Managing soil potassium through green manuring with gliricidia for improving cotton yield and quality of shrink-swell soils of Central India.

Soil potassium (K) content in the swell-shrink soils of Central India has been decreasing in recent decades due to higher inputs of N and P fertilizers concomitant with lower or no inputs of K fertilizers. Therefore, nutrient management to mitigate the negative K budget is urgently required. Therefore, we aimed to exploit the abundance of K in gliricidia (Gliricidia sepium) to substitute the fertilizer K requirement to improve soil quality and sustain cotton productivity. Results indicated a significant (p < 0.05) improvement in soil physical properties and organic carbon under treatment 100% NP + 10 kg K (inorganic) + 20 kg K (gliricidia) (T4). The same treatment had 18.2 and 11.4, 36.22 and 4.7, and 17.8 and 9% higher content of available N, P, and K compared to the control and 100% RDF, respectively. Available micronutrients and biological properties were significantly higher under treatment T4 and 100% NP + 15 kg K (inorganic) + 15 kg K (gliricidia) (T3). Hydraulic conductivity, organic carbon, and microbial biomass carbon were identified as key SQ indicators for the experimental soil. The treatments T3 and T4 had about 105 and 122% more seed cotton yield compared to the control and 17 and 27% more than 100% RDF treatment (T2). We conclude that gliricidia can be efficiently utilized in the nutrient management packages to partially substitute the fertilizer K requirement of rainfed cotton. This will further address the K depletion and nutrient imbalances and help to restore the soil K in shrink-swell soils of Central India. [ABSTRACT FROM AUTHOR]