PART V The Effects of Climatic Variations on Agriculture in Dry Tropical Regions of
Contents, Part V List 0/ Contri6utors 499 A6stract 501 1. Introduction 503 N.S. Jotll&a 1.1. Background to the case study 503 1.2. Aims and approach 505 1.3. The study area 506 1.4. Drought as a policy and planning issue 510 1.5. A brief evaluation of public interventions 516 2. Effects of Monsoon Variability on Agriculture 523 S. Gadgil 2.1. The setting 523 2.2. Monsoons, the ITCZ and the spatial variation of rainfall 524 2.3. Climatic clusters of the n region 525 2.4. Agricultural zones of Karnataka 527 2.5. Coherent regions 530 2.6. Variability of rainfall and yield 533 3. Effects on Agricultural Productivity 537 A.K.S. Huda and S.M. Virmani 3.1. The setting 537 3.2. Agroclimatic description 538 3.3. The crop simulation model 544 3.4. Crop simulation results 547 3.5. Conclusions 555 4. Village-Level Farm Adjustment to Rainfall Variability 557 N.S. Jotll&a and B.P. Singl& 4.1. The farmer context 557 4.2. Long-term adaptations 558 4.3. Short-term adjustments 560 4.4. Reduced efficacy of the strategies 564 4.5. Complementary roles of technology and public interventions 566 497
498 5. Conclusions and Implications N.S. JodJ&a. a.nd S.M. Virma.ni 5.1. The scope ofthis study 5.2. Summary of results 5.3. Policy and planning implications A cbowledgments References 569 569 570 571 575 576
List of Contributors GADGIL, Dr. S. Centre for Ecological Science n Institute of Science Bangalore 560 012 HUDA, Dr. A.K.S. International Crops Research Institute for the Semi-Arid Tropics (ICRISAT) Patancheru P.O., Andhra Pradesh 502 324 JODHA, Dr. N.S. International Centre for Integrated Mountain Development G.P.O. Box 3226 Kathmandu Nepal SINGH, Dr. R.P. International Crops Research Institute for the Semi-Arid Tropics (ICRISAT) Patancheru P.O., Andhra Pradesh 502 324 VIRMANI, Dr. S.M. International Crops Research Institute for the Semi-Arid Tropics (ICRISAT) Patancheru P.O., Andhra Pradesh 502 324
Abstract of Part V This study relates to the dry tropical regions of. The major problem facing the area is inter- and intrayear variability of rainfall. Farmers have adapted to this by building diversity and flexibility into their farming systems. Policy makers and planners have also attempted to reduce the instability of dryland agriculture and its impact on the rest of the economy. However, the measures adopted by them have often in the past been designed to protect against drought rather than to respond to both negative (drought) and positive (high rainfall) aspects of rainfall variability. More recently, advances in science and technology have provided new methods and data enabling improved understanding of the agroclimatic, agrobiological and other environmental variables affecting agriculture; and these have demonstrated the extent to which it is possible to obtain higher and more stable crop production. In addition, drought relief interventions, which originally were mainly short-term and purely welfare-oriented ad hoc activities, have recently acquired productivity orientation and long-term focus. Section 1 considers these developments in some detail. In Section 2 a method of assessing the impact of rainfall variability on crop yields was demonstrated with respect to sorghum in a semi-arid tropical subregion in Karnataka State in South. The large variation of the distribution of seasonal rainfall has led farmers to devote a large proportion of their annual crop production to post-rainy cropping, so that the crops are raised on residual moisture. This practice has led to increased soil erosion as bare lands are exposed during the rainy season. Section 3 considers the variations in sorghum yields that occur under moist and dry scenarios. In areas where the annual rainfall exceeds 750 mm and the available moisture storage capacity of soils exceeds 150 mm, the cultivation of two crops, one in the rainy season and a sequential crop in the post-rainy season, is feasible. The study identifies the areas in which it would be worthwhile to collect surface runoff water for subsequent use for protective irrigation, to ensure crop survival during the dry season. Simulation of the response of sorghum to supplemental water provided at different growth stages during post-rainy seasons indicates that irrigations of 50 mm each at sowing and anthesis would increase sorghum yield in poor years by 136%, in average years by 38% and in good years by 17%. Short-term responses take the form of adjustments of plant population, changes in levels of input such as the application of fertilizers and variations in other agronomic practices. Adjustments to severe drought situations often include curtailment of essential consumption and the disposal of productive assets. The study concludes with a plea for dovetailing the application of technology with public interventions, and with farmers' traditional responses to climatic variability. The 501
502 EJlect. 0/ climatic tlljl'iatioru in public interventions should be more in the nature of permanent drought-relieving assets rather than short-term measures to alleviate distress. Traditional adjustment mechanisms are losing their effectiveness in the face of rising population pressure and other forces of change. These adjustments can be modernized and strengthened with the help of new technological developments that have the potential for higher productivity under the same soil-rainfall conditions.