Climate and rainfed rice cultivation in India

Enabling food production to keep pace with population growth in the face of global climate change is a significant challenge. Drought is predicted to occur more frequently under climate change, which is likely to reduce rainfed crop yields and thereby put at risk the agriculture communities in rainfed regions. Rice is a major crop that is cultivated by rainfed farmers and is therefore, vulnerable to increased variability in rainfall. The main aim of my thesis is to understand the climatic risks to rainfed rice cultivation, focusing on rainfed regions in India. I analysed historical data on monsoon and rice yield and found that more locations showed a drying trend than a wetting trend, and that within-season distribution of rainfall were a more important driver of yield than the total rainfall, or timing of monsoon. I used a climate envelope modelling approach to show that the distribution of rainfed rice can be modelled using climate variables, and that variables measuring water availability were more important predictors of rice distribution than temperature. Using climate projections from multiple general circulation models and representative concentration pathways, I concluded that by 2050, between 14% - 40% of current rainfed areas might become climatically less suitable for cultivating rice. Using rice yield trials data, I examined the yield performance of locally and widely-grown rice cultivars under water- and heat-stress. I found that cultivars showed greater yield decline under heat-stress than under water-stress. In addition, I found greater decline in yield under heat-stress in cultivars that were more drought-tolerant, suggesting potential trade-offs in continued improvement of drought-tolerant rice. I conclude that rainfed regions are at risk from climate change, and that rice yields are particularly vulnerable to short-term variability in monsoon rainfall. Trade-offs between water- and heat-stress tolerances suggest that the development of new rice cultivars needs to consider multiple plant traits and drivers of yield, in addition to drought-tolerance. Therefore, improving irrigation infrastructure for timely availability of water, and access by farmers to the most resilient crop varieties will reduce future climate risks for farmers.