Agronomic enhancements in the Indo-Gangetic Plain variably improve soil health depending on tillage and residue management

Changing climates, labor markets, scarcity of water and soil degradation threaten productivity in rice ( Oryza sativa L.) – wheat ( Triticum aestivum L.) rotations the eastern Indo-Gangetic Plain (IGP). Diversifying cropping systems, zero tillage, and residue addition can improve soil health and lead to increased system yields. This study aims to determine these effects from three long-term experiments (10-12 years) located in Bihar, India. Each site considered alternate crops in a rice-wheat (RW) rotation including maize ( Zea mays L.), chickpea ( Cicer arietinum L.), soybean ( Glycine max L.), mustard ( Brassica juncea L.) and mungbean ( Vigna radiata L.). Treatments involve various combinations of tillage, crop establishment and residue management. Soil health was determined using the comprehensive assessment of soil health (CASH) framework which measures fifteen biological, physical and chemical indicators. Reduced tillage generally improved soil health outcomes, but crop diversification showed divergent responses to soil properties. Additions of a legume significantly improved soil physical and biological properties in one experiment, but not another. The effect of crop diversification on the composite soil health index, individual soil health indicators, and yields are strongly dependent on the mix of alternate crops selected. Total biomass production (e.g., including maize) and cycling of crops (e.g., maintaining residues) appear to be a strong drivers of soil health, which suggests that simply moving away from rice-wheat is not enough to improve soil health. Overall, alternative soil and crop management may improve soil health in the eastern IGP with consideration of biomass cycling dynamics. Permanganate oxidizable carbon, subsoil hardness, and wet aggregate stability were the most suitable indicators for assessing soil health in the region. • Residue management and reduced tillage influence the effect of crop diversification • Effects of crop diversification on soil health and yields are dependent on the selected crops. • Overall biomass cycling of crop residues is a strong driver of soil health • Little accumulation of SOC is observed after decades of management