Real-time contingency measures for coping with agricultural drought in semi-arid vertisols of southern Tamil Nadu, India

Rainfed agriculture in semi-arid regions is increasingly threatened by climate change-induced rainfall deficits and erratic dry spells, especially during critical crop stages such as establishment, flowering and maturity. These weather anomalies often extend over 2–3 weeks, significantly reducing the crop yields and threatening farmers’ livelihoods. In response, real-time contingency measures (RTCM) have been introduced as a micro-level adaptive strategy to combat drought and flood events through timely and site-specific interventions. The present study conducted over five cropping seasons (2019–2024) evaluated the effectiveness of RTCM in vertisols under rainfed cultivation of drought-tolerant Sorghum K12, a short-duration climate-resilient variety. The study systematically assessed dryness and wetness periods using the rainfall-to-pan evaporation ratio and categorizing drought episodes into early, mid and terminal stages. In response to these temporal stresses, a set of climate-resilient technologies was implemented, including resowing, in-situ moisture conservation through ridge-furrow planting, closure of deep soil cracks with crop residues as mulches and foliar sprays of KCl and ZnSO4 to alleviate plant water stress. These interventions were triggered by real-time observations of soil moisture and rainfall variability. In this study, Percent Available Soil Moisture (PASM) was used as a key indicator to assess soil moisture availability, monitor agricultural drought, evaluate crop moisture stress and justify crop survival, which also supports the timely implementation of RTCM. Over the five-year period, grain yield increased by an average of 45.6 % with an annual increase ranging from 30.2 % to 58.9 % under RTC treatments compared to the control. Rainwater productivity improved significantly, ranging from 0.54 to 0.65 kg/m³ and the benefit-cost ratio (B:C) increased from 2.02 to 3.06, underscoring the economic viability of the RTCM. Biomass yield and harvest index were significantly higher under RTCM, with LSD values confirming statistical significance at 5 % level. Notably, yield stability was achieved even during low-rainfall years such as 2022–23, demonstrating the effectiveness of adaptive drought management strategies. The findings confirm that RTCM offers a robust framework to minimize drought-induced yield losses, enhance soil moisture retention and ensure profitability in vertisol-based rainfed systems of southern Tamil Nadu.