numerous impacts on crop productivity, economic growth, income distribution, food 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 treating the cause of problem. Two well-known examples are that low soil fertility and soil compaction due to soil erosion are treated with the application of inorganic fertiliser and tillage respectively, rather than attempting to control the process of soil erosion.

To conserve soil resources, the Kapirriggama Cascade project had the overall goal of achieving sustainable land management of agricultural systems to enhance the soil texture and soil productivity of the catchment; and the following specific objectives: 1) to minimise soil erosion;2) to enhance soil moisture; 3) to enhance soil fertility; 4) to decrease soil and water pollution by minimising the use of agrochemicals; and 5) to increase the resilience of upland agricultural systems against drought.

Sustainable land management is defined as ‘the use of land resources, including soils, water, animals and plants, for the production of goods to meet changing human needs, while simultaneously ensuring the long-term productive potential of these resources and the maintenance of their environmental functions’ (defined at the UN Earth Summit, 1992). There are two broad objectives of sustainable land management: 1) to maintain long term productivity of ecosystem functions; and 2) to increase productivity (quality, quantity and diversity) of goods and services.

Methodology for Sustainable Land Management

The methodology for sustainable land management comprises four different practices namely, agronomic practices, vegetative methods, structural methods and management or a combination of these.

Agronomic practices The following agronomic practices are recommended.• Mulching: A mulch is generally organic, sometimes

permanent (for example, plastic sheeting) and sometimes temporary (for example, bark chips). Mulch can be applied around plants or on bare soil. Mulching is used commercially and in home gardens. When applied correctly, mulching significantly improves the quality of soil.

• Contour planting: Crops are planted along contours or across the slope. When contour cultivation is practised in tea lands, soil erosion become negligible.

• Zero tillage: This is a way of growing crops each year, without tilling the soil. This technique increases the amount of water that percolates into the soil, increases the retention of organic matter in the soil and increases the recycling of nutrients in the soil. It has been shown to reduce or eliminate soil erosion.

• Application of organic fertiliser: Composting is defined as the natural process of decomposition of organic materials by micro-organisms under controlled conditions. Raw organic materials such as crop residues, animal wastes, green manures, aquatic plants, industrial wastes, city wastes and food garbage are excellent sources of compost.

• Mixed cropping/inter-cropping/co-cultivation: This is the practice of growing, simultaneously, two or more crops on the same land. When the crops to be grown together are selected correctly, the products and refuse from one crop plant help in the growth of the other crop plant and vice-versa.

Vegetative methodsThe following vegetative methods are recommended.• Biological hedges: Hedges are placed across the

slope to slow down the overland flow. These can consist of live or dead materials of biological origin. Alley cropping, graded hedgerows, SALT hedges are placed under this category. • Alley cropping has been found to be successful

in various parts of the dry zone on flat or gently sloping lands. Legume species such as Gliricidia sepium (Sinhala: Wetahiriya/Kona; Tamil: Kona/Seemai kiluvai) are planted across the slope with slight gradient on a soil ridge. Citronella grass is planted along with the Gliricidia. This combined hedge is pruned periodically and loppings spread on the surface between the hedges. These loppings act as mulch. Crops suitable for such alleys are vegetables, tuber crops, pulses, cereal, papaya, banana and other fruit crops.

• Sloping Agricultural Land Technology (SALT) Practice: This method is adopted for sloping lands

up to 60% slope in the mid and up country wet zone. Gliricidia is generally used as the hedge plant, but Tithonia diversifolia (Sinhala: Val-suriyakantha) and Erythrina variegata (Sinhala: Erabadu; Tamil: Mulmurukku) can also be planted. In this method, double hedgerows are established along the contour. To minimise soil erosion, the space between two rows of the double hedge is filled with stones and any other solid material.

• Grass hedges: Grass hedges are also established across the slope. Species recommended are Vetiveria zizanioides (Sinhala: Sevendra; Tamil: Vettiver), Cymbopogon nardus (Sinhala: Mana/Heen-pengiri); Cymbopogon citratus (Sinhala: Sera; Tamil: Serai).

• Cover crops: These are crops grown primarily to cover the surface of the soil , thereby reducing erosion. In Sri Lanka, cover cropping is not practised widely except in rubber and coconut plantations, as inter-spaces are not free and are often occupied with a mix of different crops. However, where it is practical, the recommended cover crops are Calopogonium mucunoides and Desmodium species.

Structural MethodsStructural methods have been considered the main focus of soil conservation by many implementing agencies. The most popular measures are:• Lock and spill drains: This is a hillside ditch unique

to Sri Lanka. This is practised for soil conservation on sloping lands exceeding 40% slope. The ditch is square in shape, placed across the slope with a slight gradient. Low cross walls are left in the bed of the drain, so that it is divided into separate basins to encourage infiltration and to trap sediment. During heavy rain, the runoff overtops these cross walls and spills towards the outlet, usually a stoned–lined channel running down the slope. Periodically, the accumulated sediment is removed and spread nearby. In order to minimise the accumulation of sediment in the drain it is recommended that a line of grass, Vetiveria zizanioides or Cymbopogon nardus, is established just above the drain.

• Stone bunds: These are used on steep slopes, where the soil is not stable enough to keep as risers (vertical walls) in terraced lands and where stone is available for such work.

• Soil bunds and drains: This type of conservation measure is adopted on lands with slopes less than 10%. In order to prevent damage or collapse of the bund, grass species such as Vetiveria zizanioides, Cymbopogon nardus and Cymbopogon citratus are planted downstream of the bund.

• Terracing: This practice converts a steep slope into a series of steps with horizontal or nearly horizontal ledges (shelves), and vertical or almost vertical walls (risers) between the ledges. The wall is vulnerable to erosion and is protected by a vegetative cover and sometimes, faced with stones or concrete. There is no channel but a storage area is created by sloping the shelf into the hillside.

• Gully control structures: Gullies are formed when runoff into natural streams is diverted or lands are opened up encouraging more overland flow. Gullying

is an advanced stage of erosion and very costly to repair. Vegetation can be used to control gully erosion, providing the soil with physical protection against scour and slowing down the velocity of flow. There is a variety of gully control structures from brushwood dams to cement structures. The brushwood dam uses small tree branches, packed as tightly as possible across the direction of flow. Stone check dams, pile stones across the gully with or without cement plastering, keeping a depression at the middle of the dam to allow spill over of the excess flow. Some plant species are established on either side of the gully of the upstream and downstream area to slow the flow and strengthen the dam.

Management Practices

Land must be managed properly to maintain long-term productivity. As soil, rainfall and terrain conditions vary from place to place, adoption of proper land use practices is essential. Along the catena (a sequence of soil profiles down a slope) what crops should be grown and what land use practices must be followed must be decided carefully. For dry zone farming communities, the most appropriate model is as follows:

Phase Appropriate land use Irrigable area

i Well-drained RBE, shallow phase < 30 cm

This upper ridge should be kept undisturbed. If cleared already, a portion can be converted to a village forest, planted with suitable species (See technical note # 2 and 3).

ii Well-drained RBE, moderate-ly deep soils < 30-60 cm

These can be used for planted forests (a mixture of forest and fruit trees

iii Well-drained RBE, deep soils > 60 cm

These lands can be used for rainfed farming, with adequate soil conser-vation measures

Irrigable area

iv Moderate-ly-drained RBE; deep soils > 60 cm

This strip of land can be allocated as a settlement area with home gardens

v Imperfect-ly-drained RBE

This can be used for paddy cultivation in the maha season and other sea-sonal crops in yala season

vi Poorly-drained LHG

This is only suitable for rice cultivation

Combined PracticesSome of the combined practices that can be recommended are described below.

Conservation FarmingIn sustainable land management, all practices other than mechanical conservation measures can be categorised as conservation farming. Conservation farming is a broad-based approach of land and water management. It exploits resources while conserving them through moisture retention, fertility and soil conservation, which make the system less dependent on expensive inputs such as energy, machines, inorganic fertilisers and other agro-chemicals. The most important practices under conservation farming applicable to dry zone conditions are:

January 2016

For more information contact

Shamen Vidanage, Programme Coordinator, IUCN Sri Lanka Country Office53, Horton Place, Colombo 7, Sri Lankatel: +94-112682418, fax: +94-112682470email: shamen.vidanage@iucn.org; https://www.iucn.org

Access technical note from here.

Photographs: Cover: Soil conservation bund in a home garden (Kumudu Herath © IUCN; page 2: Contour planting (source: http://theplanetd.com/a-little-bit-of-britain-in-sri-lanka/); above: Participatory planning of home garden development, Kumudu Herath © IUCN

i) hedge row cultivation (alley cropping and SALT, discussed previously; ii) conservation of moisture in the top soil (through mulching, and in-situ rainwater harvesting) and iii) soil fertility enhancement. Soil fertility can be improved by adding various types of fertiliser sources containing plant nutrients. Such source include plant residues (crop residues and green manure); animal wastes (animal manure and slaughter house wastes) and compost (discussed previously).

Project Interventions

• Conservation farming was demonstrated in 37 upland farms (33 acres) located in the catchments of nine tanks in the project area. About 20,000 m of soil conservation bunds were established in 100 acres of farmlands to arrest soil erosion. Soil conservation bunds reduce the runoff velocity and thereby reduce the erosive power of water. The improved drainage system associated with the soil bunds facilitates the capture of eroded soil and thereby, reduces siltation of tanks.

• By reducing the runoff velocity, the soil bunds facilitate groundwater recharge in the farmlands. This increases the soil moisture content, which, in turn, increases the resilience of the farmlands to droughts. The soil bunds were stabilised with Gliricidia sepium, Cymbopogon nardus (Sinhala: Mana/Heen-pengiri; Tamil: No name known) and Justicia adhatoda (Sinhala: Adathoda; Tamil: Pavettai). Application of the fodder obtained from farmlands increases the organic content of the soil, which, in turn, increases soil texture and soil fertility.

• Eyebrow bund and pitcher systems were introduced in 37 upland farms for micro-scale soil conservation 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 sustainable agriculture and home garden development. Eight different types of sustainable agriculture practices and five methods for bio-fertiliser preparation were demonstrated in 220 home gardens representing all 11 villages of the project area. It was emphasised that soil and water pollution is controlled by reducing the use of agrochemicals.

• Through the project, supplies such as vegetable seeds, fruit plants, watering equipment, and barrels used to produce liquid organic fertilisers were provided to the 220 beneficiaries. The villagers were motivated to grow more local varieties of fruits, vegetables, and other home garden crops to diversify not only the variety of food available to them but also the income sources from the home gardens.

• Live fencing with various multi-purpose trees for soil

conservation and manure production was promoted. • Soil quality maps of the command areas of eight

tanks were developed for parameters such as soil pH, electrical conductivity, organic matter content, potassium, phosphorous and drainage capacity. Based on the results location specific soil health cards were developed for 140 paddy lands to assist location specific fertiliser recommendations. This reduces overuse of fertilisers.

• Iswetiya (See Brief # 1 for description) were formed in the tank bunds of five tanks to reduce runoff velocity and to arrest eroded soil before reaching the tanks. Reduced runoff velocity reduces the erosive power of rainwater.

• Through the activities of ecosystem restoration of the project (See Brief # 3), barren areas of the tank catchments were replanted with multi-purpose tree species, facilitating erosion control and improving productivity of the cascade.

• Home gardens and farmlands were planned through participatory planning to optimise use of sunlight, by promoting stratification in the vegetation to keep the evergreen mixed canopy to maintain a suitable microclimate.

Recommendations for the future

• Continue establishing soil conservation bunds in the farmlands and home gardens in the immediate catchments of all the tanks in the cascade.

• Establish iswetiya in all the tanks where it is technically possible.

• Conduct soil quality testing and promote location-specific soil fertility programmes to minimise overuse of chemical fertiliser.

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