DOCSLIB.ORG

Improving the Productivity of Landscapes with Little Or No Topsoil 100 90 10 Edwin L

Total Page：16

File Type：pdf, Size：1020Kb

Download full-text PDF Read full-text
Improving the Productivity of Landscapes with Little Or No Topsoil 100 90 10 Edwin L COOPERATIVE EXTENSION SERVICE • UNIVERSITY OF KENTUCKY COLLEGE OF AGRICULTURE, LEXINGTON, KY, 40546 AGR-203 Improving the Productivity of Landscapes with Little or No Topsoil 100 90 10 Edwin L. Ritchey, Plant and Soil Sciences 100 80 20 andscapes with little or no topsoil can 90 10 make it difficult to produce a garden, 70 30 lawn,L or other plants. Topsoil, dark in 80 20 color compared to the underlying soil, is clay 60 40 the part of a soil that is most biologically 70 30 active, nutrient rich, and easily managed. SILT % clay It also is usually more easily worked than Y % 50 50 60 40 silty underlying soil, supplies most of the CLA clay SILT % plant’s water and nutrients, and is gener- 40 sandy 60 Y % 50 50clay ally best for plant growth. silty CLA clay clay silty clay Subsoil generally contains more loam 30 loam 70 clay and is usually more acidic than the 40 sandy 60 clay sandy clay loam topsoil. Soils with high amounts of clay clay silty clay 20 loam 80 are generally sticky, cloddy, generally 30 loam 70 loam hard to work, and wetter (water may not sandy clay loam sandy loam silt loam infiltrate them quickly). Clayey soils will 10 loam 90 20 80 hold appreciable amounts of water, but loam y sand silt sand they hold it tightly, so that plants cannot silt loam sandy loam 100 readily use as much of it as they would in 10 loam 100 90 80 70 60 90 50 40 30 20 10 a more loamy or silty topsoil. The reason y sand silt sand SAND % to amend clay soils is to improve 100 • structure (you cannot easily change 100 90 80 70 60 50 40 30 20 10 the texture) Figure 1. Soil texture triangle. SAND % • infiltration/drainage To determine a soil’s texture, 90 10 • plant-available water supply determine the percentages of sand, silt, and 90 10 • workability clay. The soil separates will sum to 100%. For of least two of those percentages, go to the 70 30 90 10 70 30 All these improvements will reduce side of the triangle for a least two of the sepa- 90 10 the tendency of clayey soils to form clods. rates and follow the gray line for the percent- SILT % Y % 50 50 poor age point to where70 the lines 30converge. 50 50 Soil Texture and Structure CLA 70 30 SILT % 30 70 30 medium 70 Y % poor Soil texture and structure are two 50 50 50 50 different soil properties, both often mis- CLA good understood. Soil texture is the relative 10 90 10 90 For example,30 a soil containing 30% sand,70 30 medium 70 proportions of sand, silt, and clay sepa- 60% silt, and 10% clay is classified as a silt 90 70 50 30 10 90 70 50 30 10 rates in the soil (Figure 1). Soil separates loam. good 10 90 are defined according to their size, with 10 SAND % 90 clay being the smallest separate (less than 90 70 50 30 10 90 70 50 30 10 0.002 mm), sand being the largest (2 to SAND % 0.05 mm), and silt in between (0.05 to if this change were feasible, you would slightly lower plant-available water, since 0.002 mm). Texture is hard to manipulate likely not be able to see any benefit. For sand does not hold as much water as clay. and rarely helps. An acre of soil to a depth example, adding sand to a clayey soil Soil structure is the arrangement of of about 7 inches weighs about 2 million slightly reduces proportions of clay and the primary soil particles (sand, silt, and lb, so changing textural percentage by 1% silt but does not measurably change clay) into aggregates, or peds. It affects for one separate would require 20,000 infiltration or the tendency of clayey soil soil porosity. Soil structure is influenced lb of material (1% of 2 million lb). Even to form clods. Adding sand also would by soil fauna, roots, tillage, compost, ma- Agriculture and Natural Resources • Family and Consumer Sciences • 4-H Youth Development • Community and Economic Development EXTENSION nure, and cover crops. Structure is what When purchasing/obtaining usually needs to be modified to improve topsoil, make sure that the productivity where there is little or no material is of high quality: free topsoil. of trash (bottles, cans, plas- To increase productivity of lawns, tic, etc.), rocks, construction gardens, and landscape plants in topsoil- debris, and problem weeds. deficient areas, here are some options for Be aware that Kentucky has improving soil structure and other soil no legal definition of topsoil. properties: Sometimes the material being sold as topsoil is actually less Soil Sampling and suitable for a lawn or garden Soil Testing than subsoil at the site. Adver- tising does not make any given Before amending soil, take a represen- material topsoil. Some materi- tative soil sample of the area as well as als removed from the top layer any topsoil you might plan to place over of another soil might not be it. The soil should be sampled to a depth suitable as topsoil because the of 6 to 7 inches in about a dozen places soil from the other area was using a soil probe, auger, or spade (Figure disturbed previously and its 2). The sample should be hand crushed Figure 2. A soil auger (left), spade (center), or probe topsoil removed or eroded. may be used to sample soils. If you are using a spade, and well mixed, then submitted to the High-quality topsoil should the sample should be trimmed with a knife, as shown. local county extension office or a private be dark brown to reddish soil testing laboratory. brown in color, not cloddy, A sample submitted to your local and without excessive amounts of clay Another option is to add the desired extension office will be sent it to the UK or sand. Typically, Kentucky topsoil amount of topsoil to the existing lawn in Regulatory Services soil laboratory for contains 2% to 4% organic matter. Any- one application, smothering the lawn and analysis. The cost for the test will vary thing below 1.5% organic matter is only then reseeding. Use this method when depending on the extent of analysis marginally suitable as topsoil. Off-site you want a new grass lawn as well as requested. Results will be returned in topsoil should be tested, preferably before topsoil. Replacing topsoil is usually more one to two weeks and will provide infor- purchase, for levels of available nutrients expensive than improving it. For small mation about nutrient availability and and content of organic matter, which is areas, such as garden plots and home recommendations for lime and nutrient an indication of its quality. lots, replacement may be an economi- additions. Test results typically indicate Ideally, 6 inches of topsoil would be cally feasible choice, but it becomes cost how much phosphorus (P), potassium added, but any topsoil addition, even if prohibitive for large acreages or farms. (K), (calcium (Ca), magnesium (Mg), and less than 6 inches, would be beneficial. zinc (Zn) are available in the soil and the Before adding topsoil, check your site for Building Topsoil degree of soil acidity/alkalinity (soil pH). compaction with a tiling rod or penetrom- There is no soil test for nitrogen (N), so Another option is to “build” topsoil, eter. If you suspect your site is compacted, nitrogen recommendations are based which will take several years but can your county extension agent can help you on the crop or plants to be grown and be accomplished with diligence and choose the best option to improve it. Deep whether the crop/plants are established patience. To build topsoil, the current soil disturbance may be necessary. The or a new planting. For an additional soil surface needs to be amended with or- best option is to add and then incorporate fee, soil organic matter (OM) content ganic materials. These materials include the first 2 inches of topsoil into the exist- can also be determined using the same manures as well as composts made from ing soil to prevent abrupt changes in soil sample. For more information regarding leaves, yard clippings, and kitchen wastes texture, then add and incorporate the re- soil sampling, see the UK Cooperative without the meat scraps that attract pests. maining topsoil. With a lawn, one option Extension Publication Taking Soil Test For more information on composting, is to spread layers of new topsoil over the Samples (AGR-16), online at http://www. consult University of Kentucky Coopera- existing grass, keeping those layers thin to ca.uky.edu/agc/pubs/agr/agr16/agr16.pdf. tive Extension Publication Home Com- avoid killing the lawn. Grass completely posting: A Guide to Managing Yard Waste Replacing Topsoil covered by soil will be “smothered” and (HO-75), found online at http://www. die. Multiple thin topsoil applications over ca.uky.edu/agc/pubs/ho/ho75/ho75.pdf. If topsoil has been removed during site time will slowly increase the yard’s topsoil Plant material generated in the gar- preparation and is still on the property, depth. It’s critical to spread added topsoil den or lawn should also be returned to move it back to the lawn and garden area. evenly to keep the yard from becoming the soil. Be careful, however. Disease Another option is to purchase/obtain too rough. Rake to smooth added soil if and insect buildup can occur when you topsoil, though buying it may be costly.
Load more

Recommended publications
  • Keynote: Soil Conservation for C Sequestration R
    This paper was not peer-reviewed. Pages 459-465. In: D.E. Stott, R.H. Mohtar and G.C. Steinhardt (eds). 2001. Sustaining the Global Farm. Selected papers from the 10th International Soil Conservation Organization Meeting held May 24-29, 1999 at Purdue University and the USDA-ARS National Soil Erosion Research Laboratory. Keynote: Soil Conservation For C Sequestration R. Lal* ABSTRACT fragile ecosystems such as the Himalyan-Tibean ecoregion, The atmospheric concentration of greenhouse gases the Andeas, the West African Sahel, East African Highlands, (GHG) is increasing at the rate of 0.5% yr-1 (3.2 Pg C and the Caribbean region (Scherr and Yadav, 1995; Scherr, -1 -1 -1 yr ) for CO2, 0.6% yr for CH4 and 0.25 ppbv yr for 1999). In addition to effects on productivity, soil erosion N2O. The global radiative forcing due to three GHGs is also profoundly impacts the environment. contributed by 20% due to agricultural activities and Two principal impacts of erosion on environment include 14% to change in land use and attendant deforestation. reduction in quality of water and air through pollution and Principal agricultural activities that contribute to eutrophication of surface water, and emissions of emission of GHGs include plowing, application of radioactively-active gases (e.g., CO2, CH4 and N2O) to the fertilizers and manures, soil drainage, biomass burning, atmosphere. Increasing atmospheric concentration of -1 -1 residue removal. The loss of soil C is accentuated by soil radioactively-active gases (0.5% yr for CO2, 0.6% yr for -1 degradation (due to erosion, compaction, salinization CH4, 0.25% yr for N2O) (IPCC, 1995) necessitates etc.) and the attendant decline in soil quality.
    [Show full text]
  • Contaminated Soil in Gardens
    Contaminated Soil in Gardens How to avoid the harmful effects EUR/ICP/LVNG 03 01 02(A) E64737 EUROPEAN HEALTH21 TARGET 11 HEALTHIER LIVING By the year 2015, people across society should have adopted healthier patterns of living (Adopted by the WHO Regional Committee for Europe at its forty-eighth session, Copenhagen, September 1998) Abstract In many cities, gardens are located on old, abandoned landfills and dumping sites. Cities have expanded by filling up spaces around the city with garbage, rubble and earth. The places where old landfills were have often become gardens where citizens can get away and enjoy the open air away from the noise and racket of cities. Normal garbage and rubble in landfills do not present a problem, however industrial and chemical waste can present a health hazard, especially when concentrations of contaminants are above acceptable limits. Some special precautions are proposed in this booklet so that the potential ill effects of contaminated soil can be avoided. Keywords SOIL POLLUTANTS RISK MANAGEMENT GUIDELINES URBAN HEALTH Contents The soil is contaminated – what then? .......................................................1 What is in the ground under us?.................................................................2 How harmful substances may affect the body ............................................3 How to reduce the risk................................................................................4 The best way to garden..............................................................................5
    [Show full text]
  • Agricultural Soil Compaction: Causes and Management
    October 2010 Agdex 510-1 Agricultural Soil Compaction: Causes and Management oil compaction can be a serious and unnecessary soil aggregates, which has a negative affect on soil S form of soil degradation that can result in increased aggregate structure. soil erosion and decreased crop production. Soil compaction can have a number of negative effects on Compaction of soil is the compression of soil particles into soil quality and crop production including the following: a smaller volume, which reduces the size of pore space available for air and water. Most soils are composed of • causes soil pore spaces to become smaller about 50 per cent solids (sand, silt, clay and organic • reduces water infiltration rate into soil matter) and about 50 per cent pore spaces. • decreases the rate that water will penetrate into the soil root zone and subsoil • increases the potential for surface Compaction concerns water ponding, water runoff, surface soil waterlogging and soil erosion Soil compaction can impair water Soil compaction infiltration into soil, crop emergence, • reduces the ability of a soil to hold root penetration and crop nutrient and can be a serious water and air, which are necessary for water uptake, all of which result in form of soil plant root growth and function depressed crop yield. • reduces crop emergence as a result of soil crusting Human-induced compaction of degradation. • impedes root growth and limits the agricultural soil can be the result of using volume of soil explored by roots tillage equipment during soil cultivation or result from the heavy weight of field equipment. • limits soil exploration by roots and Compacted soils can also be the result of natural soil- decreases the ability of crops to take up nutrients and forming processes.
    [Show full text]
  • Topsoil Characterization for Sustainable Land Management 1
    DRAFT FOOD AND AGRICULTURE ORGANIZATION OF THE UNITED NATIONS TOPSOIL CHARACTERIZATION FOR SUSTAINABLE LAND MANAGEMENT Land and Water Development Division Soil Resources, Management and Conservation Service Rome 1998 2 ACKNOWLEDGEMENTS This study is based upon earlier work by O.C. Spaargaren "Framework for Characterization and Classification of Topsoils in the World" (1992 unpublished) and A. Hebel "Soil Characterization and Evaluation System (SCE) with Emphasis on Topsoils and their Fertility-related Characteristics" (1994 unpublished). We would also like to acknowledge the cooperation of the University of Hohenheim, especially Dr. Gaiser and Prof. Stahr for testing the system, and various contributions, suggestions and constructive criticism received from Ms L.M. Jansen, Ms A Bot, Mr F. Nachtergaele, and last but not least, Mr M.F. Purnell. CONTENTS 1. Introduction 1 2. Topsoil Characterization Within Existing Soil Classification Systems 3 2.1 Introduction 3 2.2 Fertility Capability Classification (FCC) 3 2.3 Soil Classification Systems 3 3. Factors Influencing Topsoil Properties 7 3.1 Climate 7 3.2 Vegetation and Organic Matter 7 3.3 Topography and Physiography 8 3.4 Mineralogical Soil Constituents 9 3.5 Surface Processes 9 3.6 Biological Activity 10 3.7 Human Activity 10 4. Definition of Topsoil Properties and Modifiers 13 4.1 Texture 13 4.2 Organic Material 13 4.3 Organic Matter Status 14 4.4 Physical Features 16 4.5 Chemical Features 18 4.6 Biological Features 20 4.7 Drainage Features 21 4.8 Land Use 21 4.9 Erosion or Degradation 23 4.10 External Physical Conditions 25 4.11 Slope 26 4.12 Examples of Topsoil Characterization 26 5.
    [Show full text]
  • Soils and Soil-Forming Material Technical Information Note 04 /2017 30Th November 2017
    Soils and Soil-forming Material Technical Information Note 04 /2017 30th November 2017 Contents 1. Introduction to Soils ........................................................................................................................ 2 2. Components and Properties of Soil ................................................................................................ 7 3. Describing and Categorising soils .................................................................................................. 29 4. Policy, Regulation and Roles ......................................................................................................... 34 5. Soil Surveys, Handling and Management ..................................................................................... 40 6. Recommended Soil Specifications ................................................................................................ 42 7. References .................................................................................................................................... 52 “Upon this handful of soil our survival depends. Husband it and it will grow our food, our fuel, and our shelter and surround us with beauty. Abuse it and the soil will collapse and die, taking humanity with it.” From Vedas Sanskrit Scripture – circa 1500 BC The aim of this Technical Information Note is to assist Landscape Professionals (primarily landscape architects) when considering matters in relation to soils and soil-forming material. Soil is an essential requirement for providing
    [Show full text]
  • Addressing Pasture Compaction
    Addressing Pasture Compaction Weighing the Pros and Cons of Two Options UVM Project team: Dr. Josef Gorres, Dr. Rachel Gilker, Jennifer Colby, Bridgett Jamison Hilshey Partners: Mark Krawczyk (Keyline Vermont) and farmers Brent & Regina Beidler, Guy & Beth Choiniere, John & Rocio Clark, Lyle & Kitty Edwards, and Julie Wolcott & Stephen McCausland Writing: Josef Gorres, Rachel Gilker and Jennifer Colby • Design and Layout: Jennifer Colby • Photos: Jennifer Colby and Rachel Gilker Additional editing by Cheryl Herrick and Bridgett Jamison Hilshey Th is is dedicated to our farmer partners; may our work help you farm more productively, profi tably, and ecologically. VT Natural Resources Conservation Service UVM Center for Sustainable Agriculture http://www.vt.nrcs.usda.gov http://www.uvm.edu/sustainableagriculture UVM Plant & Soil Science Department http://pss.uvm.edu Financial support for this project and publication was provided through a VT Natural Resources Conservation Service (NRCS) Conservation Innovation Grant (CIG). We thank VT-NRCS for their eff orts to build a 2 strong natural resource foundation for Vermont’s farming systems. Introduction A few years ago, some grass-based dairy farmers came to us with the question, “You know, what we really need is a way to fi x the compaction in pastures.” We started digging for answers. Th is simple request has led us on a lively journey. We began by adapting methods to alleviate compac- tion in other climates and cropping systems. We worked with fi ve Vermont dairy farmers to apply these practices to their pastures, where other farmers could come and observe them in action. We assessed the pros and cons of these approaches and we are sharing those results and observations here.
    [Show full text]
  • Preventing Soil Compaction Preserving and Restoring Soil Fertility
    Preventing Soil Compaction Preserving and Restoring Soil Fertility Including the Classification Key for Detection and Evaluation of Harmful Soil Compaction in the Field www.umwelt.nrw.de Content Preface ............................................of the minister 2 1. Introduction ...................................................... 4 2. The importance of soil structure......................... 6 3. Causes of harmful soil compaction..................... 13 4. Effects of harmful soil compaction...................... 18 5. Detecting harmful soil compaction..................... 21 6. Preserving and improving soil structure ................ 25 7. What to do, if the soil is already compacted?...... 32 8. Final remarks.................................................... 36 Literature .............................................................. 37 4 1. Introduction Agricultural soil cultivation and harvest inevitably cause slight soil compaction. Especially detrimental is soil compaction which occurs deep in the subsoil, as this compaction cannot be reversed with normal soil cultiva- tion. Due to expected future warmer winters in Germany as a result of climate change, fewer and shorter frost periods are to be expected and with that the so-called “frost action” with its soil loosening effect will occur less frequently. This means that a natural way to loosen soil structure will be lost. Field traffic, with heavy loads on wet soils, is an especially critical contributor to severe soil compaction. With the increasing “just in time” harvest practice of farmers, this is a potential source of conflict. To address this, improved techniques to reduce soil pressure and to understand actual soil water content can be helpful. The steady increase in weight of agricultural machinery and field traffic frequency – both have increased by three- to fourfold within the last 40 years – in combina- tion with the technical ability to drive on increasingly wet soils, has led to ever greater compaction of our soils.
    [Show full text]
  • Science Literacy Warm Up
    ecology á environmental issues ENDANGERED SOIL 20 (1) The United Nations declared 2015 The International Year of Soils. There has been a growing awareness that soil isn’t only important for healthy ecosystems, but that soil is also critical to our ability to make enough food to feed the world. Food security, which is the access that humans have to healthy food, is threatened when soil is threatened. Science Literacy Warm Up (2) The way we have been conducting intensive modern agriculture, polluting our lands and expanding urban cities has had a huge effect on the Earth’s soil for the last two centuries. These things, along with the effects of climate through contact with the forces of nature. change, have made soil endangered and has Once weathering forms the initial cracks in the increased concerns over food security. rock, the eroding actions of water, chemical reactions and living organisms (like plants) can (3) Let’s first examine the soil itself. If you start to erode and break apart the rock even think that soil is just simply dirt, then you are further. This process takes a long time causing mistaken. Dirt isn’t alive while soil is brimming topsoil to form very slowly. with life. Besides minerals, water and decomposing organic matter, soil also contains (7) Edaphology helps us study and examine thousands of species of small insects, worms, how altering our soil affects the plants grown fungi and microorganisms. A handful of soil in it. Proper soil conditions are vital for healthy contains more microorganisms than there are plant growth.
    [Show full text]
  • Improving Garden Soils with Organic Matter, EC 1561
    EC 1561 • May 2003 $2.50 Improving Garden Soils with Organic Matter N. Bell, D.M. Sullivan, L.J. Brewer, and J. Hart This publication will help you understand the • Tomatoes and peppers get blossom-end rot, importance of soil organic matter levels to good even if fertilized with calcium. plant performance. It also contains suggestions • Water tends to pool on the soil surface and to for suitable soil amendments. Any soil, no drain slowly, or it runs off the surface. matter how compacted, can be improved by the addition of organic matter. The result will be a nnnn better environment for almost any kind of plant. What makes a productive soil? nnnn A productive soil provides physical support, water, air, and nutrients to plants and soil- What gardening problems are dwelling organisms (see “What is soil?” caused by poor soil quality? page 2). Like humans, roots and soil organisms Many problems with home vegetable gar- breathe and require sufficient air and water to dens, fruit trees, shrubs, and flower gardens are live. As a result, a good soil is not “solid”; caused not by pests, diseases, or a lack of rather, between 40 and 60 percent of the soil nutrients, but by poor soil physical conditions. volume is pores. The pores may be filled with Symptoms of poor soil quality include the water or air, making both available to plants following. (see illustration on page 3). • The soil is dried and cracked in summer. The largest pores control aeration and move- • Digging holes in the soil is difficult, whether ment of water through the soil and are largely it is wet or dry.
    [Show full text]
  • A 9-Step Easy Sheet Permaculture Mulching Technique Mulch Is Marvelous
    A 9-Step Easy Sheet Permaculture Mulching Technique Mulch is marvelous. It performs a variety of for many locations. functions that help save the permaculture gardener time and effort, while providing the It is intended for plots that are at the start of soil and plants with a great deal of organic a transition to a permaculture garden, and matter, making for healthier soil and, thus, for larger areas that require mulching You healthier plants. Permaculture Mulching can spot mulch around specific plants and refers to the covering of areas of soil with trees, but remember to leave some space one or more layers of material. In a around the stem or trunk to prevent permaculture garden these layers are overwhelming the plant. organic in nature, and the mulch benefits the soil in several ways. Firstly, it helps to Step 1 preserve moisture in the soil by protecting it Slash down any long grass and weeds. Leave from excessive evaporation. Mulch also the cut plants where they fall. They will add improves the health and quality of the soil by organic matter to the soil through the creating a stable environment for bacteria mulching process. Don’t worry about leaving and microorganisms to function, as well as weed seeds or roots on the ground; the via the nutrients in the mulch itself, which subsequent layers of the mulching process are slowly broken down and added to the will prevent them from re-sprouting by soil. Mulch also adds organic matter to the depriving them of the sunlight they need to soil when it is used to control weed growth.
    [Show full text]
  • Global Status, Processes and Trends in Soil Erosion
    Status of the World’s Main Report Soil Resources Chapter 6 Global soil status, processes and trends © FAO | Giuseppe Bizzarri © FAO INTERGOVERNMENTAL TECHNICAL PANEL ON SOILS Disclaimer and copyright Recommended citation: FAO and ITPS. 2015. Status of the World’s Soil Resources (SWSR) – Main Report. Food and Agriculture Organization of the United Nations and Intergovernmental Technical Panel on Soils, Rome, Italy The designations employed and the presentation of material in this information product do not imply the expression of any opinion whatsoever on the part of the Food and Agriculture Organization of the United Nations (FAO) concerning the legal or development status of any country, territory, city or area or of its authorities, or concerning the delimitation of its frontiers or boundaries. The mention of specific companies or products of manufacturers, whether or not these have been patented, does not imply that these have been endorsed or recommended by FAO in preference to others of a similar nature that are not mentioned. The views expressed in this information product are those of the author(s) and do not necessarily reflect the views or policies of FAO. ISBN 978-92-5-109004-6 © FAO, 2015 FAO encourages the use, reproduction and dissemination of material in this information product. Except where otherwise indicated, material may be copied, downloaded and printed for private study, research and teaching purposes, or for use in non-commercial products or services, provided that appropriate acknowledgement of FAO as the source and copyright holder is given and that FAO’s endorsement of users’ views, products or services is not implied in any way.
    [Show full text]
  • Soil Erosion
    Soil erosion Soil erosion in sloping agricultural land in Tunisia. Photolibrary on soil erosion processes. The most serious form of soil degradation is from accelerated erosion. Erosion is the washing or blowing away of surface soil, sometimes down to the bedrock. While some erosion takes place without the influence of man, the soil is lost so slowly that it is usually replaced through natural processes of decay and regeneration so soil loss and creation of new soil are balanced. What keeps soil in a natural state from eroding is vegetation. Undisturbed by man, soil is usually covered by a canopy of shrubs and trees, by dead and decaying leaves or by a thick mat of grass. Whatever the vegetation, it protects the soil when the rain falls or the wind blows. The leaves and branches of trees and the cushion of grass absorb the force of raindrops, and root systems of plants hold the soil together. Even in drought, the roots of native grasses, which extend several metres into the ground, help tie down the soil and keep it from blowing away. With its covering of vegetation stripped away, however, soil is as vulnerable to damage as a tortoise without its shell. Whether the plant cover is disturbed by cultivation, grazing, burning, or bulldozing, once the soil is laid bare to the erosive action of wind and water, the slow rate of natural erosion is greatly accelerated. Losses of soil take place much faster than new soil can be created, and a kind of deficit spending begins with the topsoil.
    [Show full text]