13. Vetiver grass (vetiveria zizanioides) - a method of vegetative soil and moisture conservation.
Publ. of World Bank, Agriculture Divison, New Dehli; 1988, 72 pp.
Soil conservation is a world problem.
Soil erosion has reached crisis proportions in India. Over half of India's crop land is losing productivity because top soil is being washed or blown away faster than natural forces can replace it. Reducing the topsoil layer causes part of the subsoil to be cultivated, meaning that plants will have reduced access to essential nutrients and water.
Changes in farming practices have accelerated this erosion in recent years, as farmers switched from traditional rotations to continuous row cropping in response to a growing need for grain.
Top level policy makers recognize the problem exists and have already spent Rs. 1,200 M on earthworks as preventative measures. But this has only covered a few million of India's 328 M hectares, 90% of which is afflicted with soil erosion.
The costs of constructed soil conservation measures would outrun the short-term benefits by three or four times, and these practices not only cost money, they also cut production. Farmers do not look kindly on these practices.
On the other hand, vegetative soil and moisture conservation measures are not only extremely cheap (less than 1/10-1/100 the cost of constructed banks and waterways) but the farmers can do the work themselves, and, if they have the planting material, at no cost. Once vegetative hedges are established (this usually takes two to three seasons) they are permanent. When they are followed as contour guidelines for cultivation and planting, the resulting "in-situ" moisture conservation increases yields by at least 50% over traditional methods.
Vegetative conservation measures hold the runoff water on the slopes longer than other methods, giving it a chance to soak in over a wide area and recharge the aquifers: Constructed measures are designed to dispose of runoff as fast as practicable, thus reducing any change of recharge. Dams rarely recharge aquifers; if they did, it would be considered that they were leaking.
The farmers regard the fodder value of vetiver grass as an additional merit. 3-4 cuttings can be obtained at an interval of 45 days, mainly during and shortly after the monsoon, yielding enough green fodder for two animals for 6 months in a year.
The farmers have developed their own ways of multiplying and propagating the grass. On sloped land, they form small section bunds across the slope and plant 2-3 slips per rill 20-30 cm apart on the upstream side.
In flat fields, the slips are simply planted in the plough furrow. In either case, they chop off the top of the plant and avoid planting inflorescence axles. The grass establishes well if planted after the first monsoon shower. Even without irrigation, the lines form hedges in about year. The slips for further planting are taken from 3-year-old bunds. When waste-weirs or drop structures are to be treated, even clumps of the grass are taken and placed at appropriate locations.
Vetiver has long been used by Indian farmers, but most scientists are still unaware of this. The indigenous knowledge of Indian farmers has not been appreciated. The knowledge they have gained in dealing with khus-based soil conservation systems needs to be documented and the other uses of khus, e.g. for fodder, should be studied.
This handbook has been prepared to support field workers and farmers in developing appropriate soil and moisture conservation measures using vegetative systems. Experience in India and in other countries has shown that conventional earth bunding systems on small farms have been expensive to develop and have in many cases proved ineffective.
Vegetative systems of soil and moisture conservation have proved cheaper and more effective when implemented correctly.
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Erosion and desertification control
Latin America, Colombia, Andes, hillside farming, water erosion, cassava, cropping systems, small scale agriculture, CIAT
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