Soil and water conservation measures for hill agriculture

SK Pattanaaik
Contd from previous issue
In NEH region, bench terrace cultivation exists in slopes up to100 per having terrace width as low as 3 m and situations on steep hills normally do not permit a longer length of terrace. Level beds with vertical intervals of about 1 m along with 15 sq. m cross section shoulder bunds and 1:1 batter slope for terrace risers is found. The terrace risers can be protected either through stone pitching or by raising grasses (grass or vetiver).
Half moon terrace
Where complete terracing is not desired or feasible productive, multiple use of steep slopes is possible by planting trees on half moon terraces. These are level circular beds having 1 to 1.5 m diameters, cut into half moon shape on the hill slope. These beds are used mainly for planting of fruit trees like guava, citrus etc. in horticultural land uses.
Vegetative bunds
Barrier hedges substantially reduce runoff and increase infiltration. Some runoff may cross the barrier, while the entrained soil will be partly filtered out and deposited. Pineapple plantation can be successfully used as vegetative bunds in hills.
Grassed waterway
These are trapezoidal or parabolic channels planted with suitable close growing grasses constructed along the slope preferably on natural drainage lines to act as an outlet for the terrace system. These channels along with silting basins serve the purpose of energy dissipation of flowing runoff water.
Geojute (also called as “soil saver) is a natural geotextile used as mulch. This is essentially jute matting with an open mesh of 2 to 5 mm thick jute yarn having 10 mm apertures and is bio degradable. It has been successfully tried for stabilization of landslides, mine spoils and steep slopes. The technique of geojute application included (a) spreading f geojute by overlapping and joining adjacent widths, (b) driving wooden sticks to a depth of 1m to secure matting place, (c) planting rooted slips of local grasses and cuttings of bushes in openings between the geojute strands at close spacing. It is found successful for initial establishment of vegetation on degraded slopes (up to 60-70%).
Gabion structure
Gabion is a material which is very often used for constructing various soil and water conservation control measures like control of stream bank erosion and as filtered check dam, etc. It is defined as “stones filled in wire box”. The wire boxes are generally made with a width and a height of 1.0 and 1.0/ 0.5/ 0.3 metre, respectively. The length is kept from 2 to 4 metre. The required size of length, width and height is obtained by placing adjacent boxes of the size as referred above and interconnecting faces. Galvanised iron wire of No. 8 or No. 10 gauge is used for fabricating mesh with triple twist. The wire net has mesh size varies from 7.5-15cm. Fr every 10 m wire mesh, 13 m of wire is used. Then, boxes of wire net are prepared and stones are filled in these boxes. Lastly the opening ends of wire meshes are tied with the help of rods.
Stream bank erosion control
All rivers and streams while flowing through hilly regions have a tendency to erode away their banks. The erosion destroys productive crop fields, human habitation situated on the river margin. A cheaper way of dealing with the problem of riverbed and bank maintenance is through plantation and using locally available stones. The stream banks can be protected by planting water loving vegetation particularly of out sprouting type. The effectiveness of engineering measures may be enhanced by several vegetative measures like Salix spp., Vitex negundo, Populous spp., Arundo donax, Ipomeacarnea, Tatraphacuras, Pennisetum purpureum etc.
Rain water storage tank
Rain water harvesting is a measure to reduce the splash, sheet and rill  erosion while storing the runoff water in hill terrace r valleys. The practice of rain water harvesting in ponds/tanks and reusing the stored water for life saving irrigation of crops and also for pisciculture and other domestic purposes is prevalent in India. The tank is dug out and the excavated soil is kept as an embankment surrounding the tank. A trench of 1 feet x 1 feet is made surrounding the upper surface of the tank. Construction of such a tank needs some measure to prevent the seepage of stored water is highly porous soil. The pond or the tank can be lined by 150-250 GSM polyethylene sheets. The tank can be fed by diverting streams or form in-situ high rainfall. The construction work should be completed before monsoon. The stored water can be used for irrigating the horticultural crops during winter by micro-irrigation.
Grasses proven soil erosion by intercepting rainfall, by binding the soil particles and by improving soil structures. A grass legume association is ideal for soil and water conservation. Grasses stabilize the surface of waterways, contour bunds and front faces of bench terraces while legumes build up soil fertility. Desirable characteristics of grasses are perennial nature, drought resistance, rhizomniferous, and good canopy with deep root system. The useful grasses are Cenchrusciliaris, Chloris Guyana, Cynodondactylon, Dicanthiumannulatum, Panicum antidotale, Festuca arundinaceae, Eragrostiscurvula, vetiveriazizanioides, Centrosemapubescens, Stylosanthessppl and Siratro Spp. growing a mixture of grasses instead of any single grass proved to be better to stabilize newly formed bunds or terraces.