Soil physical properties, yield trends and economics after five years of conservation agriculture based rice-maize system in north-western India

Rice-maize system (RMS) is emerging as dominant option for diversification of existing rice-wheat systems in Asia due to better suitability and higher yields of maize compared to wheat after long duration rice cultivars, and increasing demand of maize from poultry and fish industries. The conventional practice of cultivation of RMS is input intensive, deteriorates soil health and is less profitable. Conservation agriculture (CA) based management practices such as dry direct-seeded rice (DSR), zero tillage (ZT) and residue retention may hold potential to increase yields, reduce costs and increase farmers' profits in RMS. Therefore, replicated 5-year field study was conducted to evaluate the effects of six combinations of three tillage and crop establishment (TCE) techniques and two residue management options on soil physical properties, system productivity and economics of an irrigated RMS in north-west India. The TCE techniques consisted of transplanted puddled rice (TPR) followed by conventionally tilled maize (CTM); CTDSR followed by CTM; and ZTDSR followed by ZTM in main plots and two residue management options; removal of residues of both the crops (-R) and partial residue (5 t ha(-1)) either retained at soil surface on ZT plots or incorporated into the soil in CT plots (+R) for both rice and maize in sub-plots. Compared with TPR/CTM-R, soil physical parameters such as water-stable aggregates >0.2 mm were 89% higher, and bulk density, penetrometer resistance and infiltration rate showed significant (P < 0.05) improvement in ZTDSR/ZTM (+R) treatment. Similarly, root mass density was 6 to 49% greater in rice and 21 to 53% in maize under ZTDSR/ZTM (+R) plots compared to conventional RMS in different soil layers to 60 cm depth. The total amount of soil organic carbon (SOC) in 0-30 cm layer increased by 2.86 Mg ha(-1) in ZTDSR/ZTM (+R) over conventional practice. Grain yield of TPR was 5-7% higher compared to CTDSR and ZTDSR, which was attributed to increased number of grains panicle(-1) and grain weight. Maize yield under ZTDSR/ZTM was significantly higher by 4.0% and 14.2% compared to CTDSR/CTM and TPR/CTM, respectively, due to increase in number of cobs plant(-1) and grain number cob(-1). Gradual improvement in soil physical health in ZTDSR/ZTM +R system resulted in higher and stable crop productivity (17.4-17.6 kg m(-3)) with higher profitability in different years over conventional system. Our study demonstrates that CA based management practices can be adopted for RMS on sandy loam or similar soils for sustaining soil and crop productivity in South Asia. (C) 2015 Elsevier B.V. All rights reserved.