Local knowledge could help Indian irrigation
In recent years, the erosion of local knowledge about the natural environment and micro-climate has hindered agricultural production in western Rajasthan, claims freelance irrigation and drainage engineer Bhanwar Dan BithuHere he explains the need for a return to an understanding of nature in these arid and semi-arid regions if sustainable agricultural production is to be achieved.
Agricultural and livestock production in arid and semi-arid regions of western Rajasthan depends not only on availability of rain, irrigation water and fertilizers, but also on moisture conservation, soil fertility and micro-climatic variables like wind, sunshine and fog. Production failures have occurred despite good rainfall or irrigation water and use of fertilizers.
In the last few decades, production strategy has dismantled the pyramid of traditional agricultural knowledge, causing occasional production failures, land attrition and the degradation and destruction of diverse biological resources. Excessive use of chemical fertilizers and insecticides and callous ignorance of traditional knowledge and micro-climatic factors have been causing the slow and unrectifiable loss of soil fertility, genetic diversity and soil erosion.
Shifting the blame onto monsoon failures or inadequate irrigation and adopting an inappropriate chemical fertilizer-based production strategy has been unhelpful. The widespread use of tractor-driven deep plowing has also been destroying the natural diverse biological resources causing a decline in soil fertility and moisture holding capacity.
The region's trees, shrubs and grasses are vital to soil fertilization, soil moisture conservation, soil nutrient generation and conservation, hydrology, climatic regulation, the availability of plant materials for propagation. The value of arid and semi arid land trees, shrubs and grasses include:
- Khejri and khejra (Prosipis Cinerarea and Prosipis Spicigera Linn) - good quality cattle feed, vegetable leaves and fuel wood. The land under them is fertilized by bird excrement and tree leaves.
- Phog shrub (Calligonium Polgonoides) - binds soil, minimizes soil erosion and conserves sub-soil moisture and nutrients. It provides fuel wood, fodder and vegetable. The large part of the produced bio-mass functions as moisture and nutrient reserve.
- Kheep, bari bui and sinia shrubs (Leptadenia Spartium Wight, Aerva Pseudo Tomentos and Crotalaria Burhia Hamilt) - bind and conserve soil, minimize soil erosion, conserve sub-soil moisture and nutrients, encourage growth of soil micro-organisms and increases soil fertility.
- Sevan grass (Lasiutus Sindicus) - binds soil, minimises soil erosion, increases rainwater infiltration into the soil, forms a natural micro-catchments rainwater harvesting system and promotes growth of soil micro-organisms and soil fertility. Excellent protein-rich cattle feed. The micro semi-pervious layer at the root depth conserves root zone soil moisture.
- Jhar beri shrubs (Zyziphus Numnaularia and Zyziphus Mauritiana) are excellent soil binding, rainwater infiltration enhancing and soil fertility increasing shrubs. The large part of the produced biomass functions as soil moisture and nutrient reserve, and thus fluctuations in rainwater yields are smoothed out.
Traditional arid and semi-arid agriculture recognises the superiority of rainwater over canal and groundwater. Rainwater is aerated and absorbs oxygen and other gaseous minerals from the atmosphere and makes them available to the crop plants, trees, shrubs and grasses (except in the case of acidic and injurious salt rain where air is highly polluted).
Canals and groundwater contain salts and less oxygen, therefore, requisite rainfall, even in canal or groundwater irrigated areas, improves agricultural production and is desirable. In addition to natural biological diversity and rainwater, there are some micro-climatic factors that significantly affect agricultural and livestock production, for example, time- and direction-specific wind flow.