Residue and Potassium Management Strategies to Improve Crop Productivity, Potassium Mobilization, and Assimilation under Zero-Till Maize–Wheat Cropping System

Understanding of the potassium (K) nutrient cycle and its microbial transformation of unavailable forms of soil K to plant-available K is crucial in any agroecosystem for strategic nutrient management through inorganic fertilizer, crop residue (CR), and microbial applications. Therefore, the present investigation was undertaken to study the effect of crop residue and K management practices on crop productivity, K mobilization from native soil K-pool, and crop assimilation of K under a zero-till maize–wheat cropping system. The experiment consisted of four residue levels (0, 2, 4, and 6 Mg ha −1 ) and five K levels (0, 50%, 100%, 150% RDK [recommended dose of K] and 50% RDK + potassium solubilizing bacteria, KSB). Results showed that CR retention at 6.0 Mg ha −1 significantly improved grain yield (of maize by 10.17%; wheat by 9.87%), dry matter accumulation, K uptake and redistribution in native soil K pools (water soluble K (WSK), exchangeable K (EK) and non-exchangeable K (NEK)) at 30 and 60 days after sowing and at harvest as compared to no CR. Among the K management, 50% RDK+KSB reported significantly higher grain yield (of maize by 26.22%; wheat by 24.70%), dry matter accumulation, K uptake, and native K pools (WSK, EK, and NEK) at different growth stages compared to no K. Total K did not differ significantly due to residue and K management. The highest actual change of K reported with 6.0 Mg ha −1 CR (51 kg ha −1 ) and 50% RDK+KSB (59 kg ha −1 ) over control. Significant ( p ≤ 0.01) positive correlation was found among grain yield, dry matter accumulation, K uptake, the actual change in K and different native K pools. It can be concluded that retention of 6 Mg ha −1 CR and supply of 50% K through inorganic fertilizer along with seed inoculation of KSB biofertilizers, improved crop growth, productivity by enhancing K assimilation as a consequence of the release of non-exchangeable K and through the application of CR and K treatments under a zero tillage maize–wheat system.