Long-term tillage, water and nutrient management in rice–wheat cropping system: Assessment and response of soil quality

Abstract

Highly productive rice (Oryza sativa L.) and wheat (Triticum aestivum L.) systems are crucial for millions of rural and urban poor in the Indo-Gangetic Plains (IGP) of south Asia. Our objectives were to identify important biological, chemical and physical indicators of soil quality and incorporate them into a unified soil quality index (SQI) that could be used to help select best management practices for important cropping systems. Two tillage, three water management and nine nutrient management treatments were evaluated. Principal component analysis (PCA) was used to identify critical indicators and their relative weighting for a soil quality index (SQI) that was developed using the Soil Management Assessment Framework (SMAF). Two primary goals – productivity (PCASQI-P) and environmental protection (PCSQI-EP) were established. For the productivity goal, seven indicators were evaluated for their contribution to nutrient cycling, two for physical stability and support, and three for water relations. The environmental quality goal used the same functions and indicators plus three additional indicators affecting filtering and buffering, and one reflecting biodiversity and habitat. The hypothesis of the study was that the set of sensitive indicators would vary under contrasting tillage, nutrient and water management which could be encompassed to develop unified soil quality indices for assessing management induced changes in rice–wheat cropping system. The results confirmed that management goal strongly influenced indicator selection and that variations in those indicators can provide early warning against deterioration of soil quality. Puddling and irrigating rice after three days of drainage and using no tillage and two irrigations for wheat emerged as promising management for improved soil quality. Applying 25% of the recommended fertilizer N dose using farm-yard manure (FYM) for rice and domestic sewage sludge for wheat also improved soil quality. We conclude that the procedure used for indexing soil quality in this study could not only be extended to neighboring areas of Indo-Gangetic Plain but also validated and expanded for use in south and south–east Asian countries with similar soils and cropping systems.