Rainfall deficits and erratic dry spells pose major challenges in rainfed ecosystem. In-situ moisture conservation practices (MCP) like ridge–furrow methods, improve soil moisture but are inadequate during 2–3 week dry spells at critical crop stages (flowering and maturity), leading to yield loss. Supplemental irrigation (SI) using an ex-situ rainwater harvesting (RWH) pond can mitigate these effects, but optimizing the pond design is challenging due to limited runoff and storage losses. This study aims to design RWH pond for small farm holders with a 1.0 ha area and evaluate its efficient use for SI during intermittent dry spells and critical crop stages. The design volume was estimated using the SCS-CN method based on daily rainfall data (1974–2010) for the northeast monsoon. A pond with a capacity of 487.5 m³, constructed for a 1 ha micro-watershed, was used to observe the runoff for design validation. The harvested runoff can be used as SI for a cultivable area of 0.4 ha, based on the watershed-to-cultivable area ratio. Statistical analysis of observed and estimated runoff data from 2011 to 2023 revealed a strong correlation (r = 0.87), confirming the pond design. Harvested rainwater, applied through micro-irrigation (rain gun) at a depth of 50 mm during moisture stress periods, significantly improved cotton productivity. The combined use of harvested rainwater and MCP increased yield in the range of 3.8 to 25.3%, improved rainwater use efficiency (1.52 to 3.13 kg ha⁻¹ mm⁻¹), and had a higher benefit-cost ratio (1.15 to 2.43) over a 13-year period. This study concludes that integrating in-situ MCP with ex-situ RWH with micro-irrigation significantly improves rainfed crop productivity in vertisols.

A field experiment was conducted during 2022–23 to 2024–25 at the AICRPDA Research Farm, Tamil Nadu Agricultural University, Kovilpatti, India, to evaluate climate-smart agri-horti systems integrating aonla (Phyllanthus emblica Gaertn.) and custard apple (Annona squamosa L.) with annual intercrops under rainfed conditions. The experiment, laid out in a split-plot design with three replications, included fruit tree species as main plots and blackgram (Vigna mungo L.), greengram (Vigna radiata L.), clusterbean (Cyamopsis tetragonoloba L.), and foxtail millet (Setaria italica L.) as sub-plot treatments. Custard apple–based systems consistently produced higher fruit yield (2674–3306 kg ha⁻¹), intercrop biomass, and blackgram equivalent yield (1337–1653 kg ha⁻¹) than aonla-based systems (1980–2538 kg ha⁻¹ of fruit yield), and 891–1142 kg ha⁻¹ of blackgram equivalent yield of intercrops, respectively), primarily due to improved light availability and favourable canopy architecture. Clusterbean and foxtail millet recorded the highest intercrop yields, whereas pulse intercrops enhanced tree growth, soil nitrogen availability, and system sustainability through biological nitrogen fixation. Maximum rainwater use efficiency and land equivalent ratio were achieved under custard apple + clusterbean and aonla + foxtail millet combinations, indicating superior resource-use efficiency. Relative economic efficiency peaked in aonla + foxtail millet (341.2%), while the highest system profitability was recorded in custard apple + foxtail millet (₹352.4 ha⁻¹ day⁻¹). Soil fertility improved significantly over the study period, with increases in soil organic carbon (1.05–1.76 g kg⁻¹), available nitrogen (9–11 kg ha⁻¹), and potassium (8–14 kg ha⁻¹), particularly under pulse-based systems, whereas available phosphorus in soil remained unchanged. The study demonstrates that integrating short-duration legumes and millets with perennial fruit trees enhances productivity, profitability, rainwater-use efficiency, and soil health, providing a resilient and sustainable strategy for intensifying rainfed agroecosystems.