor is less than ideal, it limits a plant's growth and/or distribution. For example, only plants adapted to limited amounts of water can live in deserts. Either directly or indirectly, most plant problems are caused by environmental stress. In some cases, poor environmental conditions (e.g., too little water) damage a plant directly. In other cases, environmental stress weakens a plant and makes it more susceptible to disease or insect attack. Environmental factors that affect plant growth include light, temperature, water, humidity, and nutrition. It is important to understand how these factors affect plant growth and development. With a basic understanding of these factors, you may be able to manipulate plants to meet your needs, whether for increased leaf, flower, or fruit production. By recognizing the roles of these factors, you also will be better able to diagnose plant problems caused by environmental stress. Light Three principal characteristics of light affect plant growth: quantity, quality, and duration. Quantity Light quantity refers to the intensity, or concentration, of sunlight. It varies with the seasons. The maximum amount of light is present in summer, and the minimum in winter. Up to a point, the more sunlight a plant receives, the greater its capacity for producing food via photosynthesis. You can manipulate light quantity to achieve different plant growth patterns. Increase light by surrounding plants with reflective materials, a white background, or supplemental lights. Decrease it by shading plants with cheesecloth or woven shade cloths. Quality Light quality refers to the color (wavelength) of light. Sunlight supplies the complete range of wavelengths and can be broken up by a prism into bands of red, orange, yellow, green, blue, indigo, and violet. Blue and red light, which plants absorb, have the greatest effect on plant

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growth. Blue light is responsible primarily for vegetative (leaf) growth. Red light, when combined with blue light, encourages flowering. Plants look green to us because they reflect, rather than absorb, green light. Knowing which light source to use is important for manipulating plant growth. For example, fluorescent (cool white) light is high in the blue wavelength. It encourages leafy growth and is excellent for starting seedlings. Incandescent light is high in the red or orange range, but generally produces too much heat to be a valuable light source for plants. Fluorescent grow-lights attempt to imitate sunlight with a mixture of red and blue wavelengths, but they are costly and generally no better than regular fluorescent lights. Duration Duration, or photoperiod, refers to the amount of time a plant is exposed to light. Photoperiod controls flowering in many plants. Scientists initially thought the length of light period triggered flowering and other responses within plants. Thus, they describe plants as short- day or long-day, depending on what conditions they flower under. We now know that it is not the length of the light period, but rather the length of uninterrupted darkness, that is critical to floral development. Plants are classified into three categories: short-day (long-night), long-day (short-night), or day-neutral, depending on their response to the duration of light or darkness. Short-day plants form flowers only when day length is less than about 12 hours. Many spring- and fall-flowering plants, such as chrysanthemum, poinsettia, and Christmas cactus, are in this category. In contrast, long-day plants form flowers only when day length exceeds 12 hours. Most summer flowering plants (e.g., rudbeckia, California poppy, and aster), as well as many vegetables (beet, radish, lettuce, spinach, and potato), are in this category. Day-neutral plants form flowers regardless of day length. Examples are tomato, corn, cucumber, and some strawberry cultivars. Some plants do not fit into any category, but may respond to combinations of day lengths. Petunias, for example, flower regardless of day length, but flower earlier and more profusely with long days. You can easily manipulate photoperiod to stimulate flowering. For example, chrysanthemums normally flower in the short days of spring or fall, but you can get them to bloom in midsummer by covering them with a cloth that completely blocks out light for 12 hours each day. After several weeks of this treatment, the artificial dark period no longer is needed, and

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the plants will bloom as if it were spring or fall. This method also is used to make poinsettias flower in time for Christmas. To bring a long-day plant into flower when day length is less than 12 hours, expose the plant to supplemental light. After a few weeks, flower buds will form. Temperature Temperature influences most plant processes, including photosynthesis, transpiration, respiration, germination, and flowering. As temperature increases (up to a point), photosynthesis, transpiration, and respiration increase. When combined with day-length, temperature also affects the change from vegetative (leafy) to reproductive (flowering) growth. Depending on the situation and the specific plant, the effect of temperature can either speed up or slow down this transition. Germination The temperature required for germination varies by species. Generally, cool-season crops (e.g., spinach, radish, and lettuce) germinate best at 55° to 65°F, while warm-season crops (e.g., tomato, petunia, and lobelia) germinate best at 65° to 75°F. Flowering Sometimes horticulturists use temperature in combination with day length to manipulate flowering. For example, a Christmas cactus forms flowers as a result of short days and low temperatures (Figure 26). To encourage a Christmas cactus to bloom, place it in a room with more than 12 hours of darkness each day and a temperature of 50° to 55°F until flower buds form. If temperatures are high and days are long, cool-season crops such as spinach will flower (bolt). However, if temperatures are too cool, fruit will not set on warm-season crops such as tomato. Crop quality Low temperatures reduce energy use and increase sugar storage. Thus, leaving crops such as ripe winter squash on the vine during cool, fall nights increases their sweetness. Adverse temperatures, however, cause stunted growth and poor-quality vegetables. For example, high temperatures cause bitter lettuce.

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Photosynthesis and respiration Thermoperiod refers to daily temperature change. Plants grow best when daytime temperature is about 10 to 15 degrees higher than nighttime temperature. Under these conditions, plants photosynthesize (build up) and respire (break down) during optimum daytime temperatures and then curtail respiration at night. However, not all plants grow best under the same range between nighttime and daytime temperatures. For example, snapdragons grow best at nighttime temperatures of 55°F; poinsettias, at 62°F. Temperatures higher than needed increase respiration, sometimes above the rate of photosynthesis. Thus, photosynthates are used faster than they are produced. For growth to occur, photosynthesis must be greater than respiration. Daytime temperatures that are too low often produce poor growth by slowing down photosynthesis. The result is reduced yield (i.e., fruit or grain production). Breaking dormancy Some plants that grow in cold regions need a certain number of days of low temperature (dormancy). Knowing the period of low temperature required by a plant, if any, is essential in getting it to grow to its potential. Peaches are a prime example; most varieties require 700 to 1,000 hours between 32° and 45°F before breaking their rest period and beginning growth. Lilies need 6 weeks of temperatures at or slightly below 33°F before blooming. Daffodils can be forced to flower by storing the bulbs at 35° to 40°F in October. The cold temperature allows the bulbs to mature. When transferred to a greenhouse in midwinter, they begin to grow, and flowers are ready to cut in 3 to 4 weeks. Hardiness Plants are classified as hardy or non hardy depending on their ability to withstand cold temperatures. Hardy plants are those that are adapted to the cold temperatures of their growing environment. Woody plants in the temperate zone have very sophisticated means for sensing the progression from fall to winter. Decreasing day length and temperature trigger hormonal changes that cause leaves to stop photosynthesizing and to ship nutrients to twigs, buds, stems, and roots. An abscission layer forms where each petiole joins a stem, and the leaves eventually fall off.

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Changes within the trunk and stem tissues over a relatively short period of time "freeze-proof" the plant. Winter injury to hardy plants generally occurs when temperatures drop too quickly in the fall before a plant has progressed to full dormancy. In other cases, a plant may break dormancy in mid- or late winter if the weather is unseasonably warm. If a sudden, severe cold snap follows the warm spell, otherwise hardy plants can be seriously damaged.

It is worth noting that the tops of hardy plants are much more cold-tolerant than the roots. Plants that normally are hardy to 10°F may be killed if they are in containers and the roots are exposed to 20°F. Winter injury also may occur because of desiccation (drying out) of plant tissues. People often forget that plants need water even during winter. When the soil is frozen, water movement into a plant is severely restricted. On a windy winter day, broadleaf evergreens can become water-deficient in a few minutes, and the leaves or needles then turn brown. To minimize the risk of this type of injury, make sure your plants go into the winter well watered. Water and Humidity Most growing plants contain about 90 percent water. Water plays many roles in plants. It is:  A primary component in photosynthesis and respiration  Responsible for turgor pressure in cells (Like air in an inflated balloon, water is responsible for the fullness and firmness of plant tissue. Turgor is needed to maintain cell shape and ensure cell growth.)  A solvent for minerals and carbohydrates moving through the plant  Responsible for cooling leaves as it evaporates from leaf tissue during transpiration  A regulator of stomatal opening and closing, thus controlling transpiration and, to some degree, photosynthesis  The source of pressure to move roots through the soil  The medium in which most biochemical reactions take place Relative humidity is the ratio of water vapor in the air to the amount of water the air could hold at the current temperature and pressure. Warm air can hold more water vapor than cold air. Relative humidity (RH) is expressed by the following equation:

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RH = water in air ÷ water air could hold (at constant temperature and pressure)

Relative humidity is given as a percent. For example, if a pound of air at 75°F could hold 4 grams of water vapor, and there are only 3 grams of water in the air, then the relative humidity (RH) is:

3 ÷ 4 = 0.75 = 75%

Water vapor moves from an area of high relative humidity to one of low relative humidity. The greater the difference in humidity, the faster water moves. This factor is important because the rate of water movement directly affects a plant's transpiration rate.

The relative humidity in the air spaces between leaf cells approaches 100 percent. When a stoma opens, water vapor inside the leaf rushes out into the surrounding air (Figure 25), and a bubble of high humidity forms around the stoma. By saturating this small area of air, the bubble reduces the difference in relative humidity between the air spaces within the leaf and the air adjacent to the leaf. As a result, transpiration slows down. If wind blows the humidity bubble away, however, transpiration increases. Thus, transpiration usually is at its peak on hot, dry, windy days. On the other hand, transpiration generally is quite slow when temperatures are cool, humidity is high, and there is no wind, Hot, dry conditions generally occur during the summer, which partially explains why plants wilt quickly in the summer. If a constant supply of water is not available to be absorbed by the roots and moved to the leaves, turgor pressure is lost and leaves go limp.

Plant Nutrition Plant nutrition often is confused with fertilization. Plant nutrition refers to a plant's need for and use of basic chemical elements. Fertilization is the term used when these materials are added to the environment around a plant. A lot must happen before a chemical element in a fertilizer can be used by a plant. Plants need 17 elements for normal growth. Three of them--carbon, hydrogen, and oxygen--are found in air and water. The rest are found in the soil. Six soil elements are called macronutrients because they are used in relatively large amounts by plants. They are nitrogen, potassium, magnesium, calcium, phosphorus, and sulfur.

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Plant macronutrients

Leaches from soil/ Signs of Element Absorbed as Signs of excess Notes Mobility in deficiency plant

In general, the best NH4+:NO3- ratio is 1:1. Reduced Under low sugar growth, conditions (low Succulent yellowing light), high growth; dark (chlorosis). NH4+ can cause green color; Reds and leaf curl. Uptake Leachable, weak, spindly purples may is inhibited by NO -, 3 especially growth; few intensify in high P levels. Nitrogen (nitrate), NO -. fruits. May some plants. The N:K ratio is (N) NH + 3 4 Mobile in cause brittle Reduced extremely (ammonium) plants. growth, lateral bud important. especially breaks. Indoors, the best under high Symptoms N:K ratio is 1:1 temperatures. appear first unless light is on older extremely high. growth. In soils with a high C:N ratio, more N should be supplied.

Reduced Rapidly bound growth. (fixed) on soil Normally Color may (P) particles. not intensify; Under acid leachable, browning or conditions, fixed but may Shows up as purpling of with Fe, Mg, H PO -, leach from Phosphor 2 4 micronutrient foliage in and Al. Under HPO - soil high in us (P) 4 deficiency of some plants. alkaline (phosphate) bark or Zn, Fe, or Co. Thin stems, conditions, fixed peat. Not reduced with Ca. readily lateral bud Important for mobile in breaks, loss young plant and plants. of lower seedling growth. leaves, High P interferes

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reduced with flowering. micronutrient absorption and N absorption. Used in relatively small amounts when compared to N and K.

Reduced growth, shortened inter-nodes. N:K balance is Marginal important. High burn or Causes N N:low K favors scorch Can leach in deficiency in vegetative (brown leaf Potassiu sandy soils. plant and may growth; low K+ edges), m (K) Mobile in affect the N:high K necrotic plants. uptake of other promotes (dead) spots positive ions. reproductive in leaves. growth (flowers, Reduction of fruit). lateral bud breaks, tendency to wilt readily.

Reduction in Mg commonly is growth. deficient in Marginal foliage plants chlorosis, because it is interveinal leached and not chlorosis replaced. Epsom (yellow salts at a rate of Leachable. between the 1 teaspoon per Magnesiu Interferes with Mg++ Mobile in veins) in gallon may be m (Mg) Ca uptake. plants. some species used two times (may occur per year. Mg on middle or also can be lower absorbed by leaves). leaves if sprayed Reduction in in a weak seed solution. production, Dolomitic

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cupped limestone can be leaves. applied in outdoor situations to correct a deficiency.

Ca is important to pH control and rarely is Inhibition of High Ca deficient if the Normally bud growth, usually causes correct pH is not death of root high pH, which maintained. leachable. tips. Cupping then Water stress (too Moderately of maturing precipitates much or too Calcium limited leaves, weak Ca++ many little) can affect (Ca) mobility in growth. micronutrients Ca relations plants. Blossom-end so that they within plants, Interferes rot of many become causing with Mg fruits, pits on unavailable to deficiency in the absorption. root plants. location where vegetables. Ca was needed at the time of stress.

S often is a carrier or impurity in General Sulfur excess fertilizers and Leachable, yellowing of usually is in the rarely is Sulfur (S) SO - (sulfate) not mobile affected 4 form of air deficient. It also in plants. leaves or the pollution. may be absorbed entire plant. fro the air and is a by-product of combustion.

Eight other soil elements are used in much smaller amounts and are called micronutrients or trace elements. They are iron, zinc, molybdenum, manganese, boron, copper, cobalt, and chlorine.

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Plant micronutrients

Absorbed Element Signs of excess Signs of deficiency Notes as

Rare except on Soil high in Ca, Mn, Add Fe in the flooded soils. P, or heavy metals chelate form. Interveinal (Cu, Zn); high pH; Fe++, The type of Iron (Fe) chlorosis, primarily poorly drained soil; Fe+++ chelate needed on young tissue, oxygen-deficient soil; depends on soil which eventually nematode attack on pH. may turn white. roots.

Blackening or death Failure to set seed, BO3- Boron (B) of tissue between internal breakdown, Borate veins. death of apical buds.

"Little leaf" (reduction in leaf Shows up as Fe size), short deficiency. Also Zinc (Zn) Zn++ internodes, distorted interferes with Mg or puckered leaf absorption. margins, interveinal chlorosis.

Can occur at low New growth small, May be found in Copper (Cu) Cu++, Cu+ pH. Shows up as Fe misshapen, wilted. some peat soils. deficiency.

Reduction in Interveinal chlorosis Manganese Found under Mn++ growth, brown of leaves followed by (Mn) acid conditions. spotting on leaves. brown spots,

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Shows up as Fe producing a deficiency. checkered effect.

Interveinal chlorosis Molybdenum MoO4- on older or midstem

(Mo) leaves, twisted leaves (molybdate) (whiptail).

Leaves wilt, then Salt injury, leaf become bronze, then Chlorine (Cl) Cl- burn. May increase chlorotic, then die; succulence. club roots.

Most of the nutrients a plant needs are dissolved in water and then absorbed by its roots. In fact, 98 percent are absorbed from the soil-water solution, and only about 2 percent are actually extracted from soil particles. Fertilizers Fertilizers are materials containing plant nutrients that are added to the environment around a plant. Generally, they are added to the water or soil, but some can be sprayed on leaves. This method is called foliar fertilization. It should be done carefully with a dilute solution, because a high fertilizer concentration can injure leaf cells. The nutrient, however, does need to pass through the thin layer of wax (cutin) on the leaf surface. Fertilizers are not plant food! Plants produce their own food from water, carbon dioxide, and solar energy through photosynthesis. This food (sugars and carbohydrates) is combined with plant nutrients to produce proteins, enzymes, vitamins, and other elements essential to growth.

Nutrient absorption Anything that reduces or stops sugar production in leaves can lower nutrient absorption. Thus, if a plant is under stress because of low light or extreme temperatures, nutrient deficiency may develop.

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A plant's developmental stage or rate of growth also may affect the amount of nutrients absorbed. Many plants have a rest (dormant) period during part of the year. During this time, few nutrients are absorbed. Plants also may absorb different nutrients as flower buds begin to develop than they do during periods of rapid vegetative growth. Impact of climate change on Indian agriculture

One of the major challenges facing humankind is to provide an equitable standard of living for present and future generations: adequate food, water, energy, safe shelter and a healthy environment. But, global environmental issues such as land degradation, loss of biodiversity, stratospheric ozone depletion along with human-induced climate change, threatens our ability to meet the basic human needs. The Third Assessment Report (TAR) of the Intergovernmental Panel on Climate Change (IPCC) reaffirms that the climate is changing in ways that cannot be accounted for by natural variability and that ‘global warming’ is happening. Global mean temperatures have risen (0.6oC in the last century), with the last decade being the warmest on record. Climate change will, in many parts of the world, adversely affect socio-economic sectors, including water resources, agriculture, forestry, fisheries and human settlements, ecological systems and human health, especially in developing countries due to their vulnerability.

Vulnerability to climate change is closely related to poverty, as the poor have fewer financial and technical resources. They are heavily dependent on climate-sensitive sectors such as agriculture and forestry; they often live on marginal land and their economic structures are fragile. This is true for a developing country like India where agriculture remains the mainstay of the economy, contributing nearly 27% of the total Gross Domestic Product (GDP) and employing nearly two-thirds of the country’s population. Agriculture exports account for 13 to 18% of total annual exports of the country. However, given that 62% of the cropped area is still dependent on rainfall, Indian agriculture continues to be fundamentally dependent on the weather.

Climate change will have an economic impact on agriculture, including changes in farm profitability, prices, supply, demand and trade. The magnitude and geographical distribution of such climate-induced changes may affect our ability to expand the food production as required to feed the populace. Climate change could thus have far reaching effects on the patterns of trade

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among nations, development and food security. Agriculture is sensitive to short-term changes in weather and to seasonal, annual and long term variations in climate. Crop yield is the culmination of a diversified range of factors. Parameters like soil, seed, pest and diseases, fertilizers and agronomic practices exert significant influence on crop yield. The burgeoning population, along with human-induced climate change and environmental problems is increasingly proving to be a limiting factor for enhancing farm productivity and ensuring food security for the rural poor. Agricultural productivity can be affected by climate change in two ways: first, directly, due to changes in temperature, precipitation and/or CO2 levels and second, indirectly, through changes in soil, distribution and frequency of infestation by pests, insects, diseases or weeds. Acute water shortage conditions, combined with thermal stress, could adversely affect wheat and, more severely, rice productivity in India even under the positive effects of elevated CO2 in the future. The mean temperature in India is projected to increase by 0.10 C to 0.30C in kharif (summer) and 0.30C to 0.70C in rabi (winter) by 2010 and to 0.40C to 2.00C in kharif and 1.10C to 4.50C in rabi by 2070 (IPCC, 1996). Mean rainfall is projected not to change by 2010 but may increase by 10% during rabi by 2070. At the same time, there is an increased possibility of climate extremes, such as the timing of onset of monsoon and intensities and frequencies of droughts and floods. The findings of several studies carried out in India are given in Table-1. Crop Scenario Projection Reference Rice 20C rise -0.06 - 0.075 ton / hec Sinha & Swaminathan 1.50C rise + 2 mm +12% in South India (1991) Saseendran et al rainfall rise + 460 ppm (1999) CO2 0 Wheat 2 C rise + 425 ppm CO2 -1.5 - 5.8% in sub Aggarwal & Kalra tropical India (1994) -17-18% in tropical Kumar & Parikh (1998) India -10% in Punjab, Haryana 0 Maize 2 C rise + 425 ppm CO2 -7-12% in North India Chatterjee (1998)

From Table-1, it is clear that most of the staple food crops in India are going to be adversely affected. For sugarcane, it was observed that for every 1°C rise in temperature, there would be a marked reduction in its yield (Chattopadhayay 2000). Impact of climate change on soil

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The soil system responds to the short-term events such as episodic infiltration of rainfall and also undergoes long-term changes such as physical and chemical weathering due to climatic change. The potential changes in the soil forming factors directly resulting from global climate change would be in the organic matter supply, temperature regimes, hydrology and changes in the potential evapotranspiration. Both the organic matter and carbon to nitrogen ratio(C: N ratio) will diminish in a warmer soil temperature regime. Drier soil conditions will suppress both root growth and decomposition of organic matter and will increase vulnerability to erosion. Increased evaporation from the soil and accelerated transpiration from the plants themselves will cause soil moisture stress. Impact on pests, diseases and weeds Incidence of pest and diseases would be most severe in tropical regions due to favourable climate/weather conditions, multiple cropping and availability of alternate pests throughout the year. Climate change is likely to cause a spread of tropical and subtropical weed species into temperate areas and to increase the numbers of many temperate weed species currently limited by the low temperature at high latitudes. The above facts demand urgent measures, from the scientific community and the government. Some of the adaptation measures at the farmers’ level could be:  For short-season crops such as wheat, rice, barley, oats, and many vegetable crops, extension of the growing season may allow more crops in a year.

 Longer-season cultivars can be sown to provide a steadier yield under more variable conditions.

 Late maturing varieties and alteration of time of sowing to take advantage of the longer growing seasons needs to be adopted.

 Changes in cropping pattern (shift from rice–wheat cropping system to other favourable crop mix) may be adopted. Crop diversification in Canada and in China has been identified as an adaptive response.

 Heat and drought tolerant, pest resistant, salt tolerant varieties would be beneficial. Genetic engineering and gene mapping offer the potential for introducing a wider range of traits.

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 Minimum, reduced or conservation tillage technologies, in combination with planting of cover crops and green manure crops, offer substantial possibilities to reverse existing soil organic matter, soil moisture, soil erosion, and nutrient loss to combat further losses due to climate change.

 Water resources in the semi-arid regions are expected to decrease due to climate change. Increased evaporation (resulting from higher temperature), combined with changes in precipitation characteristics (amount, variability and frequency), has the potential to affect agriculture - the predominant user of water. Better water management is required for enhancing crop productivity and ensuring food security. Generally, irrigated agriculture is less adversely affected than dry land agriculture but adding irrigation is a costly affair as it is dependent upon the availability of water supplies.

 Added nitrogen and other fertilizers would likely be necessary to take full advantage of the CO2 effect but may have deleterious effects on humans and aquatic ecosystems.

Water and nutrient management thus, have to be redefined in various agro-ecologies to meet the future demands.

Strategies for facing the challenge

Specific measures can only provide a successful adaptive response if they are adopted in appropriate situations. A variety of issues need to be considered, including land-use planning, watershed management, disaster vulnerability assessment, consideration of port and rail adequacy, trade policy, and the various programmes countries use to encourage or control production, limit food prices, and manage resource inputs to agriculture.

Important strategies for improving the ability of agriculture to respond to diverse demands and pressures include:  Improved training and general education of populations dependent on agriculture.

 Research on new variety development, incorporating various traits such as heat and drought tolerant, salt and pest resistant should be given prime importance.

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 Food programmes and other social security programmes, to provide insurance against local supply changes.

 Infrastructure facilities like transportation, distribution and market need to be improved.

 Existing policies may limit efficient response to climate change. Changes in policies such as crop subsidy schemes, land tenure systems, water pricing and allocation, and international trade barriers could increase the adaptive capability of agriculture.

Conclusion Signals of climatic change are already visible. Global climate change is going to affect major crops like rice, wheat, maize in India. Climate is the least manageable of all resources. Hence, to avert the ill effects of climate change, more attention has to be paid to other resources and technologies viz. soil, irrigation water, nutrients, crops and their management practices, to sustain the productivity and to ensure food and environmental security to the country. Adaptive measures are to be taken in a timely fashion, both at the farmers’ level (backed by strong agriculture/climate research and application oriented outputs) as well as at the policy makers’ level to enable the small and marginal farmers to cope with the adversities of climate change.

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Chapter 2 : Conservation agriculture in India

1. Introduction Attaining food security for a growing population and alleviating poverty while sustaining agricultural systems under the current scenario of depleting natural resources, negative impacts of climatic variability, spiraling cost of inputs and volatile food prices are the major challenges before most of the Asian countries. In addition to these challenges, the principal indicators of non-sustainability of agricultural systems includes: soil erosion, soil organic matter decline, salinization. These are caused mainly by: (i) intensive tillage induced soil organic matter decline, soil structural degradation, water and wind erosion, reduced water infiltration rates, surface sealing and crusting, soil compaction, (ii) insufficient return of organic material, and (iii) monocropping. Therefore, a paradigm shift in farming practices through eliminating unsustainable parts of conventional agriculture (ploughing/tilling the soil, removing all organic material, monoculture) is crucial for future productivity gains while sustaining the natural resources. Conservation agriculture (CA), a concept evolved as a response to concerns of sustainability of agriculture globally, has steadily increased worldwide to cover about ~ 8% of the world arable land (124.8 M ha) (FAO, 2012). CA is a resource-saving agricultural production system that aims to achieve production intensification and high yields while enhancing the natural resource base through compliance with three interrelated principles, along with other good production practices of plant nutrition and pest management (Abrol and Sangar, 2006). Traditional agriculture, based on tillage and being highly mechanized, has been accused of being responsible for soil erosion problems, surface and underground water pollution, and more water consumption (Wolff and Stein, 1998). Moreover, it is implicated in land resource degradation, wildlife and biodiversity reduction, low energy efficiency and contribution to global warming problems (Boatmann et al., 1999). Hence, conservation agriculture (CA) is a way to cultivate annual and perennial crops, based on no vertical perturbation of soil (zero and conservation tillage), with crop residue management and cover crops, in order to offer a permanent soil cover and a natural increase of organic matter content in surface horizons. The main environmental consequences of this method have been investigated worldwide with the objective of presenting a synthesis of the available studies and documents to the farmers and

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scientific communities. It stresses the very beneficial impacts of a conservative way of cultivation on the global environment (soil, air, water and biodiversity), compared to traditional agriculture (Derpsch et al., 2010, Derpsch et al., 2011). Further, it also presents the actual gaps or uncertainties concerning the scientists' positions on these environmental aspects. CA promotes most soils to have a richer bioactivity and biodiversity, a better structure and cohesion, and a very high natural physical protection against weather (raindrops, wind, dry or wet periods). Soil erosion is therefore highly reduced, soil agronomic inputs transport slightly reduced, while pesticide bio-degradation is enhanced. It protects surface and ground water resources from pollution and also mitigates negative climate effects. Hence, CA provides excellent soil fertility and also saves money, time and fossil-fuel. It is an efficient alternative to traditional agriculture, attenuating its drawbacks. 2. Conservation agriculture definition and goals Conservation agriculture is a management system that maintains a soil cover through surface retention of crop residues with no till/zero and reduced tillage. CA is described by FAO (http://www.fao.org.ag/ca) as a concept for resource saving agricultural crop production which is based on enhancing the natural and biological processes above and below the ground. As per Dumanski et al. (2006) conservation agriculture (CA) is not “business as usual”, based on maximizing yields while exploiting the soil and agro-ecosystem resources. Rather, CA is based on optimizing yields and profits, to achieve a balance of agricultural, economic and environmental benefits. It advocates that the combined social and economic benefits gained from combining production and protecting the environment, including reduced input and labor costs, are greater than those from production alone. With CA, farming communities become providers of more healthy living environments for the wider community through reduced use of fossil fuels, pesticides, and other pollutants, and through conservation of environmental integrity and services. As per FAO definition CA is to i) achieve acceptable profits, ii) high and sustained production levels, and iii) conserve the environment. It aims at reversing the process of degradation inherent to the conventional agricultural practices like intensive agriculture, burning/removal of crop residues. Hence, it aims to conserve, improve and make more efficient use of natural resources through integrated management of available soil, water and biological resources combined with external inputs. It can also be referred to as resource efficient or resource effective agriculture.

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Conservation agriculture systems require a total paradigm shift from conventional agriculture with regard to management of crops, soil, water, nutrients, weeds, and farm machinery (Table 1). Table 1. Some distinguishing features of conventional and conservation agriculture systems

Conventional agriculture Conservation agriculture

 Cultivating land, using science  Least interference with natural and technology to dominate processes nature  Excessive mechanical tillage and  No-till or drastically reduced tillage soil erosion (biological tillage)  Low wind and soil erosion  Surface retention of residues  High wind and soil erosion (permanently covered)  Infiltration rate of water is high  Residue burning or removal  Use of in-situ organics/composts (bare surface)  Brown manuring/cover crops (surface retention)  Water infiltration is low

 Use of ex-situ FYM/composts  Weeds are a problem in the early  Green manuring (incorporated) stages of adoption but decrease with time  Controlled traffic, compaction in  Kills established weeds but also tramline, no compaction in crop stimulates more weed seeds to area germinate  Diversified and more efficient  Free-wheeling of farm rotations• machinery, increased soil  Mechanized operations, ensure compaction timeliness of operations  Mono cropping/culture, less  More resilience to stresses, yield

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Conventional agriculture Conservation agriculture

efficient rotations losses are less under stress  Heavy reliance on manual labor, conditions uncertainty of operations  Productivity gains in long-run are in incremental order  Poor adaptation to stresses, yield losses greater under stress conditions  Productivity gains in long-run are in declining order

Source: Sharma et al., 2012. 3. Principles of conservation agriculture Conservation agriculture practices perused in many parts of the world are built on ecological principles making land use more sustainable (Wassmann et al., 2009, Behera et al., 2010, Lal, 2013). Adoption of CA for enhancing Resource use efficiency (RUE) and crop productivity is the need of the hour as a powerful tool for management of natural resources and to achieve sustainability in agriculture. Conservation agriculture basically relies on 3 principles, which are linked and must be considered together for appropriate design, planning and implementation processes. These are: 3.1. Minimal mechanical soil disturbance The soil biological activity produces very stable soil aggregates as well as various sizes of pores, allowing air and water infiltration. This process can be called “biological tillage” and it is not compatible with mechanical tillage. With mechanical soil disturbance, the biological soil structuring processes will disappear. Minimum soil disturbance provides/maintains optimum proportions of respiration gases in the rooting-zone, moderate organic matter oxidation, porosity for water movement, retention and release and limits the re-exposure of weed seeds and their germination (Kassam and Friedrich, 2009).

3.2. Permanent organic soil cover

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A permanent soil cover is important to protect the soil against the deleterious effects of exposure to rain and sun; to provide the micro and macro organisms in the soil with a constant supply of “food”; and alter the microclimate in the soil for optimal growth and development of soil organisms, including plant roots. In turn it improves soil aggregation, soil biological activity and soil biodiversity and carbon sequestration (Ghosh et al., 2010). 3.3. Diversified crop rotations The rotation of crops is not only necessary to offer a diverse “diet” to the soil micro organisms, but also for exploring different soil layers for nutrients that have been leached to deeper layers that can be “recycled” by the crops in rotation. Furthermore, a diversity of crops in rotation leads to a diverse soil flora and fauna. Cropping sequence and rotations involving legumes helps in minimal rates of build-up of population of pest species, through life cycle disruption, biological nitrogen fixation, control of off-site pollution and enhancing biodiversity (Kassam and Friedrich, 2009, Dumanski et al., 2006). 4. Status of conservation agriculture in India and abroad Globally, CA is being practiced on about 125 M ha (Table 2). The major CA practicing countries are USA (26.5 M ha), Brazil (25.5 M ha), Argentina (25.5 M ha), Canada (13.5 M ha) and Australia (17.0 M ha). In India, CA adoption is still in the initial phases. Over the past few years, adoption of zero tillage and CA has expanded to cover about 1.5 million hectares (Jat et al., 2012; www.fao.org/ag/ca/6c.html). The major CA based technologies being adopted is zero- till (ZT) wheat in the rice-wheat (RW) system of the Indo-Gangetic plains (IGP). In other crops and cropping systems, the conventional agriculture based crop management systems are gradually undergoing a paradigm shift from intensive tillage to reduced/zero-tillage operations. In addition to ZT, other concept of CA need to be infused in the system to further enhance and sustain the productivity as well as to tap new sources of growth in agricultural productivity. The CA adoption also offers avenues for much needed diversification through crop intensification, relay cropping of sugarcane, pulses, vegetables etc. as intercrop with wheat and maize and to intensify and diversify the RW system. The CA based resource conservation technologies (RCTs) also help in integrating crop, livestock, land and water management research in both low- and high-potential environments. Table 2. Global adoption of conservation agriculture systems

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Country Area (M ha) % of Global Area

USA 26.5 21.2

Brazil 25.5 20.4

Argentina 25.5 20.4

Australia 17.0 13.6

Canada 13.5 10.8

Russian Federation 4.5 3.6

China 3.1 2.5

Paraguay 2.4 1.9

Kazakhstan 1.6 1.3

Others 5.3 4.2

Total 124.8 100.0

Source: FAO, 2012. In India, efforts to adopt and promote conservation agriculture technologies have been underway for nearly a decade but it is only in the last 8 – 10 years that the technologies are finding rapid acceptance by farmers. Efforts to develop and spread conservation agriculture have been made through the combined efforts of several State Agricultural Universities, ICAR institutes and the Rice-Wheat Consortium for the Indo-Gangetic Plains. The spread of technologies is taking place in India in the irrigated regions in the Indo-Gangetic plains where rice-wheat cropping systems dominate. Conservation agriculture systems have not been tried or promoted in other major agro-eco regions like rainfed semi-arid tropics and the arid regions of the mountain agro-ecosystems. Spread of these technologies is taking place in the irrigated regions of the Indo-Gangetic plains where the rice-wheat cropping system dominates. The focus of developing and promoting conservation technologies has been on zero-till seed-cum fertilizer drill for sowing of wheat in rice-wheat system. Other interventions include raised-bed planting systems, laser equipment

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aided land leveling, residue management practices, alternatives to the rice-wheat system etc. It has been reported that the area planted with wheat adopting the zero-till drill has been increasing rapidly (Sangar et al., 2005), and presently 25% – 30% of wheat is zero-tilled in rice-wheat growing areas of the Indo-Gangetic plains of India. In addition, raised-bed planting and laser land leveling are also being increasingly adopted by the farmers of the north-western region. 5. Potential benefits of CA Adoption and spread of ZT wheat has been a success story in North-western parts of India due to (1) reduction in cost of production by Rs 2,000 to 3,000 ha− 1 ($ 33 to 50) (Malik et al., 2005, RWC-CIMMYT, 2005); (2) enhancement of soil quality, i.e. soil physical, chemical and biological conditions (Jat et al., 2009a, Gathala et al., 2011b); (3) enhancement, in the long term C sequestration and build-up in soil organic matter constitute a practical strategy to mitigate Green House Gas emissions and impart greater resilience to production systems to climate change related aberrations (Saharawat et al., 2012); (4) reduction of the incidence of weeds, such as Phalaris minor in wheat (Malik et al., 2005); (5) enhancement of water and nutrient use efficiency (Jat et al., 2012, Saharawat et al., 2012); (6) enhancement of production and productivity (4% – 10%) (Gathala et al., 2011a); (7) advanced sowing date (Malik et al., 2005); (8) reduction in greenhouse gas emission and improved environmental sustainability (Pathak et al., 2011); (9) avoiding crop residue burning reduces loss of nutrients, and environmental pollution, which reduces a serious health hazard (Sidhu et al., 2007); (10) providing opportunities for crop diversification and intensification-for example in sugarcane based systems, mustard, chickpea, pigeon pea etc. (Jat et al., 2005); (11) improvement of resource use efficiency through residue decomposition, soil structural improvement, increased recycling and availability of plant nutrients (Jat et al., 2009a); and (12) use surface residues as mulch to control weeds, moderate soil temperature, reduce evaporation, and improve biological activity (Jat et al., 2009b, Gathala et al., 2011b). Because of the ZT wheat benefits, the CA based crop management technologies have been tried in other cropping systems in India (Jat et al., 2011), but there are large knowledge gaps in CA based technologies which indicates there is a need to develop, refine, popularize and disseminate these technologies on a large scale. Zero tillage is a technology where the crop is sown in a single tractor operation using a specially designed seed-cum-fertilizer drill without any field preparation in the absence of

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anchored residue at optimum to slightly wetter soil moisture regimes. Experiences from several locations in the Indo-Gangetic plains showed that with zero tillage technology farmers were able to save on land preparation costs by about Rs. 2,500 ($41.7) per ha and reduce diesel consumption by 50 – 60 liters per ha (Sharma et al., 2005). Zero tillage allows timely sowing of wheat, enables uniform drilling of seed, improves fertilizer use-efficiency, saves water and increases yield up to 20%. Success has also been achieved in bed planting of wheat, cotton and rice. This has resulted in savings in irrigation water, improved fertilizer use and reduced soil crusting.

6. Prospects of conservation agriculture The direction that Asian countries take to meet their food and energy needs during the coming decades will have profound impacts on natural resource bases, global climate change and energy security for India, Asia and the world. These challenges draw attention to the need and urgency to address options by which threats to Indian/Asian agriculture due to natural resource degradation, escalating production costs and climate change can be met successfully. A shift to no-till conservation agriculture is perceived to be of much fundamental value in meeting these challenges. Asian farmers/researchers will continue to need assistance to reorient their agriculture and practices for producing more with less cost through adoption of less vulnerable choices and pathways. Therefore, business as usual with conventional agriculture practices does not seem a sustainable option for sustainable gains in food-grain production, and hence CA- based crop management solutions adapted to local needs will have to play a critical role in most ecological and socio-economic settings of Asian Agriculture. The promotion of CA under Indian/Asian context has the following prospects:

(i) Reduction in cost of production – This is a key factor contributing to rapid adoption of zero-till technology. Most studies showed that the cost of wheat production is reduced by Rs. 2,000 to 3,000 ($ 33 to 50) per hectare (Malik et al., 2005, RWC-

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CIMMYT, 2005). Cost reduction is attributed to savings on account of diesel, labour and input costs, particularly herbicides. (ii) Reduced incidence of weeds – Most studies tend to indicate reduced incidence of Phalaris minor, a major weed in wheat, when zero-tillage is adopted resulting in reduced in use of herbicides. (iii) Saving in water and nutrients – Limited experimental results and farmers experience indicate that considerable saving in water (up to 20% – 30%) and nutrients are achieved with zero-till planting and particularly in laser leveled and bed planted crops. De Vita et al. (2007) stated that higher soil water content under no-till than under conventional tillage indicated the reduced water evaporation during the preceding period. They also found that across growing seasons, soil water content under no-till was about 20% greater than under conventional tillage. (iv) Increased yields – In properly managed zero-till planted wheat, yields were invariably higher compared to traditionally prepared fields for comparable planting dates. CA has been reported to enhance the yield level of crops due to associated effects like prevention of soil degradation, improved soil fertility, improved soil moisture regime (due to increased rain water infiltration, water holding capacity and reduced evaporation loss) and crop rotational benefits. Yield increases as high as 200 – 500 kg ha− 1 are found with no-till wheat compared to conventional wheat under a rice-wheat system in the Indo-Gangetic plains (Hobbs and Gupta, 2004). Review of the available literature on CA provides mixed indications of the effects of CA on crop productivity. While some studies claim that CA results in higher and more stable crop yields (African Conservation Tillage Network, 2011), on the other hand there are also numerous examples of no yield benefits and even yield reductions particularly during the initial years of CA adoption. (v) Environmental benefits – Conservation agriculture involving zero-till and surface managed crop residue systems are an excellent opportunity to eliminate burning of crop residue which contribute to large amounts of greenhouse gases like

CO2, CH4 and N2O. Burning of crop residues, also contribute to considerable loss of plant nutrients, which could be recycled when properly managed. Large scale burning of crop residues is also a serious health hazard.

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(vi) Crop diversification opportunities – Adopting Conservation Agriculture systems offers opportunities for crop diversification. Cropping sequences/rotations and agro forestry systems when adopted in appropriate spatial and temporal patterns can further enhance natural ecological processes. Limited studies indicate that a variety of crops like mustard, chickpea, pigeon pea, sugarcane, etc., could be well adapted to the new systems. (vii) Resource improvement – No tillage when combined with surface management of crop residues begins the processes whereby slow decomposition of residues results in soil structural improvement and increased recycling and availability of plant nutrients. Surface residues acting as mulch, moderate soil temperatures, reduce evaporation, and improve biological activity.

7. Constraints for adoption of conservation agriculture A mental change of farmers, technicians, extensionists and researchers away from soil degrading tillage operations towards sustainable production systems like no tillage is necessary to obtain changes in attitudes of farmers (Derpsch, 2001). Hobbs and Govaerts (2010) however, noted that probably the most important factor in the adoption of CA is overcoming the bias or mindset about tillage. It is argued that convincing the farmers that successful cultivation is possible even with reduced tillage or without tillage is a major hurdle in promoting CA on a large scale. In many cases, it may be difficult to convince the farmers of potential benefits of CA beyond its potential to reduce production costs, mainly by tillage reductions. CA is now, considered a route to sustainable agriculture. Spread of conservation agriculture, therefore, will call for scientific research linked with development efforts. The following are a few important constraints which impede broad scale adoption of CA.  Lack of appropriate seeders especially for small and medium scale farmers: Although significant efforts have been made in developing and promoting machinery for seeding wheat in no till systems, successful adoption will call for accelerated effort in developing, standardizing and promoting quality machinery aimed at a range of crop and cropping sequences. These would include the development of permanent bed and furrow planting systems and harvest operations to manage crop residues.

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 The wide spread use of crop residues for livestock feed and fuel: Specially under rainfed situations, farmers face a scarcity of crop residues due to less biomass production of different crops. There is competition between CA practice and livestock feeding for crop residue. This is a major constraint for promotion of CA under rainfed situations.  Burning of crop residues: For timely sowing of the next crop and without machinery for sowing under CA systems, farmers prefer to sow the crop in time by burning the residue. This has become a common feature in the rice-wheat system in north India. This creates environmental problems for the region.  Lack of knowledge about the potential of CA to agriculture leaders, extension agents and farmers: This implies that the whole range of practices in conservation agriculture, including planting and harvesting, water and nutrient management, diseases and pest control etc. need to be evolved, evaluated and matched in the context of new systems.  Skilled and scientific manpower: Managing conservation agriculture systems, will call for enhanced capacity of scientists to address problems from a systems perspective and to be able to work in close partnerships with farmers and other stakeholders. Strengthened knowledge and information sharing mechanisms are needed. 8. Challenges in conservation agriculture Conservation agriculture as an upcoming paradigm for raising crops willrequire an innovative system perspective to deal with diverse, flexible and context specific needs of technologies and their management. Conservation agriculture R&D (Research and Development), thus will call for several innovative features to address the challenge. Some of these are: (a) Understanding the system – Conservation agriculture systems are much more complex than conventional systems. Site specific knowledge has been the main limitation to the spread of CA system (Derpsch, 2001). Managing these systems efficiently will be highly demanding in terms of understanding of basic processes and component interactions, which determine the whole system performance. For

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example, surface maintained crop residues act as mulch and therefore reduce soil water losses through evaporation and maintain a moderate soil temperature regime (Gupta and Jat, 2010). However, at the same time crop residues offer an easily decomposable source of organic matter and could harbour undesirable pest populations or alter the system ecology in some other way. No- tillage systems will influence depth of penetration and distribution of the root system which, in turn, will influence water and nutrient uptake and mineral cycling. Thus the need is to recognize conservation agriculture as a system and develop management strategies. (b) Building a system and farming system perspective – A system perspective is built working in partnership with farmers. A core group of scientists, farmers, extension workers and other stakeholders working in partnership mode will therefore be critical in developing and promoting new technologies. This is somewhat different than in conventional agricultural R&D, the system is to set research priorities and allocate resources within a framework, and little attention is given to build relationships and seek linkages with partners working in complementary fields. (c) Technological challenges – While the basic principles which form the foundation of conservation agriculture practices, that is, no tillage and surface managed crop residues are well understood, adoption of these practices under varying farming situations is the key challenge. These challenges relate to development, standardization and adoption of farm machinery for seeding with minimum soil disturbance, developing crop harvesting and management systems. (d) Site specificity – Adapting strategies for conservation agriculture systems will be highly site specific, yet learning across the sites will be a powerful way in understanding why certain technologies or practices are effective in a set of situations and not effective in another set. This learning process will accelerate building a knowledge base for sustainable resource management. (e) Long-term research perspective – Conservation agriculture practices, e.g. no-tillage and surface-maintained crop residues result in resource improvement only gradually, and benefits come about only with time. Indeed in many situations, benefits in terms of yield increase may not come in the early years of evaluating the impact of

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conservation agriculture practices. Understanding the dynamics of changes and interactions among physical, chemical and biological processes is basic to developing improved soil-water and nutrient management strategies (Abrol and Sangar, 2006). Therefore, research in conservation agriculture must have longer term perspectives.

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Chapter 3: Precision Agriculture-Concept Scope and Indian Agriculture A small sugarcane farmer in western Maharashtra owns about 4 hectares of land, has two son who are graduate and work in Pune. When he was asked a question why he did not encourage his son to take farming as a profession, he replied, farming requires hard work, non- remunerative and it is difficult to get labour for various farming operations. Besides he also thinks that a farmer's son is a non- marriageable commodity and that his son can have a better life in Pune. He is getting old and with age he plans to sell of his land to the highest bidder. Village after village and state after state, this is the story of most farmers in India. They want to sell their land and move out of farming. Indian agriculture is in crisis. “No matter how advanced or rich we become, all of us have to eat food. We can not survive on software/ nuts and/or bolts.” The wealth and security of the country comes from its land and hence what is needed is sustainable, high-tech and high-productive agriculture which will be remunerative and provide both food and security for the country. In this context precision agriculture will help in bringing in the next green revolution to Indian agriculture. An agricultural production system is the outcome of a complex interaction of seed, water and agro-chemicals including fertilizers and pesticides. Therefore, careful management of all inputs is essential for the sustainability of such complex system. The focus on enhancing the productivity without considering the ecological impacts of the input resources has resulted into environmental degradation. Increasing environmental consciousness of the general public is necessitating us to modify agricultural management practices for sustainable conservation of natural resources such as water, air and soil quality, while staying economically profitable. The productivity can be increased without any adverse effect by maximizing the resource input efficiency. It is also certain that availability of labor for agricultural activity is going to be in short supply in future. The time has now arrived to bring information technology and agricultural science together for improved economic and environmentally sustainable crop production. This gives birth to Precision Agriculture or Precision Farming. The concept of precision farming is strictly based on the Global Positioning System (GPS), which was initially developed by U.S. (United States of America) defense scientists for the exclusive use of the U.S. Defense Department. The unique character of GPS is precision in time and space. Precision agriculture (PA), as the name implies, refers to the application of

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precise and correct amounts of inputs like water, fertilizers, pesticides etc. at the correct time to the crop for increasing its productivity and maximizing its yields. The use of inputs (i.e. chemical fertilizers and pesticides) based on the right quantity, at the right time and in the right place. This type of management is commonly known as “Site-Specific Management”. Precision Farming or Precision Agriculture is generally defined as information and technology based farm management system to identify, analyse and manage spatial and temporal variability within fields for optimum productivity and profitability, sustainability and protection of the land resources by minimizing the production costs. The productivity gain in global food supply have increasingly relied on expansion of irrigation schemes over recent decades, with more than a third of the world's food now requiring irrigation for production. Rapid socio- economic changes in some developing countries, including India, are creating new scopes for application of precision agriculture (PA). All-together, market-based global competition in agricultural products is challenging economic viability of the traditional agricultural systems, and requires the development of new and dynamic production systems. TOOLS AND EQUIPMENT Precision Farming is a combination of application of different technologies. All these combinations are mutually inter related and responsible for developments. The same are discussed below: 1. Global Positioning System (GPS): It is a set of 24 satellites in the Earth orbit. It sends out radio signals that can be processed by a ground receiver to determine the geographic position on earth. It has a 95% probability that the given position on the earth will be within 10-15 meters of the actual position. GPS allows precise mapping of the farms and together with appropriate software informs the farmer about the status of his crop and which part of the farm requires what input such as water or fertilizer and/or pesticides etc. 2. Geographic Information System (GIS): It is software that imports, exports and processes spatially and temporally geographically distributed data. 3. Grid Sampling: It is a method of breaking a field into grids of about 0.5-5 hectares. Sampling soil within the grids is useful to determine the appropriate rate of application of fertilizers. Several samples are taken from each grid, mixed and sent to the laboratory for analysis.

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4. Variable Rate Technology (VRT): The existing field machinery with added Electronic Control Unit (ECU) and onboard GPS can fulfill the variable rate requirement of input. Spray booms, the Spinning disc applicator with ECU and GPS have been used effectively for patch spraying. During the creation of nutrient requirement map for VRT, profit maximizing fertilizer rate should be considered more rather than yield maximizing fertilizer rate. 5. Yield Maps: Yield maps are produced by processing data from adapted combine harvester that is equipped with a GPS, i.e. integrated with a yield recording system. Yield mapping involves the recording of the grain flow through the combine harvester, while recording the actual location in the field at the same time. 6. Remote Sensors: These are generally categories of aerial or satellite sensors. They can indicate variations in the colours of the field that corresponds to changes in soil type, crop development, field boundaries, roads, water, etc. Arial and satellite imagery can be processed to provide vegetative indices, which reflect the health of the plant. 7. Proximate Sensors: These sensors can be used to measure soil parameters asuch as N status and soil pH) and crop properties as the sensor attached tractor passes over the field. 8. Computer Hardware and Software: In order to analyze the data collected by other Precision Agriculture technology components and to make it available in usable formats such as maps, graphs, charts or reports, computer support is essential along with specific software support. 9. Precision irrigation systems: Recent developments are being released for commercial use in sprinkler irrigation by controlling the irrigation machines motion with GPS based controllers. Wireless communication and sensor technologies are being developed to monitor soil and ambient conditions, along with operation parameters of the irrigation machines (i.e. flow and pressure) to achieve higher water use efficiency. 10. Precision farming on arable land: The use of PA techniques on arable land is the most widely used and most advanced amongst farmers. CTF (contolled Traffic Farming) is a whole farm approach that aims at avoiding unnecessary crop damage and soil compaction by heavy machinery, reducing costs imposed by standard methods. Controlled traffic methods involve confining all field vehicles to the minimal area of permanent traffic lanes with the aid of decision support systems. Another important application of precision agriculture in arable land is to optimize the use of fertilizers especially, Nitrogen, Phosphorus and Potassium.

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Need for Precision Farming In India: To meet the huge food grain requirement of 480 million tonnes (Mt) by the year 2050, with the increasing challenges of biotic and abiotic stresses experienced by crops, introduction and adoption of modern technology in Indian agriculture is inevitable. The global food system faces formidable challenges and that will increase over the next 40 years. More radical changes to the food system and investment in research are required to cope up with future challenges and their solutions. The decline in the total productivity, diminishing and degrading natural resources, stagnating farm incomes, lack of eco-regional approach, declining and fragmented land holdings, trade liberalization on agriculture, limited employment opportunities in non-farm sector, and global climatic variation have become major concerns in agricultural growth and development. Therefore, the use of newly emerged technology adoption is seen as one key to increase agriculture productivity in the future. It is expected that application of balanced soft and hard PA technologies based on the need of specific socio-economic condition of a country will make PA suitable for developing countries also. ‘Soft’ PA depends mainly on visual observation of crop and soil and management decision based on experience and intuition, rather than on statistical and scientific analysis. ‘Hard’ PA utilizes all modern technologies such as GPS, RS, and VRT. Three components, namely, ‘single PA technology’, ‘PA technology package’ (for the user to select one or combination) and ‘integrated PA technology’, have been identified as a part of adoption strategies of PA in the developing countries like India. Precision Farming in Sugarcane Agriculture is inevitable as India is second largest producer of sugar and sugarcane. Sugarcane is cultivated in about 4.09 million hectares, producing about 283 million tonnes of cane with an average productivity 69.19 MT/ha. Of the several agriculture crops, sugarcane is the most remunerative, its requirement for water and fertilizer is also equally very high.

Precision farming within the fruits & vegetables and viticulture sectors: In fruit and vegetable farming, the recent rapid adoption of automation systems for recording parameters related to product quality, allows growers to grade products and to monitor food quality and safety, including colour, size, shape, external defects, sugar content, acidity, and other internal

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qualities. Additionally, tracking of field operations such as spraying chemicals and use of fertilizers can be possible to provide complete fruit and vegetable processing methods. Scope and Adoption of Precision Farming in India: PA for small farms can use small farm machinery and robots which will not compact the soil and may also run on renewable fuels like bio oil, compressed biogas and electricity produced on farms by agricultural residues. For small farms, precision agriculture may include sub-surface drip irrigation for precise water and fertilizer application, weed removal, harvesting and other cultural operations. Some of these robots are already being used on small farms in the US and Europe and it is expected that they may be deployed in large scale in the near future. For small farms, precision agriculture may help in sub-surface drip irrigation for precise water and fertilizer application and robots for weed control, harvesting and other operations. Similarly, drones have also been introduced in Japan and the U.S. for mapping the farms, identifying diseases and so on. Most robotic machines and drones are compact and thus suitable for small farms. India's small farms, therefore, are ideal for the large-scale application of precision agriculture. The way forward The most important component in taking PA forward will be in creating a huge resource of engineers, scientists and agriculturists to develop various components of the technology. Without excellent manpower and consequently good R & D, PA will not succeed. Unfortunately, most good students want to get into engineering and medical streams and ignorantly, agriculture becomes an afterthought. There is also a need for excellent engineers from institutions like IITs, NITs, etc. to design machinery like robots and drones for PA. This can be facilitated by establishing a new branch of engineering called agricultural mechanotrics or robotics where faculty and students from ICAR institutes, IITs, industries and farmers work together, interact and collaborate to develop smart systems for PA. Industries have to take charge since they will develop the machinery and set up the leasing agencies resulting in jobs creation in PA system and better students will pursue a career in agriculture. Conclusion: Precision farming in many developing countries including India has numerous opportunities for farmers to identify better high yielding location specific crops and in fect a farmer turns in to a breeder to produce better and higher yielding varieties by using PA system. Three components, namely, ‘single PA technology’, ‘PA technology package’ and ‘integrated

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PA technology’, have been identified as part of the general adoption strategies of PA in developing countries. Suitable application sectors of these strategic components have been highlighted. PA may provide a platform for industrial corporate social responsibility (CSR) activity by helping the rural poor to improve their livelihood through high-tech farming. The government of India can facilitate in this process by giving soft loans to the industry so that they get encouraged and engaged themselves in agriculture and PA activities. High-tech PA therefore can help in bringing next green revolution in India and can produce tremendous rural wealth in a sustainable and environmentally sound way. In the light of today’s urgent need, there should be an all out effort to use new technological inputs to make the ‘Green Revolution’ as an ‘Evergreen Revolution’.

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Chapter 4: Soil and Soil quality Soil health is the foundation of productive farming practices. Fertile soil provides essential nutrients to plants. Important physical characteristics of soil-like structures and aggregation allow water and air to infiltrate, roots to explore, and biota to thrive. Diverse and active biological communities help soil resist physical degradation and cycle nutrients at rates to meet plant needs. Soil health and soil quality are terms used interchangeably to describe soils that are not only fertile but also possess adequate physical and biological properties to "sustain productivity, maintain environmental quality and promote plant and animal health" (Doron 1994). According to the (USDA) Natural Resource Conservation Service, "Soil quality is how well soil does what we want it to do." In order to grow our crops, we want the soil to hold water and nutrients like a sponge where they are readily available for plant roots to take them up, suppress pests and weeds that may attack our plants, sequester carbon from the atmosphere, and clean the water that flows through it into rivers, lakes, and aquifers. Healthy, high-quality soil has:  Good soil tilth  Sufficient depth  Sufficient, but not excessive, nutrient supply  Small population of plant pathogens and insect pests  Good soil drainage  Large population of beneficial organisms  Low weed pressure  No chemicals or toxins that may harm the crop  Resilience to degradation and unfavorable conditions --from Soil Health Training Manual Remember, soil fertility is only one component of soil quality. Fertile soils are able to provide the nutrients required for plant growth. These are the chemical components of soil. Some plants need certain nutrients in large amounts, like nitrogen, phosphorus, and potassium, which are called macronutrients. Other nutrients, like boron and manganese, plants only need in very small amounts. In high-quality soil, nutrients are available at rates high enough to supply plant needs, but low enough that excess nutrients are not leached

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into groundwater or present at high levels toxic to plants and microbes. For more information on soil fertility, see Start Farming--Introduction to Soils: Managing Soils. All these characteristics sound great. But when you look at your field, how do you tell whether you have high-quality soil and how do you improve it? The first step is to learn about the properties of your soil. The following describes soil properties and indicators of soil quality that are important for healthy, productive crops. Indicators are easily measurable things that allow us to see what is happening in soil. Soil Texture We cannot change certain aspects of a given soil. Soil texture is one such aspect. Soil texture is a good place to start when you look at your soil. When you understand your soil's texture, you know more about the possible restrictions on your particular piece of land as well as any advantages. (Find where your farm is on the soil texture triangle.)

Illustration 1: Soil Texture Triangle. The soils texture triangle shows different amounts of water and air in soil with different sized and shaped particles. Illustration courtesy of C. Saylers.

The terms sand, silt, and clay refer to particle size; sand is the largest and clay is the smallest. Gravel particles are larger than 2 millimeters (mm), sand particles are 0.05-2 mm,

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silt particles are 0.002-0.05 mm, and clay is smaller than 0.002 mm. To put this in perspective, if a particle of clay were the size of a BB, then a particle of silt would be the size of a golf ball and a grain of sand would be the size of a chair (FAO 2007). (See Illustration 2)

Illustration 2: Particle Size. To put particle size in perspective, if a particle of clay were the size of a BB, then a particle of silt would be the size of a golf ball and a grain of sand would be the size of a chair. Even though the definition is based on particle size, the shape of the particles is important for thinking about how soil texture relates to soil quality. Sand particles are generally round, while silt and clay particles are usually thinner and flatter. In a soil with larger, round particles, more space is available for the water and air that our plants need. Also, the air space between the particles is larger, providing good aeration. However, in a sandy soil, many of the air spaces are too large to hold water against the force of gravity, creating a soil with low water-holding capacity that is prone to drought.

How Do I Tell What Texture My Soil Is?

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You can determine a soil's texture by how the soil feels. Does it feel gritty, greasy, or floury? Gritty soils are sandy. Silty soils feel floury when they are dry and greasy when they are wet. Clay will always feel greasy. Take a small handful of soil and drop enough water on it that you can form a ball. When you rub it in the palm of your hand, it will fall apart and you will feel the grit rub into your palm if it is sand. A silt will form a ball, but when you try to roll it out into a ribbon it will crack. A clay soil will roll out into a long ribbon. Differences Between Sand, Silt, and Clay You are probably familiar with the characteristics of a clay soil. We call them heavy soils for a reason. They can be difficult to work. They dry out slowly and can leave a hard crust that does not allow the rain to penetrate. Clays are made up of very small particles. Some kinds of clay are layered together in sheets. Think of a piece of baklava or a deck of cards with many thin layers stacked on top of one another. Clay can hold water and nutrients between those fine layers. Another important aspect of clays is that each of these individual layers has many "parking spaces" for plant nutrients. In reality, these "parking spaces" are negatively charged sites on the surface of the layer, as well as within the structure of the clay layer. Many of the nutrients are positively charged (called "cations") and, therefore, are attracted to the negatively charged "parking space," just like the opposite ends of a magnet are attracted to each other. Tiny clay particles have more surface area than larger particles of sand or silt (FAO, 2007). That means more area is available for positively charged plant nutrients to stick to. (See Illustration 3.)

Illustration 3: Clay Particles Holding Nutrients. Some clays hold water and nutrients between fine layers. Negative charges act like "parking spaces" holding positively charged plant nutrients in place. Illustration adapted from FAO, Farmer Field Schools.

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Sand is loose and single grained. The individual grains can be easily seen and felt. If you squeeze a handful of dry sand, it will fall apart. If you squeeze wet sand, it will form a cast and then crumble when you touch it. Loam is a mix of sand, silt, and clay. It is mellow with a somewhat gritty feel, yet fairly sticky and slightly plastic (Russell 2005). Soil Structure In pursuit of high-quality soil we generally try to build highly "structured" soils. While the texture of the soil is inherent and difficult, if not impossible, to change, we can influence the structure of the soil with our management practices. When we plow, cultivate, lime, add organic matter, and stimulate biological activity, we change soil structure. Whereas texture is the composition or relative proportion of three soil particle types (sand, silt, clay), soil structure is the arrangement or geometry of these soil particles. Soil with good structure has a wide range of pore spaces or empty space between the soil particles. For example, in a good loam soil, 40-60 percent of the soil volume is pore space filled with air and water (Brady 1996). To understand this concept, compare your soil to a building. If a building is made out of bricks, the "texture" of the building would be the proportion of cement, sand, and brick (clay, silt, and sand) that makes up the building. The "structure" would be the arrangement of these bricks to form large rooms, small rooms, hallways, etc. If an earthquake should cause the building to collapse into a pile of bricks, the texture would remain the same, but the structure would have been radically altered. To follow on our analogy, just as before the earthquake, the structure of the building provided much better living conditions than after (big and small rooms in which to move and live); similarly, a soil that has a good structure provides better living conditions for soil organisms and roots. It has many large and small pore spaces through which air, water, roots, and living organisms can move freely (FAO 2007). Soil scientists call soils with good structure "granular" or "crumb" type soils. These soils are loose and fluffy. Generally they are high in organic matter and have large soil aggregates. Think about what the soil looks like when you dig under a thick layer of sod. It has many crumbly pieces, large pores, clumps, roots, and decaying pieces of organic material. In contrast, platy soils have thin layers of horizontal plates or leaflets. These plates are often inherited by the way the soil was formed, but we can also create them by overuse

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of heavy machinery on clayey soils. Deeper soil layers may be prismlike, columnar, or block-like. (See Illustrations 4 and 5.)

Illustration 4: Soil Structure. Soil particles are arranged in different ways to constitute the soil's structure. We don't generally change the structure of deeper soil layers with our management practices, but it is good to check the soil survey to find out what lies beneath your soil layer because it may affect drainage and root penetration.

Illustration 5: Soil Structure Affects Water Movement. Soil structure affects how quickly water moves through soil. Water moves quickly through soils with many small grains. Soils with larger aggregates in the form of blocks or prisms have moderate drainage.

Soil Aggregates The aspect of soil structure that often interests us most as soil managers and that we can most easily change is soil aggregation. Bacteria and roots produce sticky substances that glue soil particles together. Fungi and root hairs wrap soil particles into balls. These

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groups of soil particles are called aggregates. (See Illustration 6.) One important type of soil aggregate is water-stable aggregates. Water-stable aggregates are measured by the extent to which soil aggregates resist falling apart when wetted and hit by rain drops. (Gugino 2007)

Illustration 6: Soil Aggregate. Bacteria and roots produce sticky substances that glue soil particles together. Fungi and root hairs wrap soil particles into balls called aggregates. Why Does It Matter? The number of water-stable aggregates in your soil shows its capacity to sustain its structure during the most extreme conditions (e.g., a heavy rainstorm after weather had dried the surface). Soils with low aggregate stability can constrict crops because they form surface crusts--which can reduce both water infiltration and air exchange, make the soil more difficult to manage, and reduce its ability to dry off quickly--and often have low biological activity. Aggregates are formed in part by exudates from bacteria, entanglement of soil particles in fungal hyphae, and digestion by earthworms. (See Illustration 6.) Low biological activity means reduced mineral cycling and competition with pest organisms. (Gugino 2007) How Can I Improve It?

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As soil managers we can help build soil aggregates by growing green manure cover crops or adding animal manure. Also think about your tillage regime. Over the long term, repeated soil tillage can reduce soil tilth and break down stable soil aggregates. Such soils can be so degraded that they become addicted to tillage and crop establishment requires a soil-loosening operation. If you can reduce your tillage operations, you may reduce the disturbance to the soil biota that are essential for building aggregation. Feeding the soil food web with cover crops or other organic materials also increases the numbers of these organisms. Then bacteria and fungi work to help make aggregation happen. Compaction When soil has poor structure or we mistreat it, we compact the soil. A good loam soil is about 50 percent soil particles and 50 percent pore space filled with air and water (Brady 1996). When we run over the soil when it is too wet or with equipment that is too heavy, we are pushing the soil particles closer together.

Illustration 7: Compaction Reduces Root Growth. Roots occupy a larger soil volume in non compacted soil layer (30-60 cm) than in compacted soil (15-30 cm). Source: Adapted by Sjoerd Duiker from Keisling, Batchelor, and Porter, "Soybean root morphology in soils with and without tillage pans in the lower Mississippi River Valley," Journal of Plant Nutrition 18 (1995): 373-84. As a result, the pores are small and can hold less air and water for plants. When soils become extremely compacted, roots can no longer penetrate the soil. Compacted soils have fewer and smaller roots. In a normal soil, crop roots are only in contact with less than

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1 percent of the total soil volume. The roots have to be able to continually grow and explore to find new nutrient reserves, and water needs to be able to move easily through the soil where it can reach roots and wash nutrients to where roots are. Compaction not only directly affects root growth, it also reduces the amount of air-filled pores and thus oxygen in the soil. The increase in carbon dioxide (CO2) in relation to oxygen can be toxic to plant roots. For more information see Duiker publications listed in References.

Illustration 8: Plant growth is limited in compacted soils. Managing soil compaction can be achieved through appropriate application of some or all of the following techniques: (a) adding organic matter; (b) controlling traffic; (c) mechanically loosening (e.g., deep ripping); and (d) selecting a rotation that includes crops with strong taproots able to penetrate and break down compacted soils. Deep ripping can reduce compaction initially. Unfortunately, unless it is combined with additions of organic matter or reduction in traffic, the benefits of ripping may only be seen for one to two years before the soil settles and recompacts.

Water-Holding Capacity High-quality soils have a high available water-holding capacity.

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Soil compaction causes reduced infiltration. Source: Duiker, Effects of Soil Compaction (University Park: Penn State Extension, 2004). Plants are like people, right? They need food, water, and oxygen to grow. Soils with a high available waterholding capacity have a larger reservoir and can supply water over time when plants need it. Technically, a soil's available water-holding capacity is the amount of water the soil can hold between field capacity (after gravity has drained the soil) and the permanent wilting point. So what is field capacity? Imagine you just had a heavy rain that fully saturated the soil. Then you wait two days just until the point that the soil has stopped draining. That is field capacity. The permanent wilting point is defined as the soil moisture level at which a wilted plant cannot recover even after 12 hours in a remoistened soil. So, available water-holding capacity is the amount of water a soil can hold between the time it is fully saturated but drained and when it is so dry that plants die. Clay and sandy soils will have different water holding capacities. The available water- holding capacity is an indicator of how much water the soil can store. Sandy soils often cannot store as much water for crops between rains.

How Can I Improve Its Water-Holding Capacity?

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The addition of organic matter to soils either from manure, compost, or cover crops can improve the soil's capacity to hold water. In the short term, you may want to consider adding stable organic materials like compost or crop residue high in lignin or cover crops high in carbon. In the long term, rotation to sod and reduced tillage are known to help.

Illustration 9: Water-Holding Capacity. (a) Saturated soil; (b) Field capacity; (c) Permanent wilting point. The water-holding capacity is the amount of water in soil field capacity (b) minus wilting point (c). Organic Matter Soil organic matter (SOM) is a complex of diverse components, including plant and animal residues, living and dead soil microorganisms, and substances produced by these organisms and their decomposition. SOM influences the chemical, biological, and physical properties of the soil in ways that are almost universally beneficial to crop production. The most common sources of SOM in farming are crop residues, cover crop residues, manures, and composts. Why Is Soil Organic Matter So Important? This tiny fraction of the soil volume (agricultural soils average 1-6 percent) has an overwhelming influence on most other soil properties. Often classified as "the living, the dead, and the very dead," it is composed of three components: living organisms, fresh residue, and well-decomposed residue. Each of these components contributes to the vital functions of soil.

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Bacteria, fungi, protozoa, earthworms, tiny insects, and other organisms form the living fraction of soil organic matter. Much to the surprise of anyone who considers soil to be dead dirt, living organisms compose about 15 percent of total soil organic matter, weighing between 2,000 and 30,000 pounds per acre (Gugino 2007; Brady 1996). This live fraction of the soil does a host of functions described below. The second fraction of soil organic matter is the "dead"--fresh residues that have been recently added to soil. This is active, easily decomposed material that provides the fuel for soil organisms. When fresh SOM is added to the soil, most of it decays to CO2, water, and minerals within a few months to years. This process provides energy (e.g., via respiration) for soil microbes and mineral nutrients for both microbes and plants (e.g., crops). Just like cornflakes provide sugar and carbohydrates for humans, decaying leaves, manure, and plant roots provide sugars and carbohydrates for bacteria, fungi, and the soil food web. Some soil organic matter is very resistant to (further) decay and can last (often bound tightly to clay particles) for hundreds of years. This very stable form of SOM is commonly referred to as humus. In fact, the average humus particle is one thousand years old. Humus is typically about 70 percent of the total SOM in agricultural soils. Humus, in particular, and SOM, in general, are important in enhancing soil nutrient-holding (especially cation) and water-holding capacities, soil structure and tilth, and general fertility (see Illustration 10). Organic matter management is an important part of farming, but our understanding of it is quite elementary. We know that soil fertility tends to increase with increasing SOM and that continual depletion of SOM eventually leads to very poor soils. Soil Biota The soil is alive. In just one teaspoon of agricultural soil there can be one hundred million to one billion bacteria, six to nine feet of fungal strands put end to end, several thousand flagellates and amoeba, one to several hundred ciliates, hundreds of nematodes, up to one hundred tiny soil insects, and five or more earthworms. These organisms are essential for healthy growth of your plants. For example, tiny insects in the soil rip and shred leaves and other organic material, breaking it down into smaller pieces that are then consumed by bacteria and fungi. These

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bacteria and fungi excrete sticky substances that hold the soil together into aggregates and provide food for an entire web of organisms in the soil. When these bacteria and fungi are consumed by other soil organisms, like the microscopic worms called nematodes, the nematodes excrete ammonia, an important source of nitrogen for plants. Adding organic matter to soil is essential for all these soil organisms. Cover crops, leaves, compost, and other organic materials that we add to soil are food for these organisms. Which type of organic material we add to the soil changes which type of organisms will have the largest numbers. For example, adding material very high in carbon will encourage fungi that excrete enzymes such as chitinase, which can break down tough- to-digest material.

Illustration 10: Organic Matter Holds Nutrients. Cations held on negatively charged organic matter and clay. Source: Magdoff and van Es, Building Soils for Better Crops (Beltsville, Md.: Sustainable Agriculture Research and Education Program, 2009), 15.

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Chapter 5: Tillage and Modern concept of Tillage Tillage Tillage operations in various forms have been practiced from the very inception of growing plants. Primitive man used tools to disturb the soils for placing the seeds. The word tillage is derived from ‘Anglo-Saxon’ words Tilian and Teolian, meaning ‘to plough and prepare soil for seed to sow, to cultivate and to raise crops’. Jethrotull, who is considered as father of tillage suggested that thorough ploughing is necessary so as to make the soil into fine particles. Tillage is the mechanical manipulation of soil with tools and implements for obtaining conditions ideal for seed germination, seedling establishment and growth of crops. Tilth is the physical condition of soil obtained out of tillage (or) it is the result of tillage. The tilth may be a coarse tilth, fine tilth or moderate tilth. Objectives of tillage The main objectives of tillage are, • To prepare a good seed bed which helps the germination of seeds. • To create conditions in the soil suited for better growth of crops. • To control the weeds effectively. • To make the soil capable for absorbing more rain water. • To mix up the manure and fertilizers uniformly in the soil. • To aerate the soil. • To provide adequate seed-soil contact to permit water flow to seed and seedling roots. • To remove the hard pan and to increase the soil depth. To achieve these objectives, the soil is disturbed / opened up and turned over. Types of tillage: Tillage operations may be grouped into a) On season tillage 2. Off-season tillage 1. On-season tillage Tillage operations that are done for raising crops in the same season or at the onset of the crop season are known as on-season tillage. They may be preparatory cultivation and after cultivation.

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A. Preparatory tillage: This refers to tillage operations that are done to prepare the field for raising crops. It consists of deep opening and loosening of the soil to bring about a desirable tilth as well as to incorporate or uproot weeds and crop stubble when the soil is in a workable condition. Types of preparatory tillage a. Primary tillage b. Secondary tillage a. Primary tillage: The tillage operation that is done after the harvest of crop to bring the land under cultivation is known as primary tillage or ploughing. Ploughing is the opening of compact soil with the help of different ploughs. Country plough, mould board plough, bose plough, tractor and power tiller drawn implements are used for primary tillage. b. Secondary tillage: The tillage operations that are performed on the soil after primary tillage to bring a good soil tilth are known as secondary tillage. Secondary tillage consists of lighter or finer operation which is done to clean the soil, break the clods and incorporate the manure and fertilizers. Harrowing and planking is done to serve those purposes. Planking is done to crush the hard clods, level the soil surface and to compact the soil lightly. Harrows, cultivators, Guntakas and spade are used for secondary tillage. C. Layout of seed bed: This is also one of the components of preparatory tillage. Leveling board, buck scrapers etc. are used for leveling and markers are used for layout of seedbed. B. After cultivation (Inter tillage): The tillage operations that are carried out in the standing crop after the sowing or planting and prior to the harvesting of the crop plants are called after tillage. This is also called as inter cultivation or post seeding/ planting cultivation. It includes harrowing, hoeing, weeding, earthing up, drilling or side dressing of fertilizers etc. Spade, hoe, weeders etc. are used for inter cultivation. 2. Off-season tillage: Tillage operations done for conditioning the soil suitably for the forthcoming main season crop are called off-season tillage. Off season tillage may be, post harvest tillage, summer tillage, winter tillage and fallow tillage. Special purpose tillage: Tillage operations intended to serve special purposes are said to be special purpose tillage. They are,

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a. Sub-soiling: To break the hard pan beneath the plough layer, special tillage operation (chiseling) is performed to reduce compaction. Sub-soiling is essential and once in four to five years where heavy machineries are used for field operations, seeding, harvesting and transporting. Advantages of sub-soiling are, greater volume of soil may be obtained for cultivation of crops, excess water may percolate downward to recharge the permanent water table, reduce runoff and soil erosion and roots of crop plants can penetrate deeper to extract moisture from the water table. b. Clean tillage: It refers to working of the soil of the entire field in such a way no living plant is left undisturbed. It is practiced to control weeds, soil borne pathogen and pests. c. Blind tillage: It refers to tillage done after seeding or planting the crop (in a sterile soil) either at the pre-emergence stage of the crop plants or while they are in the early stages of growth so that crop plants (sugarcane, potato etc.) do not get damaged, but, extra plants and broad leaved weeds are uprooted. d. Dry tillage: Dry tillage is practiced for crops that are sown or planted in dry land condition having sufficient moisture for germination of seeds. This is suitable for crops like broadcasted rice, jute, wheat, oilseed crops, pulses, potato and vegetable crops. Dry tillage is done in a soil having sufficient moisture (21-23%). The soil becomes more porous and soft due to dry tillage. Besides, the water holding capacity of the soil and aeration are increased. These conditions are more favourable for soil micro-organisms. e. Wet tillage or puddling: The tillage operation that is done in a land with standing water is called wet tillage or puddling. Puddling operation consists of ploughing repeatedly in standing water until the soil becomes soft and muddy. Puddling creates an impervious layer below the surface to reduce deep percolation losses of water and to provide soft seed bed for planting rice. Puddling is done in both the directions for the incorporation of green manures and weeds. Wet tillage destroys the soil structure and the soil particles that are separated during puddling settle later. Wet tillage is the only means of land preparation for transplanting semi-aquatic crop plant such as rice. Planking after wet tillage makes the soil level and compact. Puddling hastens transplanting operation as well as establishment of seedlings. Wet land ploughs or worn out dry land ploughs are normally used for wet tillage.

Depth of ploughing

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The desirable depth of ploughing is 12 to 20 cm for field crops. The ploughing depth varies with effective root zone of the crop. The depth of ploughing is 10-20 cm for shallow rooted crops and 15-30 cm for deep rooted crops. Number of ploughing Number of ploughing depends on soil conditions, time available for cultivation between two crops and type of cropping systems. Zero tillage is practiced in rice fallow pulses. Minimum number of ploughing is taken up at optimum moisture level to bring favourable tilth depending on need of the crop. Time of ploughing The optimum soil moisture content for tillage is 60% of field capacity. Modern concepts in tillage: Conventional tillage involves primary tillage to break open and turn the soil followed by secondary tillage to obtain seed bed for sowing or planting. With the introduction of herbicides in intensive farming systems, the concept of tillage has been changed. Continuous use of heavy ploughs create hard pan in the subsoil, results in poor infiltration. It is more susceptible to run-off and erosion. It is capital intensive and increase soil degradation. To avoid these ill effects, modern concepts on tillage is in rule. 1. Minimum tillage: It aims at reducing tillage operations to the minimum necessity for ensuring a good seed bed. The advantages of minimum tillage over conventional tillage are, • The cost and time for field preparation is reduced by reducing the number of field operations. • Soil compaction is comparatively less. • Soil structure is not destroyed. • Water loss through runoff and erosion is minimum. • Water storage in the plough layer is increased. Tillage can be reduced in 2 ways 1. By omitting operations which do not give much benefit when compared to the cost. 2. By combining agricultural operations like seeding and fertilizer application. The minimum tillage systems can be grouped into the following categories, A) Row zone tillage

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Primary tillage is done with mould board plough in the entire area of the field; secondary tillage operations like discing and harrowing are reduced and done only in row zone. B) Plough plant tillage After the primary tillage, a special planter is used for sowing. In one run over the field, the row zone is pulverized and seeds are sown by the planter C) Wheel track tillage Primary ploughing is done as usual. Tractor is used for sowing; the wheels of the tractor pulverize the row zone in which planting is done. In all these systems, primary tillage is as usual. However, secondary tillage is replaced by direct sowing in which sown seed is covered in the row zone with the equipment used for sowing. 2. Zero tillage (No tillage): In this, new crop is planted in the residues of the previous crop without any prior soil tillage or seed bed preparation and it is possible when all the weeds are controlled by the use of herbicides. Zero tillage is applicable for soils with a coarse textured surface horizon, good internal drainage, high biological activity of soil fauna, favourable initial soil structure and an adequate quantity of crop residue as mulch. These conditions are generally found in Alfisols, Oxisols and Ultisols in the humid and sub-humid tropics. Till planting Till planting is one method of practicing zero tillage. A wide sweep and trash bar clears a strip over the previous crop row and planter opens a narrow strip into which seeds are planted and covered. Here, herbicide functions are extended. Before sowing, the vegetation present has to be destroyed for which broad spectrum non selective herbicides like glyposate, paraquat and diquat are used. Advantages • Zero tilled soils are homogenous in structure with more number of earthworms. • Organic matter content increases due to less mineralization Surface run-off is reduced due to presence of mulch. Disadvantages • Higher amount of nitrogen has to be applied for mineralization of organic matter in zero tillage. • Perennial weeds may be a problem. • High number of volunteer plants and buildup of pests.

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3. Stubble mulch tillage or stubble mulch farming Soil is protected at all times either by growing a crop or by leaving the crop residues on the surface during fallow periods. Sweeps or blades are generally used to cut the soil up to 12 to 15 cm depth in the first operation after harvest and depth of cut is reduced during subsequent operations. When large amount of residues are present, a disc type implement is used for the first operation to incorporate some of the residues into the soil. This hastens the decomposition but still keeps enough residues on top soil. Two methods for sowing crops in stubble mulch tillage are, 1. Similar to zero tillage, a wide sweep and trash bars are used to clear a strip and a narrow planter shoe opens a narrow furrow into which seeds are placed. 2. A narrow chisel of 5-10 cm width is worked through the soil at a depth of 15-30 cm leaving all plant residues on the surface. The chisel shatters the tillage pans and surface crusts. Planting is done with special planters. Disadvantages of stubble mulch farming • The residues left on the surface interfere with seed bed preparation and sowing operations. • The traditional tillage and sowing implements or equipments are not suitable under these conditions. 4. Conservation tillage: The major objective is to conserve soil and soil moisture. It is a system of tillage in which organic residues are not inverted into the soil such that they remain on surface as protective cover against erosion and evaporation losses of soil moisture. If stubble forms the protective cover on the surface, it is usually referred to as stubble mulch tillage. The residues left on soil surface interfere with seed bed preparation and sowing operations. It is a year round system of managing plant residue with implements that undercut residues, losses the soil and kills the weeds. Advantages • Energy conservation through reduced tillage operations. • Improve the soil physical properties. • Reduce the water runoff from fields.

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Chapter 6: Integrated Nutrient Management (INM) Meaning of Integrated Nutrient Management (INM) Integrated nutrient management is the combined application of chemical fertilizers along with organic resource materials like, organic manures, green manures, bi-fertilizers and other organic decomposable materials for crop production. The basic concepts of IPNS is the maintenance or adjustment of soil fertility and supply of plant nutrients to an optimum level for sustaining desired crop productivity through optimization of benefits from all possible sources of plant nutrients in an integrated manner. IPNS is ecologically, socially and economically viable and environment friendly which can be practiced by farmers to derive higher productivity with simultaneously maintaining soil fertility. Integrated nutrient management encourages the use of on-farm organics, thus it saves on the cost of fertilizers for crop production. The basic concept of integrated nutrient management (INM) or integrated plant nutrition management (IPNM) is the adjustment of plant nutrient supply to an optimum level for sustaining the desired crop productivity. It involves proper combination of chemical fertilizers, organic manure, crop, residues, N2~fixing crops (like pulses such as rice bean, Black gram, other pulses and oilseeds such as soybean and bio-fertilizers suitable to the system of land use and ecological, social and economic conditions. The cropping system rather than an individual crop, and farming system rather than an individual field, is the focus of attention in this approach for development INM practices for various categories. The basic concept of INM is the maintenance of soil fertility, sustainable agricultural productivity and improving profitability through judicious and efficient use of fertilizers as mentioned. Concepts of INM: INM use five major sub-concepts, viz: 1. Plant nutrients stored in the soil. 2. Plant nutrients, those present in the crop residues, organic manure and domestic wastes. 3. Plant nutrients purchased or obtained from outside the farm. 4. Plant nutrient looses e.g. those removed from the field in crop harvest and lost from the soil through volatilization (ammonia and nitrogen oxide gases and leaching (nitrate, sulphate etc.)

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5. Plant nutrient outputs e.g. nutrient uptake by the crops at harvest time. The integrated plant nutrition management on integrated nutrient management thus firstly operates at plot level, optimizing the utilization of plant nutrients from diverse sources which are locally available, in order to improve the agronomic efficiency of such nutrient and at the same time reducing the losses of nutrients. Organic recycling is especially promoted through INM for facilitating nutrient recycling to improve soil fertility and productivity as low cost. Goals of INM: To Maintain Soil Poductivity: To ensure productive and sustainable agriculture. To reduce expenditure on costs of purchased inputs by using farm manure and crop residue, etc. To utilize the potential benefits of green manures, leguminous crops and bio-fertilizers. To prevent degradation of the environment. To meet the social and economic aspiration of the farmers without harming the natural resource base of agricultural production. Implementation of INM Activities: Different stages of implementation of INM are as follows: 1. Diagnosis phase: collection of background information. 2. Analysis of constraints. 3. Preparing potentiality and feasibility summary 4. On-farm demonstrations. 5. Evaluation of INM activities. Components of INM: Components of INM and their use: Major components of integrated nutrient management are: i. Integration of soil fertility restoring crops like green manures, legumes etc. ii. Recycling of crop residues iii. Use of organic manures like FYM, compost, vermicompost, biogas, slurry, poultry manure, bio-compost, press mud cakes, phosphocompost iv. Utilization of Bio fertilizers v. Efficient genotypes and lastly vi. Balanced use of fertilizer nutrients as per the requirement and target yields.

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Diagnostic Phase of INM: In the first stage of diagnostic phase information with regard to the following is collected and analysed: i. Farming/cropping systems ii. Crop varieties grown iii. Awareness about soil fertility problems. iv. Use of chemical fertilizers, lime/dolomite and other agro-chemicals. v. Use of organic manure. vi. Availability of fertilizer and other inputs. vii. Irrigation sources and practices. viii. Soil testing service facility. ix. Constraints in the adoption of INM technologies. x. Consideration of market opportunities. The INM technologies must be compatible with the local farming system if they are to find acceptance and adoption. Therefore, attention must be paid to examine the interaction among different components of INM and the management of crops and animals that form the farming system. Some of the agronomic parameters which need attention are cropping pattern, intercropping practices, biological condition of the field (weeds, diseases, and insects), soil conditions, irrigation facilities and climatic conditions. Common Constraints of INM: Common constraints encountered by the farmers in adoption of INM technology are as follows: 1. Non-availability of FYM. 2. Difficulties in growing green manure crops. 3. Non-availability of bio-fertilizers. 4. Non-availability of soil testing facilities. 5. High cost of chemical fertilizers. 6. Non-availability of water. 7. Lack of knowledge and poor advisory services. 8. Non-availability of improved seeds.

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Site Specific Nutrient Management (SSNM) Meaning of Site Specific Nutrient Management (SSNM): Site specific nutrient management is a set of nutrient management principles combined with good crop management practices that will help farmers to attain high yield and achieve high profitability both in the short and medium-term. The principles of SSNM are generic and also applicable to other crops including rice. SSNM provides an approach for the timely application of fertilizers at optimal rates to fill the deficit between the nutrient needs of a high yielding crops and the nutrient supply from naturally occurring indigenous sources, including soil, crop residues, manures and irrigation water. Applying the right nutrient source, at the right rate, at the right time, in the right place is essential to nutrient stewardship and is the core of the 4 Rs. Such 4 R nutrient stewardship for fertilizer best management practices is an approach that considers economic, social and environmental dimensions of nutrient management. Concept of Site Specific Nutrient Management (SSNM): Nutrient management and recommendation process in India is still based on response data arranged over large domains. The SSNM provides an approach for need based feeding of crops with nutrients while recognizing the inherent spatial variability. It involves monitoring of all pathways of plant nutrient flows/supply, and calls for judicious combination of fertilizers, bio-fertilizers, organic manures, crop residues and nutrient efficient genotypes to sustain agricultural productivity. It avoids indiscriminate use of fertilizers and enables the farmer to dynamically adjust the fertilizer use to fill the deficit optimally between nutrient needs of the variety and nutrient supply from natural resources, organic sources, irrigation water etc. It aims at nutrient supply at optimal rates and times to achieve high yield and efficiency of nutrient use the crop. SSNM approach involves three steps—establishing attainable yield targets, effectively use existing nutrient sources and application of fertilizers to fill the deficit between demand and supply of nutrients. Soil nutrient supply potential and its spatial variability, productivity potential and targets for crops and cropping systems, estimation of nutrient requirements, and fertilizer use efficiency

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besides assessment of resource quality and socio-economic background of the farmers are essential for developing site specific IPNS. The soil, crop, nutrient and resource related parameters that are essential for suggesting and practicing site specific IPNS include: i. Soil testing-nutrient supply potential. ii. Productivity targets of crops and cropping systems and nutrient needs each ton of grain removes about 82 kg nutrients which do vary with crops and productivity, iii. Efficiency of nutrient source fertilizers organic nutrient sources like FYM, green manures. iv. Composts, bio fertilizers, organic industrial wastes and soil amendments. v. Nutrient efficient genotypes. vi. Selection of suitable crops and cropping systems involving N fixing crops and their management. vii. Correction of soil and nutrient related problems. Soil Test based Nutrient Management: Evaluation of soil fertility and making fertilizer prescriptions for sustained crop production is of importance to the farming section. Considerable progress has been made to understand the contribution of soil and fertilizer to crop nutrition and the influence of nutrient levels and management on crop productivity and nutrient use efficiency. Soil testing to assess the nutrient supply capacity provided an opportunity for practical solutions to nutrient management. Soil test based recommendations will be useful only when it is based on important factors like soil, crop, variety, fertilizer and management interaction for a given soil condition.

The soil test based crop response (STCR) project of ICAR provided the right impetus to understand the variability in the soil and crop with practical solutions to enhance nutrient use efficiencies narrowing down to each farm or field. The on-farm trials provided further need and scope for refinement, and recommendations of fertilizer nutrient use over large domains. Any deficit application of fertilizers will limit crop yields, facilitate nutrient mining and result in depletion of soil fertility. Excessive or imbalanced application not only wastes limited

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sources but also has the potential to pollute the environment. An approach towards mitigating such concern is site specific nutrient management (SSNM), which takes into account spatial variations in the landscape. Use of GPS and GIS Systems: Wide spread adoption of SSNM technologies based on soil testing require extensive soil sampling and analysis which could be a hindrance considering the available infrastructure. Use of Global Positioning system (GPS) and Geographical Information System (GIS) and mapping can provide the right support as cost effective alternative.

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Chapter 7: INTEGRATED WEED MANAGEMENT (IWM) Integrated weed management is defined as the combined use of all the methods of weed control i.e. cultural, physical, chemical and biological methods in such a balanced way so that there is no harmful effect of weed control practices on nature and side by side weeds are controlled and managed effectively. It aims at bringing down the weeds intensity to such low levels so that they do not pose any significant danger to crops and humans. It uses the creative application of agronomic, biological and chemical methods to control weeds. IWM is the need of the situation as today the world is facing the problem of environment pollution due to the use of harmful and strong chemicals in curing weeds which pollute the land, air & water very badly. So pollution free environment is essential for sustaining life on earth, weeds .which can be brought by using

IWM in weeds. The certain advantages of integrated weed management are listed below: a. The shift in crop weed competition in favour of crops. b. Prevents the weeds from changing into perennial nature. c. Prevents the resistance to herbicides in weeds. d. Minimum pollution of the environment. e. Contribute towards the economic crop production. f. Minimization of the danger of herbicide residue in soil or in plants.

CHEMICAL METHODS OF WEED CONTROL Chemical methods offer a great potential for weed control in crops. There are certain chemicals which function on the basis of selectivity by killing only the weed plants and not affecting the crop or valuable plants. Such chemicals are known as herbicides. Chemicals or herbicides were first invented in 1933 as Dinoseb, MCPA & 2,4-D in 1945. The usage of herbicides consumption is 43% which is highest among insecticides (34%), fungicides (21%) & 5% with other agrochemicals .herbicide market in the overall world is increased by many folds in past 20 years or so. The various groups of chemicals used are: a. Chlorophenoxy compounds b. Substituted aliphatic acids

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c. Benzoic acids d. Anilides e. Triazines f. Carbamates g. Thiocarbamates h. Nitriles i. Organophosphates j. Substituted ureas k. Sulphonyl ureas The main advantages of chemical weed control are as follows: 1. Most effective as compared to other methods of weed control. 2. Very suitable for closely spaced crops. 3. Provides early season weed control. 4. Suitable for adverse soil conditions. 5. Controls many perennial weeds very effectively. The main drawbacks of chemical methods of weed control are that they must be applied at the proper time & with proper care; also they have harmful residue problem which has an effect on succeeding crop & also they require some technical knowledge to use. MECHANICAL OR PHYSICAL METHODS OF WEED CONTROL The mechanical or physical methods of weed control are being used since man used to grow crops. It includes various methods like hand hoeing, hand pulling, tillage, digging, sickling, burning, flooding & mulching etc. But each of these methods is labour & time consuming as well as not of complete or full weed control. These methods are listed in detail below:

1. Hand hoeing: Hand hoe is the simplest tool to control annual & biennial weeds which have shallow root system under this system, but it can not be able in controlling deep rooted & perennial weeds. 2. Hand pulling: It is pulling out of weeds by hand. It is very economical in those areas where weeds are scattered & very effective against annual & biennial weeds as they do not regenerate from pieces of roots left in the ground.

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3. Tillage: Weeds can be controlled by various tillage operation such as ploughing, harrowing, planking, levelling etc. Many perennial weeds ca also be controlled by deep ploughing continuously for a period of 3 or 5 years. 4. Digging: Under digging the underground propagating parts of perennial weeds are removed from the deep layers of soil. It is followed by hand pulling the weeds. But it is a labour intensive method which is its main drawback. 5. Sickling: Sickling is mostly used in case of sloppy lands to remove top weed growth & to prevent weed seed production. 6. Burning: In this method, the weeds are burnt with fire along with crop residues in certain crops like sugarcane, potato, maize, cotton etc. 7. Flooding: Here the weeds are managed by flooding the field with 20 -30cm standing water for 5 to 10 weeks. It is very much useful in some perennial weeds like Cyperus sp., Cynodon dactylon & Convolvulus arvensis. 8. Mulching: It has a smothering effect on weeds by restricting the photosynthesis. Mulching is effective against Sorghum halepense, Cynodon dactylon etc. Mulching can be done by straw, hay, paper, polythene films etc. in cash crops. AGRONOMIC OR CULTURAL METHODS OF WEED CONTROL These practices for weed control are mostly non-monetary & relatively of less expenditure these methods can be used to reduce the intensity of weeds to improve crop yield. The main objective of cultural practices is to provide a short-term relief to crop during initial growth periods of crop production. The various practices involved under the cultural method of weed control are listed below:-

1. Planting or Sowing time :As it is a proved fact that weed seeds are thermo sensitive in nature, so by adjusting the planting or sowing time of crop plants we can exert a smothering effect on the weeds so that the crop plants have the early advantage over the weeds & therefore, offers less competition for the crop plants. For eg.) if wheat is early sown then Phalaris minor has less advantage over the wheat crop. 2. Use of clean seed: To ensure that the crops must be free of primary weed infestation the crop seed must be free from weed seeds. Phalaris minor was imported along with

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Mexican wheat seed & then spread to many parts of Indian subcontinent through movement of wheat seeds from place to place. 3. Stale seedbed preparation: The main objective of this technique is to induce germination of weed seed with irrigations before sowing the crop so that 2-3 flushes of germinated weeds are destroyed. This method is ideal for the crops in which germination of crop & weed seed is synchronised. 4. The method of sowing: Closed spacing of crops always gives a chance to the crop plants ahead of weeds. Also, bidirectional sowing of crops helps in reducing weed growth as the distribution of plants over the space becomes adequate & healthy crop canopy structure can be generated which can cover the weeds effectively. 5. Proper seed rate : higher seed rate enjoys an advantage over the weeds as thick crop stand reduces space for weeds to grow & establish themselves. 6. Crop rotation: Crop rotation is also helpful as monoculture or growing of same cropping system allows the pure stand of some permanent weeds which are very difficult to control .for eg.) some permanent weeds of rice -wheat cropping system such as Phalaris minor & Echinocolona sp. can be controlled by replacing wheat with berseem, raya or winter maize. Wild oat can be completely managed from wheat by replacing it with berseem for 3-4 years. 7. Intercropping: Weeds can also be manged effectively by intercropping of wide row- spaced crops with closed row-spaced crops & of tall growing crops with short growing crops. Efficient intercrops are cowpea, green gram, black gram, soybean etc. 8. Water management: weeds can also be managed properly by managing irrigation. The role of land submergence in lowland rice has been well noticed all over the world. Under normal irrigations to wheat crop wild oat make luxuriant growth & affect the wheat crop, but in limited irrigation, the wheat plants overtake the wild oat & suppress their growth & development.

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BIOLOGICAL METHODS OF WEED CONTROL These methods involve the utilisation of natural living organisms i.e. bioagents such as insects, pathogens & competitive plants to limit the weed infestation .the objective of biological control are not the complete eradication of weed population but bring their population below the economic injury level the merits of biocontrol agents are their relative cheapness, environment comparatively long lasting effects & least environment & the non-target organisms. Some outstanding examples of biological control of weeds are: a. Control of Eichhornia crassipes (water hyacinth) using Necochetina eichhorniae (hyacinth weevil); b. Salvinia molesta (water fern) is controlled by Crystobagus spp. ; c. Lantana camara in India has been effectively controlled by a moth Crocidosema lantana; d. Zygograma bicolorata beetle feeds on Parthenium plants during the rainy season. Weeds can also be controlled by this method with the help of bioherbicides such as Collego, Devine, Biopolaris, Tripose etc. Integrated weed management Rice Critical period of weed control 20-30 DAT Cultural method 1) Hand weeding 2) Hand pulling 3) Pudding 4) Flooding Mechanical method 1) Weeder (Float) 2.Conoweeder/Rotary weeder Chemical method Apply pendimethalin 1.0kg/ha on 5 days after sowing or Pretilachlor + safener (Sofit) 0.45kg/ha on the day of receipt of soaking rain followed by one hand weeding on 30 to 35 days after sowing. Biological method 1. Hirsch – Manniella spinicaudata is a rice root nematode which controls most upland rice weeds 2. Azolla Remarks I. Substitution and preventive method: a) Stale seed bed technology b) Land preparation c) Water management

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WHEAT Critical period of 15 – 30 DAS weed control Cultural method a) Hand Hoeing b) Inter cultivation c) Criss-cross sowing Chemical method 1. 2, 4D (1 – 1.5 kg ai/ha) 2. Mixture of Isoproturan (0.75 kg ai/ha) and 2, 4D (0.4 kg ai/ha) during 30- 35 DAS Remarks II. Complimentary weed control methods a) Cultivars b) Seedling age /planting method c) Fertilizer management d) Cropping system

SORGHUM Critical period of 21 – 42 DAS weed control Cultural method 1. Hoe and hand weed on the 10th day of transplanting if herbicides are not used. 2. Hoe and weed between 30 - 35 days after transplanting and between 35 - 40 days for a direct sown crop Chemical method 1. Apply the pre-emergence herbicide Atrazine 50 WP - 500 g/ha on 3 days after sowing as spray on the soil surface 2. If pulse crop is to be raised as an inter-crop in sorghum do not use Atrazine. Remarks 1. Inclusion of cotton crop in the rotation

MAIZE Critical period of Maize 2 to 6 Weeks weed control Cultural method One hand weeding on 40-45 days after sowing Chemical method 1. Pre-emergence application of Atrazine (1-2 kg ai/ha) 2. Combined application of Alachlor (2 kg/ha) and atrazine (1kg/ha) is more effective and have wider spectrum of control

GROUNDNUT Critical period of Upto 45 days weed control Cultural method After 35 - 40 days one hand weeding may be given. Chemical method 1. Alachlor (1-5 kg/ha) – pre emergence application

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SUNFLOWER Critical period of 4-6 weeks weed control Cultural method Hoe and hand weed on the 15th and 30th day of sowing and remove the weeds. Allow the weeds to dry for 2 - 3 days in the case of irrigated and then give irrigation. Chemical method 1. Apply Fluchloralin at 2.0 l/ha before sowing and incorporate or apply as pre-emergence spray on 5 day after sowing followed by irrigation or apply Pendimethalin as pre-emergence spray 3 days after sowing.

COTTON Critical period of First 45 days weed control Cultural method 1. One hand weeding on 45 DAS will keep weed free environment upto 60 DAS 2. Hoe and hand weed between 18th to 20th day of sowing, if herbicide is not applied at the time of sowing Chemical method 1. Diuron (0.5 – 1.5 kg/ha), Monuron (1-1.5 kg/ha), Fluchloralin (1-1.5 kg/ha) applied as preemergence/ preplanting PULSES Critical period of First 30-35 days weed control Cultural method 1. One hand weeding on 30 days after sowing gives weed free environment throughout the crop period 2. If herbicides are not applied give two hand weedings on 15 and 30 days after sowing. Chemical method 1. Fluchloralin (1-1.5 kg/ha ), Pendimethalin (0.5-1.0 kg/ha) as Pre emergence (preplanting incorporation) TOBACCO Critical period of First 9 weeks weed control Chemical method 1. Fluchloralin (2-3 kg/ha), Pendemethalin (1-1.5 kg/ha) as pre-emergence application

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SUGARCANE Critical period of 4 to 5 months weed control Cultural method Remove the weeds along the furrows with hand hoe. Mechanical method If herbicide is not applied work the junior-hoe along the ridges on 25, 55 and 85 days after planting for removal of weeds and proper stirring Chemical method 1. Pre-emergence herbicides like atrazine (2 to 3 kg/ha) Simazine (2 to 3 kg/ha), Alachlor (1.3 to 2.5 kg/ha) etc., will generally last for 8 to 12 weeks 2. To obtain best results sequential application of Preemergence and post emergence herbicides or post emergence herbicides like Glyphosate (0.8 to 1.6 kg/ha) Paraquat (0.4 to 0.8 kg/ha).

Latest development in Weed management

Development and testing of new molecules are the never ending tasks for the weed scientists. The new molecules are regularly being evolved and are finding place in integrated weed management programmes under diverse cropping and farming situations. The integrated weed management mostly utilized herbicides at low doses and the manual weeding later on to remove the left over weeds. But the scarcity of labour for manual weeding compels to find out alternative weed control strategy. With the availability of a wide range of pre and post- emergence herbicides, sequential application of pre and post emergent herbicides was the need with due attention to the environmental concerns. A lot of research findings started down pouring involving the benefits of sequential application of herbicides. The adoption of transgenic herbicide-resistant crops has increased dramatically in the last decade. Most of the increase in hectares of transgenic crops planted is attributable to glyphosate- resistant soybean, maize, canola and cotton. Glyphosate-resistant soybean and canola were introduced in 1996, cotton in 1997, and maize in 1999. Glyphosate-resistant cotton accounts for 56% of the cotton hectares planted in the USA in 2001. In 2001, glyphosate-resistant soybean and maize cultivars accounted for over 70 and 10%, respectively, of the hectares planted in the Mid-west USA and the adoption trend is increasing. In Argentina, glyphosate-resistant soybean accounts for 98% of the hectares planted in 2001. The results of this unprecedented change in agriculture have been many, but perhaps most dramatic is the simplification of weed-control

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tactics; growers can now apply a single herbicide (glyphosate) at elevated rates of active ingredient and at multiple times during the growing season without concern for injury to the crop. While a number of agriculturalists and economists suggest that the adoption of herbicide- resistant crops will reduce herbicide use dramatically, others suggest that herbicide use will actually increase. Regardless, the number of herbicides applied has declined, thus increasing the ecological implications such as reducing the biodiversity of arable land, facilitating population shifts in weed communities and the evolution of herbicide-resistant biotypes. Historically, a number of significant changes in agricultural systems have occurred with significant impact on weed communities. Adoption of conservation tillage practices and concomitant changes in herbicide use in the 1980s resulted in more small-seeded annual weeds. The development and commercialization of herbicides that inhibit acetolactate synthase (ALS) resulted in another significant change in weed communities and ushered in the widespread problems with common waterhemp (Amaranthus tuberculatus (Moq) Sauer) and the evolution of herbicide-resistant biotypes. The question that must be addressed is whether or not the most recent major change in agroecosystems, the adoption of herbicide-resistant crops, represents a different risk than previous changes. The biological approach (a deliberate use of natural enemies to suppress the growth or reduce the population of the weed species) of managing weeds is gaining momentum. This approach involves two strategies: the classical or inoculative strategy, and the inundative or bioherbicide strategy. In the inoculative approach, an exotic biocontrol agent is introduced in an infested area. This method is slow and is dependent on favourable ecological conditions, which limits its success in intensive agriculture. Whereas in the inundative approach, bioherbicides are employed to control indigenous weed species with native pathogen, applying them in massive doses in the area infested with target weed flora. Bioherbicides offer many advantages. They include a high degree of specificity of target weed; no effect on non-target and beneficial plants or man; absence of weed resistance development, and absence of residue build-up in the environment.

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Commercial bioherbicides first appeared in the market in USA in early 1980s with the release of the products Devine, Collego and Biomal. Success stories of these products and the expectation of obtaining perfect analogues of chemical herbicides have opened a new vista for weed management. Plant pathologists and weed scientists have identified over 100 microorganisms that are candidates for development as commercial bioherbicides. Some of these are described here. Devine, developed by Abbott Laboratories, USA, the first mycoherbicide derived from fungi (Phytophthora palmivora Butl.), is a facultative parasite that produces lethal root and collar rot of its host plant Morrenia odorata (stangler wine) and persists in soil saprophytically for extended periods of residual control. It was the first product to be fully registered as a mycoherbicide. It infects and kills strangler wine (control 95 to 100%), a problematic weed in citrus plantation of Florida. Commercially Collego, a formulation of endemic anthrocnose fungus Collectotrichum gleosporiodes f. sp. Aeschynemone (cga) was developed to control northern joint vetch (Aeschynemone virginica) in rice and soybean field. Dry powder formulation containing 15% spores (condia) of cga as an active ingredient was registered in 1982 under the trade name Collego, having a shelf-life of 18 months. It is the first commercially available mycoherbicide for use in annual weed in annual crops with more than 90% control efficiency. The successful development of Collego led to the discovery of another Collectotrichum- based mycoherbicide, ‘Biomal’ by Philom Bios Inc., Canada. It contains spores of C. gleosporiodes (Penz.) Sacc. f. sp. Malavae. It is used to control Malva pusilla (round-leaved mallow) in Canada and USA. The most effective period of application is at an early stage, although it can be effective at any stage of weed growth. Further, the rust fungus Puccinia canalicuta (Schw) legrah is commercialized under the name Dr. Biosedge for control of Cyprus esculantus L. (yellow nut sedge). Recently the potential of many microorganisms, especially fungus to control weeds in several crops has been reported. Some of them are listed here. Alternaria cassiae (Casst), Cercospora rodmani (ABG-5003), Cercospora coccodes (Velgo), Collectotrichum orbicular, Fusarium aonifliral, Deleterious rhizobacteria (DRB), Pseudomonas spp., Agrobectarium, Xanthomonas spp., Ervinia herbicola, Pseudomonas syringae pv. Tagetis (Pst), Xanthommonas campaestris pv. Poannua, (Xcp), S. hygroscoplus (Bialaphos).

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Besides many advantages of bioherbicides, certain factors have been reported to limit the development of bioherbicides into commercial products. These include biological constraints (host variability, host range resistance mechanisms and interaction with other microorganisms that affect efficacy), environment constraints (epidemiology of bioherbicides dependent on optimum environmental conditions), technical constraints (mass production and formulations development of reliable and efficacious bioherbicide), and commercial limitations (market size, patent protection, secrecy and regulations). The bioherbicides approach is gaining momentum. New bioherbicides will find place in irrigated lands, wastelands as well as in mimic parasite weeds or resistant weed control. Research on synergy test of pathogens and pesticides for inclusion in IPM, developmental technology, fungal toxins, and application of biotechnology, especially genetic engineering is required. However, bioherbicides should not be viewed as a total replacement to chemicals, but rather as complementary in integrated weed management systems. In developed countries chemical weeding is more prominent than mechanical weeding. However in the recent times the problem of environmental degradation and pollution is making the world to have a re think on the adoption of mechanical weeders. Development of row crop weeders is the viable option in order to ensure sustainable crop production and optimum environmental conditions. It is very easy to use ploughs, harrows and mowers to control weeds in the open field where crop had not been planted. However special care must be taken when using weeders in row crop plantations. Research efforts over the globe are continuing and have yielded some results. Ademosun et al. (2003) reported the development of various machines for weeding and harvesting. One of the latest developments for mechanized hand weeding is a controversial human-hybrid weeding machine which supports several workers prostrate on their abdomens and allows them to pull weeds by their hands, literally laying down on the job! This practice was recently described as inhumane in a Southern California periodical La Opinión. Robotic Suit for Farmers: Japanese scientists at the Tokyo University of Agriculture and Technology in early 2009 demonstrated a prototype wearable assistance machine equipped with eight motors and 16 sensors. This robot suit for farmers is designed to allow a farm worker to lift heavy objects, pull weeds and reduce the heavy burden of harvesting as the nation's farm industry faces an ageing, shrinking workforce. The 25-kilogramme (55-pound) device is

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intended to assist elderly farmers who need support for their leg muscles and joints when they keep a crouching position or lift their arms high. The researchers said they were looking to commercial use of the suit in two to three years at an initial price ranging from 500,000 yen to one million yen (about 5,000 to 10,000 dollars). That's a lot of yen, and 55 pounds is a lot of weight for an ageing farmer or itinerant farm worker, but it may be a good deal if they include a Turbo Weed Twister with a built-in torque power supply in the final package! At least this outfit supports an upright farmer, as opposed to the prostrate bedweeder design shown above.

Robotic Cultivator System Sometimes within the next few years, there may be a new mechanized weeding system available to growers, which will save them hundreds of dollars per ha. Over the past three years, David Slaughter, a researcher at the University of California-Davis, has been working on perfecting a precision weed control robotic cultivator system that can tell the difference between weed seedlings and tomato seedlings in the field. On the back of the mechanism, there would be several mounted miniature hooded sprayers that would go in between the rows and spot spray the weeds, leaving the tomato plants and everything else in the field untouched. Machine vision based detection of volunteer potatoes in cropped fields is also being studied by the Wageningeh University, a Dutch university in Europe. A solar-powered robot with 20/20 vision, on a search-and-destroy quest for weeds, will soon be moving up and down the crop rows at the experimental fields at the University of Illinois. What's more, this robot has the potential to control weeds while significantly reducing herbicide use. The robot uses GPS for navigation, and there are two small cameras mounted on a frame on top

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of the machine to give the robot depth perception, just like a human, according to Lei Tian, agricultural engineer at the U of I. "If he sees a weed, he can actually tell how far away it is." An on-boardcomputer offers access to information that provides the morphological features of plants, to help the robot determine just what is and isn't a weed. Once a weed is identified, a robotic arm attached to the front of the machine engages a device the researcher calls "a custom-designed end effector."

Using similar image analysis techniques to those used on the Robocrop 2 high speed hoes, Robocrop In Row analyses images of the crop immediately in front of the weeder. Applying a predetermined grid and best fit logical deduction techniques individual plants are pinpointed and tracked through the image. The weeding rotors are then synchronised to work around each individual plant, the rotor speed being continually adjusted to take into account plant spacing variations. The InRow rotors are then followed up by a set of inter-row cultivation units to complete the all round cultivation process. Performance is 2 plants per second per row.

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Chapter 8: Soil-plant water relationships Soil-plant-water relationships treat those properties of soils and plants that affect the movement, retention, and use of water. These properties must be considered in designing and operating conservation irrigation systems. In planning an irrigation system, an agronomist/engineer is concerned primarily with 1. the water-holding capacity of a soil, particularly in a plant's root zone; 2. the water-intake rate of the soil; 3. the root system of the crop to be grown; and 4. the amount of water that the crop uses. But he must also have a working knowledge of all soil-plant water relationships in order to plan efficient irrigation for particular crops grown on particular soi1 and to adjust the design to various conditions. This general knowledge also enables him to assist an irrigator in managing the system efficiently. Soils Soil is a three phase system comprising of the solid phase made of mineral and organic matter and various chemical compounds, the liquid phase called the soil moisture and the gaseous phase called the soil air. Besides a storehouse of plant nutrients and a reservoir that holds the water needed for plant growth, it is a habitat for bacteria and an anchorage for plants. The amount of water a soil can hold available for plant use is determined by its physical properties. This amount determines the length of time a plant can survive without water being added. It determines both the frequency of irrigation and the capacity of the irrigation system needed to ensure continuous crop growth. Physical properties of soil Mineral soils are porous mixtures of inorganic (mineral) particles, decaying organic matter, air and water. They also contain a variety of living organisms. The parent material of mineral soils consists of loose unconsolidated fragments of weathered rocks or unconsolidated sediments of various kinds. Physical and chemical weathering gives rise to a horizontal layering in the soil mass. These different soil layers can be seen in trenches, eroded banks, and road cuts. Collectively these layers (horizons) from top to bottom are called the soil profile. Their arrangement and the kinds of material in the layers affect both root growth and the movement and retention of water in the soil.

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Two important physical properties of soils are texture and structure. Soil texture refers to the relative proportion of the various size groups of mineral particles in a given soil. Soil structure refers to the manner in which the soil particles are arranged in groups or aggregates. Together, soil texture and soil structure help to determine the supply of water and air in a soil. Unlike texture, structure of the surface soil can be changed. Excellent structure develops in the surface layer of soils high in organic matter and on which a perennial grass is growing. Cycles of wetting and drying or of freezing and thawing improve structure in the plough layer. On the other hand, cultivation of medium or fine textured soils when their moisture content is high tends to destroy structure. Irrigation water containing large amounts of sodium causes very undesirable structure by dispersing the soil aggregates. The physical condition of the soil in relation to plant growth and ease of tillage is commonly called tilth. It depends partly on granulation and on stability of the granules. Tilth is commonly evaluated as good, fair, or poor, according to the ease with which the soil can be worked and the rate at which it takes in water. Soils in good tilth are mellow, crumbly, and easily worked; they take up water readily when dry. Soils in poor tilth generally are hard, cloddy, and difficult to work; they take up water slowly and run together when wet. Good soil tilth can be developed and maintained on most soils by using good soil management practices. Soil water Since a constant supply of water in the soil is necessary for plant survival and growth, the irrigation agronomist/engineer is concerned with how water moves in a given soil, how much water a soil can hold and how much of it is available to plants, and how the water supply can be replenished. The first two are related to size and distribution of the soil pores and to size of the soil particles and their attraction for moisture. The amount of water a soil holds also depends on the amount of organic matter in the soil. Generally, the finer the soil particles and the larger the amount of organic matter, the more water a soil holds. Kinds of water in the Soil The soil pores, spaces between the particles, form a network of connected cavities of every conceivable shape and size. When water is added to a dry soil by either rain or irrigation, it is distributed around the soil particles where it is held by adhesive and cohesive forces; it displaces air in the pore spaces and eventually fills the pores. When all the pores, large and small, are filled, the soil is said to be saturated and is at its maximum retentive capacity.

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The water in the large pores that moves downward freely under the influence of gravity is called gravitational water or free water. When the supply of water to the surface is cut off, water continues to drain from the large pores for a few days. In well-drained soils, the free water near the surface usually has moved out before crops are damaged. The large pores are again filled with air; water in the small pores moves because of capillary forces and is called capillary water. It moves more slowly than free water; it can move in any direction but always in the direction of the greatest tension. Evaporation from the surface and absorption of moisture by growing plants further reduce the amount of water in the soil until water no longer moves because of capillary forces. It is held so tightly as very thin films around the soil particles and in minute wedges between the particles at their points of contact that it cannot be used by plants and they begin to wilt. Eventually the soil is so dry that plants die if water is not added to the soil. The remaining water is held on the particle surfaces, particularly the soil colloids, so tightly that much of it is non- liquid and moves as a vapour. This is called hygroscopic water. Of these three forms of water, gravitational, capillary, and hygroscopic, the irrigation agronomist/engineer is concerned primarily with gravitational and capillary water since hygroscopic water is not available to plants. Movement of water in the Soil The movement of water in the soil is complex because of the various states and directions in which water moves and because of the forces those cause it to move. Because of gravity, water moves downward. Because of adhesive and cohesive forces, it moves in small pores by capillarity. Because of heat, it vaporizes and diffuses through the soil air. The rate at which gravitational water percolates through the soil is determined chiefly by the size and continuity of the pore spaces. Water usually moves freely through the large pores in coarse textured soils. It moves less rapidly through fine-textured soils because of the resistance to flow in small pores, which may also be blocked by swollen colloidal gels and trapped air. Percolation is retarded by a slowly permeable layer such as a claypan or ploughpan. A sand lens temporarily halts percolation; but once water penetrates such a layer, it continues to move downward. Irrigation water moves as a front--from a saturated soil layer to an unsaturated layer. Movement of the front is unsteady; water builds up behind the front until the large pores are

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filled and then moves to the next layer of large pores. In moist soils water movement is more uniform than in dry soils. The movement of capillary water is affected by soil texture. The forces that cause capillary movement in small pores result largely from the difference in tension between films of different thickness around soil particles; the movement is from thick films to thin films. If these forces are expressed in terms of tension, water moves from an area where tension is low to an area where tension is high. At saturation, capillary movement is most rapid in sandy soils and slowest in clay soils. But in drier or unsaturated soils capillary water moves slowly in sands and more rapidly in clays. Heat causes water to move as a vapour. As water vapour diffuses through the soil air near the surface, it either condenses in another part of the pore space or escapes into the atmosphere. As water is evaporated from the surface, capillary water rises and replaces part of the evaporated water. This continues until the upper few inches of the soil become dry and capillarity is broken. Water then leaves the soil only by vaporizing at the upper capillary fringe and diffusing through the overlying dry soil. How Water Is Held in the Soil Work must be done (energy used) to remove water from a soil. The force (tension) with which water is held depends on the amount in the soil—the smaller the amount, the greater the tension. The forces that determine tension are adhesion, the attraction of soil-particle surfaces for water, and cohesion, the attraction of water molecules for each other. By adhesion water is held tightly at the soil-water interface. By cohesion these water molecules hold other water molecules. Because of these forces water fills the small pores in the soil and is in fairly thick films in the large pores. As the films become thicker, however, the water molecules at the outer surface, the liquid-air interface, are held less tightly. They can move in response to the pull of gravity and to the pull of less thick films nearby. Thus not much work or energy is required to remove water from a soil near saturation. But as more and more water is removed, more and more energy is required. Soil-moisture tension Soil-moisture tension is a measure of the tenacity with which water is retained in the soil and shows the force per unit area that must be exerted to remove water from a soil. It is usually

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expressed in atmospheres, the average air pressure at sea level, but other pressure units can be used. At a temperature of 21 oC (69.8 oF), 1 atmosphere = a pressure of 14.71 pounds per square inch, = a column height of 76.39 centimetres of mercury = a column height of 34.01 feet or 1,036 centimetres of water. An expression of soil-moisture tension does not indicate the amount of water a soil contains nor does it indicate the amount of water that can be removed at that tension. These amounts, which depend on both texture and structure, must be determined. Generally sandy soils drain almost completely at low tension, but fine-textured clays still hold a considerable amount of moisture even at such high tensions that plants growing in the soil wilt. To show the amount of moisture a given soil holds at various tensions, moisture- extraction curves (moisture characteristic curves) must be developed. This can be done by plotting tension in atmospheres against moisture content in percentage by weight. Tension values indicate the ease or difficulty with which moisture can be removed from a soil and moisture percentage indicates the amount of water still in the soil. Soil-moisture tension as discussed in the preceding paragraphs is based on pure water. Salts in soil water increase the force that must be exerted to extract water and thus affect the amount of water available to plants. The increase in tension caused by salts is from osmotic pressure. If two solutions differing in concentration are separated by a membrane impermeable to the dissolved substance, such as a cell membrane in a plant root, water moves from the solution of lower concentration to the one of higher concentration. The force with which water moves across such a membrane is called osmotic pressure and is measured in atmospheres. In many irrigated soils, the soil solution contains an appreciable amount of salts. The osmotic pressure developed by the soil solution retards the uptake of water by plants since the total moisture stress is the sum of the soil-moisture tension and the osmotic pressure of the soil solution. Plants growing in a soil in which the soil-moisture tension is 1 atmosphere apparently can extract enough moisture for good growth. But if the osmotic pressure of the soil solution is 10 atmospheres, the total stress is 11 atmospheres and plants cannot extract enough water for good growth. Available Water

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In designing an irrigation system and in making recommendations for improved techniques of applying water, the agronomist/engineer needs to know how much of the water in a soil is available to plants. The soil is like a tank and holds just so much available water. Its capacity is limited by the total amount of water it can hold between field capacity and the permanent wilting point. In addition to soil-moisture tension and the osmotic pressure of the soil solution, availability of water also depends on the temperature of the soil. Low soil temperatures decrease availability. Field capacity is usually considered as the amount of water a well drained soil holds after free water has drained off or the maximum amount it can hold against gravity. The large pores in the soil are filled with air, the micropores are filled with water, and any further drainage is slow. In this condition, the soil is said to be at field capacity. Soil-moisture tension in a salt-free soil at field capacity ranges from less than 0.1 to nearly 0.7 atmosphere, depending on soil texture. Sands are at field capacity when tension is near 0.6 atmosphere and loamy sands when tension is near 0.1 atmosphere. Silt loams are at field capacity when tension is about 0.3 atmosphere. Clays and clayey soils are at field capacity when tension is about 0.6 atmosphere. Field capacity of a soil can be determined, after it has been thoroughly wetted by rain or irrigation water, by covering a small area to prevent evaporation and determining the moisture content after drainage has taken place. One method is to take soil samples, weigh them, dry them in the oven, and reweigh them. The permanent wilting point, also known as permanent wilting percentage, is the soil-moisture content at which plants can no longer obtain enough moisture to meet transpiration requirements; they wilt and remain wilted unless water is added to the soil. The moisture tension of a soil at the permanent wilting point ranges from 7 to 32 atmospheres, depending on soil texture, on the kind and condition of the plants, on the amount of soluble salts in the soil solution, and to some extent on the climatic environment. Since this point is reached when a change in tension produces little change in moisture content, there is little difference in moisture percentage regardless of the tension taken as the permanent wilting point. Therefore 15 atmospheres is the pressure commonly used for this point. During periods of low humidity, high temperature, and high wind velocity many plants with a large leaf surface show wilting even though the moisture content of the soil is higher than that at the permanent wilting point. This occurs because the transpiration

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rate exceeds the rate at which the plant can extract moisture from the soil. When a plant wilts, growth stops. Irrigation water, therefore, should always be applied to a soil before the moisture content of the root zone is reduced to the permanent wilting point. The wilting range is the range in soil-moisture content through which plants undergo progressive degrees of permanent or irreversible wilting, from wilting of the oldest leaves to complete wilting of all leaves. At the permanent wilting point, which is the top of this range, plant growth ceases. Small amounts of water can be removed from the soil by plants after growth ceases, but apparently the water is only slowly absorbed and is only enough to maintain life until more water is available. The bottom of the range is called the ultimate wilting point. When the moisture level reaches this point, wilting is complete and plants die. Although the difference in the amount of water in the soil between the two points may be small, there may be a big difference in tension. At the ultimate wilting point soil moisture tension may be as high as 60 atmospheres. Since the moisture available for plant growth is the capillary water between field capacity and the permanent wilting point, the available water holding capacity of a soil can be determined by subtracting the amount of moisture remaining in the soil at the permanent wilting point from the amount held at field capacity. Soil texture is of primary importance. For soils low in soluble salts, the finer the texture, the greater the available moisture holding capacity. But some sandy soils actually hold more available water than some clays, chiefly because in fine-textured soils so much water is held on the particles. Even at the permanent wilting point, the moisture content of some clays is fairly high. Well-drained sandy soils have a low available water holding capacity. At field capacity, most of the pore space in sandy soils is filled with air and thus there is little available moisture. Silty soils generally have a good available water holding capacity since a soil made up of silty particles of about the same size releases most of its moisture at tensions ranging from one-third atmosphere to 15 atmospheres. But in some silty soils the spaces between large particles may be filled with smaller particles, resulting in a low available moisture holding capacity. Some silt loams hold more than 2 inches of available moisture per foot of soil, but some silty soils are very droughty. Clays and clay loams are usually high in available water - about 2 inches per foot of soil—and still hold a considerable amount of unavailable moisture at the wilting point. Organic

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soils hold a considerable amount of water at field capacity, but since much of the water is not available, they also have a high moisture content at the wilting point. So far in this discussion, field capacity has been considered the upper limit of available moisture. This is not entirely true. In sprinkler and surface irrigation, water applied to the surface of the soil moves downward as a front, saturating the upper layers in most soils before the irrigation application is completed. Plant roots in the upper soil layers take up some of the water between saturation and field capacity. The amount plants use depends on how fast the soil drains to field capacity and on how often it is irrigated. Under good irrigation management on most soils, the length of time in which plants can use the extra moisture before the soil reaches field capacity is limited. For design purposes, therefore, this water is not considered. Water intake The movement of irrigation water from the surface into and through the soil is called water intake. It is the expression of several factors, including infiltration and percolation. Infiltration The downward flow of water from the surface into the soil is known as infiltration. Water enters the soil through pores, cracks, worm and decayed-root holes, and cavities introduced by tillage. In many places infiltration is restricted by surface sealing or crusting. Percolation For irrigation water to be effective in replenishing the soil's water supply, it must be able to move down, or percolate, through the soil to a predetermined irrigation depth. This movement of water through the soil profile is known as percolation. The percolation rate is governed by the permeability of the soil or its hydraulic conductivity. Both terms are used to describe the ease with which soil transmits water. Permeability is the quality of soil that enables it to transmit air and water. It is independent of the viscosity of water. The relative permeability of soils is described in general terms as rapid, moderate, and slow. Hydraulic conductivity is determined by both the soil and the fluid transmitted. It expresses the readiness of a soil to let a particular fluid flow through it for a given potential gradient. It is the coefficient "k" in Darcy's Law (v = ki) in which v is the effective flow velocity and i is the hydraulic gradient. The values of k depend on the properties of the fluid as well as on

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those of the soil, and they reflect any interactions of the fluid with the porous medium, such as swelling of a soil and the attendant reduced porosity. Since water percolates chiefly through the large pores in a soil, percolation depends on the relative number and continuity of these pores. A soil that has high porosity and coarse open texture has a high hydraulic-conductivity value. For two soils of the same "total" porosity, the soil with small pores has lower conductivity than the soil with large pores because of the resistance to flow in small pores. A soil with pores of many sizes conducts water faster if the large pores form a continuous path through the profile. In fine-textured soils, conductivity depends almost entirely on structural pores. In some soils, particles are cemented together to form nearly impermeable layers commonly called hardpans. In other soils, very finely divided or colloidal material expands on absorbing water to form an impervious gelatinous mass that restricts the movement of water. The quality of the water transmitted, particularly its salinity and alkalinity, has a marked effect on hydraulic conductivity. A change in the viscosity of water has an effect. A chemical change in water may greatly affect hydraulic conductivity without changing viscosity. The addition of a small amount of sodium chloride to the soil water, insufficient to make any noticeable difference in viscosity, may affect soil structure so much that hydraulic conductivity is greatly reduced. Factors Affecting Intake Rate The intake rate of a soil is a measure of its capacity to take in and absorb irrigation water applied to the soil surface during the period of time in which water is applied. The amount of moisture already in the soil greatly influences the rate at which water enters the soil. The soil takes in and absorbs irrigation water rapidly when water is first applied to the field surface. As the irrigation application continues, the surface soil gradually becomes saturated and the intake rate decreases until it reaches a nearly constant value. The intake rate of any soil is limited by any restriction to the flow of water into or through the soil profile. The soil layer with the lowest transmission rate, either at the surface or below it, usually determines intake rate. The most important general factors that influence intake rate are the physical properties of the soil and in sprinkler irrigation the plant cover. But for any given soil other factors may affect the intake rate. SURFACE SEALING: The formation of a thin compact layer on the ground surface rapidly reduces the rate of water intake through the surface. This layer results from a breakdown in

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structure, in part because of the beating action of raindrops or sprinkler drops and in part because of the action of water flowing over the surface whereby fine particles are fitted around larger particles to form a relatively impervious seal. The effect of surface sealing on intake can be greatly reduced, if not eliminated, by protecting the soil surface with mulch or some other permeable material. Grasses or other close-growing vegetation will help to prevent surface sealing. The hardened or compact surface of a soil subject to surface sealing can be broken up by a light cultivation before irrigation water is applied. SOIL COMPACTION: On some wet soils tillage operations may cause compaction and the formation of a ploughpan just below cultivation depth. A ploughpan impedes water movement and reduces the intake rate. The intake rate is materially reduced in furrows where tractor wheels operate. Subsoiling helps to improve the movement of water through a ploughpan and thus the intake rate, particularly in soils that have a relatively impermeable sublayer that can be broken up. The soil takes in more water through the enlarged openings and continues to take in water so long as they remain. SOIL CRACKING: On heavy clay soils that crack on drying, irrigation generally can be accomplished by rapidly filling the cracks before the soil starts to swell. The amount of water that can be applied depends on the number and size of the cracks. As soon as the soil particles become wet, they begin to swell; eventually the cracks are closed so that further intake is either impossible or extremely slow. TILLAGE: The intake rate may be increased by ploughing, cultivating, or any other stirring that increases the size of openings. But the beneficial effect of cultivation on soil porosity and intake lasts only until the soil settles back to its former condition of density because of subsequent rain or irrigation. The intake rate of loose, porous sands is not likely to be increased by any artificial disturbance. On some soils, cultivation reduces intake by closing up the natural surface openings that lead into the body of the soil. The most important effect of tillage on water movement is to break up a surface seal. CROP ROTATIONS: If coarse organic materials are evenly incorporated into the soil, porosity remains high for comparatively long periods, depending mostly on the rate of decomposition of the materials. The intake rate can be maintained and even increased by using a cropping system that provides for incorporating crop residues in the upper few inches of the soil, growing grasses and legumes, and using any other methods that increase the organic-matter content of the soil. If

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a good crop rotation is followed, the proportion of stable soil aggregates is increased, which means large pores and consequently a high water-intake rate SOIL AND WATER SALTS: Any salts contained in irrigation water accumulate in irrigated soils and in time may change their character. This accumulation is serious in the arid West where almost all water is supplied by irrigation. In humid areas rainwater percolating through the soil leaches out most accumulated substances. But, in arid regions it is often necessary to over irrigate (leach) periodically to remove soluble salts from the soil. Some soluble salts in irrigation water such as potassium nitrate may be directly beneficial to crops. Under some conditions, calcium and magnesium have a beneficial effect on the physical condition of the soil. High concentrations of sodium chloride or sodium sulfate, however, have a detrimental effect. If the sodium concentration is high, soil structure breaks down and eventually the soil colloids are dispersed, resulting in a tough or rubbery condition. Tilth and permeability are reduced. This sealing is noticeable even in some sandy soils. The physical properties of some alkali soils, including intake, can be improved by adding chemicals or soil amendments through which exchangeable sodium is replaced by calcium. A comparatively economical and often used soil amendment is calcium sulfate, or gypsum. In some soils, its use results in improved permeability and aeration and thus better root development and plant growth. Other chemicals that can be used on some soils are sulfur and aluminum sulfate. SEDIMENTS IN IRRIGATION WATER: In some places, fine silt and clay particles carried in suspension affect the quality of irrigation water. Whether this is detrimental or beneficial depends on the amount of silt transported, the length of time the silty flow continues, and the texture of the soil to which the water is applied. Occasional deliveries of silty water may be beneficial on coarse sandy soils inasmuch as the sediments improve the physical condition of the root zone, thereby reducing the rate of water movement. They also add some plant nutrients such as potassium, calcium, and phosphates to the soil. But silty water applied to fine-textured soils generally makes the surface of the soil still more slowly permeable and difficult to cultivate. SOIL EROSION: As erosion progresses, the intake rate of many soils is reduced since less permeable material such as a dense clay subsoil is uncovered. In other soils erosion exposes coarse-textured layers such as sand and gravel. Here the intake rate is increased and irrigation efficiency is greatly reduced.

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LAND LEVELING: The moving and mixing of soil in land leveling may change the water- intake rate of any given area. The effects are similar to those of erosion in that either more permeable or less permeable soil material is uncovered. Earth-moving equipment used in land leveling may compact the soil and thereby reduce the intake rate. Subsoiling is often necessary after land leveling. TEMPERATURE: Tests show that water intake is greater during summer rains than during winter rains. Apparently the temperature of irrigation water has some effect on intake rate since the coefficient of viscosity of water decreases rapidly as temperatures increase. This effect is not considered significant by most authorities. Plants Almost every plant process is affected directly by the water supply. Water constitute about 80-90% of most plant cells and tissues in which there is active metabolism. The factors influencing the water relations of plants and thus their growth and yield responses, may be grouped into the following:  Soil factors – soil moisture content, texture, structure, density, salinity, fertility, aeration, temperature and drainage.  Plant factors – type of crop, density and depth of rooting, rate of root growth, aerodynamic roughness of the crop, drought tolerance and varietal effects.  Weather factors – sunshine, temperature, humidity, wind and rainfall.  Miscellaneous factors – soil volume and plant spacing, soil fertility, and soil and crop management. The size of the soil reservoir that holds water available to a plant is determined mostly by that plant's rooting characteristics. The distribution of its roots determines its moisture-extraction pattern. How Plants Get Their Moisture Most plants have an enormous absorbing root surface. Near the growing tip of each root or rootlet, there are many root hairs in close contact with soil particles and with the air spaces from which roots get their oxygen. Through osmotic and other forces, root hairs extract moisture from the film of water that surrounds each soil particle. Two phenomena seem to explain how a plant gets the enormous amount of water it takes in and transpires: (1) Capillary movement of water to plant roots and (2) growth of roots into moist soil.

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As roots take up moisture, tension around the soil particles increases and water moves toward these points of plant absorption. How effective capillary movement is depends on how much water canbe delivered to the soil around the roots and how fast it gets there. But since there is little root extension when the soil-moisture content is low, it is likely that near the wilting point any water that reaches plant roots must move-to them. During favourable growing periods, roots often elongate so rapidly that satisfactory moisture contacts can be maintained even when the soil moisture content declines and without much help from capillary movement. Where a good root system has developed during favourable growing periods, a plant can draw its moisture supply from deeper soil layers. Thus if the roots in the upper part of the soil have depleted the moisture there to below the wilting point, plant needs can still be met provided roots have already grown into deeper layers that contain an adequate moisture supply.

Kinds of Root Systems The kind of root system a plant develops is fixed by heredity. Each species has its own characteristic growth habit. Some plants have a tap root that penetrates deeply into soil under favourable conditions. Other plants are slow growing and develop shallow primary roots and many lateral roots. Most of the roots of spinach and celery are in the surface foot of soil, and those of potatoes are within the upper 2 feet. Corn, cotton, and tomatoes permeate an open soil to a depth of 4 feet or more. Alfalfa and asparagus roots penetrate good soils to a depth of 8 to 10 feet or more. Cucumber roots extend laterally 5 or 6 feet in the ploughed layer. Asparagus roots make little lateral spread in comparison with their depth. CONSUMFTIVE USE Consumptive use, often called evapotranspiration, includes water used by plants in transpiration and growth and that evaporated from the adjacent soil and from precipitation

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intercepted by plant foliage. It is expressed in acre-feet or acre-inches per acre or in depth in feet or inches. Transpiration is the process by which water is removed from the soil by a plant, moved through the plant to the leaves, and lost to the atmosphere in vapor form. For irrigation, the moisture used in plant growth and that retained by the plant is included. Evaporation from the soil surface is not included in transpiration but is included in consumptive use. Transpiration occurs mostly from the leaves of a plant, but a small part of the emitted moisture comes from the younger stems. It occurs mostly during the daylight hours, and only a small amount, possibly 5 to 10 %, occurs during the night. The rate of transpiration is lowest just before sunrise and usually reaches a maximum shortly before noon. Transpiration accounts for a substantial part of the total consumptive use of a crop. Some of the factors that affect the rate of transpiration are moisture available in the soil, kind and density of plant growth, amount of sunshine, temperature, and soil fertility. In summer when exceedingly hot winds blow over a field, transpiration may take place more rapidly than moisture can be absorbed by plant roots even when the soil contains an ample supply of moisture. When this occurs, plants wilt. In some the foliage may be dried beyond recovery.

Evaporation is the diffusion of water as a vapour from a surface into the atmosphere. Factors that affect the rate of evaporation are the nature of the evaporating surface and differences in vapour pressure as determined by temperature, wind, and atmospheric pressure. In determining consumptive use, evaporation includes both evaporation from the ground surface and evaporation of the water intercepted by vegetation. In irrigated fields, frequent shallow irrigations tend to increase water loss by soil evaporation. If less frequent heavy irrigations are used, the soil surface is wetted less often and water penetrates to agreater depth in the soil. Consequently, a larger part of the irrigation water is available "for crop use. In fields of hay, pasture, or other close growing crops, evaporation from the soil is reduced not only because the plants transpire a large proportion of the soil moisture but also because they shade the soil. Soil texture affects evaporation. Evaporation is higher in soils in which capillary movement of water to the surface is rapid. Conversely, evaporation is not so high in soils through

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which water percolates freely. Losses of water from soil by evaporation vary greatly not only in different areas but also at different times and under different conditions in the same area. Appreciable wind movement, high temperature, and low humidity generally result in a high rate of evaporation if there is enough moisture at the soil surface. After irrigation, evaporation from the surface of the soil is high so long as the topsoil remains saturated; the rate is about the same as that from a water surface of the same temperature. Depletion of the moisture in the topsoil rapidly reduces the rate of evaporation. The evaporation rate between irrigations depends somewhat on tillage operations, cultivation, and mulching as well as on soil texture, weather conditions, kind of crop, stage of crop growth, and the method, frequency, and depth of irrigation. As plants develop and provide increasingly more shade, the amount of evaporation is progressively reduced. Daily Consumptive Use Daily consumptive use, that in a 24-hour period, varies as the factors that influence evaporation and transpiration vary. Consumptive use is low at the start of the growing season, increases as plant foliage develops and days become longer and warmer, generally reaches a peak during the fruiting period, and then rapidly declines to the end of a crop's growing season. From the time seed is planted until plants emerge, soil-moisture loss is by evaporation. As plants emerge, transpiration begins and increases in amount as they develop. After the plants die, transpiration ceases and further soil moisture loss is by evaporation. If all the physical and climatic conditions remain the same, daily consumptive use drops in hay and pasture fields immediately after cutting or grazing because of the reduction in transpiration. If the field is irrigated immediately after cutting, however, there is no reduction in daily consumptive use and the rate may even increase because of high evaporation. Seasonal Consumptive Use The total amount of water used in evaporation and transpiration by a crop during its growing season is called seasonal consumptive use. It is expressed usually as acre-inches per acre or as depth in inches but sometimes as acre-feet per acre or depth in feet. Seasonal consumptive use values are needed to evaluate and determine seasonal irrigation water supplies. Peak-Period Consumptive Use The average daily water-use rate during the 6 to 10 days of the highest consumptive use of the season is called the peak-period use rate and is the design rate to be used in planning an

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irrigation system. The peak-use period generally occurs when the crop is starting to produce its harvest, vegetation is most abundant, and temperatures are high. Since the average consumptive- use rate is higher for a very short peak-use period (2 or 3 days) than for a longer peak-use period, the design rate varies with the amount of water that can be used from the root zone (the normal depth of water application per irrigation). In shallow soils, in soils with a low water-holding capacity, or for plants with shallow root systems, the depth to which water is applied is shallow and irrigation frequency during the peak-use period ranges from 3 to 6 days. The peak-use period for plants with a moderately deep root system growing in deep soils with a good water-holding capacity may range from 8 to 15 days. The average use rate for these short periods is considerably higher than the average rate for the month of greatest moisture use and is generally less than the peak daily-use rate. Deep-rooted crops, such as alfalfa, growing in deep soils have a large reservoir to draw on, and the irrigation interval may range from 3 weeks to 1 month; the design rate is equal to or possibly slightly higher than the average rate in the month of greatest moisture use. The peak-use period for various crops in a given area may occur at different times in the growing season. Early-maturing crops have their peak-use period in late spring or early summer and late maturing crops, in late summer or early fall. Knowing when these peaks occur is important in working out a cropping plan in which the peak-use periods are staggered, thus reducing the total capacity requirement of the irrigation system. If two or more crops are grown in the same field, such as a permanent cover crop in an orchard or grain with a new alfalfa seeding, the peak moisture requirement of the crop or crop combination that uses more water must be met. Water movement along soil-plant-atmosphere system The complete path of water from the soil through the plant to the atmosphere forms a continuous system which may be analysed by evaluating the potential difference between soil and atmosphere in contact with root and leaf, respectively. The path of water may be divided into four sequential processes as follows: the supply of liquid water to the root surface, the entry of water into the root, the passage of water in the conducting elements and the movement of water vapour through and out of the leaves. The rate of water movement is everywhere proportion to the potential gradient and inversely proportional to the resistance to flow. It is desirable to consider water absorption in the total soil plant- atmosphere system instead of the roots alone. In

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this system one can partition the system in such a manner so that the involvement of different plant parts is taken into account. Irrigation Water Quality Criteria Salt-affected soils develop from a wide range of factors including: soil type, field slope and drainage, irrigation system type and management, fertilizer and manuring practices, and other soil and water management practices. In Colorado, perhaps the most critical factor in predicting, managing, and reducing salt-affected soils is the quality of irrigation water being used. Besides affecting crop yield and soil physical conditions, irrigation water quality can affect fertility needs, irrigation system performance and longevity, and how the water can be applied. Therefore, knowledge of irrigation water quality is critical to understanding what management changes are necessary for long-term productivity.

Irrigation Water Quality Criteria Soil scientists use the following categories to describe irrigation water effects on crop production and soil quality:  Salinity hazard – total soluble salt content  Sodium hazard – relative proportion of sodium to calcium and magnesium ions  pH – acid or basic  Alkalinity – carbonate and bicarbonate  Specific ions: chloride, sulfate, boron, and nitrate. Another potential irrigation water quality impairment that may affect suitability for cropping systems is microbial pathogens.

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Table 1. General guidelines for salinity hazard of irrigation water based upon conductivity.

Limitations for use Electrical Conductivity

(dS/m)*

None ≤0.75

Some 0.76 – 1.5

Moderate1 1.51 – 3.00

Severe2 ≥3.00

*dS/m at 25ºC = mmhos/cm1Leaching required at higher range.2Good drainage needed and sensitive plants may have difficulty at germination.

Salinity Hazard The most influential water quality guideline on crop productivity is the water salinity hazard as measured by electrical conductivity (ECw). The primary effect of high ECw water on crop productivity is the inability of the plant to compete with ions in the soil solution for water (physiological drought). The higher the EC, the less water is available to plants, even though the soil may appear wet. Because plants can only transpire “pure” water, usable plant water in the soil solution decreases dramatically as EC increases. The amount of water transpired through a crop is directly related to yield; therefore, irrigation water with high ECwreduces yield potential (Table 2). Actual yield reductions from irrigating with high EC water varies substantially. Factors influencing yield reductions include soil type, drainage, salt type, irrigation system and management. Beyond effects on the immediate crop is the long term impact of salt loading

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through the irrigation water. Water with an ECw of only 1.15 dS/m contains approximately 2,000 pounds of salt for every acre foot of water.

Table 2. Potential yield reduction from saline water for selected irrigated crops.1 % yield reduction Crop 0% 10% 25% 50% 2 ECw Barley 5.3 6.7 8.7 12 Wheat 4.0 4.9 6.4 8.7 Sugarbeet3 4.7 5.8 7.5 10 Alfalfa 1.3 2.2 3.6 5.9 Potato 1.1 1.7 2.5 3.9 Corn (grain) 1.1 1.7 2.5 3.9 Corn (silage) 1.2 2.1 3.5 5.7 Onion 0.8 1.2 1.8 2.9 Dry Beans 0.7 1.0 1.5 2.4 1Adapted from “Quality of Water for Irrigation.” R.S. Ayers. Jour. of the Irrig. and Drain. Div., ASCE. Vol 103, No. IR2, June 1977, p. 140. 2 ECw = electrical conductivity of the irrigation water in dS/m at 25oC. 3 Sensitive during germination. ECw should not exceed 3 dS/m for garden beets and sugarbeets. Other terms that laboratories and literature sources use to report salinity hazard are: salts, salinity, electrical conductivity (ECw), or total dissolved solids (TDS). These terms are all comparable and all quantify the amount of dissolved “salts” (or ions, charged particles) in a water sample. However, TDS is a direct measurement of dissolved ions and EC is an indirect measurement of ions by an electrode. Although people frequently confuse the term “salinity” with common table salt or sodium chloride (NaCl), EC measures salinity from all the ions dissolved in a sample. This includes – – ++ + negatively charged ions (e.g., Cl , NO 3) and positively charged ions (e.g., Ca , Na ). Another common source of confusion is the variety of unit systems used with ECw. The preferred unit is deciSiemens per meter (dS/m), however millimhos per centimeter (mmho/cm) and micromhos

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per centimeter (µmho/cm) are still frequently used. Conversions to help you change between unit systems are provided in Table 3.

Table 3. Conversion factors for irrigation water quality laboratory reports. Component To Convert Multiply By To Obtain Water nutrient or TDS mg/L 1.0 ppm Water salinity hazard 1 dS/m 1.0 1 mmho/cm Water salinity hazard 1 mmho/cm 1,000 1 µmho/cm

Water salinity hazard ECw (dS/m) 640 TDS (mg/L) for EC <5 dS/m

Water salinity hazard ECw (dS/m) 800 TDS (mg/L) for EC >5 dS/m

Water NO3N, SO4-S,B applied ppm 0.23 lb per acre inch of water

Definitions

Abbrev. Meaning

mg/L milligrams per liter

meq/L Milli equivalents per liter

ppm parts per million

dS/m Deci Siemens per meter

µS/cm Micro Siemens per centimeter

mmho/cm Milli mhos per centimeter

TDS total dissolved solids

Irrigation water acre inch 27,150 gallons of water Sodium Hazard

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Infiltration/Permeability Problems

Although plant growth is primarily limited by the salinity (ECw) level of the irrigation water, the application of water with a sodium imbalance can further reduce yield under certain soil texture conditions. Reductions in water infiltration can occur when irrigation water contains high sodium relative to the calcium and magnesium contents. This condition, termed “sodicity,” results from excessive soil accumulation of sodium. Sodic water is not the same as saline water. Sodicity causes swelling and dispersion of soil clays, surface crusting and pore plugging. This degraded soil structure condition in turn obstructs infiltration and may increase runoff. Sodicity causes a decrease in the downward movement of water into and through the soil, and actively growing plants roots may not get adequate water, despite pooling of water on the soil surface after irrigation. The most common measure to assess sodicity in water and soil is called the Sodium Adsorption Ratio (SAR). The SAR defines sodicity in terms of the relative concentration of sodium (Na) compared to the sum of calcium (Ca) and magnesium (Mg) ions in a sample. The SAR assesses the potential for infiltration problems due to a sodium imbalance in irrigation water. The SAR is mathematically written below, where Na, Ca and Mg are the concentrations of these ions in milliequivalents per liter (meq/L). Concentrations of these ions in water samples are typically provided in milligrams per liter (mg/L). To convert Na, Ca, and Mg from mg/L to meq/L, you should divide the concentration by 22.9, 20, and 12.15 respectively. For most irrigation waters encountered in Colorado the standard SAR formula provided above is suitable to express the potential sodium hazard. However, for irrigation water with high bicarbonate (HCO3) content, an “adjusted” SAR (SARADJ) can be calculated. In this case, the amount of calcium is adjusted for the water’s alkalinity, is recommended in place of the standard SAR (see pH and Alkalinity section below). Your laboratory may calculate an adjusted SAR in situations where the HCO3 is greater than 200 mg/L or pH is greater than 8.5.

meq/L = mg/L divided by atomic weight of ion divided by ionic charge (Na+=23.0 mg/meq, Ca++=20.0 mg/meq, Mg++=12.15 mg/meq)

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The potential soil infiltration and permeability problems created from applications of irrigation water with high “sodicity” cannot be adequately assessed on the basis of the SAR alone. This is because the swelling potential of low salinity (ECw) water is greater than high

ECw waters at the same sodium content (Table 4). Therefore, a more accurate evaluation of the infiltration/permeability hazard requires using the electrical conductivity (ECw) together with the SAR.

Table 4. Guidelines for assessment of sodium hazard 2 of irrigation water based on SAR and ECw . Potential for Water Infiltration Problem Irrigation water SAR Unlikely Likely 2 ———–ECw (dS/m)——— - 0-3 >0.7 <0.2 3-6 >1.2 <0.4 6-12 >1.9 <0.5. 12-20 >2.9 <1.0 20-40 >5.0 <3.0 2Modified from R.S. Ayers and D.W. Westcot. 1994. Water Quality for Agriculture, Irrigation and Drainage Paper 29, rev. 1, Food and Agriculture Organization of the United Nations, Rome. Many factors including soil texture, organic matter, cropping system, irrigation system and management affect how sodium in irrigation water affects soils. Soils most likely to show reduced infiltration and crusting from water with elevated SAR (greater than 6) are those containing more than 30% expansive (smectite) clay. Soils containing more than 30% clay include most soils in the clay loam, silty clay loam textural classes and finer and some sandy clay loams. In Colorado, smectite clays are common in areas with agricultural production.

Table 5. Susceptibility ranges for crops to foliar injury from saline sprinkler water.

Na or Cl concentration (mg/L) causing foliar injury

Na concentration <46 46-230 231-460 >460

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Cl concentration <175 175-350 351-700 >700

Apricot Pepper Alfalfa Sugarbeet

Plum Potato Barley Sunflower

Tomato Corn Sorghum

Foliar injury is influenced by cultural and environmental conditions. These data are presented only as general guidelines for daytime irrigation. Source: Mass (1990) Crop salt tolerance. In: Agricultural Assessment and Management Manual. K.K. Tanji (ed.). ASCE, New York. pp. 262- 304. pH and Alkalinity The acidity or basicity of irrigation water is expressed as pH (< 7.0 acidic; > 7.0 basic). The normal pH range for irrigation water is from 6.5 to 8.4. Abnormally low pH’s are not common in Colorado, but may cause accelerated irrigation system corrosion where they occur. – 2– High pH’s above 8.5 are often caused by high bicarbonate (HCO3 ) and carbonate (CO3 ) concentrations, known as alkalinity. High carbonates cause calcium and magnesium ions to form insoluble minerals leaving sodium as the dominant ion in solution. As described in the sodium hazard section, this alkaline water could intensify the impact of high SAR water on sodic soil conditions. Excessive bicarbonate concentrates can also be problematic for drip or micro-spray irrigation systems when calcite or scale build up causes reduced flow rates through orifices or emitters. In these situations, correction by injecting sulfuric or other acidic materials into the system may be required. Chloride Chloride is a common ion in Colorado irrigation waters. Although chloride is essential to plants in very low amounts, it can cause toxicity to sensitive crops at high concentrations (Table 6). Like sodium, high chloride concentrations cause more problems when applied with sprinkler irrigation (Table 6). Leaf burn under sprinkler from both sodium and chloride can be reduced by night time irrigation or application on cool, cloudy days. Drop nozzles and drag hoses are also

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recommended when applying any saline irrigation water through a sprinkler system to avoid direct contact with leaf surfaces.

Table 6. Chloride classification of irrigation water.

Chloride (ppm) Effect on Crops

Below 70 Generally safe for all plants.

70-140 Sensitive plants show injury.

141-350 Moderately tolerant plants show injury.

Above 350 Can cause severe problems.

Chloride tolerance of selected crops. Listing in order of increasing tolerance: (low tolerance) dry bean, onion, carrot, lettuce, pepper, corn, potato, alfalfa, sudangrass, zucchini squash, wheat, sorghum, sugar beet, barley (high tolerance). Source: Mass (1990) Crop Salt Tolerance. Agricultural Salinity Assessment and Management Manual. K.K. Tanji (ed.). ASCE, New York. pp 262-304.

Boron Boron is another element that is essential in low amounts, but toxic at higher concentrations (Table 7). In fact, toxicity can occur on sensitive crops at concentrations less than 1.0 ppm. Colorado soils and irrigation waters contain enough B that additional B fertilizer is not required in most situations. Because B toxicity can occur at such low concentrations, an irrigation water analysis is advised for ground water before applying additional B to irrigated crops.

Table 7. Boron sensitivity of selected Colorado plants (B concentration, mg/ L*)

Sensitive Moderately Moderately Tolerant Sensitive Tolerant

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0.5-0.75 0.76-1.0 1.1-2.0 2.1-4.0 4.1-6.0

Peach Wheat Carrot Lettuce Alfalfa

Onion Barley Potato Cabbage Sugar beet

Sunflower Cucumber Corn Tomato

Dry Bean Oats

Source: Mass (1987) Salt tolerance of plants. CRC Handbook of Plant Science in Agriculture. B.R. Cristie (ed.). CRC Press Inc. *Maximum concentrations tolerated in soil water or saturation extract without yield or vegetative growth reductions. Maximum concentrations in the irrigation water are approximately equal to these values or slightly less.

Sulfate The sulfate ion is a major contributor to salinity in many of Colorado irrigation waters. As with boron, sulfate in irrigation water has fertility benefits, and irrigation water in Colorado often has enough sulfate for maximum production for most crops. Exceptions are sandy fields with <1 percent organic matter and <10 ppm SO4-S in irrigation water. Nitrogen

Nitrogen in irrigation water (N) is largely a fertility issue, and nitrate-nitrogen (NO3-N) can be a significant N source in the South Platte, San Luis Valley, and parts of the Arkansas River basins. The nitrate ion often occurs at higher concentrations than ammonium in irrigation water. Waters high in N can cause quality problems in crops such as barley and sugar beets and excessive vegetative growth in some vegetables. However, these problems can usually be overcome by good fertilizer and irrigation management.

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Chapter 9: Cropping System

Cropping systems Farmers resort to cultivation of a number of crops and rotate particular crop combinations. More than 250 cropping systems are being followed in India, of which 30 cropping systems are more prevalent. Some of the important cropping systems are: 1. Sequential cropping system: Growing crops in sequence within a crop year, one crop being sown after the harvest of the other. For example, rice followed by pigeonpea, pigeonpea followed by wheat. 2. Intercropping System: Growing more than one crop in the same area in rows of definite proportion and pattern. The following intercropping practices were found to be remunerative in India’s groundnut growing states. State Crop combination Maharashtra Groundnut + Red gram (6:1/4:1) Groundnut + Soybean (6:2) Groundnut + Sunflower (6:2/3:1) Gujarat Groundnut + Castor (9:2/3:1) Groundnut + Sunflower (3:1/2:1) Groundnut + Red gram (4:1) Alley cropping Is an agroforestry practice in which perennial, preferably leguminous, trees or shrubs are grown simultaneously with an arable crop. The trees, managed as hedgerows, are grown in wide rows and the crop is planted in the inter space or ‘alley’ between the tree rows. During the cropping phase, the trees are pruned. Prunings are used as green manure or mulch on the crop to improve the organic matter status of the soil and to provide nutrients, particularly nitrogen, to the crop.

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a. Season based cropping system i. Kharif rice based cropping system ii. Kharif maize based cropping system iii. Kharif sorghum based cropping system iv. Kharif millet based cropping system v. Kharif groundnut based cropping system vi. Winter wheat and chickpea based cropping system vii. Rabi sorghum based cropping system b. Mixed cropping In order to minimise the risk and uncertainty of mono cropping and to have sustainable yield and income, farmers are advised to go for mixed cropping. Integrated farming System (IFS) To feed ever-increasing population of the country, extensive cropping system give ways to intensive cropping which are exploiting natural resources. Therefore in future more thrust will be on efficient natural resource management and sustainable production system. This encompasses an animal component, an perennial and annual crop component, aqua culture, agro based production and processing units. Integrated farming system typically involves: o Many enterprises including animal component o Planning is based on resource available o It is purely location specific/farmer/holding specific activity plan o Very high resource use efficiency o Sustainable farming Objectives of IFS o To compliment and maximize use of by products o To provide useful employment to all the family members o Maximizing land use o Value addition o Self sustainability o Less dependence on external resources Crop production in IFS o Food crop should find a place

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o Family food requirement should be planned o Fodder production to meet the demand of animal component o Specific enterprise based crops; e.g. mulberry/ sunflower linked to honey o Infrastructure based cropping o Sufficient employment to family members Animal component in IFS o One or more animal components or combination of animal component may be planned o Complimentary enterprises should be identified o Composting should be the interface between animal and crop enterprises o Market should be considered before hand o Need based demand driven enterprises should be prioritize Allocation of resource in IFS o List the resources available and required o Prioritize the resources based on scarcity o Resource demand will be prioritized based on o economic impact and sustainability o Scares resource on the farm should be allocated o for the most important activity o Recycling of resources should be planned o Resource based contingent plan should be prepared in advance. o This will serve as a security and sustainable alternative in case of crisis

Cropping systems trends The research efforts over last two decades (1989-90 to 2010) under the aegis of AICRP–CS have lead to several significant findings. The summary of major achievements is listed hereunder.  Resource efficient alternative cropping systems to rice-wheat system were developed for 11 states viz. Haryana, Punjab, U.P., Bihar, Uttaranchal, parts of Orissa, M.P., W.B., Jammu Kashmir, H.P. and Gujarat, involving potato, maize, onion, sunflower, green gram, brinjal, berseem (F), cabbage, okra, radish, potato etc, which gave average

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productivity of 20 t/ha as rice equivalent yield as compared to 11-13 t/ha, which led to induce the scope of increasing per unit productivity substantially.  Likewise, efficient alternatives to pearl millet-wheat system in five states, viz.; Haryana, Gujarat, U.P., Rajasthan and Maharashtra, involving potato, green gram, cowpea, mustard, cluster bean, chickpea etc. were identified, which gave the productivity up to 12 tonnes per ha as compared to existing 8 t/ha.  Efficient alternatives to soybean-wheat system in three states, viz.; M.P., Rajasthan and Maharastra, were developed. Diversification options involving high value crops like isabgol, groundnut, soybean, potato, turmeric etc resulted in average productivity of 15 tonnes/ha as compared to existing 12 t/ha (rice equivalent) yield.  Integrated plant nutrient supply systems have been established to be beneficial and standardized. Substitution of 25-50% N with FYM or green manure in rice-wheat system was found to increase the productivity by 4%, which may save chemical fertilizers worth Rs. 7.0 crores. It also helped in increase of soil organic carbon by 55.9%. In rice-rice system, green manuring increased the yield by 3.6%.  Site Specific Nutrient Management Technology has been proven to be a potential tool in breaking the yield barrier through efficient and balanced nutrient management leading to significant productivity increase. Results clearly show that by adoption of SSNM, across the locations, grain yields of more than 13 t/ha in rice - wheat system (with a contribution of 58% rice and 42% wheat) and 12-15 t/ha in rice-rice system (with a contribution of 48% kharif rice and 52% rabi rice), are achievable. It also helped in increase of organic carbon by 55.9%.

 The use of different resource conservation technologies in rice-wheat system has been established to help in significant improvement of crop productivity and resource saving. Adoption of RCTs lead to an improvement in productivity of rice by 1 to 7% in mechanical transplanting, 3 to 8% in drum seeding, 1 to 2% in zero till drilling and 10 to 13% in system of rice intensification (SRI) compared to traditional hand transplanting at different locations. Similarly, in wheat, productivity increased by 5 to 29% in zerotill drilling, 4 to 11% in striptill drilling and 3 to 23% in bed planting compared to conventional sowing.

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 With the application of recommended technologies and balanced fertilization to at least 10% of the area under different cropping systems, spread over various agroclimatic regions as indicated by on-farm research on cultivator’s fields, India can easily add about 5 million tonnes of food grain equivalent to rice to its food bowl.  Through long-term studies in all the major cereal-cereal cropping systems, it has been proved that continuous use of chemical fertilizers (NPK) only and omitting P or K application leads to occurrence of deficiency of these nutrients and decline in yield of crops. However, the extent of yield reduction and occurrence of P or K deficiency is governed by the inherent soil supplying capacity and cropping system adopted.  On-farm crop response to N, P and K application in different cropping systems has been determined. The average response of different cropping systems was 8-12 kg rice equivalent yield/kg of any of the major plant nutrients like N, P or K with mean economic responses of 7-10 Rs./Re invested on N, 4 Rs./Re spent on P and 6-8 Rs./Re spent on K.  To improve the sustainability of rice-wheat system over the years, growing of legumes as break crop showed a marked influence on weed flora over the years and a reduction of 45 to 61% weed count was noted in succeeding rice-wheat crop cycle. To improve upon soil organic carbon and micro-nutrients application of organic manures has been proven very effective.  In hybrid as well as inbred rice, N management through LCC proved superior to locally recommended N application in three splits and it was found possible to curtail 20-30 kg of fertilizer N/ha without sacrificing rice yield, when N is applied as per LCC values. N application at LCC<3 in Basmati 370 and at LCC<4 in coarse and hybrid rice was found optimum. Moreover, in LCC-based N management, basal application of N can be skipped without any disadvantage in terms of grain yield, and agronomic, physiological or recovery efficiency of fertilizer N.  Similarly, nitrogen application as per soil supplying capacity and crop demand based on SPAD reading (35) produced highest yield of rice (4.92 t/ha) and wheat (4.55 t/ha). Skipping basal N application in both rice and wheat led to higher use efficiency of N (partial factor productivity, uptake efficiency and internal efficiency) and better crop productivity.

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 Crop residue recycling in rice-wheat was found to increase rice as well as wheat yields by 13 and 8%, decrease cost effectiveness by 5 and 3% and energy efficiency by 13 and 6%, respectively, compared to residue retrieval, whereas yield advantage was to the tune of 9 and 3% compared to residue burning. Recycling improved SOC by 31 and 2% and MWD by 11 and 10%, compared to residue retrieval and burning after seven crop cycles. It also improved soil moisture content (15%), bulk density (3%), cone index (14%), total N (17%), available P2O5 (12%) and K2O (8%) compared to residue retrieval.  A comparison of yield, economics and energy of mechanical and manual transplanting revealed that the transplanting by rice transplanter provided 85 and 72% savings in labour and cost of transplanting including nursery raising, respectively; provided higher rice yield (10%), net returns (26%), benefit: cost ratio (29%) and energy efficiency (7%); compared to manual transplanting of rice.  During 3-4 years of conversion period, crop yields under organic farming were recorded to be comparable with conventional (chemical) farming in many regions. Some of these crops and their percent improvement in yield are coarse rice (+2%), garlic (+20.4%), maize (+22.8%), turmeric (+51.5%), fodder crops (+14.4 to 89.9%) and basmati rice (- 6%) at Ludhiana; kharif French bean (+19.0%), veg. pea (+62.1%), cabbage (+9.5%), garlic (+7.0%) and kharif cauliflower (-4.6%) at Bajaura; fodder berseem (+6.5%), chickpea (+1.5%), soybean (-2.3%) and mustard (-6.6%) at Raipur; Rice (+12.9%), Wheat (+24.4%), Potato (+7.3%), mustard (+9.6%) and lentil (+2.5%) at Ranchi, groundnut (+6.9%), rabi sorghum (+15.8%), soybean (+9.5%), durum wheat (+32.4%), chilli (+18.8%), cotton (+35.5%), potato (+3.3%), chickpea (+3.2%) and maize (-1.1%) at Dharwad; soybean (+10.7%), isabgol (+11.2%), durum wheat (+1.1%), mustard (+3.1%) and chickpea (+4.2%) at Bhopal; okra (+1.0%), berseem (-0.2%) and veg. pea (+1.8%) at Jabalpur; Dolichos bean (+16.6%) at Karjat; maize (+18.2%), cotton (+38.7%), chilli (+8.2%), brinjal (+14.9%) and sunflower (+29.1%) at Coimbatore; rice (+1.9%) at Pantnagar; fodder sorghum (+32.5%), okra (+11.3%), baby corn (+11.8%) and veg. pea (+2.2%) at Modipuram; and carrot (+5.8%), tomato (+30.6%), rice on raised beds (+7.3%), french bean (+17.7%) and potato (+3.0%) at Umiam.  Improvement of different magnitudes was recorded in respect of soil organic carbon (negligible at Pantnagar to 45.9% at Ludhiana), available-P (negligible at Pantnagar to

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45.9% at Ludhiana), and available-K (up to 28.8% at Modipuram). However, available-N content was, in general, lower under organic systems.  An improvement in some of the quality parameters of ginger (oleoresin by 11.5% and starch content by 10.6%), turmeric (oil by 10.8%, oleoresin by 12.4%, starch by 20.0% and curcumin by 21.7%), chillies (ascorbic acid content by 2.1%), cotton (ginning percentage), and vegetables (iron, manganese, zinc and copper content in tomato, French bean, cabbage, cauliflower, pea and garlic) was recorded.

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Chapter 10: Crop residue management in multiple cropping systems

Over two-thirds of world’s 1.3 billion impoverished people live in rural areas and rely on agriculture for a significant part of their livelihoods. Livestock are important assets of this group and play a critical role in both sustainability and intensification of agricultural productivity in most farming systems. Increasing human population and changes in dietary habits associated with urbanisation and higher incomes are causing increased demands for food of animal origin. Pastures (herbaceous plants, fodder trees/shrubs), crop residues, cultivated forages, concentrate feeds (agro-industrial by-products, grains, feed supplements, etc.) and household wastes are the main resources used as livestock feed. Availability of grazing land is decreasing due to expansion of cropping to meet the demands for food, urbanisation and land use for other activities such as industries. The adoption of introduced forages in tropical developing countries has been limited due to lack of evidence of economic profitability or inadequate technical support, such as seed availability. Small farmers in rural areas will increasingly depend on crop residues to feed livestock among other feed resources for some time to come (Mannetje, 1997). Availability and use of crop residues as feed is increasing. Over one billion metric tonnes of residues are produced worldwide (Kossila, 1984) and provide much of the feed resources for ruminants in developing countries (Owen and Jayasurirya, 1989). The feed value of crop residues has been largely ignored and this has resulted in development of crop varieties and hybrids that produce less residues than unimproved varieties (Williams et al., 1997). However, crop residues are still the most important feed for ruminants in small-holder crop–livestock production systems of Asia and Africa. Although in the recent years, the use of cereal grains as feed has increased—Delgado et al. (1999) estimated that between 1982 and 1994, the global use of cereal grain as livestock feed increased at the rate of 0.7% annually. In spite of increased use of grain as feed, developing countries still use less than half the cereal grain proportions for feed compared to those used by developed countries and this is likely to continue. Crop residues still contribute substantially to the supply of nutrients for animals in mixed farms in the tropical and sub-tropical developing countries.

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In the early days of cereal crop improvement, emphasis was placed on grain yield, and many dwarf, high-yielding varieties were released. However, in recent years, recognising the need for crop residues as feed for livestock, the emphasis has shifted to dual purpose cultivars. In most crops, intermediate optima were observed for many traits including grain and fodder yield and quality. In sorghum, for example, grain and fodder (crop residue) yields increased positively up to 1.8 m plant height with 68–70 days to flowering but the relationship reversed beyond 2.0 m plant height (Rao and Rana, 1982) Crops used as residues The crops whose residues are commonly used as livestock feed and the area under each are given in Table below. Wheat occupies the highest acreage in the world followed by rice, maize, barley, sorghum and millets (includes pearl millet and several minor millets). Maize is prominently grown in Africa, while rice predominates in India. Worldwide, nearly 70.64 million hectares are covered by pulses with 24.75 million hectares under groundnut (FAO, 1999).

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Crop wise residue generated in various states of India.

Benefits of crop residues (and the detrimental effects of removing them) As a physical buffer, crop residues protect soil from the direct impacts of rain, wind and sunlight leading to improved soil structure, reduced soil temperature and evaporation, increased infiltration, and reduced runoff and erosion. While some studies suggest that plant roots contribute more carbon to soil than surface residues (Gale and Cambardella, 2000), crop residue contributes to soil organic matter and nutrient increases, water retention, and microbial and macroinvertebrate activity. These effects typically lead to improved plant growth and increased soil productivity and crop yield. The basic relationships between these effects are shown in Table below.

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Crop residue is managed using conservation tillage systems, such as notill, strip till, ridge till, mulch till, and other reduced tillage methods (see NRCS Conservation Practice Standards 329, 344, 345, and 346). Most studies involving the effects of crop residues have compared no- till systems with residues to conventional tillage without residues, a presumed best case – worst case comparison, overlooking the interaction effects between tillage and residues. Karlen et al. (1994) found that 10 years of residue removal under no-till continuous corn in Wisconsin resulted in deleterious changes in many biological indicators of soil quality, including lower soil carbon, microbial activity, fungal biomass and earthworm populations compared with normal or double rates of residue return. Lindstrom (1986) found increased runoff and soil loss with decreasing residue remaining on the soil surface under notill, with the study results suggesting a 30% removal rate would not significantly increase soil loss in the systems modeled. Reduction in these properties and populations suggests loss of soil function, particularly reduced nutrient cycling, physical stability, and biodiversity.

Despite the many important benefits of crop residues, research shows some of their effects can vary. For example, some reports showed lower yields in systems with high crop residues due to increased disease or lower germination (e.g. Linden et al., 2000). Dam et al. (2005) reported poorer emergence under no-till corn with residues intact compared with residues removed and conventional till with and without residues, which they attributed to cooler soil temperatures and higher soil moisture associated with climatic conditions. Power et al. (1986) found increased crop yields for corn and soybean when residues were left on the soil surface compared with yields under residue removal in Nebraska. This yield effect was most pronounced in drier years, leading them to attribute yield increases to residue induced water conservation. Rate of residue decomposition varies by climate and crop, leading to varying amounts of erosion protection and organic matter additions to the soil. Due to these and other site-specific effects of

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residue on soil function, residue removal recommendations need to consider soil type, climate, cropping system, and management in order to protect soil quality while allowing for residue harvest for biofuel production. Crop residue management in rice-wheat cropping system Crop residues are good sources of plant nutrients and are important components for the stability of agricultural ecosystems. About 400 million tons of crop residues are produced in India alone. In areas where mechanical harvesting is practiced, a large quantity of crop residues are left in the field, which can be recycled for nutrient supply. About 25% of N and P, 50% of S, and 75% of uptake by cereal crops are retained in crop residues, making them valuable nutrient sources. Both rice and wheat are exhaustive feeders, and the double cropping system is heavily depleting the soil of its nutrient content. A rice-wheat sequence that yields 7 t/ha of rice and 4 t/ha of wheat removes more than 300 kg N, 30 kg P, and 300 kg K/ha from the soil. Traditionally, wheat and rice straw were removed from the fields for use as cattle feed and for other purposes in South Asia. Recently, with the advent of mechanized harvesting, farmers have been burning in situ large quantities of crop residues left in the field. As crop residues interfere with tillage and seeding operations for the next crop, farmers often prefer to burn the residue in situ, causing loss of nutrients and organic matter in the soil. Unlike removal or burning, incorporation of straw builds up soil organic matter, soil N, and increases the total and available P and K contents of the soil. The major disadvantage of incorporation of cereal straw is the immobilization of inorganic N and its adverse effect due to N deficiency. Incorporation of cereal crop residues immediately before sowing/transplanting into wheat or rice significantly lowers crop yields. Due to straw incorporation, wheat yield depression (mean of 10 years) decreases from 0.54 t/ha to 0.08 t/ha with the application of 60 kg N/ha and 180 kg N/ha, respectively. Residue characteristics and soil and management factors affect residue decomposition in the soil. Under optimum temperature and moisture conditions, N immobilization can last from four to six weeks. Adverse effects of wheat straw incorporation can be averted by incorporating both green manure (having narrow C:N ratio) and cereal straw (having wide C:N ratio) into the soil before rice transplanting. Legume Crop Residues and Green Manures

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In northwestern India, short-duration legumes (e.g., mungbean and cowpea) can be grown in the fallow period after wheat harvest. In the rice-wheat system, incorporation of mungbean residue after picking pods, significantly increases rice yield and saves 60 kg N/ha. The advantages of incorporation of legume crop residues and green manuring to rice are similar. Green manures are a valuable potential source of N and organic matter. Green manure crops (e.g., Sesbania sp.) can be used in rice-based cropping systems. A 45- to 60-day-old green manure crop can generally accumulate about 100 kg N/ha, which corresponds to the amount of mineral fertilizer N applied to crops. Sometimes green manure crops accumulate more than 200 kg N/ha. Integrated use of green manure and chemical fertilizer can save 50-75% of N fertilizers in rice. Green manuring also increases the availability of several other plant nutrients through its favourable effect on chemical, physical, and biological properties of soil. In Bangladesh, N supplied by Sesbania green manure was effective for rice grown in coarse-textured soils but its residual effect on the following crop of wheat was negligible. Rice Straw Management Practices Incorporation of rice straw before wheat planting compared to wheat straw before rice planting is difficult due to low temperatures and the short interval between rice harvest and wheat planting. Farmers use different straw management practices: burning, removal, or incorporation. Rice and wheat yields under these practices are generally similar. In few studies, wheat yields were lower during the first one to three years of rice straw incorporation 30 days prior to wheat planting, but in later years, straw incorporation did not affect wheat yields adversely. In contrast, rice straw incorporation gave significantly higher wheat yields of 3.51 t/ha compared to 2.91 t/ha with straw removal in Pakistan. Incorporation of rice straw three weeks before wheat sowing significantly increases wheat yields on clay loam but not on sandy loam soil. About 10-20% of N supplied through organic materials having high C:N ratio such as rice straw and stubble is assimilated by the rice crop, 10-20% is lost through various pathways, and 60-80% is immobilized in the soil. Addition of 10 t/ha rice straw at four to five weeks before transplanting rice is equivalent to the basal application of 40 kg N/ha through urea.

Proper fertilizer management practices can reduce N-immobilization due to incorporation of crop residues into the soil. These practices include appropriate method, time, and rate of fertilizer-N application. The following options can reduce the adverse effects of N immobilization:

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. Place N-fertilizer below the surface soil layer which is enriched with carbon after incorporation of crop residue. . Apply N-fertilizer at a higher dose than the recommended dose. Starter N-Fertilizer Effects on Crop Residue Management Application of 15 to 20 kg N/ha as starter dose with straw incorporation increases yields of wheat and rice compared to either burning of straw or its incorporation in the soil. At recommended fertilizer-N level, rice straw incorporation reduces rice yields than urea alone. Therefore, a higher dose of urea-N application with rice straw incorporation is necessary to get good yields. The beneficial effect of straw incorporation before rice planting does not carry over to the succeeding wheat crop. Application of 30 kg extra N/ha than the recommended fertilizer dose, increases rice yields only slightly. Beneficial Effects of Wheat Crop Residues During a 10-year (1984 to 1994) long-term field experiment conducted in India, comparisons were made between the application of wheat crop residues versus inorganic fertilizers on rice and wheat. In the first year, inorganic fertilizer-treated plots of rice and wheat yielded the highest. However, in the second and third year, yield from the treatment with combined application of wheat straw and inorganic fertilizer was similar to that with inorganic fertilizer alone. Beyond fourth year, plots treated with a combination of wheat straw and inorganic fertilizer outyielded all other treatments. Another long-term study (1988 to 2000) conducted in Punjab, India showed that wheat straw could be combined with green manure with no adverse effect on rice yield. Yield and N-use efficiency in rice, however, were reduced with wheat straw incorporation. Results from the All India Coordinated Agronomic Research Project showed the beneficial effects of wheat crop residues when applied as a substitute for chemical fertilizer needs of rice in the rice-wheat cropping system. In another study, incorporation of wheat straw (10 t/ha) saved 50% of the recommended fertilizer dose (60 kg N + 13.1 kg P + 25 kg K/ha) and helped achieve higher yield of rice.

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Chapter 11 : Organic farming The term organic farming was coined by Lord Northbourne in his book Look to the Land (written in 1939, published 1940). From his conception of "the farm as organism," he described a holistic, ecologically balanced approach to farming. Organic agricultural methods are internationally regulated and legally enforced by many nations, based in large part on the standards set by the International Federation of Organic Agriculture Movements (IFOAM), an international umbrella organization for organic organizations established in 1972. IFOAM defines the overarching goal of organic farming as follows: "Organic agriculture is a production system that sustains the health of soils, ecosystems and people. It relies on ecological processes, biodiversity and cycles adapted to local conditions, rather than the use of inputs with adverse effects. Organic agriculture combines tradition, innovation and science to benefit the shared environment and promote fair relationships and a good quality of life for all involved.." —IFOAM. In 1980, the USDA released a landmark report of organic farming. The report defined organic farming as a production system, which avoids or largely excludes the use of synthetic organic fertilizers, pesticides, growth regulators and livestock feed additives. Organic farming systems largely depends on crop rotations, crop residues, animal manures, green manures, off- farm organic wastes, mechanical cultivation, mineral bearing rocks and aspects of biological control to maintain soil productivity, supply plant nutrients and to control insects, pathogens and weeds (Sharma 2002). According to Codex definition (FAO), organic agriculture is production management system, which promotes and enhances agro-ecosystem health, including biodiversity, biological cycles and biological activity. It emphasizes the use of management practices in preferences to the use of off farm inputs, taking into account that regional conditions require locally adopted systems. This is accomplished by using, where possible, on-farm agronomic, biological and mechanical methods, as opposed to using synthetic materials to fulfil any specific function within the system. As per NPOP (India), it is a system of farm design and management to create an eco system, which can achieve sustainable productivity without the use of artificial external inputs such as chemical fertilizers and pesticides.

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The concept of organic farming is based on following principles  Nature is the best role model for farming, since it does not use any inputs nor demand unreasonable quantities of water.  The entire system is based on intimate understanding of nature’s ways. The system does not believe in mining of the soil of its nutrients and do not degrade it any way for today’s needs.  The soil in this system is a living entity.  The soil’s living population of microbes and other organisms are significant contributors to its fertility on a sustained basis and must be protected and nurtured at all cost.  The total environment of the soil, from soil structure to soil cover is more important.  Thus in today’s terminology it is a method of farming system which primarily aims at cultivating the land and raising crops in such a way, as to keep the soil alive and in good health by use of organic wastes (crop, animal and farm wastes, aquatic wastes) and other biological materials along with beneficial microbes (biofertilizers) to release nutrients to crops for increased sustainable production in an eco-friendly pollution free environment. The IFOAM laid down four principles of Organic agriculture:  The principle of health – Organic Agriculture should sustain and enhances the health of soil, plant, animal, human and planet as one and indivisible.  The principles of ecology – Organic Agriculture should be based on living ecological systems and cycles, work with them, emulate them and help sustain them.  The principles of fairness – Organic Agriculture should build on relationships that ensure fairness with regard to the common environment and life opportunities and  The principle of care - Organic Agriculture should be managed in a precautionary and responsible manner to protect the health and well being of current and future generations and the environment.

Marketing and export potential of organic products Since 1990, the market for organic products has grown from nothing, reaching $51 billion in 2008. This demand has driven a similar increase in organically managed farmland.

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Approximately 35,200,000 hectares (87,000,000 acres) worldwide are now farmed organically, representing approximately 0.8 % of total world farmland (2008). In addition, as of 2008 organic wild products are harvested on approximately 31 million hectares. Estimating area under organic agriculture in India is a difficult task as there is no central agency that collects and compiles this information. Different agencies have estimated the area under organic agriculture differently for instance the study undertaken by FIBL and ORG- MARG (Garibay S V and Jyoti K, 2003) the area under organic agriculture to be 2,775 hectares (0.0015% of gross cultivated area in India). But other estimation undertaken by SOEL-Survey shows that the land area under organic cropping is 41000 hectare. The total numbers of organic farms in the country as per SOEL Survey are 5661 but FIBL and ORG-MARG survey puts it as 1426. Some of the major organically produced agricultural crops in India include crops like plantation, spices, pulses, fruits, vegetables and oil seeds etc (Table below). Major products produced in India by organic farming Type of Product Products Commodity Tea, Coffee, Rice, Wheat Spices Cardamom, Black pepper, white pepper, Ginger, Turmeric, Vanilla, Tamarind, Clove, Cinnamon, Nutmeg, Mace, Chili Pulses Red gram, Black gram Fruits Mango, Banana, Pineapple, Passion fruit, Sugarcane, Orange, Cashew nut, Walnut Vegetables Okra, Brinjal, Garlic, Onion, Tomato, Potato Oil seeds Mustard, Sesame, Castor, Sunflower Others Cotton, Herbal extracts

India is best known as an exporter of organic tea and also has great export potential for many other products. Other organic products for which India has a niche market are spices and fruits. Org Marg’s survey also proves this fact as around 30% of respondents that includes producer, exporters and traders has responded that organic tea is produced in India and this is

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highest response for any single crop, next are spices, fruits, vegetables, rice and coffee (Garibay S V and Jyoti K, 2003). There is small response for cashew, oil seed, wheat and pulses. Among the fruit crops Bananas, Mangos and oranges are the most preferred organic products. Organic food exports from India are increasing with more farmers shifting to organic farming. With the domestic consumption being low, the prime market for Indian organic food industry lies in the US and Europe. India has now become a leading supplier of organic herbs, organic spices, organic basmati rice, etc. RCNOS recently published a report tilted ‘Food Processing Market in India (2005)’. According to its research, exports amount to 53% of the organic food produced in India. This is considerably high when compared to percentage of agricultural products exported. In 2003, only 6-7% of the total agricultural produce in India was exported. Exports are driving organic food production in India. The increasing demand for organic food products in the developed countries and the extensive support by the Indian government coupled with its focus on agri-exports are the drivers for the Indian organic food industry. Organic food products in India are priced about 20-30% higher than non-organic food products. This is a very high premium for most of the Indian population where the per capita income is merely USD 800. Though the salaries in India are increasing rapidly, the domestic market is not sufficient to consume the entire organic food produced in the country. As a result, exports of organic food are the prime aim of organic farmers as well as the government. The Indian government is committed towards encouraging organic food production. It allocated Rs. 100 crore or USD 22.2 million during the Tenth Five Year Plan for promoting sustainable agriculture in India. APEDA (Agricultural and Processed Food Export Development Authority) coordinates the export of organic food (and other food products) in India. The National Programme for Organic Production in India was initiated by the Ministry of Commerce. The programme provides standard for the organic food industry in the country. Since these standards have been developed taking into consideration international organic production standards such as CODEX and IFOAM, Indian organic food products are being accepted in the US and European markets. APEDA also provides a list of organic food exporters in India. Organic food costs in India are expected to decrease driving further exports in future. Organic food production costs are higher in the developed countries as organic farming is labour

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intensive and labour is costly in these countries. However, in a country like India, where labour is abundant and is relatively cheap, organic farming is seen as a good cost effective solution to the increasing costs involved in chemical farming. Currently most of the organic farmers in India are still in the transition phase and hence their costs are still high. As these farmers continue with organic farming, the production costs are expected to reduce, making India as one of the most important producers of organic food. Certification Organic certification is a certification process for producers of organic food and other organic agricultural products. In general, any business directly involved in food production can be certified, including seed suppliers, farmers, food processors, retailers and restaurants. Requirements vary from country to country, and generally involve a set of production standards for growing, storage, processing, packaging and shipping that include: o avoidance of most synthetic chemical inputs (e.g. fertilizer, pesticides, antibiotics, food additives, etc), genetically modified organisms, irradiation, and the use of sewage sludge; o use of farmland that has been free from synthetic chemicals for a number of years (often, three or more); o keeping detailed written production and sales records (audit trail); o maintaining strict physical separation of organic products from non-certified products; o undergoing periodic on-site inspections. In some countries, certification is overseen by the government, and commercial use of the term organic is legally restricted. Certified organic producers are also subject to the same agricultural, food safety and other government regulations that apply to non-certified producers.

Purpose of certification Organic certification addresses a growing worldwide demand for organic food. It is intended to assure quality and prevent fraud. For organic producers, certification identifies suppliers of products approved for use in certified operations. For consumers, "certified organic" serves as a product assurance, similar to "low fat", "100% whole wheat", or "no artificial preservatives".

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Certification is essentially aimed at regulating and facilitating the sale of organic products to consumers. Individual certification bodies have their own service marks, which can act as branding to consumers. Most certification bodies operate organic standards that meet the National government's minimum requirements. Some certification bodies, certify to higher standards. The certification process To certify a farm, the farmer is typically required to engage in a number of new activities, in addition to normal farming operations:  Study the organic standards, which cover in specific detail what is and is not allowed for every aspect of farming, including storage, transport and sale.  Compliance — farm facilities and production methods must comply with the standards, which may involve modifying facilities, sourcing and changing suppliers, etc.  Documentation — extensive paperwork is required, detailing farm history and current set-up and usually including results of soil and water tests.  Planning — a written annual production plan must be submitted, detailing everything from seet to sale: seed sources, field and crop locations, fertilization and pest control activities, harvest methods, storage locations, etc.  Inspection — annual on-farm inspections are required, with a physical tour, examination of records, and an oral interview.  Fee — an annual inspection/certification fee (currently starting at $400–$2,000/year, in the US and Canada, depending on the agency and the size of the operation).  Record-keeping — written, day-to-day farming and marketing records, covering all activities must be available for inspection at any time. In addition, short-notice or surprise inspections can be made, and specific tests (e.g. soil, water, plant tissue) may be requested. For first-time farm certification, the soil must meet basic requirements of being free from use of prohibited substances (synthetic chemicals, etc) for a number of years. A conventional farm must adhere to organic standards for this period, often, two to three years. This is known as being in transition. Transitional crops are not considered fully organic. Certification for operations other than farms is similar. The focus is on ingredients and other inputs, and processing and handling conditions. A transport company would be required to

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detail the use and maintenance of its vehicles, storage facilities, containers, and so forth. A restaurant would have its premises inspected and its suppliers verified as certified organic. Participatory certification “Participatory Guarantee Systems are locally focused quality assurance systems. They certify producers based on active participation of stakeholders and are built on a foundation of trust, social networks and knowledge exchange” (IFOAM definition, 2008). Participatory Guarantee Systems (PGS) represent an alternative to third party certification, especially adapted to local markets and short supply chains. They can also complement third party certification with a private label that brings additional guarantees and transparency. PGS enable the direct participation of producers, consumers and other stakeholders in: o the choice and definition of the standards o the development and implementation of certification procedures o the certification decisions Participatory Guarantee Systems are also referred to as “participatory certification”. History of Participatory Guarantee Systems The organic movement has been a pioneer in the implementation and definition of Participatory Guarantee Systems (PGS). Organic certification started in various parts of the world in the 70s and 80s based on associative systems that were very close to what is now called PGS. Some of these associations are still doing participatory certification today, such as for example Nature & Progrès in France. Even though third party certification (following ISO 65 requirements) has become the dominant form of certification in the food sector, as well as many other sectors, alternative certification systems have never ceased to exist.

In 2004, IFOAM, the International Federation of Organic Agriculture Movements, and MAELA, the Latin American Agroecology Movement, jointly organized the first International Workshop on Alternative Certification that took place in Torres, Brazil. It is at that workshop that the concept of “Participatory Guarantee Systems” was adopted. At this event, an international working group on PGS was established, which later became an official Task Force under the umbrella of IFOAM. The Task Force worked on further defining PGS, and established

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the key elements and key features of PGS in a document entitled “Shared Visions – Shared Ideals”. Since then, IFOAM has continuously supported the development of PGS in the organic sector. In parallel, other sectors have been looking into the concept to certify various products or processes. Still, IFOAM and the organic movement remain a leader in the concept of PGS at the international level, and are now advocating for their recognition by governments as valid local certification systems in cases where the organic sector is legally regulated. Certification & product labeling In some countries, organic standards are formulated and overseen by the government. The United States, the European Union, Canada and Japan have comprehensive organic legislation, and the term "organic" may be used only by certified producers. Being able to put the word "organic" on a food product is a valuable marketing advantage in today's consumer market, but does not guarantee the product is legitimately organic. Certification is intended to protect consumers from misuse of the term, and make buying organics easy. However, the organic labeling made possible by certification itself usually requires explanation. In countries without organic laws, government guidelines may or may not exist, while certification is handled by non- profit organizations and private companies. Internationally, equivalency negotiations are underway, and some agreements are already in place, to harmonize certification between countries, facilitating international trade. There are also international certification bodies, including members of the International Federation of Organic Agriculture Movements (IFOAM) working on harmonization efforts. Where formal agreements do not exist between countries, organic product for export is often certified by agencies from the importing countries, who may establish permanent foreign offices for this purpose. In India, APEDA regulates the certification of organic products as per National Standards for Organic Production. "The NPOP standards for production and accreditation system have been recognized by European Commission and Switzerland as equivalent to their country standards. Similarly, USDA has recognized NPOP conformity assessment procedures of accreditation as equivalent to that of US. With these recognitions, Indian organic products duly certified by the accredited certification bodies of India are accepted by the importing countries." In March 2000, the Ministry of Commerce launched NPOP (National Programme for Organic Production) design to establish national standards for organic products which could then be sold under the logo India

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Organic. For proper implementation of NPOP, NAPP (National Accreditation Policy and Programme) has been formulated, with Accreditation Regulations announced in May 2001. These make it mandatory that all certification bodies whether internal or foreign operating in the country must be accredited by an Accreditation Agency. The regulations make provision for export, import and local trade of organic products. However, currently only the exports of organic products come under government regulations. Thus an agricultural product can only be exported as an organic product if it is certified by a certification body duly accredited by APEDA. Organic crop production, organic animal production, organic processing operations, forestry and wild products are the categories of products covered under accreditation. Labelling LABELLING means any written, printed or graphic matter that is present on the label, accompanies the food, or is displayed near the food, including that for the purpose of promoting its sale or disposal. Labelling shall convey clear and accurate information on the organic status of the product. When the full standards requirements are fulfilled, products shall be sold as "produce of organic agriculture" or a similar description. The name and address of the person or company legally responsible for the production or processing of the product shall be mentioned on the label. Product labels should list processing procedures which influence the product properties in a way not immediately obvious. Additional product information shall be made available on request. All components of additives and processing aids shall be declared. Ingredients or products derived from wild production shall be declared as such. NPOP declares following standards for labelling: 1. The person or company legally responsible for the production or processing of the product shall be identifiable. 2. Single ingredient products may be labelled as "produce of organic agriculture" or a similar description when all Standards requirements have been met. 3. Mixed products where not all ingredients, including additives, are of organic origin may be labelled in the following way (raw material weight):

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 _ Where a minimum of 95% of the ingredients are of certified organic origin, products may be labelled "certified organic" or similar and should carry the logo of the certification programme.  Where less than 95% but not less than 70% of the ingredients are of certified organic origin, products may not be called "organic". The word "organic" may be used on the principal display in statements like "made with organic ingredients" provided there is a clear statement of the proportion of the organic ingredients. An indication that the product is covered by the certification programme may be used, close to the indication of proportion of organic ingredients.  Where less than 70% of the ingredients are of certified organic origin, the indication that an ingredient is organic may appear in the ingredients list. Such product may not be called "organic". 4. Added water and salt shall not be included in the percentage calculations of organic ingredients. 5. The label for in-conversion products shall be clearly distinguishable from the label for organic products. 6. All raw materials of a multi-ingredient product shall be listed on the product label in order of their weight percentage. It shall be apparent which raw materials are of organic certified origin and which are not. All additives shall be listed with their full name. If herbs and/or spices constitute less than 2% of the total weight of the product, they may be listed as "spices" or "herbs” without stating the percentage. 7. Organic products shall not be labelled as GE (genetic engineering) or GM (genetic modification) free in order to avoid potentially misleading claims about the end product. Any reference to genetic engineering on product labels shall be limited to the production method. Accreditation procedures Accreditation n. The act of accrediting or the state of being accredited, especially the granting of approval to an institution of learning by an official review board after the school has met specific requirements. Or The act of granting credit or recognition (especially with respect to educational institution that

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maintains suitable standards) Accreditation is a process in which certification of competency, authority, or credibility is presented. Organizations that issue credentials or certify third parties against official standards are themselves formally accredited by accreditation bodies; hence they are sometimes known as "accredited certification bodies". The accreditation process ensures that their certification practices are acceptable, typically meaning that they are competent to test and certify third parties, behave ethically and employ suitable quality assurance. Position of Accreditation in India As per the National Programme for Organic Production (NPOP) an accreditation refers registration by the accreditation agency for certifying agency for certifying organic farms, products and processes as per the guidelines of the National Accreditation Policy and Programme for Organic Product. NPOP programme in context of Indian accreditation scenario, defined the function of accreditation agencies like o Prescribe the package of practices for organic products in their respective schedule; o Undertake accreditation of inspection and certifying agencies who will conduct inspection and certify products as having been produced in accordance with NPOP; o Monitor inspection made by the accredited inspection agencies; o Lay down inspection procedures; o Advise the National Steering Committee on Organic Production; o Accept Accredited certification programmes if such programme confirm to National Standard; o Accreditation Agencies Shall evolve accreditation criteria for inspection and/or certifying agencies and programme drawn up by such agencies for their respective area of operation and products; o Accreditation agencies shall prepare an operating manual to assist accredited agencies to abide by such a manual must contain appropriate directions, documentation formats and basic agency and farm records for monitoring and authentication of adherence to the organic production programme;

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o Eligible inspection and certification agencies implementing certification programmes will be identified by the Accreditation Agency.

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CHAPTER 12: Latest developments in crop management Plant/crop management At present mainly in the rice-wheat cropping system biological research is focusing on issues related to natural resource management (NRM). Its most notable success to-date has been the recent development of several resource conservation technologies (RCTs) due to the efforts championed by rice and wheat coordinating (RWC) units with its NARS (National Agricultural Research System) partners, including the private-sector machinery manufacturers. There is evidence of a significant change in the tillage and crop establishment methods being used by farmers in the wheat-based system of the northwest IGP. This impact is a major achievement for the RWC of regional significance and contributes to the global application of RCTs into a new ecosystem. However, the success of the tillage practices raises a number of concerns as well as opportunities. The chief of these is the lack of farm-level impact studies that can guide the process of adaptation to other zones, and identify emerging issues that need to be addressed by the RWC partners. Although, some monitoring studies were launched a few years ago, e.g., on soil health, there is need for more holistic monitoring of long-term impacts on the productivity and sustainability of the RWSs in the context of RCTs. Resource Conservation Equipment & Technology Laser land leveller 30-50% saving in water Rotavator 50% fuel saving & better quality seed bed Zero till drill/minimum till drill/ multipurpose 5-10% increase in yield and saving of Rs. tool bar/ raised bed planter 2000- 3000/ha. Pressurized irrigation 20-30% saving in water Rotary power weeder 20-30% saving in time and labour Vertical conveyor reaper/ combine Timely harvesting, more yield Multi-crop thresher 50% saving in labour and time and 54% saving in cost of threshing Straw combine Recovers 50% straw and also 70-100 kg grain/ha resulting into an average saving of Rs. 1250/ha. Straw baler Makes bales and checks environmental pollution Straw cutter-cum-spreader Cuts and spreads the straw evenly and helps in sowing by zero till drill. Improved manual harvester for mango & No damage to fruit and higher capacity kinnow

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The focus on RCTs is important for reasons other than efficiency and sustainability per se. The new RCTs provide a novel ‘platform’ for land and water management approaches and to introduce new crops and varieties into the systems, which may also help to re-establish better ecological balance. However, the work to foster greater diversification of the RW systems lacks a comprehensive strategy, including policy and market analysis, to guide the research and development efforts in the region. Agreement on an overall strategy would help to set more appropriate priorities for fostering systems diversification suited to needs of different transects of the IGP. The biophysical and socio-economic heterogeneity in different IGP transects must be borne in mind in planning future programs. In the west, traditionally a wheat-based production system, introduction of intensive rice cultivation has raised concern about environmental sustainability due to antagonism between the current soil-water production requirements of the two crops. The challenge for RWC is to undertake research to determine what possibilities exist to grow rice in different ways to the benefit of the RWSs in terms of productivity, diversity and sustainability (particularly of water use) and determine under what circumstances (including national policies) such changes are appropriate. The RWC can make significant contributions both by improving water use efficiencies at farm-level through new RCTs, including laser land leveling and bed planting, and by joining with the CGIAR’s Challenge Program on Water and Food. In the east, where the production systems are traditionally rice-based, intensification and diversification in the winter (non-monsoon) season will need to be focused on enhancing economic viability, learning from farm-level experiences with diversification in Bangladesh. The RWC has facilitated a change towards a systems approach and use of farmer participatory methods for location-specific multidisciplinary research. It has successfully linked NRM with production systems research. While these processes have been adopted in some institutes, especially in the context of RWS research, much greater effort is needed through the national research establishments to mainstream these processes as a regular feature of program planning and implementation. RWC can play a bigger role towards this goal by influencing national research policy, disseminating benefits and continued efforts to build capacity of the national partners.

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There are opportunities for greater contributions from IARCs/ARIs in support of RWC’s need for attention to policy analysis work and new knowledge about the system processes impacting on its long-term resilience and profitability in the context of full exploitation of RCTs and distinctly different needs of the western and the eastern transects of the IGP. These include strategic research themes of regional and global significance related to land, nutrient, water and crop component management and safeguarding the environment (global warming gas emissions and carbon balance). IARCs are well placed to assist by developing/introducing new tools and techniques and establishing new theme-based partnerships for pioneering research. Planning of future research should be backed up with a formal analysis of research priorities, and development of a Medium-Term Plan (MTP). It is not about tradeoffs, but about better targeting of limited resources available for research to both the national and the international partners of the RWC. The System of Rice Intensification, or SRI for short, is a fascinating case of rural innovation that has been developed outside the formal rice research establishment both in India and the rest of the world. In the recent past there was complex and continuing evolution of SRI in India and it is an important innovation in process and not as a completed product. The System of Rice Intensification (SRI) is new technique of rice cultivation which changes the management of soil, water and nutrients that support optimal growing environment for rice. The SRI showed that keeping paddy soils moist gives better results, both agronomically and economically, than flooding the soil throughout its crop cycle. This benefit is enhanced by complementary agronomic practices that greatly increase the growth of roots and of soil biota which make it possible to grow more productive phenotypes from any rice genotype. The SRI, thus is currently attracting the greatest attention to address the issue of ‘more yield with less water'. The SRI can also reduce GHG emission and improves soil health. A study at IARI, New Delhi showed that the global warming potential (GWP) in the SRI was only 28.9% over the conventional method. It increased the water productivity by 44% compared to conventional planting method. The seed rate in SRI was much lower which reduced the input cost. The SRI, therefore, seems to be a ‘win-win’ technology. However, there are some concerns and bottlenecks in its adoption.

One of the most promising developments in the controversial field of genetic engineering is the success obtained in breeding a nutritionally enriched rice variety now popularly being referred to

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as 'golden rice'. This golden rice is genetically modified rice which contains genes that produce high levels of beta carotene and related compounds. Beta carotene is contained in yellow fruits like carrots (from which it gets its name) and mangoes and in vegetables like spinach. Beta carotene and other related compounds are converted in the human body to the crucially needed vitamin A. Unfortunately, many in the developing world that do not have access to fruits and vegetables, suffer from chronic vitamin A deficiency which results in night blindness. Night blindness plagues millions of undernourished people in Asia, including India, crippling their lives. According to the WHO, vitamin A deficiency hits the poor in 96 countries of the world, resulting in over five lakh blind children every year. This blindness is irreversible, these children will never see. Maize is a major cereal crop for both human and livestock nutrition, worldwide. Protein from cereals including normal maize, have poor nutritional value because of reduced content of essential aminoacids such as lysine and tryptophan leading to harmful consequences such as growth retardation, protein energy mal-nutrition, anemia, pellagra, free radical damage etc. As a consequence, the use of maize as food is decreasing day by day among health conscious people. The complex nature of these problems posed a formidable challenge. This challenge was gladly accepted by two distinguished scientists of CIMMYT, Mexico, Dr. S. K. Vasal and Dr. Evangelina Villegas whose painstaking efforts for a period of 3 decades led to development of Quality Protein Maize (QPM) with hard kernel, good taste and other consumer favouring characteristics. This work is globally recognized as a step towards nutritional security for the poor. QPM research and development efforts appropriately spread from Mexico to Central and South America, Africa, Europe and Asia. India also benefited with such germplasm and developed its first QPM composite variety ‘Shakti–1’ released in 1997 for commercial cultivation across the country. In 1998, the Rajendra Agricultural University (RAU) stepped ahead with further R & D towards the development of QPM variety and popularization of QPM as food. Research priorities were fixed by the university both for varietals development and product development through the process of value addition by way of value chain management. The breeding programme on QPM was focused at AICRP Centre on Maize located at Tirhut College of Agriculture, Dholi (Muzaffarpur) whereas value addition activities were carried out at the Department of Food and Nutrition, College of Home Science, Pusa. As of today, RAU has marched ahead in both areas and has its own success story upon QPM. It is an improved variety of maize which contains higher amount of lysine and tryptophan with lower amount of leucine

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and isoleucine in the endosperm than those contained in normal maize. Such balanced combination of amino acids in the endosperm results into its higher biological value ensuring more availability of protein to human and animal than normal maize or even all cereals and pulses. Vertical farming is a concept that argues that it is economically and environmentally viable to cultivate plant or animal life within skyscrapers, or on vertically inclined surfaces. The idea of a vertical farm has existed at least since the early 1950s. Vertical farming discounts the value of natural landscape in exchange for the idea of "skyscraper as spaceship". Plant and animal life are mass produced within hermetically sealed, artificial environments that have little to do with the outside world. In this sense, they could be built anywhere regardless of the context. This is not advantageous to energy consumption as the internal environment must be maintained to sustain life within the skyscraper. The concept of "The Vertical Farm" emerged in 1999 at Columbia University. It promotes the mass cultivation of plant and animal life for commercial purposes in skyscrapers. Using advanced greenhouse technology such as hydroponics and aeroponics, the skyscrapers could theoretically produce fish, poultry, fruit and vegetables. While the concept of stacked agricultural production is not new, scholars claim that a commercial high-rise farm such as 'The Vertical Farm' has never been built, yet extensive photographic documentation and several historical books on the subject suggest that research on the subject was not diligently pursued. New sources indicate that a tower hydroponicum existed in Armenia prior to 1951. Proponents argue that, by allowing traditional outdoor farms to revert to a natural state and reducing the energy costs needed to transport foods to consumers, vertical farms could significantly alleviate climate change produced by excess atmospheric carbon. Critics have noted that the costs of the additional energy needed for artificial lighting, heating and other vertical farming operations would outweigh the benefit of the building’s close proximity to the areas of consumption.

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Chapter 13: Allelopathy Simply put, allelopathy refers to an ecological phenomenon of plant-plant interference through release of organic chemicals (allelochemicals) in the environment. These chemicals can be directly and continuously released by the donor plants in their immediate environment as volatiles in the air or root exudates in soil or they can be the microbial degradation products of plant residues. The chemicals may interfere with survival and growth of neighboring or succeeding plants. Black walnut, eucalyptus, sunflower, sorghum, sesame and alfalfa are common examples of plants with allelopathic property as well as some staple crops such as rice, wheat, barley and sorghum. Plants can emit chemicals that also discourage insects and pathogens. To maintain sustained productivity, knowledge of this form of plant interference on other plants and on disease causing organisms has been used in agriculture since prehistoric time by manipulating cropping pattern and sequence such as mixed cropping and crop rotation. During the last two decades, the science of allelopathy has attracted a great number of scientists from diverse fields world wide and is now viewed from a multifaceted approach (Putnam and Tang 1986; Chou et al. 1999; Reigosa and Pedrol 2002). This diverse interest has been greatly driven by the prospects that allelopathy holds for meeting increased demands for sustainability in agriculture and quality food production for humans, on reducing environmental damage and health hazards from chemical inputs, minimizing soil erosion, reducing reliance on synthetic herbicides and finding alternatives for their replacement. The thirtieth anniversary of the publication of the first edition of Professor Elroy Rice’s book titled, simply, “Allelopathy” fell in 2004. Surely, no work on the discipline has been more influential or more widely cited in the literature. A flavour of this work is given in an autobiographical contribution to the ‘Pioneers in Allelopathy’ series (Rice, 1996). Significantly, much of what Rice wrote and described 30 years ago has been neither surpassed nor superceded in the literature. The potential scope of allelopathy in natural and managed ecosystems; the means of liberation of allelochemicals from plants; the families of compounds themselves, and their likely modes of action are all included (Rice, 1974). All that has been accomplished since is the refinement that accompanies the application of ever more sophisticated technology….. Such an appraisal would be unfair to the undoubted flowering of allelopathy which occurred during the1970s, through the 1980s and into the 1990s. During this period allelopaths were active around the World. They included, in Canada, Neil Towers; in Europe, Michael Wink; in Japan,

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Junya Mizutani; in Korea, Bong-Seop Kil; in Mexico, Ana Luisa Anaya; in Taiwan, Chang- Hung Chou and CC Young; in India, Syamasundar Joshi – who published one of the rare examples of allelopathy being deployed to good effect in the field by living plants, in this case the effect of Cassia sericea Sw. on Parthenium hysterophorus L.- and in the USA, HH Cheng, Stephen Duke; Frank Einhellig; Stephen Gliessman; Gerald Leather; Al Putnam; CD Tang, Doug Worsham, and George Waller, of whom, more later. These are examples, only, of the ‘multidisciplinary international audience’ for allelopathy and no disrespect is intended to the many workers who do not receive specific mention. As noted, above, there was much activity behind the ‘Iron Curtain’ a great deal of which remains inadequately explored. Gerald Leather and Bong-Seop Kil were guests at the University of New England (New South Wales) which, along with Rick Willis’ laboratory in Melbourne, were the main centres for allelopathy in Australia at that time. The topics covered by this large group of very productive workers illustrates the extent to which allelopathy must be viewed in breadth. Allelopathy was, for example, recognized as but one of the many stresses which impact plants in their environment. In some instances allelopathy may emerge as a dominant, identifiable influence. In others it is merely part of the background. An allelopathic effect which is stark in one season may be invisible in the next. Allelopathy was recognized in fresh water and marine systems, demonstrating the capacity for allelochemicals to retain their bioactivity even when greatly diluted. Similarly, the fate of allelochemicals in the rhizosphere and, more generally, in soil was being explored. Emergent, contemporary interest in sustainability of natural and managed systems focused workers on the role which allelopathy might play, for example, in reducing reliance on synthetic pesticides. The application of mass spectrometry and high pressure liquid chromatography greatly facilitated the identification and quantification of allelochemicals. Perhaps most important of all was the recognition that those compounds which are to allelopaths, ‘allelochemicals’, have a broad role in phytochemical ecology (Towers et al, 1989), and that they have a long history which has witnessed their employment by man for a variety of purposes. This has never been put better than by Whittaker (1970) who wrote, specifically of the alkaloids: “Man’s use of alkaloids for flavour, mild stimulation, medicinal effect, or pleasurable self-destruction should not obscure a common theme: they are probably, although not necessarily in all cases, repellents and toxins, evolutionary expressions of quiet antagonism of a

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plant to its enemies”. This antagonism may be perceived as being part of the array of defences which plants use to offset their sedentary habit (Lovett, 1985) and/or as a means of conveying messages: “Allelochemicals may, therefore, be considered as part of a network of communication in which disparate organisms give similar responses to similar compounds or families of compounds. Plants producing biologically active compounds at relatively high concentrations may be perceived as utilizing chemical defences” (Lovett et al,1989). Taking advantage of an author’s prerogative to be a little nationalistic, it is worth recording that Australia well illustrates the rich diversity of allelopathy (Lovett, 1986). As in other countries, allelopathy has often been observed but not recognized, for example, in early studies of phytotoxicity occurring from the decomposition of stubble in the field (Lovett, 1987). Nevertheless, allelopathy in Australia has been identified with plants native and introduced; in communities from rangelands to eucalypt forests; in pasture and crop systems, and in situations where bacterial involvement may be a pre-requisite for its expression (Lovett, 1987). Later, it has been recognized that chemical compounds which may act as plant messengers between plants and widely disparate organisms have potential as management tools in agricultural and other production systems (Lovett, 1989). The alkaloids of Datura interfere with cell division, damage mitochondria and interfere with energy metabolism (Lovett and Ryuntyu, 1988). Although recognised as being attenuated, as a consequence of selection for other attributes, crop plants also exhibit allelopathy. Studies of allelopathy with Brassica crop residues (Mason-Sedun et al 1986) showed that not only Brassica species but also cultivars differed in their expression of allelopathy. The release of the alkaloids gramine and hordenine from growing barley plants affected the growth of a test plant, Sinapis alba L., but it was also found that hordenine affected the growth of the common armyworm, Mythimna convecta, an insect pest of barley and the fungal pathogen Drechslera teres (Lovett, 1991).

Towards an allelopathic future? Contemporary with Elroy Rice for much of his career, Professor George Waller ranks among the pioneers of allelopathy (Waller, 1998) in bringing the rigour of the chemist to his studies of agricultural and biochemical topics. He was founding editor of Mass Spectrometry Reviews (Vols 3-18) and is an authority on two classes of compound widely associated with allelopathy, the alkaloids and the terpenoids.

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In September 1994, with Professor Shamser S Narwal, George Waller led the establishment of the International Allelopathy Society. The Society exists to promote understanding of allelopathy, referring to any process involving compounds produced by plants, microorganisms, fungi and viral secondary metabolites that influence the growth and development of agricultural, forestry, biological and ecological systems (excluding animals). Writing a decade later, Waller (2004) avers that, in order to sustain production while preserving resources for the future “The world’s need for research and development in allelopathy in agriculture, forestry, and ecology is of extreme urgency”. To meet this need will require allelopathy to contribute as part of the natural and managed systems of which it is a part. Are we meeting this challenge? Certainly, a new generation of allelopaths is active. But, pondering on this retrospective, it would be easy to argue that the promise of allelopathy, pre- and post-Molisch, has remained exactly that. For example, papers describing apparent allelopathic phenomena continue to abound in the literature. The dictionary definition of this term is thought-provoking: ‘Phenomenon: a fact or occurrence that appears or is perceived, especially one of which the cause is in question’ (Oxford, 1996). Interesting as the reported phenomena may be allelopathy runs the risk of becoming an evolutionary dead end unless its practitioners can translate phenomena into performance: ‘Performance: achievement under test conditions’ (Oxford, 1996) An analysis of papers published in Allelopathy Journal is instructive. Up to April 2005 (Volume 15 No.2) some 294 papers, including short communications, had appeared. Of these, 125 (42.5%) describe phenomena, typically, ‘the allelopathic potential of species x against species y’. There is some cause for optimism in that up to the end of the year 2000 the percentage was 47%, falling to 38% in the ensuing years. There were some of the latest and most stimulating contributions to the discipline in which the plant victims have been dried, ground and extracted with solvents for anything up to two weeks, or more; the resulting solutions have been applied to Petri dishes containing the hapless target seeds, and claims of discovery of allelochemicals and apparent allelopathic activity have duly been made. Frequently, it is told that roots appear to be more sensitive than shoots, and that low concentrations of allelochemicals stimulate while higher ones inhibit. The

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most sophisticated chemistry is sometimes applied but the compounds identified are depressingly familiar. The scope and fascination of allelopathy are so broad that it is all too easy to fall into this trap of reinventing the wheel. But the new generation of allelopaths must be encouraged to pay full attention to the work of the pioneers and, rather than mimicking their achievements, strive to move the discipline forward. In an equivalent context the German philosopher GWF Hegel (1770-1831) observed: “What experience and history teach is this – that nations and governments have never learned anything from history, or acted upon any lessons they might have drawn from it” (Hegel, 1830). So many enthusiastic authors, the present writer among them, have identified the potential of allelopathy to play an important role in the management of plant-based systems, including agriculture, horticulture and forestry. Yet, with relatively few exceptions, allelopathy has not made a recognized impact as a management tool in common use. Lest it appear unduly censorious there are, among the 294 papers in Allelopathy Journal, some excellent examples of ‘performance’. In an analysis it looked, especially, for the word ‘management’ in the title of a paper as this implies that allelopathy is actually being applied to deliver useful outcomes. Four papers, 1.4% of total contributions, meet this criterion. All are from Asian countries. In chronological order, the first example is from India and describes the application of oilseed cakes containing extracts of neem (Azadirachta indica A.Juss), castor (Ricinus cimmunis L.), mustard (Brassica campestris L.) and rocket salad (Eruca sativa Mill.) to soil under controlled conditions. The amended cakes reduced the multiplication of two species of applied nematode, the effects being similar to those achieved with commercial nematicides (Anver and Alam, 2000). The findings are relevant to crop protection in several leguminous crops which are important in the sub-continent. Eiji Tsuzuki commenced allelopathy research in Japan in the 1970s and is recognized as a pioneer of allelopathy (Xuan, 2004). With a strong background in agronomy, Professor Tsuzuki’s contribution lies in the exploitation of allelochemicals in crops to reduce dependence on synthetic pesticides. This has long been one of the objectives of allelopathy researchers. Thus, as the second example of ‘management’ papers, Tsuzuki and Dong (2003) applied pellets of several species of buckwheat (Fagopyrum spp.) containing a number of commonly identified

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allelochemicals (for example, ferulic and caffeic acids) to several plant species under controlled conditions, where inhibitory activity was observed. Most importantly, the work was translated to the field where buckwheat pellets were shown to inhibit weeds in rice fields without adverse effects on the crop. Finally, Ni and Zhang (2005) reviewed the use of allelopathy for weed management in China, citing mulching with wheat straw as an effective technique for use in the field. They also found that while rice accessions showed differences in allelopathic potential these were not expressed in the field. Nevertheless the variation present may provide the basis for further selection for enhanced allelopathic activity in this important crop. This work echoes the promise of selection for allelopathic activity in crops foreshadowed by the work of Putnam and Duke (1974) with cucumber (Cucumis sativus L.). The impossible dream? It seems clear that allelopaths, in general, often supported by increasingly sophisticated chemistry, molecular biology and mathematical modeling, are not engaged in translating even well established and documented manifestations of allelopathy to the field. Why is this the case? One reason is that, for the scientist, bioassays are easy to carry out and complex chemical tests are becoming more readily available. Work in controlled environments yields quicker results than does field work, and the flow of publications is concomitantly greater. A less cynical view is that allelopathy is one component, only, of a complex system. To deploy it requires a multidisciplinary effort, as exemplified by the ‘pioneers of allelopathy’. In other words, allelopathy is but one thread in the web of life and it can be extremely difficult to disentangle it and to establish its importance. Fitter (2003) points to this complexity in his paper ‘Making allelopathy respectable’, suggesting that there are several cases where successful invasion by weeds is due, at least in part, to phytochemical activity. One example cited is that of the success of the European Vulpia spp. in Australia, An et al (2005). However, it is cause for reflection that Fitter chose this title 66 years after Molisch’ published his treatise on allelopathy. A third reason is that even where allelopathy has been shown to have a role in, say, weed management, for the farmer to use it as part of a management system is much more difficult than the simple alternative of employing a commercial herbicide. This point leads to another cherished but largely unrealized allelopathic objective. Allelochemicals have been repeatedly heralded as the basis for new families of herbicides. Sadly,

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their impact has been very limited and commercial interest in allelochemicals has languished. The compounds involved are well known and probably not patentable. While, in some instances, they have been elucidated the modes of action of allelochemicals have not been sufficiently novel as to excite investment. The work of Tsuzuki and Dong (2003) does, at least, indicate that allelochemicals can hold their own with synthetic pesticides in some circumstances and the diminishing number of affordable, effective pesticides gives cause for some optimism as to the future of allelopathy as an element in crop protection. This may be particularly the case in those countries where economic considerations preclude the routine use of conventional chemical approaches. Developing economies in Asia and in eastern Europe fit this category and they are proving to be a rich source of papers on allelopathy. What may offer a renewed vision for allelopathy is that, in these early years of the twenty-first century, the global consumer is exerting increasing influence on production systems. To employ the jargon, ‘market pull’ is being exerted. Consumers are demanding fresh, healthy and ‘natural’ foods which are definitely not transgenic (GM) in origin. Conventional plant breeding to develop the inherent self defence of crop plants, reducing the need for pesticide and herbicide application, may yet deliver benefits in this context (see, for example, Dilday et al, 1998; Wu et al, 2002). The market for alternative pharmaceuticals, too, is reaching new heights. ‘Bioactives’ are recognized and acceptable, not least because the technology to quantify, evaluate, dispense and deploy them with confidence now exists. The wide publicity which the carotenoid, lycopene, found principally in tomatoes, has received as an antioxidant which reduces the risk of prostate, lung, stomach and a range of other cancers (Giovannucci, 1999) is an excellent example. Thus, the climate is right to promote allelopathy and allelochemicals in their own right, that is, not as substitutes for or as competitors with conventional technologies. Consistent with this approach, Zhuoquan et al (2005) refer to recent researches on biogenic volatile organic compounds (BVOCs) produced by plants and their relations with other plants, insects, pathogens, nematodes and other microbes. The volatiles concerned appear to be known allelochemicals but the paper stresses that their role in non ‘plant-plant’ relations warrants a distinction between a broader ‘chemoecology’ and allelopathy. It is this distinction which may be the basis for a new allelopathy dream.

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Chapter 14: Genetically Modified (GM) Crops Genetic modification refers to techniques used to manipulate the genetic composition of an organism by adding specific useful genes. A gene is a sequence of DNA that contains information that determines a particular characteristic/trait. All organisms have DNA (genes). Genes are located in chromosomes. Genes are units of inheritance that are passed from one generation to the next and provide instructions for development and function of the organism. Crops that are developed through genetic modification are referred to as genetically modified (GM) crops, transgenic crops or genetically engineered (GE) crops. In 2011, farmers worldwide planted 160 million acres of Bt cotton and Bt corn. The percentage of cotton planted with Bt cotton reached 75 per cent in the U.S. in 2011, but has exceeded 90 per cent since 2004 in northern China, where most of China's cotton is grown. The main steps involved in the development of GM crops are: 1. Isolation of the gene(s) of interest: Existing knowledge about the structure, function or location on chromosomes is used to identify the gene(s) that is responsible for the desired trait in an organism, for example, drought tolerance or insect resistance. 2. Insertion of the gene(s) into a transfer vector: The most commonly used gene transfer tool for plants is a circular molecule of DNA (plasmid) from the naturally occurring soil bacterium, Agrobacterium tumefaciens. The gene(s) of interest is inserted into the plasmid using recombinant DNA (rDNA) techniques. For additional information see Plasmids link 3. Plant transformation: The modified A. tumefaciens cells containing the plasmid with the new gene are mixed with plant cells or cut pieces of plants such as leaves or stems (explants). Some of the cells take up a piece of the plasmid known as the T-DNA (transferred-DNA). The A. tumefaciens inserts the desired genes into one of the plant’s chromosomes to form GM (or transgenic) cells. The other most commonly used method to transfer DNA is particle bombardment (gene gun) where small particles coated with DNA molecules are bombarded into the cell. For additional information see Plant Transformation using Agrobacterium tumefaciens and Plant Transformation using Particle Bombardment links. 4. Selection of the modified plant cells: After transformation, various methods are used to differentiate between the modified plant cells and the great majority of cells that have not incorporated the desired genes. Most often, selectable marker genes that confer antibiotic or herbicide resistance are used to favor growth of the transformed cells relative to the non

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transformed cells. For this method, genes responsible for resistance are inserted into the vector and transferred along with the gene(s) conferring desired traits to the plant cells. When the cells are exposed to the antibiotic or herbicide, only the transformed cells (containing and expressing the selectable marker gene) will survive. The transformed cells are then regenerated to form whole plants using tissue culture methods. 5. Regeneration into whole plants via tissue culture involves placing the explants (plant parts/cells) onto media containing nutrients that induce development of the cells into various plant parts to form whole plantlets (Figure 1). Once the plantlets are rooted they are transferred to pots and kept under controlled environmental conditions. 6. Verification of transformation and characterization of the inserted DNA fragment. Verification of plant transformation involves demonstrating that the gene has been inserted and is inherited normally. Tests are done to determine the number of copies inserted, whether the copies are intact, and whether the insertion does not interfere with other genes to cause unintended effects. Testing of gene expression (i.e., production of messenger RNA and/or protein, evaluation of the trait of interest) is done to make sure that the gene is functional. 7. Testing of plant performance is generally carried out first in the greenhouse or screen house to determine whether the modified plant has the desired new trait and does not have any new unwanted characteristics. Those that perform well are planted into the field for further testing. In the field, the plants are first grown in confined field trials to test whether the technology works (if the plants express the desired traits) in the open environment. If the technology works then the plants are tested in multi-location field trials to establish whether the crop performs well in different environmental conditions. If the GM crop passes all the tests, it may then be considered for commercial production. 8. Safety assessment. Food and environmental safety assessment are carried out in conjunction with testing of plant performance. Descriptions of safety testing are described in the Food Safety Assessment and Environmental Safety Assessment links.

Positive Impacts of GM crops For the development of improved food materials, GM has the following advantages over traditional selective breeding:

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 Allows a much wider selection of traits for improvement: e.g. not only pest, disease and herbicide resistance (as achieved to date in plants) but also potentially drought resistance, improved nutritional content and improved sensory properties  It is faster and lower in cost  Desired change can be achieved in very few generations  Allows greater precision in selecting characteristics  Reduces risk of random occurrence of undesirable traits. These advantages could, in turn, lead to a number of potential benefits, especially in the longer term, for the consumer, industry, agriculture and the environment: o Improved agricultural performance (yields) with less labour input and less cost input o Benefits to the soil of “notill” farming practice o Reduced usage of pesticides and herbicides o Ability to grow crops in previously inhospitable environments (e.g. via increased ability of plants to grow in conditions of drought, soil salinity, extremes of temperature, consequences of global warming, etc.). Improved sensory attributes of food (e.g. flavour, texture, etc.). o Removal of allergens or toxic components, such as the research in USA to produce a nonallergenic GM peanut (University of Arkansas) and a nonallergenic GM prawn (Tulane University); and in Japan, to produce a GM Nonallergenic rice. • Improved nutritional attributes such as:

 Ingo Potrykus's EU research project jointly funded by the Rockefeller Foundation, resulting in increased Vitamin A content in rice, which will help to prevent blindness among children in Southeast Asia;  the announcement in September 2003 by Edgar Cahoon and his team at the Donald Danforth Plant Science Center in Missouri that by inserting a gene extracted from barley into a common type of field corn, they have created a strain that grows with six times the usual amount of vitamin E, a powerful antioxidant.

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 Improved processing characteristics leading to reduced waste and lower food costs to the consumer.  Prevention of loss of species to endemic disease (e.g. the Cavendish dessert banana which is subject to two fungal diseases that have struck Africa, South America and Asia, but could be reprieved by GM development of a disease resistant version). GM has huge potential for mankind in medicine, agriculture and food. In food, the real benefits are not the early instances that have been appearing so far, but its longer term benefit to the world and especially the developing countries its potential for developing crops of improved nutritional quality, and crops that will grow under previously inhospitable conditions (see above), thereby contributing to alleviating hunger and malnutrition, while helping to prevent the otherwise inevitable future pressure to encroach on natural resources. Even today, there are 840 million people. 800 million of them in the developing countries and 200 million of them children, who regularly do not receive enough food to alleviate hunger, still less provide adequate nutrition. 24,000 people die of malnutrition related causes daily. That situation will be greatly worsened as a result of the world's escalating population over the coming decades. There are those who allege that “scientists claim that GM will solve the problem of world hunger”. This is a familiar "straw man". It is frequently argued by some that there is more than enough food to feed the world and all that is needed is "fairer distribution" (which so far mankind has signally failed to achieve) – or a variant of that, "the real problem is not shortage of food, it is poverty". Whatever may be done by way of improved yields through conventional methods, attempted population control and more effective distribution would, however, be inadequate for the future. There are probably enough cereals to feed the present world population (if only they could be distributed to the right places at the right times and could be afforded). But there will be substantial shortfalls in cereals in the next two decades. Moreover, "world hunger" is a complex not only of inadequate quantity where it is needed but also of inadequate quality i.e. for vast numbers of people the lack of foods with the necessary micronutrients and of clean water, for reasonable nutrition and health.

However, in decades to come, with the expected substantial increase in the world population, mostly in the poorest, least developed countries, the demand for increased

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agricultural land and for water will greatly increase. The important point is not only how to feed the world now but addressing and trying to solve the problem of "How shall mankind feed the world in a few decades from now?” Of course the problem that has huge political and economic dimensions will not be solved by GM alone, or even by science alone but will certainly not be solved without the contribution of science, including GM. Food scientists and technologists can support the responsible introduction of GM techniques provided that issues of product safety, environmental concerns, ethics and information are satisfactorily addressed. so that the benefits that this technology can confer become available both to improve the quality of the food supply and to help feed the world's escalating population in the coming decades. Negative Impacts of GM crops There are following unintended impacts on environment, health, markets Environment: Unintended environmental impacts include harming non-target and/or beneficial species in the case of crops with engineered insecticidal properties, as well as the development of new strains of resistant pests. Additionally there is concern that pollen from genetically engineered herbicide resistant crops could reach wild, weedy relatives of the crop and create so called super weeds. This is of particular concern in the U.S. with crops such as canola and squash. Health: At present, there is no evidence to suggest that GM foods are unsafe. However, there are no absolute guarantees, either. Unintended health impacts from GMOs concern allergens, antibiotic resistance, decreased nutrients, and toxins.  Allergens Because protein sequences are changed with the addition of new genetic material, there is concern that the engineered or modified organism could produce known or unknown allergens. A recent National Research Council committee report on GMOs recommended the development of improved methods for identifying potential allergens, "specifically focusing on new tests relevant to the human immune system and on more reliable animal models."  Antibiotic resistance Plant genetic engineers have frequently attached genes they are trying to insert to antibiotic resistance genes. This allows them to readily select the plants that acquire the new genes by treating them with the antibiotic. Sometimes these genes remain in the transgenic crop that has lead critics to charge that the antibiotic resistance

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genes could spread to pathogens in the body and render antibiotics less effective. However, several panels of antibiotic resistance experts have concluded that the risk is miniscule.  Decreased nutrients Because the DNA of genetically engineered plants is altered, there is concern that some GMOs could have decreased levels of important nutrients, as DNA is the code for the production of nutrients. However, it must be noted that nutritional differences also have been documented with traditionally bred crops.  Introduced toxins Residual toxins resulting from introduced genes of the bacteria Bacillus thuringiensis in so called Bt crops are unlikely to harm humans. This is because the toxin produced by the bacteria is highly specific to certain types of insects. Prior to its inclusion in GE/GM crops, Bt has been used as a biological insecticide, causing no adverse effects in humans consuming treated crops.  Naturally occurring toxins There is concern that genetic engineering could inadvertently increase naturally occurring plant toxins. However, traditional plant breeding also can result in higher levels of plant toxins. Moral Issues "Moving genes from animals to plants gets you into a whole moral, religious, and political firestorm..." This statement illustrates the primary contention point for the most common ethical moral argument against GMOs. For those who believe that humans do not have the right to create life that humans are stewards of the earth's species, or that humans are equals with other species, combining genes in ways that would not occur in the normal process of evolution conflicts with their personal philosophy of life. However, the argument has been made that genetic engineering is morally justified as it can be used to alleviate disease and starvation. While the argument for alleviating disease is supported by the case of genetically engineered human insulin and not yet commercialized projects that seek to deliver vaccines via food crops, the argument for alleviating hunger has yet to be borne out. GM crops have yet to increase yields on par with hybridization in corn, and it must be remembered that simply growing more of a crop does not guarantee that it will reach people who are starving. A member of the European Parliament, speaking at the European Voice Conference on GMOs in Brussels in March 1999, blasted biotech [companies' public relations campaigns] saying while they "attempt to convince people they just want to save

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the environment and feed the starving, people know that wealthy companies have not been created to feed the poor." That said, on August 3, Monsanto announced that it would not charge licensing fees for the use of its patented technology for producing golden rice.

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Chapter 15: Dryland farming Indian agriculture is predominantly a rainfed agriculture under which both dry farming and dry land agriculture is included. Dry farming was the earlier concept for which amount of rainfall (less than 500 mm annually) remained the deciding factor for more than 50 years. In modern concept, dry land areas are those where the balance of moisture is always on the deficit side. In other words, annual evapotranspiration exceeds precipitation. In dry land agriculture, there is no consideration of amount of rainfall. It may appear quiet strange to a layman that even those areas which receive 1100 mm or more rainfall annually fall in the category of dry land agriculture under this concept. To be more specific, the average annual rainfall of Varanasi is around 1100 mm and the annual potential evapotranspiration is 1500 mm. Thus the average moisture deficit so created comes to 400 mm. This deficit in moisture is bound to affect the crop production under dry land situation ultimately resulting into total or partial failure of the crops. Accordingly the production is either low or extremely uncertain and unstable which are the real problems of dry land in India. The success of crop production in these areas depends on the amount and distribution of rainfall, as these influences the stored soil moisture and moisture used by crops. The amount of water used by the crop and stored in the soil is governed by the water balance equation: ET = P- (R+S). When the balance of the equation shifts towards right, precipitation (P) is higher than ET, so that there may be water logging or it may even lead to run off (R) and flooding. On the other hand, if the balance shifts to the left, ET becomes higher than the precipitation, resulting in drought in the various severity. Taking the country as a whole, as per meteorological report, severe drought as large area is experienced once in 50 years and partial drought in five years while folds are expected every year in one part of the country or the other, especially during rainy season. In fact the balance of the equation is controlled by the weather, season, crops and cropping pattern. Status Out of 14.2 million ha of net sown area in the country, rainfed agriculture is practiced in 95 million ha (67%). Nearly 67 m ha of rainfed area falls in the mean annual precipitation range of 500-1500 mm.

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The average annual rainfall of the country is 1200 mm amounting to 400 million ha-m of rain water over the country's geographical area (329 m ha). However, the distribution across the country varies from less than 100 mm in extreme arid areas of western Rajasthan to greater than 3600 mm in NE states and 1100 mm from east coast 2500-3000 mm in the west coast. The broad area of the summer monsoon activity extends between 300 N to 300 S and from 300 W to 16.50 E. the detail information on rain fall and monsoonal pattern in India has been summarized in the following table: Rainfall pattern in fall Season/Period m ha m % Winter (Jan-Feb) 12 3 Pre-monsoon (Mar-May) 52 13 South-west monsoon (Jun- 296 74 Sept) North-east monsoon (Oct- 40 10 Dec) Total for the year 400 100

Rainfed farming comprises about 91% area of coarse cereals (sorghum, pearl millet, maize and finger millet), 91% pulses (chickpea and pigeon pea), 80% of oilseeds (groundnut, rape seed, mustard and soybeen), and 65% of cotton. Also, about 50% area under rice and 19% area under wheat is rainfed. During the past 25 years there occurred significant changes in the area and yield of important crops of rainfed farming areas. The area under coarse cereals decreased by about 10.7 million ha and most of this was under sorghum. The area under oilseeds increased by 9.2 million ha and most of this increase was due to irrigated rapeseed and mustard and soybean. The total area under pulses and cotton remained constant but more of cotton became irrigated and shifts in the area occurred from one agroecological region to others. Area under chickpea in the northern belt decreased but increase in the central belt. This change occurred due to increase in area under rice-wheat cropping system which displaced chickpea and also pearl millet to a great extent and maize to a small extent.

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According to the present concept, there are 128 districts in the country which face the problems of dry land. Of these 25 districts covering 18 m ha of net area sown with 10% irrigation receive 375 750 mm rainfall annually spread over Central Rajasthan, Saurashtra region of Gujarat and rain shadow region of Western Ghats in Maharashtra and Karnataka. Twelve districts have irrigation covering 30 50% of the cropped area and do not pose serious problems. The remaining 91 districts covering mainly Madhya Pradesh, Gujarat, Maharashtra, Andhra Pradesh, Karnataka, Uttar Pradesh, parts of Haryana, Tamil Nadu etc., represent typical dry land area. The total net sown area in these districts is estimated to be 42 million hectares of which 5 m ha are irrigated. Rainfall in these districts varies from 375 to 1125 mm. Therefore, more and more efforts are to be made for enhanced and stable production in these areas so that the recurring droughts do not stand in the way of meeting the growing food demands. It is not that no attention has been paid in the country towards the development of dryland farming. Efforts were made right from 1923 to improve crop yields with the establishment of a research projects at Manjari in Maharashtra and later at Solapur, Bijapur, Raichur and Hagari in Deccan and Rohtak (Haryana) in the north. An All India Coordinated Research Project for Dry land Agriculture was launched by ICAR in 1970 in collaboration with Government of Canada. Later Central Research Institute for Dryland Agriculture (CRIDA) was established in 1985 at Hyderabad. These projects generated technology, which, if followed, can bring marked improvement in cropping intensity, productivity and stability in production. Problems In dry land agriculture, scarcity of water is the main problem. Apart from the low and erratic behavior of rainfall, high evaporative demand and limited water holding capacity of the soil constitute the principle constraint in the crop production in dry land area. Yield fluctuations are high mainly due to vagaries of weather, often much behind the risk bearing capacity of the farmers. It is surprising to a layman that even humid areas with 2000 mm of annual rainfall not only suffer from moisture stress, but also face drinking water scarcity. Monsoon starts in the month of June and ends in last week of September or sometimes in the first week of October. Most of the rainfall is received during this period. With undulating topography and low moisture retention capacity of the soil, major portion of the rain water is lost through runoff, causing erosion and adding to the water logging of low lying areas. After the rain stops, very little moisture is left in the profile to support plant growth and grain production.

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In dry land area deficiency and uncertainty in rainfall of high intensity causes excessive loss of soil through erosion which leaves the soil infertile. Owing to erratic behaviour and improper distribution of rainfall, agriculture is risky, farmers lack resources, tools become inefficient and ultimately productivity is low. Vertisoles have high clay content and high moisture retention capacity. Owing to its swelling and shrinking characteristics, permeability is low and hence the rate of infiltration of water is minimum. This causes more surface and high soil loss from the top layer owing to surface erosion. It is estimated that 68.5 tones/ha per year soil is lost from vertisoles. Due to high clay content it develops cracks during Rabi season at flowering stage of crops. Alfisols are, by and large, light textured soils which have low moisture holding capacity but high water intake. The rain water falling in such areas gets soaked up and saturates the profile. The soil water percolation is more and therefore, is lost for crop use. Owing to faster intake of water in the profile the surface runoff is limited and soil loss from erosion is low (3.05 t/ha/year). Soil crusting is a common problem in low rainfall areas. Entisols are generally loamy sand or sandy loam. Depth in these soils is not a constraint. These soils have very low clay content and hold water up to 200 mm per meter of soil profile. Its nutrient holding capacity is poor. In low rainfall areas monsoon cropping is practiced and in high rainfall areas double cropping is possible. Submontane soils are medium in texture and depth is medium to deep as well as moderate in clay content. Moisture retention capacity is high (300 mm/m. profile). These soils are poor in nitrogen but in other nutrients. Phosphorous may be limiting in high production system. Due to high rainfall double cropping is possible in these soils. Sierozems are extremely light soils, effectively depth being influenced by the CaCo3 concentration in soil profile. Its moisture holding capacity is low (150 mm water.m). Sierozemic soils are low in nitrogen and sometimes inadequate in phosphorous. Subsoil salinity is common. These soils are mostly monsoon cropped, except in deep sandy loams where post-monsoon cropping is also possible. Crusting is very frequent.

Improved Dryland Technology

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The improved techniques and practices, which have so far been generated and recommended for achieving the objective of increased and stable crop production in dryland areas, have been summarized in following lines. Crop Planning The farmers of the dry land areas, prior to the development of dry land techniques, were growing a crop either on rainwater in kharif or on conserved soil moisture during the winter. The crop varieties are grown when moisture is sufficiently available. Such varieties have low genetic potential for yield. Selecting suitable crops and varieties capable of maturing within actual rainfall periods will not only help in enhancing production of a single crop but in intensifying the cropping intensity. Many criteria have been laid out for selecting a crop variety for drylands. The capacity to produce a fairly good yield under limited soil moisture conditions is the most desirable criteria. The duration of kharif crops/varieties should not normally exceed the number of rainy days. In other words, crop varieties for dryland areas should be of short duration, through resistant tolerant and high yielding which can be harvested with in rainfall periods and have sufficient residual moisture in soil profile for postmonsoon cropping. Under dry land agriculture determination of length of growing period (LPG) i.e., moisture availability of a given soil type, provides better index than total rainfall based crop planning. LPG is defined as the period when the moisture and temperature regimes are suitable for crop growth and the period is determined by the FAO method (1983). The LPG is computed as the sum of the period when P is more than 0.5 PET plus time taken to utilize stored soil moisture (assured 100 mm) after P falls short of PET. For example 'Nagpur' and Ratnagiri in Maharashtra receive mean annual rainfall of 1120 mm and 2500 mm, respectively but LPG determination indicates that both the places have LPG of 210 days in deep black soils. Therefore, both the places are suitable for single long duration on a short duration crop with a relay rabi crop.

Planning for aberrant weather

Dryland agriculture is subject to high variability in areas sown, yields and output. These variations are the results of aberrations in weather conditions, especially rainfall. Delay in

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normal monsoonal pattern causes problems of timing and the organization of preparatory tillage and other initial activities for commencing cultivation processes for the season. Such monsoonal delays have repercussions on the programme of activities for the entire agricultural year. Even after the onset of monsoon and the commencement of planting, there may be monsoonal withdrawal causing moisture stress on plants and creating difficulties in the adoption and timing of approval cultural practices ultimately causing reactions in yields and outputs. Some crops are highly susceptible to such mid-season variations in moisture availability such as at the flowering stage in rice. Major crops like rice and maize get seriously affected if monsoonal rains cease early. The need for modifying and introducing and introducing new technology for increasing and sustaining yield in dry land areas can hardly be overemphasized. Equally urgent is the need to decelerate and ultimately eliminate the process of damage to agricultural assets which are proceeding unabated in dry land areas. Erratic rainfall results in fluctuating production. This in turn leads to frequent scarcities, like the ones experienced in Indonesia and Vietnam in 1977 which created severe food shortages. Droughts in China in 1972, 1974 and 1985 brought depression of food grain production by up to about 25 million t. Frequent droughts in India during 1966, 1968, 1972, 1974, 1979, 1982 and 1987 seriously affected the food and fodder production in the country. Hence, it is necessary to understand the distribution of South-West monsoon within the season to determine the extent to which the crop productions are likely to be affected by the vagaries of monsoon. Several attempts have been made to understand the behavior of South-West monsoon rainfall in different agro-climatic regions on the basis of historical rainfall records. These studies (Singh, 1987, Ramanna Rao, 1988) have brought out that (i) there is large variation in dates of commencement of South-West monsoon from year to year in different parts of the country, (ii) the monsoon rainfall is of sequential nature with long dry spells or breaks extends sometimes to the period of even one month or more, (iii) there is large year to year variation in dates of withdrawal of South-West monsoon, (iv) there is variation in quantum of rainfall received from year to year and (v) high intensity rainfall occurs in association with movement of cyclones or depression resulting in sizeable loss of rainwater through run-off and deep drainage. Thus, crop production in dry lands fluctuates widely from year to year due to vagaries of weather. An aberrant weather can be categorized under three heads i.e. (i) delayed onset of monsoon, (ii) long

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gaps or breaks in rainfall, and (iii) early stoppage of rains towards the end of monsoon season. Therefore, to mitigate such weather situations, farmers should make some changes in normal cropping schedule for getting some production in place of total crop failure. Crop Substitution Alternate crop strategies have been worked out for important regions of the country for vertisols, alfisols, entisols, submontane and sierozemic soils. Strategy has also been evolved for normal onset of rains, breaks in rains, early withdrawal, its uneven distribution; through selection of crops/varieties which efficiently utilize the soil moisture, responsive to production input and potential producers. Appropriate crops, suiting varying rainfall situations, have been identified for most of the dry land regions of India (Table below). Crops which do better under normal rainfall years may not do so under abnormal years. Studies conducted in agro climatic conditions of Varanasi (eastern U.P.) revealed that under normal monsoon crops like short duration upland rice, maize, pearl millet, blackgram, greengram, sesame, pigeon pea etc. should be taken up on the basis of needs. These crops should be followed by chickpea, lentil, barley, mustard, safflower, linseed etc. on residual moisture during winter season. If monsoon sets in as late as second week of July, short duration upland rice (variety - NDR-97 and NDR-118) may be included in place of Akashi and Cauvery. If the rains are delayed beyond the period but start somewhere in last week of July or first week of August and growing season is reduced to 60-70 days, then cultivation of hybrid pearl millet (NHB 3-4, B.J. 104), blackgram (Type 9), greengram (var-Jagriti and Jyoti) may be included in place of T-44 and K-851 etc. Yet another alternative could be to harvest a fodder of either pearl millet, maize, sorghum or a mixture of cowpea, blackgram and one of the above fodder crops.

In case monsoon rains stop early towards the end of season, normal sowing of short duration upland rice, black gram and sesame may be taken up. If the rain stops very early, i.e. by the end of August or first week of September, only fodder crops or grain legumes could be harvested. Depending upon the soil moisture condition, relay sowing of crops like chickpea, lentil, mustard, linseed and barley could be done in rabi season.

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Table: Traditional and Alternate Efficient crops in Different Dryland Regions of India

S.No Region Traditional crop Alternate efficient crop

1 Deccan Rabi season Cotton, wheat Safflower

2 Malwa Plateau Wheat Safflower, Chick pea

3 Uplands of Bihar Rice Ragi, Black gram, Plateau and Orissa Groundnut

4 South-easy Rajasthan Maize Sorgham

5 North Madhya Maize Soybean Pradesh

6 Eastern UP Kalitur Chick pea

7 Sierozems of North- Wheat Mustard, Taramira west India ( Eruca Sativa)

During the recent drought, it was found that farmers in Karnataka, Andhra Pradesh and Maharashtra who went in for sunflower cultivation were in gainers. Sunflower succeeded where other crops failed. In other dry land regions, alternative efficient crops can profitably substitute the traditional ones (Table below).

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Table: Relative Yield of Traditional and Efficient Crops in Dryland Areas Region Traditional Yield (q/ha) Efficient Yield (q/ha) crops Bellary Cotton 2.0 Sorghum 26.70 Varanasi Wheat 8.6 Chickpea 28.50 Ranchi Upland Rice 28.8 Maize 33.60 Indore Green gram 11.8 Soybean 33.33

Wheat 11.0 24.20 Safflower Agra Wheat 10.3 Mustard 20.40 Hisar Wheat 3.0 Taramira 16.00 Udaipur Maize 18.0 Hybrid 29.00 sorghum Dry land research has remained confined to important traditional crops such as sorghum, millet, pulse and oilseeds and has not explored the possibility of growing non-traditional crops such as dye providing crops {e.g. Henna (Lawsonia inermis: mehadi) and jaffra (Bixa ovellana) species (e.g. cumin), and medicinal value crops (e.g. citronella, lemon grass, senna and isabgol)}. These crops need to find an important place in research agenda of dry land farming. Time has come for the relevant researchers to plan a joint integrated research programme for maximizing the profitability, productivity and sustainability of learning systems of rainfed areas. Sericulture offers great promise in rainfed farming strategy, particularly of the watershed approach in peninsular India. Efficient Cropping System Besides putting various measures to increase the productivity levels of dry land crops, efforts would also be needed to increase the cropping intensity in dry land areas which was generally 100%, implying that a single crop was taken during the year. Cropping intensities of these areas could be increased by practice of inter cropping and multi cropping (sequential) by way of more efficient utilization of resources. The cropping intensity would depend on the length of growing season which in turn depends on rainfall pattern and the soil moisture storage capacity of the soil. For example in Indore region, receiving 1000 mm annual rainfall, only single crop can be taken on shallow soils, inter cropping in medium depth soils and double

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cropping on deep soils. Similar crop combinations have been identified for different regions of the country. In dry land of Varanasi region upland rice chickpea/lentil sequence can be practices with advantage. Inter cropping of vegetables with grain crops was pursued vigorously in some centers such as Varanasi and Phulbani. At both the places long duration pigeon pea was inter cropped with vegetables such as okra, radish and chilli. Such inter cropping systems would be very useful to get maximum returns from rainfall agriculture. Even at Solapur, leafy vegetables and some short duration beans were grown as intercrops during the rainy season. Fertilizer Use

Soils of dry lands in the country are not only thirsty but hungry also because these soils are severely eroded horizontally as well as vertically. Whenever efforts are made towards bunding and levelling of the fields in dry land areas, it is the surface soil which is removed. The resultant effect is that the fields are rendered shallow in depth and completely deprived of plant nutrients, particularly nitrogen, phosphorus and potassium. It is, therefore, necessary to apply all the three major nutrients in adequate amounts. Since soil moisture is limiting in dry lands, the availability of nutrients becomes limited, attempt should always be made to apply fertilizers in furrows below the seed. If seed-cum-fertilizer drills drawn by bullocks or tractors are available, this very objective can be fulfilled. There has been belief among the farmers of dry land areas that use of fertilizer increases the chances of crop failure but recent findings have shown that the use of fertilizer is not only helpful in providing nutrients to crop but also helpful in efficient use of profile soil moisture (Table below). If dry land farmers are shown such results, they will be convinced to use more and more fertilizers.

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Table. Effect of N on Yield and Moisture Use Efficiency (MUE) of Barley and Wheat (Varanasi)

Nitrogen Grain yield (q/ha) Total moisture use (mm) MUE (kg/mm) levels (kg/ha) Barley 0 14.05 133.7 10.50 30 20.45 136.3 15.00 60 30.00 142.3 21.00 90 37.20 141.6 26.30 Wheat 0 9.55 145.5 6.60 30 13.55 144.4 9.30 60 18.55 153.6 11.9 90 24.15 155.1 13.6

Studies on the management of legumes in crop sequences for their residual effect indicated that in alluvial soils an advantage of 25-30 kg N/ha could be obtained in barley or mustard grown after black gram or green gram. Another possibility for nitrogen management in cropping system is to use legumes as green manures either at flowering stage or after one picking. Studies conducted at Varanasi clearly showed that general yield levels of barley and mustard were greater when legumes raised in the previous season was incorporated I soil after first picking as compared to that harvested at normal maturity (Table below).

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Table. Nitrogen Economy to Legume-Cereal System (4 years average) Nitrogen (kg/ha) Crop yield (q/ha) Green gram Unincorporated Incorporated Mustard 1.89 2.23 Barley 0 16.98 13.65 30 21.30 18.64 60 24.43 21.84 90 27.27 25.20

Rain water management Efficient management of rain water can boost agricultural production from dry lands. The broad bed and furrow system of the Inernational Crop Research Institute for the Semi Arid Tropics (ICRISAT) for managing rain water in vertisols made it possible to increase crop yields four to five times as compared to normal practice. However, this method could not be adopted widely by the farmers in India because it is costly and labour intensive. The vertical mulching developed at Bellary centres increases the infiltration of water in soil profiles and improves in situ moisture conservation. The scope for managing profile moisture is limited in alfisols but the surface run off in such soils can be reduced by ridge-and-furrow technique. Alternatively, application of compost and farm yard manure as well as raising legumes will add the organic matter to the soil and increase the water holding capacity. The winter rain which is not retained by the soil flows out as surface runoff. The run-off- recycling holds immense prospects in deep black soils where the seepage losses are very much less. This runoff water, if not permitted to drain out safely, causes erosion. Therefore, safe disposal of excess water from the field drains to the disposal system should be planned properly. This excess runoff water can also be harvested in storing dug out ponds and recycled to donor area in the event of severe moisture stress during rainy season or for raising crops during the winter.

Water-shed Approach for Resource Improvement and Utilization

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Watershed management is a holistic approach arrived at optimizing the use of land, water and vegetation in an area and thus, providing solution to alleviate drought, moderate floods, prevent soil erosion, improve water availability and increase fuel, fodder and agricultural production on a sustained basis. On the basis of the experiences of ICAR Operational Research Projects, which attracted the attention of our farmers, State departments, administrators and scientists, 47 model watersheds were established during the year 1983 for development, jointly by the Ministry of Agriculture, ICAR and various State Government Department and Agricultural Universities, in 16 states and then the Department of Agriculture and Co-operation launched the National Watershed Development Project for Rainfall Areas (NWDPRA) covering almost the same states. Out of these 47 model watersheds, the Central Research Institute for dryland Agriculture (CRIDA), Hyderabad has been entrusted with 30 watersheds. These activities were in micro and mini-watersheds covering 500-2000 ha. Major components in these model watersheds are: (i) Improvement of water resources, (ii) In situ soil and water conservation: rain water harvesting for safe disposal of surface runoff, (iii) increase in cropping intensity and (iv) alternate land use system for efficient use of lands as per land capabilityto provide stability in productivity. The model watersheds in operation have provided a fruitful experience of how development can lead to all round improvement in food and fodder production, economic condition of the farmers. Sakhomajori model, where creation of eater source worked as a catalyst and triggered the development process can be repeated under similar situations. Similar experiences have been gained at Tejpura (Jhansi), Ariel (Bareilly District) and Tejpura watersheds which have been awarded the First and Second Prizes respectively by the President of India on 14-11-1988 based on the recommendation of National Productivity Council. Alternate land use system All dry lands are not suitable for crop production. Some lands may be suitable for range/pasture management, while others for tree farming, lay farming, dry land horticulture, agro-forestry systems including alley cropping. All these systems which are alternatives to crop production are called as alternate land use systems. This system not only helps in generating much needed off-season employment in mono crop dry land but also minimizes risk, utilizes off season rains which may otherwise go waste as runoff, prevents degradation of soils and restores balance in the ecosystem. Crop production may be disastrous in the years of drought, whereas

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drought resistant grasses and trees could be remunerative. Scientists of dry land have developed many alternate land use systems which may suit different agro ecological situations. These are alley cropping, agri-horticultural system and silvi-pastoral systems which utilize the resources in better way for increased and stabilized production from dry lands. Alley Cropping: For imparting stability and providing sustainability to the farming system, a tree cum- crop system will be one most appropriate for such situations. One such system called 'alley cropping' - a version of agro-forestry system, could meet the multiple requirements of food, fodder, fuel, fertilizer etc. Alley cropping is a system in which food crops are grown in alleys formed by hedge rows of trees or shrubs. The essential feature of the system is that hedge rows are cut back at planting and kept pruned during cropping to prevent shading and to reduce competition with food crops. For example, fast growing leguminous trees such as Leucaena leucocephala or Gliricidia spp. Are planted in rows. During the cropping season, trees are lopped at about 0.5 m height. These loppings are used as mulch to reduce moisture loss and improve the nutrient status of soil. Arable crops like maize, rice, pearl millet, legumes, oilseeds etc. are planted in the alleys formed by the two rows of trees. This is also known as agri-silvi culture. Alley cropping is also a form of conservation farming which enhances soil fertility and prevents erosion. One very strong argument in favour of alley cropping is its ability to produce usable material even in years of severe drought. At Rajkot in 1985, rainfall received during the season was only 30% of the normal. There was total failure of grain production of the three legume crops tried in the system. In sole crop plots production was limited to 5.0 q/ha to 17.0 q/ha of green fodder. However, in alley cropped plots, Leucaena hedge-rows produced over 50.0 q/ha of green fodder. Agri-horticultural system: Agri-horticultural system plays an important role in dry land areas, especially in semi-arid regions where production of annual crops is not only low but also highly unstable. Fruit trees if suitably integrated in dryland farming system could add significantly to overall agricultural production including food, fuel and fodder, conservation of soil and water and stability in production and income. Dry land fruit trees being deep rooted and hardy, can better tolerated monsoonal aberrations than short duration seasonal crops. Hence, in drought year when annual crops usually fail or their production is highly depressed, fruit trees species yield considerable food, fodder and fuel. A suitable example of agri-horti-system is growing of cow pea/green gram/horse gram in inter space of ber (Zizyphus mauritiaria) at 6 x 6 m spacing at

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Hyderabad. Phalsa (Grewia asiatica) may be planted in between two ber plants in a row with a view to intensify the system. A well managed dry land orchard of ber should give 50 kg fruits per tree/year. There should be 250 plants/ha for optimized production. The grow income would touch around Rs. 50,000/ha (250 x 50 x 4), assuming that one kg ber fetches Rs. 4. One could get an additional income of Rs. 800-Rs. 1000 from green gram/cow pea (2.5-3.0 q/ha). Silvi-Pastoral System: This system is suited to marginal dry lands and is most preferable where the fodder shortages are experienced frequently. The system essentially consists of a top feed tree species carrying grasses on legumes (preferable perennial) as understorey crops. Dry land farmers having larger holdings and keeping a land fallow for a longer period for one reason on the other, should go in for this system which could provide both fodder and fuel. In a survey carried out in Andhra Pradesh, Karnataka and Maharashtra by CRIDA scientists, it was revealed that after food it is the fodder which is of paramount importance for sustaining animal wealth in rural areas. In years to come, fuel will assume greater importance. In August, 1981 Leucaena leucocephalla was planted in contour trenches 7.5 m apart, the plant to plant spacing being maintained at 2.0 m at CRIDA. Four strips at upper reaches of plot (2% slope) were put under Cenchrus ciliaris, while lower four strips were seeded with Stylosanthes hamata. The system has come up very well. Efficient Implements In order to take full advantage of annual precipitation in dry land agriculture, higher doses of energy input is essential. Farmers in dry lands have been using traditional and outdated farm equipments which not only perform poorly but also demand a lot of energy and time and post-harvest operations. Farm implements can help to conserve as much rain water in situ as possible and to harvest rain water. Shallow off season tillage with pre-monsoon showers ensures better moisture conservation and lesser weed intensity. It has resulted in 20% yield increase in sorghum in Andhra Pradesh. Deep tillage helps in increasing water in soils having textural profiles and hard pan. This has resulted in 10% yield increase in sorghum and 9% yield increase in case of caster. For in-situ moisture conservation, land has to be opened so that it can cause hurdle to flow of rain water. Tillage machines of appropriate size and type matching the power sources need to be used. Location specific seeders have been developed for dry land areas and these have shown good prospects and promise. A feature of these machines is that the seeds and fertilizers are placed in the moist zone of the soil resulting in a high percentage of seed

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germination and good crop vigour. In deciding farm mechanization in dry land areas, where farmers are generally poor, and their socio-economic condition should always be kept in mind. The foregoing discussions show that technology of crop production in dry land areas have been generated to a great extent. What is important now is to view it in socio-economic context of the farmers. Once the technology is adopted by the farmers, the contribution of dry land areas to the total production can be sizably improved and the living standards of the farmers of these areas can be improved. This has been clearly shown in selected watershed areas and what is needed is to have more watersheds identified, proper technology to be developed and implemented.

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Chapter 16: Sustainable Agriculture

The word "sustain," from the Latin sustinere (sus-, from below and tenere, to hold), to keep in existence or maintain, implies long-term support or permanence. As it pertains to agriculture, sustainable describes farming systems that are "capable of maintaining their productivity and usefulness to society indefinitely. Such systems must be resource-conserving, socially supportive, commercially competitive, and environmentally sound." " Under Food, Agriculture, Conservation, and Trade Act of 1990 (FACTA, Washington, DC,), "the term sustainable agriculture means an integrated system of plant and animal production practices having a site-specific application that will, over the long term: o satisfy human food and fiber needs; o enhance environmental quality and the natural resource base upon which the agricultural economy depends; o make the most efficient use of nonrenewable resources and on-farm resources and integrate, where appropriate, natural biological cycles and controls; o sustain the economic viability of farm operations; and o enhance the quality of life for farmers and society as a whole." Various definitions have been provided for what constitutes sustainable agriculture, ranging from the narrow focus on economics or production to the incorporation of culture and ecology. Wendell Berry has simply said, “A sustainable agriculture does not deplete soils or people." Sustainable agriculture is a form of agriculture aimed at meeting the needs of the present generation without endangering the resource base of the future generations. In order to feed the burgeoning population more food has to be produced and this has to be done without degradation of the resource base. Expanding agriculture to ecologically fragile areas means greater threat to environment. According to some, sustainable; agriculture is minimal dependence on synthetic fertilizers, pesticides and antibiotics. It is also considered as a system of' cultivation with use of manures, crop rotations and minimal tillage. A group of Canadian scientists have defined sustainable agriculture as a philosophy and system of farming with its

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roots in a set of values that reflect a state of empowerment of awareness of ecological and social realities and of one's ability to take effective action which involves design and management procedures that work with natural processes to conserve all resources, promote agro-ecosystem resilience and self-regulation, and minimize waste and environmental impact, while maintaining or improving farm profitability.

Sustainable agriculture is a balanced management system of renewable resources including soil, wildlife, forests, crops, fish, livestock, plant genetic resources and ecosystems without degradation and to provide food, livelihood for current and future generations maintaining or improving productivity and ecosystem services of these resources. Sustainable agriculture system has to be economically viable both in the short and long term perspectives.

Natural resources- not only provide food, fiber, fuel and fodder but also perform ecosystem services such as detoxification of noxious chemicals within soils, purification of waters, favourable weather and regulation of hydrological process within watersheds. Sustainable agriculture has to prevent land degradation and soil erosion. It has to replenish nutrients and control weeds, pests and diseases through biological and cultural methods.

Because agricultural systems are so diverse, based on farm size, location, crop being grown, socioeconomic background, among many other factors, and because the movement has become so widespread globally, sustainable agriculture has come to represent different things to different people. Nevertheless there are some common threads, concepts, and beliefs. In the most general terms, sustainable agriculture describes systems in which the farmer reaches the goal of producing adequate yields and good profits following production practices that minimize any negative short-and longterm side effects on the environment and the well-being of the community. The major goals of this approach are thus to develop economically viable agro- ecosystems and to enhance the quality of the environment, so that farmlands will remain productive indefinitely.

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Over time, the International Alliance for Sustainable Agriculture and an increasing number of researchers, farmers, policy-makers and organizations worldwide have developed a definition that unifies many diverse elements into a widely adopted, comprehensive, working definition: A sustainable agriculture is ecologically sound, economically viable, socially just and humane. These four goals for sustainability can be applied to all aspects of any agricultural system, from production and marketing to processing and consumption. Rather than dictating what methods can and can not be used, they establish basic standards by which widely divergent agricultural practices and conditions can be evaluated and modified, if necessary to create sustainable systems. The result is an agriculture designed to last and be passed on to future generations. Conceived in this sense, sustainable agriculture presents a positive response to the limits and problems of both traditional and modern agriculture. It is neither a return to the past nor an idolatry of the new. Rather, it seeks to take the best aspects of both traditional wisdom and the latest scientific advances. This results in integrated, nature-based agro-ecosystems designed to be self-reliant, resource-conserving and productive in both the short and long terms. Ecological soundness: Aldo Leopold summed up this concept quite simply, "A thing is right when it tends to preserve the integrity, stability and beauty of the biotic community. It's wrong when it tends to be otherwise." Derived from the Greek word for house, in current usage "eco" implies the wisdom and authority to manage in the best interests of the household. Species diversity is essential to achieve self-regulation and resultant stability. An ecologically sound agriculture also must be resource efficient in order to conserve precious resources, avoid systems toxicity and decrease input costs. Economic viability: Essential to this perspective is that there be a positive net return, or at least a balance, in terms of resources expended and returned. Ignored in current accounting are numerous subsidies that make agriculture appear economically viable, and hidden costs such as loss of wildlife and health care costs from chemical exposure. In addition to short-term market factors relating to supply and demand, real viability requires an understanding of a number of other considerations, including relative risk and qualitative factors (security, beauty, satisfaction), which are often ignored in economists' models because they are difficult to quantify. Asked Leopold, "Do economists know about lupines?" Humaneness: Agriculture must embody our highest values (kindness, mercy, sympathy) in all aspects- from respect for life to the protection of diverse cultures. Humans clearly have an

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interdependent relationship with animals- from their physical labour and companionship to their invaluable recycling of organic matter and provision of food- but too often animals are seen only as objects to be exploited. Humane agriculture must be based on a fundamental respect for animals and recognition of their rights. Cultural roots are as important to agriculture as plant roots. Without strong communities and vibrant cultures, agriculture will not flourish. The increasing substitution of the term "agribusiness" for "agriculture" reflects a fundamental shift to a monetized economy in which everything, including human beings, is assigned a certain value. Such a system leads to an increased sense of competition, isolation and alienation. As rural societies break down, their values are lost as the backbone of the larger society. Without such a backbone, agriculture is neither humane nor sustainable. Sustainable agriculture involves farming systems that are environmentally sound, profitable, productive, and compatible with socioeconomic conditions (J. Pesek, in Hatfield and Karlen, Sustainable Agriculture Systems). The definitions of sustainable agriculture as described above and various others those in the literature, may be analyzed in terms of three components viz., unit; form and criteria. The unit referred to by the authors to define sustainable agriculture are as follow: o Development of future generations; o Farming or agriculture; o Agricultural programme policy or practice; o Agro-ecosystem; o Integrated systems of plant and animal production practices; land use system and o Natural resource base. In terms of economy it was referred to as follow: o Maintenance or enhancement of biological production and productivity; o Development that meet the needs of future generations; o Attainment and continued satisfaction of changing human needs; o Economically viable; o Makes use of low-cost inputs and less dependence on high inputs; o More dependence on intensive management; o Use of the very best of the technology in a balanced and well managed system; o Make efficient management of renewable, non-renewable and human resources; o Steady state between what is harvested and what is replenished;

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o Maintains soil fertility; and o Capacity to recover from stresses and disturbances. In terms of ecology it was referred to as follow: o Conserves land, water, plant and animal genetic resources; o Development without compromising the ability of future generations to meet their own needs; o Maintains soil fertility; o Conserves man-made resources; is environmentally non-degradable; o Ecologically sound; o Enhance the integrity, diversity of the managed agricultural ecosystem; o Maintains a steady state between what is harvested and what is replenished; o Utilizes natural biological cycles and controls; o Minimizes dependence of production on external inputs; and resilience of resource base or capacity to recover from stresses and disturbances. A few authors have referred sustainable agriculture in terms of social benefits also viz. socially acceptable, socially just, culturally adapted, equity of resource access and integrating into existing social organization. It can be seen that benefits of farm diversification (Farming system approach) and the conditions to be fulfilled for a system to be pronounced as sustainable are similar. The criteria used by the authors while defining sustainable agriculture are as follows: o Maintenance or constant; o Enhancement; and o Long term; Based on the above analysis, sustainable agriculture is referred to be an agro ecosystem which maintains or enhances biological production and productivity and results in attainment and continued satisfaction of changing human needs by conserving and efficiency using the renewable, nonrenewable and human resources.

Some Key Undesirable Side Effects of Modern Agriculture  Unsustainable irrigation programs throughout the world are resulting in an undesirable buildup of salinity and toxic mineral levels in one out of five hectares

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under irrigation. Thus, agricultural water, a nonrenewable resource whose use has tripled globally since 1950, has to be used more efficiently to minimize salinization problems.  Excessive soil erosion, in the range of fifteen to forty tons per hectare annually, results in the loss of productive farmland in many parts of the world. Forested areas, a refuge for wildlife and biodiversity (biological diversity), are then often turned into agricultural fields to compensate for the loss of the abandoned eroded areas.  The indiscriminate use of pesticides is affecting human health and wildlife populations, as first reported to the population at large in Rachel Carson's book Silent Spring (1962).  The increased concentration of farms into larger and larger farm holdings is reducing the number of small family farms, believed by many to represent the heart of rural communities and to be key stewards of the environment.  The trend toward larger farms and plantation-type monocultures is leading to a loss of global biodiversity. Biodiversity, many argue, may be a critical ecological feature that allows the continued survival of humans on earth.  The excessive reliance on synthetic fertilizers, and the improper use and disposal of animal wastes is leading to the breakup of natural nutrient cycles. This causes an undesirable buildup of nutrients and salts in aquifers, affecting wildlife in aquatic habitats.

Driving forces for sustainable agriculture How have we come to reconsider our food and fiber production in terms of sustainability? What are the ecological, economic, social and philosophical issues that sustainable agriculture addresses? The long-term viability of our current food production system is being questioned for many reasons. The prevailing agricultural system, variously called "conventional farming," "modern agriculture," or "industrial farming" has delivered tremendous gains in productivity and efficiency. Food production worldwide has risen in the past 50 years;

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the World Bank estimates that between 70 % and 90 % of the recent increases in food production are the result of conventional agriculture rather than greater acreage under cultivation. Philosophical underpinnings of industrial agriculture include assumptions that "a) nature is a competitor to be overcome; b) progress requires unending evolution of larger farms and depopulation of farm communities; c) progress is measured primarily by increased material consumption; d) efficiency is measured by looking at the bottom line; and e) science is an unbiased enterprise driven by natural forces to produce social good." Significant negative consequences have come with the bounty associated with industrial farming. Concerns about contemporary agriculture are presented below. While considering these concerns, keep the following in mind: a) interactions between farming systems and soil, water, biota, and atmosphere are complex—we have much to learn about their dynamics and long term impacts; b) most environmental problems are intertwined with economic, social, and political forces external to agriculture; c) some problems are global in scope while others are experienced only locally; d) many of these problems are being addressed through conventional, as well as alternative, agricultural channels; e) the list is not complete; and f) no order of importance is intended Ecological Concerns Agriculture profoundly affects many ecological systems. Negative effects of current practices include the following: o Decline in soil productivity can be due to wind and water erosion of exposed topsoil; soil compaction; loss of soil organic matter, water holding capacity, and biological activity; and salinization of soils and irrigation water in irrigated farming areas. Desertification due to overgrazing is a growing problem, especially in parts of Africa. o Agriculture is the largest single non-point source of water pollutants including sediments, salts, fertilizers (nitrates and phosphorus), pesticides, and manures. Pesticides from every chemical class have been detected in groundwater and are commonly found in groundwater beneath agricultural areas; they are widespread in the nation’s surface waters. Eutrophication and "dead zones" due to nutrient runoff affect many rivers, lakes, and oceans. Reduced water quality impacts agricultural production, drinking water supplies, and fishery production. Economic and Social Concerns

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Economic and social problems associated with agriculture cannot be separated from external economic and social pressures. As barriers to a sustainable and equitable food supply system, however, the problems may be described in the following way: o Economically, agricultural sector includes a history of increasingly large expenditures and corresponding government involvement in planting and investment decisions; widening disparity among farmer incomes; and escalating concentration of agribusiness—industries involved with manufacture, processing, and distribution of farm products—into fewer and fewer hands. Market competition is limited. Farmers have little control over farm prices, and they continue to receive a smaller and smaller portion of consumer money spent on agricultural products. o Economic pressures have led to a tremendous loss of farms, particularly small farms, and farmers during the past few decades. This contributes to the disintegration of rural communities and localized marketing systems. Economically, it is very difficult for potential farmers to enter the business today. Productive farmland also has been pressured by urban and suburban sprawl.

Impacts on Human Health Potential health hazards are tied to sub-therapeutic use of antibiotics in animal production, and pesticide and nitrate contamination of water and food. Farm workers are poisoned in fields, toxic residues are found on foods, and certain human and animal diseases have developed resistance to currently used antibiotics. Philosophical Considerations Historically, farming played an important role in our development and identity. From strongly agrarian roots, we have evolved into a culture. Can sustainable and equitable food production be established when most consumers have so little connection to the natural processes that produce their food? What intrinsically human values have changed and will change with the decline of rural life and farmland ownership? World population continues to grow. According to recent United Nations population projections, the world population will grow from 5.7 billion in

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1995 to 9.4 billion in 2050, 10.4 billion in 2100, and 10.8 billion by 2150, and will stabilize at slightly under 11 billion around 2200. Finally, the challenge of defining and dealing with the problems associated with today's food production system is inherently laden with controversy and emotion. "It is unfortunate, but true, that many in the agriculture community view sustainable agriculture as a personal criticism, or an attack, on conventional agriculture of which they are justifiably proud. Basic Features and Concepts of Sustainable Systems o The need to maintain or improve soil quality and fertility. This is often attained by increasing the organic matter content of the soil, and by minimizing losses from soil erosion. o Production programs are designed to improve the efficiency of resource utilization. This will result in the most cost-effective use of water, fertilizers, and pesticides. o An attempt is made to improve internal nutrient cycles on the farm, which will reduce the dependence on external fertilizers..

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Chapter 17: Nanotechnology in crop production The First Green Revolution during 1970 s targeted to the four basic elements of production system viz. semi-dwarf high yielding varieties of rice and wheat, extensive use of irrigation, fertilizers and agro-chemicals and consequently resulted in terrific increase in the agricultural production. However, the agricultural production is experiencing a plateau nowadays, which has adversely affected the livelihood base of the farming community at large. In fact, the country is in need of a Second Green Revolution (Singh 2012). Nanoscale science and nanotechnologies are envisioned to have the potential to revolutionize agriculture and food systems (Norman and Hongda 2013). The term "Nanotechnology" was first defined in 1974 by Norio Taniguchi of the Tokyo Science University. Nanotechnology, abbreviated to "Nanotech", is the study of manipulating matter on an atomic and molecular scale. By and large nanotechnology deals with structures in the size range between 1 to 100 nm and involves developing materials or devices within that size (Arivalagan et al. 2011). At the nanoscale the matter presents altered properties which are novel and very different from those observed at macroscopic level. . The change in properties is due to the reduced molecular size and also because of changed interactions between molecules. The properties and possibilities of nanotechnology, which have great interest in agricultural revolution, are high reactivity, enhanced bioavailability and bioactivity, adherence effects and surface effects of nanoparticles (Gutiérrez et al. 2011). Customized manufactured products are made from atoms; their properties depend on how those atoms are arranged. Nanotechnology may be able to create many new materials and devices having vast range of applications, such as medicine (e.g. engineered stem cells, implantable devices, customized antibodies), electronics (e.g. nano-chips, nano-sensors), materials (e.g. green concrete, smart polymers), food production (e.g. nano-modified, nanoadditives) and energy creation (e.g., solar cells, light-trapping photo-voltaics) (Lu and Bowles 2013). Other properties and possibilities of nanotechnology, which have great interest in agricultural revolution, are high reactivity, enhanced bioavailability and bioactivity, adherence effects and surface effects of nanoparticles (Gutiérrez et al. 2011).

The key focus areas for nanotechnology agricultural research are:

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 Nanogenetic manipulation of manipulation of agricultural crops  Agricultural Diagnostics, Drug Delivery and Nanotechnology  Controlled release of nanofertilizers and nano-complexes  Nano-Biosensors  Nano pesticides and Nanoherbicides  Nano-Bio farming 1. Nanogenetic Manipulation of Agricultural Crops Nano biotechnology offers a new set of tools to manipulate the genes using nanoparticles, nanofibers and nano capsules. Properly functionalized nanomaterial serve as vehicles and could carry a larger number of genes as well as substances able to trigger gene expression or to control the release of genetic material throughout time in plants (Nair et al. 2010 and Gutiérrez et al. 2011). Proponents say nanotechnology is heading towards taking the genetic engineering of agriculture to the next level down atomic engineering. Atomic engineering could enable the DNA of seeds to be rearranged in order to obtain different plant properties including colour, growth season and yield. Nanofiber arrays with potential applications in drug delivery, crop engineering and environmental monitoring can deliver genetic material to cells quickly and efficiently. Controlled biochemical manipulations in cells have been achieved through the integration of carbon nanofibers which are surface modified with plasmid DNA (Miller and Kinnear, 2007). 2. Nanosensors for monitoring soil conditions and plant growth hormone The proficient use of agricultural natural assets like water, nutrients and chemicals during farming as nanosensors is user friendly. It makes use of nanomaterials and global positioning systems with satellite imaging of fields and might make farmers to detect crop pests or facts of stress such as drought. Nanosensors disseminated in the field are able to sense the existence of plant viruses and the level of soil nutrients. They also minimize fertilizer consumption and environmental pollution. Nano-encapsulated slow- release fertilizers have been widely used To check the quality of agricultural manufacture, nanobarcodes and nanoprocessing could be used the idea of grocery barcodes for economical, proficient, rapid effortless decoding and recognition of diseases. They created nanobarcodes that may tag perhaps multiple pathogens in a farm, which may simply be detected using any fluorescent based tools. Nanotechnocrates are capable of studying plant’s regulation of hormones such as auxin, which is accountable for root growth

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and seedling organization. Nanosensors that react with auxin have been developed. This is a step forward in auxin research, as it helps scientists to know how plant roots acclimatize to their environment, particularly to marginal soils. For the improvement of soil retention of water or liquid by Nanomaterials, e.g. zeolites and nano-clays, for retention of water or liquid agrochemicals in the soil for their slow release to the plants. 3. Detoxification or remediation of harmful pollutants Using synthetic clay nanomineral does not require expensive laboratory equipment for arsenic removal. The water to be filtered is percolated through a column of hydrotalcite (synthetic clay mineral). suggests that this technology can be coupled with leaching through porous pots or filter candles, the technology available in many developing countries to filter organisms from drinking water. Zinc oxide nanoparticles can be used to remove arsenic using a point-of-source purification device. Nanoscale zero-valent iron is the most widely used the set of nanomaterials that could be deployed to remediate pollutants in soil or groundwater. Other nanomaterials that could be used in remediation include nanoscale zeolites, metal oxides, carbon nanotubes and fibers, enzymes, various noble metals (mainly as bimetallic nanoparticles) and titanium dioxide. Nanoparticle filters can be used to remove organic particles and pesticides (for example, dichorodiphenyl-trichloroethane (DDT), endosulfan, malathion and chlor-pyrifos) from water. A variety of nanoparticle filters have been used in remediation of waste sites in developed countries . 4. Nanocapsules for efficient delivery of pesticides, fertilizers and other agrochemicals Nanoencapsulation is a process through which chemicals like insecticides are slowly but efficiently released to a particular host plant for insect pest control. Nanoencap-sulation with nanoparticles in the form of pesticides allows for proper absorption of the chemicals into the plants. This process can also deliver DNA and other desired chemicals into plant tissues for protection of host plants against insect pests . Release mechanisms of nanoencap-sulation include diffusion, dissolution, biodegradation and osmotic pressure with specific pH. Nanoencapsulation is cur-rently the most promising technology for protection of host plants against insect pests. Now, most leading chemical companies focus on formulation of nanoscale pesticides for delivery into the target host tissue through nanoencapsulation. Fertilizer plays a pivotal role in agriculture production (35 to 40%). To enhance nutrient use efficiency and overcome the chronic problem of eutrophication, nano-fertilizer might be a best alternative. Nanofertilizers are

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synthesized in order to regulate the release of nutrients depending on the requirements of the crops, and it is also reported that nanofertilizers are more efficient than ordinary fertilizer. Nanofertilizers could be used to reduce nitrogen loss due to leaching, emissions, and long-term incorporation by soil microor-ganisms. They could allow selective release linked to time or environmental condition. Slow controlled release fertilizers may also improve soil by decreasing toxic effects associated with fertilizer over- application . Technologies such as encapsulation and controlled release methods have revolutionised the use of pesticides and herbicides. Pesticides inside nanoparticles are being developed that can be timely released or have release linked to an environmental trigger. Combined with a smart delivery system, herbicide could be applied only when necessary, resulting in greater production of crops and less injury to agricultural workers. Many companies make formulations which contain nanoparticles within the size ranges of 100-250 nm; they are able to dissolve in water more effectively than existing ones (thus increasing their activity). Other companies employ suspensions of nanoscale particles (nanoemulsions) which can be either water or oil-based and contain uniform suspensions of pesticidal or herbicidal nanoparticles in the range of 200-400 nm. These can be easily incorporated in various media such as gels, creams, liquids among others, and have multiple applications for preventative measures, treatment or preservation of harvested products. Syngenta, world’s largest agrochemical corporation, is using nanoemulsions in its pesticide products. One of its successful growth regulating products is the Primo MAXX® plant growth regulator, which if applied prior to the onset of stress such as heat, drought, disease or traffic can strengthen the physical structure of turf grass and allow it to withstand ongoing stresses throughout the growing season. Another encapsulated product from Syngenta delivers a broad control spectrum on primary and secondary insect pests of cotton, rice, peanuts and soybeans. Marketed under the name Karate® ZEON this is a quick release microencapsulated product containing the active compound lambda-cyhalothrin (a synthetic insecticide based on the structure of natural pyrethrins) which breaks open on contact with leaves. In contrast, the encapsulated product “gutbuster” only breaks open to release its contents when it comes into contact with alkaline environments, such as the stomach of certain insects. Application of nanotechnology in the agri-food sector is still a relatively new concept; the main reasons for its late incorporation are mainly due to issues relating to product labelling, potential consumer health risks, and a lack of unifying regulations and guidelines on nanotechnology governance

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The nanoparticles like Ag, ZnO and CuO are relevant in the growth of agriculture by bioactivity and bio-modification. For Fertilizers the use of Nano capsules, nano particles and viral capsids is useful for the enhancement of nutrients absorption by plants and the delivery of nutrients to specific sites. 5. Nanotechnology in organic farming Organic farming has been a long-desired goal to increase productivity (that is, crop yields) with low input (that is, fertilizers, pesticides, herbicides among others) through monitoring environmental variables and applying targeted action. Organic farming makes use of computers, GPS systems, and remote sensing devices to measure highly localized environmental conditions, thus determining whether crops are growing at maximum efficiency or precisely identifying the nature and location of problems. By using centralised data to determine soil conditions and plant development, seeding, fertilizer, chemical and water use can be fine-tuned to lower production costs and potentially increase production all benefiting the farmer. Precision farming can also help to reduce agricultural waste and thus keep environmental pollution to a minimum. The product for plant production with Nano capsules, nano particles, nano emulsions and viral capsids acts as smart delivery systems of active ingredients for disease and pest control in plants. The carbon nanotubes plays a beneficial role in mustard plant growth and the TiO2 treatment by Nitrogen. 6. Nanoherbicides The easiest way to eliminate weeds is to destroy their seed banks in the soil and prevent them from germinating when weather and soil conditions become favourable for their growth. Being very small, nanoherbicides will be able to blend with the soil, eradicate weeds in an eco- friendly way without leaving any toxic residues, and prevent the growth of weed species that have become resistant to conventional herbicides. Weeds survive and spread through underground structures such as tubers and deep roots. Ploughing infected fields while removing weeds by hand can make these unwanted plants spread to uninfected areas. Whether the nano application is due to a nanosized active ingredient or the creation of a nanosized formulation through the use of an adjuvant, the use of nano application is same. If the active ingredient is combined with a smart delivery system, herbicide will be applied only when necessary according to the conditions of the agriculture field. Lower agricultural yields are obtained in soils contaminated with weeds and weed seeds. Improvements in the efficacy of herbicides through

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the use of nanotechnology could result in more crop production without causing any harmful effects to agricultural workers who are supposed to physically remove weeds if no application of herbicides is practised 7. Nanoparticles and plant disease control Some of the nano particles that have entered into the arena of controlling plant diseases are nanoforms of carbon, silver, silica and alumino-silicates. At such a situation, nanotechnology has astonished scientific community because at nano-level, material shows different properties. The use of nano size silver particles as antimicrobial agents has become more common as technology advances, making their production more economical. Since silver displays different modes of inhibitory action to microorganisms, it may be used for controlling various plant pathogens in a relatively safer way compared to commercially used fungicides. Silver is known to affect many biochemical processes in the microorganisms including the changes in routine functions and plasma membrane. The silver nanoparticles also prevent the expression of ATP production associated proteins. In a nutshell, the precise mechanism of bio molecules inhibition is yet to be understood. Nanoparticles from plants Production of nanomaterials through the use of engineered plants or microbes and through the processing of waste agricultural products. Thus, use of nanoparticles has been considered an alternate and effective approach which is eco-friendly and cost effective for the control of pathogenic microbes[. These nanoparticles have a great potential in the management of plant diseases compared to synthetic fungicides. Zinc oxide (ZnO) and magnesium oxide (MgO) nanoparticles are effective antibacterial and anti- odour agents. The increased ease in dispensability, optical transparency and smooth-ness make ZnO and MgO nanostructures an attractive antibacterial ingredient in many products. Both have also been proposed as an anti-microbial preservative for wood or food products. Properly functionalized nanocap-sules provide better penetration through cuticle and allow slow and controlled release of active ingredients on reaching the target weed. The use of such nano- biopesticide is more acceptable since they are safe for plants and cause less environmental pollution in comparison to conventional chemical pesticides. Nanosilver is the most studied and utilized nano particle for bio-system. It has long been known to have strong inhibitory and bactericidal effects as well as a broad spectrum of antimicrobial activities Silver nanoparticles, which have high surface area and high fraction of surface atoms, have high antimicrobial effect compared to the bulk. Fungicidal properties of nano-size silver colloidal solution are used as an

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agent for antifungal treatment of various plant pathogens; the most significant inhibition of plant pathogenic fungi was observed on potato dextrose agar (PDA) and 100 ppm of AgNPs . 8. Nanoparticles as pesticides Nanoparticles are also effective against insects and pests. Nanoparticles can be used in the preparation of new formulations like pesticides, insecticides and insect repellants. Torney reviewed that nanotechnology has promi-sing applications in nanoparticle gene mediated DNA transfer. It can be used to deliver DNA and other desired chemicals into plant tissues for protection of host plants against insect pests. Porous hollow silica nanoparticles (PHSNs) loaded with validamycin (pesticide) can be used as efficient delivery system of water-soluble pesticide for its controlled release. Such controlled release behaviour of PHSNs makes it a promising carrier in agriculture, especially for pesticide controlled delivery whose imme-diate as well as prolonged release is needed for plants. According to, oil in water (nano-emulsions) was useful for the formulations of pesticides and these could be effective against the various insect pests in agriculture. Similarly, essential oil-loaded solid lipid nanoparticles were also useful for the formulations of nano-pesticides. Nanosilica, a silica product, can be effectively used as a nanopesticide reviewed the use of nano-silica as nano-insecticide. The mechanism of control of insect pest using nano-silica is based on the fact that insect pests used a variety of cuticular lipids for protecting their water barrier and thereby prevent death from desiccation. But here, the nanosili caparticles when applied on plant surface, cause death by physical means of insects by being absorbed into the cuticular lipids. Modified surface charged hydrophobic nano-silica (∼3-5 nm) could be successfully implemented to manage a variety of ectoparasites of animals and agricultural insect pests. The insecticidal activity of poly-ethylene glycol-coated nanoparticles loaded with garlic essential oil against adult Tribolium castaneum insect was found in stored products. It has been observed that the control efficacy against adult T. castaneum was about 80%; presumably due to the slow and persistent release of the active components from the nanoparticles. The applications of diverse kind of nanoparticles viz. silver nanoparticles, aluminium oxide, zinc oxide and titanium dioxide in the management of rice weevil and grasserie disease in silk worm (B. mori) are caused by Sitophilus oryzae and baculovirus BmNPV (B. mori nuclear polyhedrosis virus, respectively studied the insecticidal activity of nanostructured alumina against two insect pests viz. S. oryzae L. and Rhyzopertha dominica (F.),

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which are major insect pests in stored food supplies throughout the world. Significant mortality was observed after 3 days of continuous exposure to nanostructured alumina-treated wheat. Therefore, compared to commercially available insecti-cides, inorganic nanostructured alumina may provide a cheap and reliable alternative for control of insect pests, and such studies may expand the frontiers for nanoparticle-based technologies in pest management.

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Chapter 18: Crop modeling: A tool for agricultural research

INTRODUCTION Studies on crop production are traditionally carried out by using conventional experience-based agronomic research, in which crop production functions are derived from statistical analysis without referring to the underlying biological or physical principles involved. The application of correlation and regression analysis has provided some qualitative understanding of the variables and their interactions that were involved in cropping systems and has contributed to the progress of agricultural science (Kumar and Chaturevdi, 2009). However, the quantitative information obtained from this type of analysis is very site specific. The information obtained can only be reliably applied to other sites where climate, important soil parameters and crop management are similar to those used in developing the original functions. Thus, the quantitative applicability of regression based crop yield models for decision making is severely limited. In addition, because of the unavoidable variability associated with weather, more than 10 years is required to develop statistical relationships that are useful in agricultural decision making. Ref Statistical evidence based on long-term studies generally show that more than 40% of the total variation is usually associated with experimental error (Jame and Cutforth, 1996). As knowledge is accumulated, results obtained from observation change from being qualitative to being quantitative and mathematics can be adopted as the tool to express biological hypotheses. Advances in computer technology have made possible the consideration of the combined influence of several factors in various interactions. As a result, it is possible to quantitatively combine the soil, plant, and climatic systems to more accurately predict crop yield. Thus, with the availability of inexpensive and powerful computers and with the growing popularity of the application of integrated systems to agricultural practices, a new era of agricultural research and development is emerging (Jones et al, 1993). In crop growth modeling, current knowledge of plant growth and development from various disciplines, such as crop physiology, agrometeorology, soil science and agronomy, is integrated in a consistent, quantitative and process-oriented manner.

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Computerized decision support systems that allow users to combine technical knowledge contained in crop growth models with economic considerations and environmental impact evaluations are now available. DSSAT (Tsuji et al. 1994) is an excellent example of a management tool that enables individual farmers to match the biological requirement of a crop to the physical characteristics of the land to obtain specified objectives. In the Ghanaian research sector, modeling is a new discipline and basic background information on the application of models in research is not easily available. Lack of awareness about model structure, possibilities and limitations have been identified as hindrance to model application in our society What is crop modeling?

Modeling is the use of equations or sets of equations to represent the behaviour of a system. In effect crop models are computer programmes that mimic the growth and development of crops (USDA, 2007). Model simulates or imitates the behaviour of a real crop by predicting the growth of its components, such as leaves, roots, stems and grains. Thus, a crop growth simulation model not only predicts the final state of crop production or harvestable yield, but also contains quantitative information about major processes involved in the growthand development of the crop. Reactions and interactions at the level of tissues and organs are combined to form a picture of the crop’s growth processes. Brief history of crop modeling

The development of crop growth simulation models has been a natural progression of scientific research. Jame (1992) reviewed the history of attempts to quantify the relationships between crop yield and water use from the early work on simple water-balance models in the 1960s to the development of crop growth simulation models in the 1980s. Two decades ago, it was not certain whether the complex physical, physiological and morphological processes involved in the growth of a plant could be described mathematically, except perhaps in some controlled environments. Thus, the relevance of crop growth simulation models in crop agronomy was challenged (Passioura 1973). However, during the past 40 years, crop growth modeling has changed dramatically.

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In the sixties, the first attempt to model photosynthetic rates of crop canopies was made (de Wit, 1965). The results obtained from this model were used among others, to estimate potential food production for some areas of the world and to provide indications for crop management and breeding (de Wit, 1967; Linneman et al., 1979). This was followed by the construction of an Elementary Crop growth Simulator (ELCROS) by de Wit et al. in 1970. This model included the static photosynthesis model and crop respiration was taken as a fixed fraction per day of the biomass, plus an amount proportional to the growth rate. In addition, a functional equilibrium between root and shoot growth was added (Penning de Vries et al., 1974). The introduction of micrometeorology in the models (Goudriaan, 1977) and quantification of canopy resistance to gas exchanges allowed the models to improve the simulation of transpiration and evolve into the Basic Crop growth Simulator (BACROS) (de Wit and Goudriaan, 1978). To help resource poor farmers in the tropics and sub tropics IBSNAT (International Benchmark Sites Network for Agrotechnology Transfer) began the development of a model in 1982. This was under a contract from the U.S. Agency for International Development to the University of Hawaii at Manoa, USA. IBSNAT was an attempt to demonstrate the effectiveness of understanding options through systems analysis and simulation for ultimate benefit of farm households across the globe. The purposes defined for the IBSNAT project by its technical advisory committee were to understand ecosystem processes and mechanisms, synthesize from an understanding of processes and mechanisms, a capacity to predict outcomes and enable IBSNAT clientele to apply the predictive capability to control outcomes. The major product of IBSNAT was the Decision Support System for Agro- Technology Transfer (DSSAT) which is currently being used as a research and teaching tool. As a research tool its role is to derive recommendations concerning crop management and to investigate environmental and sustainability issues. The DSSAT products enable users to match the biological requirements of crops to the physical characteristics of land to provide them with management options for improved land use planning. The package consists of: data base management system for soil, weather, genetic coefficients, and management inputs, Crop simulation models, series of utility and weather generation programs and strategy evaluation program to evaluate options including choice of variety, planting date, plant

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population density, row spacing, soil type, irrigation, fertilizer application, initial conditions on yields, water stress in the vegetative or reproductive stages of development, and net returns. In effect, DSSAT has the potential to reduce substantially the time and cost of field experimentation necessary for adequate evaluation of new cultivars and new management systems. Types of models Depending upon the purpose for which it is designed the models are classified into different groups or types. A few of them are: Empirical models: These are direct descriptions of observed data and are generally expressed as regression equations (with one or a few factors) and are used to estimate the final yield. This approach is primarily one of examining the data, deciding on an equation or set of equations and fitting them to data. These models give no information on the mechanisms that give rise to the response. Examples of such models include those used for such experiments as the response of crop yield to fertilizer application, the relationship between leaf area and leaf size in a given plant species and the relationship between stalk height alone or coupled with stalk number and/or diameter and final yield. Mechanistic models: A mechanistic model is one that describes the behaviour of the system in terms of lower- level attributes. Hence, there is some mechanism, understanding or explanation at the lower levels (eg. Cell division). These models have the ability to mimic relevant physical, chemical or biological processes and to describe how and why a particular response occurs. The modeler usually starts with some empirism and as knowledge is gained additional parameters and variables are introduced to explain crop yield. The system is therefore broken down into components and assigned processes. Static and dynamic models: A static model is one that does not contain time as a variable even if the end- products of cropping systems are accumulated over time. In contrast dynamic models explicitly incorporate time as a variable and most dynamic models are first expressed as differential equations

Deterministic models: A deterministic model is one that makes definite predictions for quantities (e.g. crop yield or rainfall) without any associated probability distribution, variance, or random element. However, variations due to inaccuracies in recorded data and to

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heterogeneity in the material being dealt with are inherent to biological and agricultural systems (Brockington, 1979).In certain cases, deterministic models may be adequate despite these inherent variations but in others they might prove to be unsatisfactory e.g. in rainfall prediction. The greater the uncertainties in the system, the more inadequate deterministic models become. Stochastic models: When variation and uncertainty reaches a high level, it becomes advisable to develop a stochastic model that gives an expected mean value as well as the associated variance. However, stochastic models tend to be technically difficult to handle and can quickly become complex. Hence, it is advisable to attempt to solve the problem with a deterministic approach initially and to attempt the stochastic approach only if the results are not adequate and satisfactory. Simulation models: These form a group of models that is designed for the purpose of imitating the behaviour of a system. Since they are designed to mimic the system at short time intervals (daily time-step), the aspect of variability related to daily change in weather and soil conditions is integrated. The short simulation time-step demands that a large amount of input data (climate parameters, soil characteristics and crop parameters) be available for the model to run. These models usually offer the possibility of specifying management options and they can be used to investigate a wide range of management strategies at low costs. Optimizing models: These models have the specific objective of devising the best option in terms of management inputs for practical operation of the system. For deriving solutions, they use decision rules that are consistent with some optimizing algorithm. This forces some rigidity into their structure resulting in restrictions in representing stochastic and dynamic aspects of agricultural systems. Crop model applications Simulation modeling is increasingly being applied in research, teaching, farm and resource management and policy analysis and production forecasts. They can be applied, namely, research, crop system management and policy analysis.

Research understanding: Model development ensures the integration of research understanding acquired through discreet disciplinary research and allows the identification of the major factors that drive the system and can highlight areas where knowledge is

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insufficient. Thus, adopting a modeling approach could contribute towards more targeted and efficient research planning Integration of knowledge across disciplines: Adoption of a modular framework allows for the integration of basic research that is carried out in different regions, countries and continents. This ensures a reduction of research costs (e.g., through a reduction in duplication of research) as well as the collaboration between researchers at an international level. Improvement in experiment documentation and data organization: Simulation model development, testing and application demand the use of a large amount of technical and observational data supplied in given units and in a particular order. Data handling forces the modeler to resort to formal data organization and database systems. Site-specific experimentation: Specific site selection can be using the model Crop models can be used to predict crop performance in regions where the crop has not been grown before or not grown under optimal conditions. Yield analysis: When a model with a sound physiological background is adopted, it is possible to extrapolate to other environments. Simulation models are used to climatically- determined yield in various crops. Through the modeling approach, quantification of yield reductions caused by non-climatic causes (e.g., delayed sowing, crop spacing, soil fertility, pests and diseases) becomes possible. Simulation models have also been reported as useful in separating yield gains into components due to changing weather trends, genetic improvements and improved technology. Climate change projections: The variability of our climate and especially the associated weather extremes is currently one of the concerns of the scientific as well as general community. The application of crop models to study the potential impact of climate change has been widely used across the continents. The increased concentration of carbon dioxide and other greenhouse gases are expected to increase the temperature of earth. Crop production is highly dependent on variation in weather and therefore any change in global climate will have major effects on crop yields and productivity. Elevated temperature and carbon dioxide affects the biological processes like respiration, photosynthesis, plant growth, reproduction, water use etc. Proper understanding of the effects of climate change will therefore help scientists to guide farmers to make crop management decisions such as selection of crops, cultivars, sowing dates and irrigation scheduling to minimize the risks

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Scoping best management practices: Simulation can be done to determine the best management practices under a certain cropping system. In the past, the main focus of agronomic research has been on crop production. Recently, in addition to profitable crop production, the quality of the environment has become an important issue that agricultural producers must address. Agricultural managers require strategies for optimizing the profitability of crop production while maintaining soil quality and minimizing environmental degradation. Solutions to this new challenge require consideration of how numerous components interact to effect plant growth. To achieve this goal, future agricultural research will require considerably more effort and resources than present research activity. Models having chemical leaching or erosion components can be used to determine the best farming practices over the long-term. Investment decisions like purchase of irrigation systems can be taken with an eye on long term usage of the equipment when irrigation schedules are done using the modeling approach. Yield forecasting: Reasonably precise estimates of crop yield over large areas before the actual harvest are of immense value to both the researcher and the farmer in terms of planning. In this approach the model is run using actual weather data during the cropping season for the geological region of interest. Weather years for typical years are used to continue simulations until harvest. Breeding and introduction of a new crop variety: Development and release of a variety is a complex process that may extend over a period of 5 – 15 years. Since the modeling systems approach integrates different components of agro ecosystems, it can be used to conduct multi-location field experiments to understand genotype by environment (G x E). Such studies can help in reducing the number of sites/seasons required for field evaluation and thus increase the efficiency of the process of variety development.

Crop model applications in crops research: Amissah-Arthur and Jagtap (1995) successfully assessed nitrogen requirements by maize across agroecological zones in Nigeria using CERES-maize model. Hammer et al. (1995) using local weather and soil information correlated peanut yields with estimates from PEANUTGRO, a model in the CERES family

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2 and gave a regression with high coefficient (r = 0.93) of variation. Clifford et al (2000) tested the effects of elevated CO2, drought and temperature on the water relations and gas exchange of groundnut. Hammer and Muchow (1994) used the modeling approach to quantify climatic risk to sorghum in Australia’s semi arid tropics and subtropics. The EPIC, ALMANAC, CROPSYST, WOFOST, ADEL and CERES-Maize models are being successfully used to simulate maize crop growth and yield. The SORKAM, SorModel, and SORGF models are being used to address specific tasks of sorghum crop management. CERES – pearl millet model, CROPSYST, PmModels are being used to study the suitability and yield simulation of pearl millet genotypes across the globe. Similarly, the two most common growth models used in application for cotton are the GOSSYM (Mckinion et al, 1989) and COTONS models. On the same analogy the PNUTGRO (Boote et al, 1989) for groundnut, CHIKPGRO for chick pea, WTGROWS for wheat, SOYGRO for soybean, BEANGRO (Hogenboom et al, 1994) for beans QSUN for sunflower are in use to meet the requirements of farmers, scientists, decision makers, etc., at present. The APSIM, GROWIT added with several modules are being used in crop rotation, crop sequence and simulation studies involving perennial crops. Model Parameterization (calibration, evaluation and validation) Model calibration involves the modification of some model parameters such that data simulated by the error- free model fit the observed data. In many instances, even if a model is based on observed data, simulated values do not exactly comply with the observed data and minor adjustments have to be made for some parameters. Non- compliance may arise from sampling errors as well as from incomplete knowledge of the system. Alternatively, it may arise when the model is used in a situation that is markedly different from the one under which it was developed.

The model validation stage involves the confirmation that the calibrated model closely represents the real situation. The procedure consists of a comparison of simulated output and observed data that have not been previously used in the calibration stage. However, validation of all the components is not possible due to lack of detailed datasets and the option of validating only the determinant ones are adopted. For example, in a soil- water crop model,

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it is important to validate the extractable water and leaf area components since biomass accumulated is heavily dependent on these. Evapotranspiration also becomes a determinant to validate. Crop model limitations: Crop models are not able to give accurate projections because of inadequate understanding of natural processes and computer power limitation. As a result, the assessments of possible effects of climate changes, in particular, are based on estimations. Moreover, most models are not able to provide reliable projections of changes in climate variability on local scale, or in frequency of exceptional events such as storms and droughts (Shewmake, 2008). General Circulatory Models (GCMs) have so far not been able to produce reliable projections of changes in climate variability, such as alterations in the frequencies of drought and storms, even though these could significantly affect crop yields. As different users possess varying degrees of expertise in the modeling field, misuse of models may occur. Since crop models are not universal, the user has to choose the most appropriate model according to his objectives. As a result, the assessments of possible effects of climate changes are based on estimations. Moreover, most models are not able to provide reliable projections of changes in climate variability on local scale, or in frequency of exceptional events such as storms and droughts (Shewmake, 2008). General Circulatory Models (GCMs) have so far not been able to produce reliable projections of changes in climate variability, such as alterations in the frequencies of drought and storms, even though these could significantly affect crop yields. GCMs do a reasonable job in simulating global values of surface air temperature and precipitation, but do poorly at the regional scale (Grotch, 1988). Furthermore, biological and agricultural models are reflections of systems for which the behaviour of some components is not fully understood and differences between model output and real systems cannot be fully accounted for. Crop models are therefore not able to give accurate projections because of inadequate understanding of natural processes and computer power limitation. Again, methodology of model validation is still rudimentary. The main reason is that, unlike the case of disciplinary/traditional experiments, a large set of hypotheses is being tested simultaneously in a model. The validation of models at present is further complicated by the fact that field data are rarely so definite that validation can be conclusive. This results from the fact that model parameters and driving variables are derived from site-specific situations that ideally should be measurable and available. However, in

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practice, plant, soil and meteorological data are rarely precise and may come from nearby sites. At times, parameters that were not routinely measured may turn out to be important and they are then arbitrarily estimated. Measured parameters also vary due to inherent soil heterogeneity over relatively small distances and to variations arising from the effects of husbandry practices on soil properties. Crop data reflect soil heterogeneity as well as variation in environmental factors over the growing period. Model performance is limited to the quality of input data. It is common in cropping systems to have large volumes of data relating to the above-ground crop growth and development, but data relating to root growth and soil characteristics are generally not as extensive. Most simulation models require that meteorological data be reliable and complete. Finally, sampling errors also contribute to inaccuracies in the observed data. An ultimate crop model would be one that physically and physiologically defines all relations between variables the model reproduces and universally real- world behaviour. However, such a model cannot be developed because the biological system is too complex and many processes involved in the system are not fully understood (Jame and Cutforth, 1996). Even if an ideal crop model could be produced, the collection of the highly precise system parameters and of the input data for the crop environment would be a formidable task in itself. Thus, the level of detail involved in a crop model is closely linked to the end use of the model and the precision required. Even when a judicious choice is made, it is important that aspects of model limitations be borne in mind such that modeling studies are put in the proper perspective and successful applications are achieved.

CONCLUSION As a research tool, model development and application can contribute to identify gaps in our knowledge, thus enabling more efficient and targeted research planning. Models that are based on sound physiological data are capable of supporting extrapolation to alternative cropping cycles and locations, thus permitting the quantification of temporal and spatial variability. Most models are virtually untested or poorly tested, and hence their usefulness is unproven. Indeed, it is easier to formulate models than to validate them. Many agronomists have been

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confused by the situation. They are discouraged by the complexity of the models, the lack of model testing, and the inevitable inaccuracies that arise when such testing is done. Consequently, they have seriously doubted the usefulness of crop models in agronomy. Unfortunately, this confusion is caused partly by those who are naively optimistic that crop modeling is the panacea for agricultural problems and apply crop models indiscriminately. Because most agronomists do not fully understand the concept of crop growth modeling and systems-approach research, training in this area is required. An intensely calibrated and evaluated model can be used to effectively conduct research that would in the end save time and money and significantly contribute to developing sustainable agriculture that meets the world’s needs for food.

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Chapter 19: Research methodology in Agronomy The livelihood of 70% of Indian population is based on agriculture. Therefore, economy of the country is agriculture dependent. More than 65% area is dependent on rains for successful cultivation of crops. The productivity of crops in these rainfed and dryland areas is very variable. It is therefore, necessary to m increasing the productivity of crops. Similarly irrigation management is very essential in irrigated areas for enhancing crop productivity. Different disciplines of agriculture (mainly agronomy, Genetics, Horticulture, Crop Physiology, Agricultural Engineering, Animal Husbandary and Dairy, Economics and Extension) play important role in increasing crop production through different agrotechniques viz. tailoring crop genotypes, suitability of soil type, standardization of sowing time, seed rate, plant population, plant geometry, nutrient management, irrigation and rainwater management, weed management, insect-pests and diseases management, animal nutrition and dairy management, technology transfer, economics of different crops/cropping systems/farming systems, suitable farm machinery, implements etc., In different disciplines, research work is continuously being carried out to cater the need of the changing problems arise in crop production. Research Research refers to a search for knowledge. One can also define research as a scientific and systematic search for relevant information on a specific topic. In short, the search for knowledge through objectives and systematic method of finding to a problem is research. Characteristic of research  Research originates with a question of a problem.  Research requires a clear articulation of a goal.  Purpose is understanding.  Oriented towards discovery.  Research follows a specific plan of procedure.  Research usually divides principal problem into more manageable sub-problems.  Research is guided by the specific research problem, question or hypothesis.  Research accepts certain critical assumptions.  Focus is holistic.

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Types of Research The various kinds of human science research can be subdivided to three criteria: 1. The measure of generality and applicability:  Basic research  Applied research  In-service research  Action research 2. The level of ordering:  Descriptive research  Prophetic research  Diagnostic research 3. The measure of control by researchers  Library research  Field research  Laboratory research

Agricultural research can be categorised into three types Basic research: It deals with the development of the principles and concepts of major technological advances. Basic research is the generation of knowledge. Example – study of the genetic resistance of rice to blast. Applied research or development research: It is the application of basic research to immediate problems. Applied research is the generation of technology. Example – recommendation of fertilizer doses, herbicides, insecticides etc, hybrid maize, insect resistance high yielding rice variety. Adaptive research: Adaptive research is the repetitive developmental research under varied conditions. Example – Development of specific variety of rice for Aus or Aman or Boro season, fertilizer recommendation for specific location or land type or soil type.

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Purpose/objective of research The purpose of research is to discover answers to questions through the application of scientific procedures. The main aim of research is to find out the truth which is hidden and which has not been discovered as yet. Though each research study has its own purpose, we may think of research. Objectives as falling into a number of following broad groups:  To gain familiarity with a phenomenon or to achieve a new insight into it.  To attain the goal.  To solve the problem.  To maintain the system or to improve the system  To portray accurately the characteristic of a particular individual situation or a group.  To determine the frequency with which something occurs or with it is associated with something else.  To test a hypothesis of a causal relationship between variables. Requirements of research For a successful research 4 Ms (Man, Money, Masonary and materials) are required. Research planning Plan is a predetermined course of action. Planning is defined as the act or process of making a plan which is termed as a programme, a project or a schedule. Purpose of planning is to evolve a sound, defensible and realistic programme of action. Plan gives a detail answer to all pertinent questions involving in conducting a project. Characteristic of a research Programme  Research programme should have following characteristics-  Clear and understandable  Impact oriented and measureable  Within nations development goals and mandate  Within capabilities of resources  Flexible and adjustable

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Strategies in Research Planning 1. Plan should cover a period of time 2. Plan of action should be flexible 3. Bottom to top levels of hierarchy should be involved in the planning process. Senior scientists give more time in planning due to their critical views and experience. Research planning Methodology (Scientific Method) 1. Identification of problem 2. Prioritization of the identified problem 3. Present status of the problem 4. To set goal, objectives or target for the research 5. To formulate operational hypothesis for undertaking the research 6. To select research/experimental materials to workout the hypothesis to achieve the goal/objective/target. 7. To select method of testing the hypothesis. 8. To put the materials and methods in operation. 9. To collect relevant predetermined data from the materials in accordance with the hypothesis. 10. To compile and analysis the data and interpret. 11. To draw conclusion about the hypothesis with reference to the objective(s) 12. Communication of the results to the desired audience (publication, demonstration, workshop etc.). Research Problem A problem is a deviation from some standard of performance. Problem may be defined as result of constraints that prevent from reaching their goal. An agricultural problem may be defined as any difficulty in converting efforts into economic agricultural production. A problem may be the result of one or several causes which one cause may result several problems. A problem may be national, regional or local. For example, nutrition deficiency is a national problem, flood is a regional problem and Ufra disease of rice is a local problem.

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Steps for identifying a research problem 1. Statement of the problem in general way 2. Understanding the nature of problem 3. Surveying the available literature 4. Developing the ideas through discussion 5. Rephrasing the research problem into a working proposition Factors to be considered in determining the priority of researchable problems 1. Economic importance of the problem 2. Technology/innovation available to overcome such a problem 3. Cost and time needed to carry out the research 4. Availability of the resources 5. The ease of implementing the new technologies (probability of adoption of the new technology) 6. Probable distribution of benefits within the society.

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REFERENCES: Amissah-Arthur A, Jagtap SS (1995). Application of models and geographic information system based decision support system in analysis the effect of rainfall on maize yield stability. Sustain Africa 3: 2-15. Boote KJ, Jones JW, Hoogenboom G, Wilkerson GG, Jagtap SS (1989). PNUTGRO VI.0, Peanut crop growth simulation model, user’s guide. Florida Agric. Experiment Station J., 8420: 1-83. University of Florida, Gainesville, Florida, USA. Brockington NR (1979). Computer Modeling in Agriculture. Clarendon Press New York, 156 pp. Dahiya BS & Rai KN. 1997. Seed Technology. Kalyani Publishers. Govardhan V. 2000. Remote Sensing and Water Management in Command Areas: Agroecological Prospectives. IBDC. ICAR. 2006. Hand Book of Agriculture. ICAR, New Delhi. Narasaiah ML. 2004. World Trade Organization and Agriculture. Sonali Publ. Palaniappan SP & Annadurai K. 2006. Organic Farming - Theory and Practice. Scientific Publishers. Sen S & Ghosh N. 1999. Seed Science and Technology. Kalyani Publishers. Tarafdar JC, Tripathi KP & Mahesh Kumar 2007. Organic Agriculture. Scientific Publishers.

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