The Vaippar basin in southern India is economically important for rainfed and irrigated agriculture, mainly depending on the northeast monsoon (NEM) during October–December, and any changes in rainfall patterns directly affect crop ecosystems. This study aimed to analyze spatio-temporal rainfall changes using the monthly data from 13 scattered rain gauge stations in the Vaippar basin, India. They were converted into gridded rainfall data by creating 26 equally spaced grids with a spacing of 0.125° × 0.125° for the period between 1971 and 2019 through interpolation technique. Three methods, namely Simple Linear Regression (SLR), Mann–Kendell/modified Mann–Kendell (MK/MMK), and Sen’s Innovation trend analysis (ITA), were employed to detect trends and magnitudes for annual and seasonal gridded rainfall series. The results showed significant trends at 2.3%, 7.7%, and 44.6% of grid points using SLR, MK/MMK, and ITA methods, respectively. Notably, ITA analysis revealed significant trends in annual and NEM rainfall at 57.69% and 76.92% of the grid points, respectively, at a 5% significance level. The southwestern and central parts of the basin exhibited a higher number of significant upward trends in annual rainfall. Similarly for the NEM season, the south-eastern, central, and extreme southern parts experienced significant upward trend. The western part of the basin exhibited significantly upward trend with a slope value of 2.03 mm/year, while the central part showed non-significant downward trend with a slope value of −1.89 mm/year for the NEM series. This study used the advantage of ITA method, allowing for exploration of monotonic/non-monotonic trends, as well as subtrends of low, medium, and high rainfall segments within the series. The key findings of this study serve as a scientific report from a policy perspective, aiding in the preparation and management of extreme climate effects on land and water resources in the Vaipaar basin.

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.

Improving soil carbon quality and biological fertility through long-term nutrient management is essential for sustaining productivity, reducing input dependence and enhancing climate resilience in rainfed Vertisols. This study evaluated the effects of nine treatments including control, inorganic fertilisation (50 % RDF, 100 % RDF, RDF + Zn), organic amendments [farmyard manure (FYM) (50 % NFYM, sole FYM), crop residues (CR) (50 % NCR)] and integrated nutrient management (INMFYM, INMCR) on soil carbon pools, oxidisable carbon fractions, carbon management indices (CMI) and enzyme activities in a permanent manurial experiment. Soil organic carbon (SOC) ranged from 5.66 (control) to 11.19 g kg-1 (INMFYM), both in the cotton phase. Inorganic treatments enhanced soil inorganic carbon (SIC), suggesting an inverse relationship with organic inputs. Sole FYM enriched the very labile fraction, whereas INM enhanced the labile and less labile fractions and non-labile carbon was highest under RDF + Zn. CMI ranged from 136.7–307.1 and was highest under sole FYM. The 50 % NFYM recorded higher permanganate oxidisable carbon (POXC) and microbial biomass carbon (MBC) than 100 % RDF despite lower SOC, highlighting the importance of substrate quality. Enzyme activities were consistently lower in the cotton phase. Structural equation modelling indicated that SOC was associated with dehydrogenase activity indirectly through MBC, which mediated 86.5 % of this effect, whereas POXC was the primary driver of β-glucosidase (BGA) and cellulase activities (CA). These findings demonstrate that biological fertility in dryland Vertisols is governed by active, biologically accessible carbon pools rather than total SOC and that sustained organic and integrated inputs are essential for enhancing carbon quality and microbial enzyme function.

Zinc (Zn) is a crucial micronutrient for crop growth and enzymatic regulations. The present study was formulated to reveal the effect of organic fortified Zn composite on the development and yield of sorghum. The field screening experiment was laid out in a factorial arrangement of Randomized Block Design (FRBD) with three replications. The treatments consisted of factor 1 were four microbial inoculants viz. M1: Plant Growth-Promoting Rhizobacteria (PGPR), M2: Zinc-Solubilizing Bacteria (ZSB), M3: Vesicular-Arbuscular Mycorrhiza (VAM), M4: Control, 100 % recommended NPK at 40:20:0 kg ha-1 with Zn was applied as a common dose to all treatment plots and 20 sorghum genotypes considered as another factor 2. Among the genotypes, the variety K12 recorded the highest Dry Matter Production (DMP) (5069 kg ha-1) at vegetative and other genotypes like TKSV 1036, PYT CO 30, TKSV 1315 and TKSV 1307 recorded DMP of 4950, 4946, 4921 and 4910 kg ha-1 were found efficient and responsive. Among the screened genotypes K12 and TKSV 1036 were found to be responsive genotypes. Further, various zinc levels of field experiments II were conducted with the efficient and responsive genotypes K12 and TKSV 1036, which were studied by imposing fifteen treatments in a split plot design and replicated thrice. Higher mean Zn uptake of 10.4, 59.9 and 41.9 g ha-1 was also recorded by Zinc Solubilising Bacteria (M1) at vegetative, flowering and harvest respectively. The highest grain yield of 4334 kg ha-1 was registered by S15, which was comparable with S14 (4291 kg ha-1). The highest grain zinc uptake of 48.42 g ha-1 was recorded with the application of S9 + Zn-EOM at 50 kg ha-1. Farmers in saline soil can adopt this integrated zinc nutrient management to enrich zinc and enhance the growth and yield of sorghum in potentially zinc-deficient soil.