Organic inputs and tillage differentially impact soil health and yield in rice–wheat systems in the eastern gangetic plain

The rice (Oryza sativa L.) – wheat (Triticum aestivum L.) rotation is the dominant cropping system of the Indo-Gangetic Plain and is experiencing challenges from a variety of environmental and socio-economic factors. Organic matter cycling and zero-tillage (ZT) have been encouraged in the region to address concerns with soil health, climate variability, and water scarcity. The objective of this study is to quantify the long-term effects of ZT as well as residue and manure addition in rice–wheat systems on a comprehensive set of soil health indicators and crop yields. Soils were analyzed from three long-term experiments (28, 34 and 16 years) located in Bihar, India. Treatments involved various combinations of tillage, crop establishment, and organic management practices in a rice–wheat rotation. Fifteen biological, physical and chemical soil health indicators and yields were determined. Crop residue and manure additions have positive effects on biological properties and pH, while reduced tillage largely benefits soil physical properties. A composite soil health index (SHI) and biological indicators notably are well correlated with rice and especially wheat yields. Addition of residue and manure amendments increase yields at all sites, but zero-till without residue addition shows a yield penalty at one site. Overall, agronomic management practices for the rice–wheat system in the Indo-Gangetic Plain result in nuanced soil health benefits from reduced tillage and organic matter returns. Interventions that enhance organic cycling and reduce tillage are important to crop productivity improvement.