Soil quality effects of tillage and residue under rice–wheat cropping on a Vertisol in India M. Mohanty * , D.K. Painuli, A.K. Misra, P.K. Ghosh Indian Institute of Soil Science, Indian Council of Agricultural Research, Nabibagh, Berasia Road, Bhopal 462038, MP, India Received 27 February 2005; received in revised form 18 February 2006; accepted 17 March 2006 Abstract Soil quality in rice (Oryza sativa L.)–wheat (Triticum aestivum L.) cropping systems is governed primarily by the tillage practices used to fulfill the contrasting soil physical and hydrological requirements of the two crops. The objective of this study was to develop a soil quality index (SQI) based on bulk density (BD), penetration resistance (PR), water stable aggregates (WSA) and soil organic matter (OM) to evaluate this important cropping system on a Vertisol in India. Regression analysis between crop yield and SQI values for various tillage and crop residue management treatments indicated SQI values of 0.84–0.92, 0.88–0.93 and 0.86– 0.92 were optimum for rice, wheat and the combined system (rice + wheat), respectively. The maximum yields for rice and wheat were 5806 and 1825 kg ha 1 occurred at SQI values of 0.85 and 0.99, respectively. Using zero tillage (ZT) for wheat had a positive effect on soil quality regardless of the treatments used for rice. Regression analyses to predict sustainability of the various tillage and crop residue treatments showed that as puddling intensity for rice increased, sustainability without returning crop residues decreased from 6 to 1 years. When residue was returned, the time for sustainable productivity increased from 6 to 15 years for direct seeded rice, 5 to 11 years with low-intensity puddling (P 1 ) and 1 to 8 years for high-intensity (P 2 ) puddling. For sustainability and productivity, the best practice for this or similar Vertisols in India would be direct seeding of rice with conventional tillage and residues returned. # 2006 Elsevier B.V. All rights reserved. Keywords: Soil quality index; Rice–wheat cropping system; Vertiols; India; Zero-tillage; Sustainability 1. Introduction The rice–wheat cropping system is one of the oldest and most prevalent agricultural practices in India and many other regions of the world. In these areas, wetland culture is the predominant soil management system. Rice occupies 153 m ha land throughout the world. In India, out of the 43 m ha area under rice cultivation puddled rice culture occupies 24 m ha, about 56% of the area (Anonymous, 2005; Singh, 2001). This involves plough- ing the soil when wet, puddling it and keeping the area flooded for the duration of the rice crop. Wetland rice culture thus destroys soil structure and creates a poor physical condition for the following wheat crop. This soil condition can reduce wheat yield (Sur et al., 1981; Boparai et al., 1992) presumably by limiting root growth and distribution (Oussible et al., 1992). Puddled soils shrink on drying, become compact and hard and produce surface fissures of varying size and shape. Ploughing of puddled soils after rice results in the formation of large clods with high breaking strength (Sharma and Bhagat, 1993). Creating an appropriate seedbed requires a large amount of energy and time. For regeneration and maintenance of soil structure within this cropping system, plant residue is very important (Verma and www.elsevier.com/locate/still Soil & Tillage Research 92 (2007) 243–250 * Corresponding author. Tel.: +91 755 2730970; fax: +91 755 2733310. E-mail address: mmohanty@iiss.ernet.in (M. Mohanty). 0167-1987/$ – see front matter # 2006 Elsevier B.V. All rights reserved. doi:10.1016/j.still.2006.03.005