If you’ve ever wondered why, despite the advances in irrigation tech, the country and its farmers wait so anxiously for the monsoons, here’s the answer: Sixty per cent of India’s crops comes from rainfed areas of the country. But there’s hope yet. Scientists at the Indian Institute of Science, Bangalore, and the Indian Agricultural Research Institute, New Delhi, believe that development and application of regional rainfall models will help farmers reduce risks and increase productivity.In three research articles in Current Science, Dr Sulochana Gadgil and team members Dr P R Seshagiri and Dr S Sridhar of IIS, and Dr Y P Abrol of IARI explain that they have had excellent results in experiments with just such composite models among groundnut growers in Anantapur, Andhra Pradesh, and Pavagada, Karnataka.The secret of their success lies in an experimental model that assesses the indirect impact of climate variability — including pests, disease and weeds — on a crop. Helping this model is a simple two-layer hydrological model, which determines soil moisture affected by evaporation or evaportransiration at various stages of cultivation and crop development.Since the timing of farming operations, as well as onset of some pests and diseases, is dependent on soil moisture, the hydrological model is pressed into service first. Then the heuristic (or experimental) model is used to determine timing as also triggers for pests, disease and weeds. Then, in conjunction with the PNUTGRO model (applicable only to peanut crops, it projects the yield in the absence of any pest or disease), the heuristic model provides the indirect impact of climate variability.The authors believe that climate variability impacts the growth and development of crops directly as well as through incidence of pests, disease and weeds. ‘‘Crop models developed over the last few decades for different crops such as rice, wheat, groundnut, sorghum etc incorporate only some facets of the direct impact of climate variability. Thus, while all the models incorporate the impact of radiation on photosynthesis, and hence growth and development of plant, only few models, eg PNUTGRO, incorporate the effects of moisture stress induced by dry spells.’’Studying rainfall data for the Anantapur region for the past 80 years, the scientists related large year-to-year variations in rainfall to corresponding variations in yields. These rainfall data collected for past 80 years have been used to construct the heuristic model.
