This chapter discusses the past and present trends and future direction of rainfed agriculture. Topics covered include: the relationship between rainfed agriculture and water stress; crop yields in rainfed areas; constraints in rainfed agriculture areas; the potential of rainfed agriculture; and the new paradigm in rainfed agriculture.
Rainwater is the main source of water for agriculture but its current use efficiency for crop production ranges between only 30 and 45%. Annually, 300-800 mm of seasonal rainfall are not used productively, as the rainfall becomes surface runoff or deep drainage. The International Crops Research Institute for the Semi-Arid Tropics (ICRISAT)'s long experience, in partnership with national agricultural research systems, in integrated watershed management has clearly demonstrated that areas with good soils in the semi-arid tropics (SAT) in Asia can support double-cropping, while surplus rainwater could recharge the groundwater. In the integrated watershed approach, the emphasis is on in situ conservation of rainwater at farm level, with the excess water being taken out of the fields safely through community drainage channels and stored in suitable low-cost structures. The stored water is used as surface irrigation or for recharging groundwater. Following conservation of the rainwater, its efficient use is achieved through choosing appropriate crops, improved varieties, cropping systems and nutrient and pest-management options for increasing productivity and conserving natural resources. Longterm, on-station watershed experiments have demonstrated that Vertisols with a rainfall of 800 mm have the capacity to feed 18 persons ha Ϫ1 (4.7 t of food grains ha Ϫ1) compared with their current productivity of 0.9 t ha Ϫ1 supporting four persons ha Ϫ1. This increased productivity can be achieved if the productivity of rainwater is doubled (from 30% to 67%) and the soil loss is reduced by 75% compared with the loss under traditional methods of cultivation. By adopting such a holistic approach to the management of rainwater in partnership with the communities, crop productivity in the watersheds is substantially increased (up to 250%), groundwater levels improved and soil loss minimized. Results from such on-farm integrated watersheds are discussed. Conditions for success in the improved management of rainwater are: community participation, capacity building at local level through appropriate technical guidance and the use of new scientific tools to manage the watersheds efficiently. To sustain agricultural productivity in the SAT, this holistic approach of watershed management needs to be scaled up through appropriate policy and institutional support and its on-site and off-site impacts need to be studied.
Soaring prices of fossil fuels, geo-political issues and environmental pollution associated with fossil fuel use has led to worldwide interest in the production and use of bio-fuels. Both the developed and developing countries have developed a range of policies to encourage production of combustible fuels from plants that triggered public and private investments in bio-fuel crop research and development, and bio-fuels production. In this article, we discuss the potential benefits of bio-fuels in increasing the farmers' incomes, reducing environment pollution, the crop options and research and development interventions required to generate feedstocks to produce bio-fuels to meet projected demand without compromising food/fodder security in developing countries.
Many environmental benefits result from watershed interventions in the semi-arid tropics. Environmental benefits may be defined as the condition and process through which ecosystems sustain and fulfill human life, including the provision of food and other goods. The spillover effects of these benefits range from an increase in household welfare condition to ecosystem sustainability. An attempt is made in this paper to assess these benefits in the context of Indian Semiarid tropics using primary data collected from two micro watersheds (Rajasamadhiyala and Shekta watersheds). Results indicate that groundwater availability has substantially increased and soil conservation has brought changes in cropping patterns with high-value crops. Rainwater harvesting through check dams, causeway cum check dams, percolation tanks, farm ponds and earthen bunds have significantly increased water storage capacity and water availability along with doubling the production of major crops. Significant increases in irrigated area, cropping intensity along with diversification of crops from traditional to commercial cash crops were recorded in the watersheds. Assessing the environmental benefits accrued from the watershed development approach may lead to the identification of 'keystone elements' in a landscape that have a substantial impact by providing multi-functions. The integrated watershed management practices adopted in the two micro watersheds substantially improved the sustainability in these watersheds. Using available methods we have assessed the environmental benefits of micro watersheds in the Indian semi-arid tropics.
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