Utilizing rain for grain

Dr Chinmoy Kumar Sarma

(Assam Agricultural University. Can be reached at drcksarma@gmail.com)

An increase in the use of fertilizers or irrigation or farming techniques would not make agriculture entirely independent of rainfall. Therefore, rain-dependent forms of agriculture continue to dominate in the world. A study revealed that rain-fed agriculture is in practice in 80% of the world's agricultural land area and generates 65-70% of the world's staple foods. It produces most of the food for the poor communities in developing countries. Rain-fed areas are characterized by low and variable productivity of crops which is the major cause of poverty for 70% of the world's poor, where both productivity improvement and expansion have been slower relative to irrigated agriculture. Yield gap analyses, undertaken by the Comprehensive Assessment for major rain-fed crops found farmers' yield to be a factor of 2-4 times lower than the achievable yields and offered substantive opportunities for realizing the potential of rain-fed agriculture. Experts realize the scope for 100% improvement potential in yield in rain-fed agriculture in the developing countries, compared to only 10% for irrigated crops.

Indian agriculture registered remarkable gains in food production and rural poverty reduction which moved the country from severe food crises of the 1960s to aggregate food surpluses today. But the impact of the green revolution remained confined to well-endowed and irrigated areas and also in some selected crops and yet, many backward regions mainly rain-fed areas remain untouched in the country.

Rain-fed areas in India are highly diverse, ranging from resource-rich areas with good agricultural potential to resource-constrained areas with much more constrained potential. Rain-fed agriculture supports 40% of India's population contributing about 45 per cent of food production against nearly 55 per cent by the irrigated area. In our country, rain-fed farming is always risk-prone and less productive owing to variation and uncertainty of rainfall with no mechanisms of harvesting the surplus rain to support life-saving irrigation at critical stages of crop growth. However, if managed properly, rain-fed areas have the potential to contribute a larger share to agricultural production in our country. Some of the available estimates suggest that a 1% increase in agricultural productivity translates to a 0.6–1.2% decline in the percentage of rural poor (Thirtleet et al. 2002). By 2025, one-third of India's cereal production shall be contributed by rain-fed areas as per the IMPACT model study by Rosegrant and his group. Therefore, considering the rising demand for food projected over the next several decades and the limitation in the continuous expansion of the irrigated area in our country, planners are now focusing on improving the productivity in rain-fed, or un-irrigated agriculture through efficient management of resources.

The major challenges in rain-fed agriculture are to minimize yearly variation in crop yields due to aberrant weather conditions and to stabilize production at a reasonably acceptable level. In a rain-fed system, crop production is totally dependent on rainwater and efficient rainwater management acts as insurance for the crop during the rainfall deficit period. Total rainfall in our country is distributed over a few rainy days and fewer rain events with high intensity, resulting in surface runoff and erosion or causing temporary water stagnation on agricultural fields favouring higher evaporation from surface areas. In either of the cases, this 'green water' is not available for plant growth and has become less productive. Therefore, in order to realize the potential of rain-fed agriculture in our country, a good strategy appears to be to harvest and conserve a part of available surplus runoff through various methods on a watershed basis and reutilize it for supplemental irrigation at different critical crop growth stages. The main purpose of supplemental irrigation in the rain-fed crop production system is simply to provide just enough water to overcome moisture scarcity at critical crop growth stages to produce optimum yield rather than providing stress-free conditions throughout the crop growing period for maximum yield. The existing evidence indicates that supplemental irrigation ranging from 50-200 mm/ season is sufficient to mediate yield-reducing dry spells in most years and rain-fed systems, and thereby stabilize and optimize yield levels.

India has an annual precipitation of 1140 mm per year, which translates into 400 million hectare metres (mm) of water availability in the country. Out of 400 mm, 70mham is lost to the atmosphere through evaporation, 215 mham recharges the Ground Water, while 115 mham flows as a surface run-off. As some water comes from catchment areas of neighbouring countries also, the actual surface runoff is estimated to be 180 mham, of which utilizable flow is 70.2 mham. Out of 70.2 mham utilizable flow, the surface water utilization is to the tune of 24 mham for agricultural use and 1.5 mham for the industry. This means that India is endowed with an enormous potential of water which can be harnessed for improving productivity in rain-fed areas. The success of rain-fed farming depends on water harvesting, moisture conservation and proper utilization of moisture. India has a rich history of use of traditional systems of water harvesting in almost all states. In fact, ponds and tanks represent an important community resource for drinking water in rural India even today. Water harvesting measures involves the optimum utilization of surface and rainwater in order to sustain the heavy use of groundwater. Although, the techniques of water harvesting either in-situ or ex-situ are different depending on the physio-topography and rainfall pattern of a particular location and the extent of rainfall, but all practices aim at capturing, collecting and storing the maximum available rainwater and/or surface run-off so that the same can be used during the lean period for drinking, irrigation and other purposes. But the whole approach should be on a watershed basis instead of an individual field. The water so conserved in tanks or any other form of the reservoir would infiltrate and percolate into the soil, would raise the groundwater level and improve the soil moisture status, which would help better productivity and plant growth during the prolonged dry spell, apart from serving as an assured source of water to quench and thirst on a sustainable basis. Moisture conservation and utilization are other important factors for improving the productivity in rain-fed areas which can be achieved by improving the water holding capacity of soil through best soil management practices and by ensuring a favourable environment for crop growth for higher water use efficiency. Several crop and soil management practices such as conservation tillage practices, deep summer ploughing, levelling, bunding, contour cultivation, selection of suitable crops and cropping systems, planting system, intercultural operations, the addition of organic manure etc., are some important operations that can also be adopted for moisture conservation and its efficient utilization in rain-fed areas.