Dry Spell Dynamics Impacting the Productivity of Rainfed Crops Over the Semi-Arid Regions of South-East India

The crop productivity in rainfed regions is driven by the quantum and distribution of rainfall during the crop growth period. The dry spell index (DSI) was used in the present investigation to quantify the cumulative impact of dry spells on major rainfed crops of the kharif season (June–September) in India's semi-arid regions of Andhra Pradesh. The effect of DSI on the yield of major rainfed crops, i.e., groundnut, pigeon pea, cotton, maize and pearl millet was estimated and compared with the widely used standard precipitation index (SPI). Our results revealed that among the various districts, a higher DSI (> 16.1) was noticed in Anantapur that experienced a DSI of 8.1–16.0 in 77% of the years during the study period (1998–2019), which indicated that the crop suffered stress conditions during the season affecting the crop yields. Moreover, a significant negative correlation was observed between the yields of various crops (groundnut, pigeon pea, maize and pearl millet) and DSI. On the other hand, SPI analysis showed that 74%–83% of the years experienced normal (−0.99 to 0.99) to moderately dry (−1.00 to −1.49) conditions, indicating normal rainfall status during the season. At the same time, no significant correlation was found between the SPI and crop yields. Therefore, the present study revealed that the DSI performed better in quantifying the dry spells and their impact on crop yields, especially under rainfed conditions in the semi-arid regions of south-east India.