Estimating the potential of rainfed agriculture in India: Prospects for water productivity improvements

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Abstract

A detailed district and agro-ecoregional level study comprising the 604 districts of India was undertaken to (i) identify dominant rainfed districts for major rainfed crops, (ii) make a crop-specific assessment of the surplus runoff water available for water harvesting and the irrigable area, (iii) estimate the efficiency of regional rain water use and incremental production due to supplementary irrigation for different crops, and (iv) conduct a preliminary economic analysis of water harvesting/supplemental irrigation to realize the potential of rainfed agriculture. A climatic water balance analysis of 225 dominant rainfed districts provided information on the possible surplus runoff during the year and the cropping season. On a potential (excluding very arid and wet areas) rainfed cropped area of 28.5 million ha, a surplus rainfall of 114 billion m3 (Bm3) was available for harvesting. A part of this amount of water is adequate to provide one turn of supplementary irrigation of 100 mm depth to 20.65 Mha during drought years and 25.08 Mha during normal years. Water used in supplemental irrigation had the highest marginal productivity and increase in rainfed production above 12% was achievable even under traditional practices. Under improved management, an average increase of 50% in total production can be achieved with a single supplemental irrigation. Water harvesting and supplemental irrigation are economically viable at the national level. Net benefits improved by about threefold for rice, fourfold for pulses and sixfold for oilseeds. Droughts have very mild impacts on productivity when farmers are equipped with supplemental irrigation.

Introduction

Rainfed agriculture is practiced on 80% of the world's agricultural land area, and generates about 70% of the world's staple foods, including most of the food in poor communities in developing and least-favoured areas (CA, 2007). The most recent estimates have put global rainfed croplands at 1.75 billion ha (Bha) at the end of the last millennium, or about 5.5 times the irrigated area in the world (GIAM, 2006). India ranks first among the countries that practice rainfed agriculture both in terms of extent (86 Mha) and value of production. Due to low land and labour productivity, poverty is concentrated in rainfed regions (Singh, 2001). While farmers in some high potential regions have increased yields by about 5% per annum in recent years, farmers in the semi-arid tropics of Asia (including India) have increased agricultural growth by less than 1%. Yield gap analyses for major rainfed crops find that farmers’ yields are about one-half to one-quarter of achievable yields (CA, 2007). Grain yields vary from 1 to 2 tons t ha−1 in many rainfed areas, compared to attainable yields of more than 4 t ha−1 (Falkenmark et al., 2001). The large yield gap suggests there is much to gain by improving productivity in rainfed agriculture.

Rainfed agriculture in India is practiced under a variety of soil type, agro-climatic and rainfall conditions ranging from 400 mm to 1600 mm per annum. Rainfall is a random input and its variation and intensity are high in areas of low rainfall. Rockstrom and Falkenmark (2000) note that a decrease of one standard deviation from the mean annual rainfall often leads to a complete loss of the crop. Dry spells (or monsoonal breaks), which generally involve 2–4 weeks of no rainfall during critical crop growth stages, causing partial or complete crop failures, often occur every cropping season. Kanwar (1999) has identified adverse meteorological conditions resulting in long dry spells and droughts, unseasonal rains and extended moisture stress periods, with no mechanisms for storing or conserving the surplus rain to use during the scarcity/deficit periods, which comprise the major cause of low yields and heightened distress in rainfed regions.

Supplemental irrigation is a key strategy, so far underutilized on a regional basis, to unlock rainfed yield potentials. The existing evidence indicates that supplemental irrigation ranging from 50 to 200 mm/season (500–2000 m3 ha−1) is sufficient to mediate yield reducing dry spells in most years and in rainfed systems (Wani et al., 2003). Since irrigation water productivity is much higher when used conjunctively (supplemental) with rainwater, it is logical that, under limited water resources, priority in water allocation may be given to supplementary irrigation (Agarwal, 2000, Joshi et al., 2005). On a regional basis, collecting small amounts of runoff using limited macro-catchments during the rainy season, using this resource for supplementary irrigation and adopting improved agronomic practices can improve agricultural production in rainfed areas (Pathak et al., 2009). The Consultative Group on International Agricultural Research (CGIAR) Challenge Program on Water and Food supported a study of the available runoff in the dominant rainfed regions of India, with the goal of examining the hydrologic and economic potential for improving agricultural productivity. That study, as a part of the ‘Strategic Analysis of India's National River Linking Project,’ had the following objectives:

  • (i)

    To identify the dominant rainfed districts for major rainfed crops in India.

  • (ii)

    To assess surplus runoff for water harvesting and supplemental irrigation and the irrigable area at the district level.

  • (iii)

    To estimate regional (district level) water use efficiency and the effect of supplemental irrigation on production of selected rainfed crops.

  • (iv)

    To conduct a preliminary economic analysis of water harvesting and supplemental irrigation in rainfed areas.

Section snippets

Methods of analysis

Districts are the primary administrative and planning units in India, and all data sets pertaining to agriculture, water resources, climate, human development and related parameters are available at the district level. There are 604 districts in India and the average size of a district is about 500,000 ha. We chose districts as the level of analysis for this research.

Dominant rainfed districts for different crops in India

Rainfed areas in India are highly diverse, ranging from resource-rich areas with good agricultural potential to resource-constrained areas with limited potential. At present, an estimated 60% of the 142.2 Mha net cultivated area is rainfed, which contributes to 44% of total food grain production. Rosegrant et al. (2002) have estimated that even by 2025, one-third of India's cereal production will be contributed by rainfed areas. Most of India's (coarse) cereals (91%), pulses (91%), oilseeds

Conclusions

Rainfed lands have substantial unexploited potential for growth, yet the risks of crop failures, low yields and the insecurity of livelihoods are high due to the random behaviour of the monsoonal rainfall. Rainfed agriculture is mainly and negatively influenced by intermittent dry spells during the cropping season and especially at critical growth stages. A district-level analysis of rainfed crops in India shows that total water availability may not be the major problem in rainfed areas. For

Acknowledgements

The support provided by CGIAR Challenge Program on Water and Food and International Water Management Institute, Colombo for implementation of “Strategic Analysis of National River Linking Project” is gratefully acknowledged. Sincere thanks to Dr. J S Samra, Chief Executive Officer, National Rainfed Area Authority of India, New Delhi, India.

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