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Home , Soil conservation

Conservation of of the Kapiriggama Village Tank Cascade System

Background is natural, but anthropogenic activities have increased the rate of erosion to 40-50 times the natural provide many essential services in both natural rate. Such human activities include intensive agriculture, and human-made ecosystems: they serve as a medium deforestation, infrastructure development, urbanisation, on which different kinds of grow; they absorb and and climate change. emit gases (such as carbon dioxide, methane, vapour) and dust and thereby modify the atmosphere; The most important impacts of accelerated they provide a habitat for soil-dwelling organisms; they include the decrease in agricultural productivity in soak up, retain, release and alter most of the water in agricultural systems and ecological collapse in natural systems; they recycle nutrients, including carbon, so ecosystems, as a consequence of the loss of upper soil that living things can use them over and over again; they layers, which are rich in nutrients. Off-site, as a result serve as a medium for engineering for the construction of soil erosion, waterways become sedimented and of foundations, roadbeds, dams and buildings; and they eutrophication of water bodies occurs (where excess function as a living filter to purify water before it moves nutrients runoff from land, causes an excessive growth into . of plants and algae, cutting off from the depths below). Soil is created through a process of weathering, and simultaneously eroded, through natural processes. Such In Sri Lanka, soil erosion is a serious problem. It has

IUCN Cascade Development Project Information Brief No. 6 numerous impacts on crop productivity, economic growth, income distribution, production and long-term environmental stability. Studies have shown that soil loss in the upper catchment area of the Mahaweli River is 130 – 2,100 tonnes per square kilometre. In cotton-cultivated plots and sorghum/pigeon pea inter-cropped plots without any soil conservation measures, the annual soil loss is 22.2 tonnes per hectare and 21.3 tonnes per hectare respectively. On hill slopes, loss is 7,000 tonnes per square kilometre per year. In comparison with natural rates of erosion, these studies show that in the agricultural areas of the central highlands of Sri Lanka, soil is lost 10-100 times faster than it is produced.

Soil erosion is a serious threat to agricultural production because of two reasons. Firstly, it takes a long period of time for anyone — even scientists — to recognise that the land is being degraded due to soil erosion. Secondly, the problem of soil erosion problem is usually addressed by looking at the consequences, rather investigating and • Contour planting: Crops are planted along contours treating the cause of problem. Two well-known examples or across the slope. When contour cultivation is are that low soil and soil compaction due to soil practised in tea , soil erosion become negligible. erosion are treated with the application of inorganic fertiliser • Zero : This is a way of growing crops each and tillage respectively, rather than attempting to control the year, without tilling the soil. This technique increases process of soil erosion. the amount of water that percolates into the soil, increases the retention of organic matter in the soil To conserve soil resources, the Kapirriggama Cascade and increases the recycling of nutrients in the soil. It project had the overall goal of achieving sustainable land has been shown to reduce or eliminate soil erosion. management of agricultural systems to enhance the soil • Application of organic fertiliser: Composting is texture and soil productivity of the catchment; and the defined as the natural process of decomposition following specific objectives: 1) to minimise soil erosion; of organic materials by micro-organisms under 2) to enhance ; 3) to enhance ; 4) controlled conditions. Raw organic materials such to decrease soil and by minimising the as crop residues, animal wastes, green manures, use of agrochemicals; and 5) to increase the resilience of aquatic plants, industrial wastes, city wastes and food upland agricultural systems against . garbage are excellent sources of compost. • Mixed cropping/inter-cropping/co-cultivation: This is Sustainable is defined as ‘the use of land the practice of growing, simultaneously, two or more resources, including soils, water, animals and plants, for crops on the same land. When the crops to be grown the production of goods to meet changing human needs, together are selected correctly, the products and while simultaneously ensuring the long-term productive refuse from one crop help in the growth of the potential of these resources and the maintenance of their other crop plant and vice-versa. environmental functions’ (defined at the UN , 1992). There are two broad objectives of sustainable Vegetative methods land management: 1) to maintain long term productivity The following vegetative methods are recommended. of ecosystem functions; and 2) to increase productivity • Biological hedges: Hedges are placed across the (quality, quantity and diversity) of goods and services. slope to slow down the overland flow. These can consist of live or dead materials of biological origin. Methodology for Sustainable Land Management Alley cropping, graded hedgerows, SALT hedges are placed under this category. The methodology for sustainable land management • Alley cropping has been found to be successful comprises four different practices namely, agronomic in various parts of the dry zone on flat or gently practices, vegetative methods, structural methods and sloping lands. Legume such as Gliricidia management or a combination of these. sepium (Sinhala: Wetahiriya/Kona; Tamil: Kona/ Seemai kiluvai) are planted across the slope with Agronomic practices slight gradient on a soil ridge. Citronella grass is The following agronomic practices are recommended. planted along with the Gliricidia. This combined • Mulching: A mulch is generally organic, sometimes hedge is pruned periodically and loppings spread permanent (for example, plastic sheeting) and on the surface between the hedges. These sometimes temporary (for example, bark chips). Mulch loppings act as mulch. Crops suitable for such can be applied around plants or on bare soil. Mulching alleys are vegetables, tuber crops, pulses, cereal, is used commercially and in home gardens. When papaya, banana and other fruit crops. applied correctly, mulching significantly improves the • Sloping Agricultural Land Technology (SALT) quality of soil. Practice: This method is adopted for sloping lands up to 60% slope in the mid and up country wet is an advanced stage of erosion and very costly to zone. Gliricidia is generally used as the hedge repair. Vegetation can be used to control gully erosion, plant, but Tithonia diversifolia (Sinhala: Val- providing the soil with physical protection against scour suriyakantha) and Erythrina variegata (Sinhala: and slowing down the velocity of flow. There is a variety Erabadu; Tamil: Mulmurukku) can also be planted. of gully control structures from brushwood dams to In this method, double hedgerows are established cement structures. The brushwood dam uses small along the contour. To minimise soil erosion, the branches, packed as tightly as possible across the space between two rows of the double hedge is direction of flow. Stone check dams, pile stones across filled with stones and any other solid material. the gully with or without cement plastering, keeping a • Grass hedges: Grass hedges are also established depression at the middle of the dam to allow spill over of across the slope. Species recommended are Vetiveria the excess flow. Some plant species are established on zizanioides (Sinhala: Sevendra; Tamil: Vettiver), either side of the gully of the upstream and downstream Cymbopogon nardus (Sinhala: Mana/Heen-pengiri); area to slow the flow and strengthen the dam. Cymbopogon citratus (Sinhala: Sera; Tamil: Serai). • Cover crops: These are crops grown primarily to cover Management Practices the surface of the soil , thereby reducing erosion. In Sri Lanka, cover cropping is not practised widely Land must be managed properly to maintain long-term except in rubber and coconut plantations, as inter- productivity. As soil, rainfall and conditions vary from spaces are not free and are often occupied with a place to place, adoption of proper practices is mix of different crops. However, where it is practical, essential. Along the catena (a sequence of soil profiles down the recommended cover crops are Calopogonium a slope) what crops should be grown and what land use mucunoides and Desmodium species. practices must be followed must be decided carefully.

Structural Methods For dry zone farming communities, the most appropriate Structural methods have been considered the main focus model is as follows: of soil conservation by many implementing agencies. The most popular measures are: Phase Appropriate land use Irrigable • Lock and spill drains: This is a hillside ditch unique area to Sri Lanka. This is practised for soil conservation i Well-drained This upper ridge should be kept on sloping lands exceeding 40% slope. The ditch RBE, shallow undisturbed. If cleared already, a is square in shape, placed across the slope with a phase < 30 cm portion can be converted to a village , planted with suitable species slight gradient. Low cross walls are left in the bed of (See technical note # 2 and 3). the drain, so that it is divided into separate basins to ii Well-drained These can be used for planted encourage and to trap . During RBE, moderate- (a mixture of forest and fruit heavy , the runoff overtops these cross walls ly deep soils < trees and spills towards the outlet, usually a stoned–lined 30-60 cm running down the slope. Periodically, the iii Well-drained These lands can be used for rainfed Irrigable accumulated sediment is removed and spread nearby. RBE, deep soils farming, with adequate soil conser- area In order to minimise the accumulation of sediment > 60 cm vation measures in the drain it is recommended that a line of grass, iv Moderate- This strip of land can be allocated as ly-drained RBE; a settlement area with home gardens Vetiveria zizanioides or Cymbopogon nardus, is deep soils > established just above the drain. 60 cm • Stone bunds: These are used on steep slopes, where v Imperfect- This can be used for paddy cultivation the soil is not stable enough to keep as risers (vertical ly-drained RBE in the maha season and other sea- walls) in terraced lands and where stone is available sonal crops in yala season for such work. vi Poorly-drained This is only suitable for rice cultivation • Soil bunds and drains: This type of conservation LHG measure is adopted on lands with slopes less than 10%. In order to prevent damage or collapse of the Combined Practices bund, grass species such as Vetiveria zizanioides, Some of the combined practices that can be recommended Cymbopogon nardus and Cymbopogon citratus are are described below. planted downstream of the bund. • Terracing: This practice converts a steep slope into Conservation Farming a series of steps with horizontal or nearly horizontal In sustainable land management, all practices other than ledges (shelves), and vertical or almost vertical walls mechanical conservation measures can be categorised (risers) between the ledges. The wall is vulnerable to as conservation farming. Conservation farming is a broad- erosion and is protected by a vegetative cover and based approach of land and water management. It exploits sometimes, faced with stones or concrete. There is no resources while conserving them through moisture retention, channel but a storage area is created by sloping the fertility and soil conservation, which make the system less shelf into the hillside. dependent on expensive inputs such as , machines, • Gully control structures: Gullies are formed when inorganic fertilisers and other agro-chemicals. The most runoff into natural streams is diverted or lands are important practices under conservation farming applicable to opened up encouraging more overland flow. Gullying dry zone conditions are: i) hedge row cultivation (alley cropping and SALT, discussed conservation and manure production was promoted. previously; ii) conservation of moisture in the top soil (through • maps of the command areas of eight mulching, and in-situ ) and iii) soil fertility tanks were developed for parameters such as soil enhancement. Soil fertility can be improved by adding pH, electrical conductivity, organic matter content, various types of fertiliser sources containing plant nutrients. , phosphorous and drainage capacity. Based Such source include plant residues (crop residues and green on the results location specific cards were manure); animal wastes (animal manure and slaughter developed for 140 paddy lands to assist location house wastes) and compost (discussed previously). specific fertiliser recommendations. This reduces overuse of fertilisers. • Iswetiya (See Brief # 1 for description) were formed in Project Interventions the tank bunds of five tanks to reduce runoff velocity and to arrest eroded soil before reaching the tanks. Reduced • Conservation farming was demonstrated in 37 upland runoff velocity reduces the erosive power of rainwater. farms (33 acres) located in the catchments of nine • Through the activities of ecosystem restoration of tanks in the project area. About 20,000 m of soil the project (See Brief # 3), barren areas of the tank conservation bunds were established in 100 acres catchments were replanted with multi-purpose tree of farmlands to arrest soil erosion. Soil conservation species, facilitating erosion control and improving bunds reduce the runoff velocity and thereby reduce productivity of the cascade. the erosive power of water. The improved drainage • Home gardens and farmlands were planned through system associated with the soil bunds facilitates the participatory planning to optimise use of sunlight, capture of eroded soil and thereby, reduces siltation of by promoting stratification in the vegetation to keep tanks. the mixed canopy to maintain a suitable • By reducing the runoff velocity, the soil bunds facilitate microclimate. in the farmlands. This increases the soil moisture content, which, in turn, increases the Recommendations for the future resilience of the farmlands to . The soil bunds were stabilised with Gliricidia sepium, Cymbopogon • Continue establishing soil conservation bunds in nardus (Sinhala: Mana/Heen-pengiri; Tamil: No name the farmlands and home gardens in the immediate known) and Justicia adhatoda (Sinhala: Adathoda; catchments of all the tanks in the cascade. Tamil: Pavettai). Application of the fodder obtained from • Establish iswetiya in all the tanks where it is technically farmlands increases the organic content of the soil, possible. which, in turn, increases and soil fertility. • Conduct soil quality testing and promote location- • Eyebrow bund and pitcher systems were introduced specific soil fertility programmes to minimise overuse of in 37 upland farms for micro-scale soil conservation chemical fertiliser. and water management. Fruit plants — such as mango (Mangifera indica); coconut (Cocos nucifera); orange (Citrus sp.); lemon (Citrus sp.); guava (Psidium guajava); pomegranate (Punica granatum) and hog plum (Spondias dulcis) — were cultivated associated with the eyebrow and pitcher system. (Each planting point receives runoff water gathered from the upstream flow pitch and diverted into the planting point by an eye-brow shaped small earth ridge. Water gathered flows freely into a clay pitcher buried close to the plant and spills off when there is any excess water to the other eye-brow bund). • The productivity of home gardens was improved through and home garden development. Eight different types of sustainable Photographs: Cover: Soil conservation bund in a home garden agriculture practices and five methods for bio-fertiliser (Kumudu Herath © IUCN; page 2: Contour planting (source: preparation were demonstrated in 220 home gardens http://theplanetd.com/a-little-bit-of-britain-in-sri-lanka/); above: representing all 11 villages of the project area. It was Participatory planning of home garden development, Kumudu emphasised that soil and water pollution is controlled Herath © IUCN by reducing the use of agrochemicals. For more information contact • Through the project, supplies such as vegetable seeds, fruit plants, watering equipment, and barrels used to Shamen Vidanage, produce liquid organic fertilisers were provided to the Programme Coordinator, IUCN Sri Lanka Country Office 220 beneficiaries. The villagers were motivated to grow 53, Horton Place, more local varieties of fruits, vegetables, and other Colombo 7, Sri Lanka home garden crops to diversify not only the variety of tel: +94-112682418, fax: +94-112682470 food available to them but also the income sources email: [email protected]; https://www.iucn.org from the home gardens. • Live fencing with various multi-purpose for soil Access technical note from here.

January 2016