Impact of tillage and fertilizer management on Soybean-Cotton rotation system: effects on yield, plant nutrient uptake, and soil fertility for sustainable agriculture.

Agricultural productivity in semiarid regions is challenged by low soil fertility, limited water availability, and unsustainable farming practices. Semiarid vertisols, commonly found in such regions, require efficient management practices to maintain long-term soil health and optimize crop yields. This study aimed to evaluate the sustainability of yield, rainwater use efficiency (RWUE), and monetary returns in a crop rotation system involving soybean and cotton under semiarid vertisols over a 10-year period (2011-2020). Fifteen treatment combinations of tillage and fertilizer were applied, with tillage treatments consisting of conventional tillage, reduced tillage with interculture, and reduced tillage with herbicide plus one interculture. Fertilizer treatments included farmyard manure (FYM) at 5 t/ha, vermicompost at 3 t/ha, 50% recommended dose of fertilizer (RDF) with FYM at 2.5 t/ha, 50% RDF with vermicompost at 1.5 t/ha, and 100% RDF (inorganic). The objective was to assess the impact of these treatments on crop yield, rainwater use efficiency (RWUE), and soil fertility. The soybean equivalent yield (SEY) ranged from 2155 kg/ha (T3 N2) to 2727 kg/ha (T1 N5), with an overall mean of 2406 kg/ha and a coefficient of variation (CV) of 6.5% indicating consistent performance of treatments over time where the yield variability was relatively low. RWUE varied from 2.96 kg/ha·mm (T3 N2) to 3.80 kg/ha·mm (T1 N5), with a mean of 3.34 kg/ha·mm (CV = 7.5%). Statistical analysis revealed significant differences in SEY and RWUE due to tillage and fertilizer treatments. Such as, T1 N5 (100% RDF with vermicompost) consistently produced the highest soybean equivalent yield and rainwater use efficiency, indicating that this treatment was more effective than others in promoting crop growth and water utilization. Principal component analysis (PCA) explained 88.19% of the variance in plant and soil considering the influencing significance parameters (soil organic carbon, nitrogen content and microbial biomass) which are positively correlated with higher yields and better water use efficiency. The treatment T1 N5 (100% RDF with vermicompost) produced the highest mean SEY (2727 kg/ha), sustainability yield index (SYI) of 66.5%, benefit-cost ratio of 3.20, and RWUE of 3.80 kg/ha·mm. This treatment also improved soil fertility over the study period, with soil organic carbon increasing by 15% and microbial biomass carbon by 20% under the T1 N5 treatment, reflecting the positive impact of combined organic and inorganic nutrient management. Based on these findings, adopting T1 N5 can be recommended to enhance soybean equivalent yield, maximize monetary returns, optimize rainwater use, and preserve soil fertility in semiarid vertisols. Further studies could focus on the long-term environmental impacts of these practices, including soil carbon sequestration and the potential for adapting these treatments to other semiarid regions with varying soil types.