Soil organic carbon (SOC) is the most often reported attribute and is chosen as the most important indicator of soil quality and agricultural sustainability. In this review, we summarized how cultivation, residue and tillage management and monoculture affect soil quality, soil organic matter (SOM) and carbon transformation. The results confirm that SOM is not only a source of carbon but also a sink for carbon sequestration. Cultivation and tillage can reduce soil SOC content and lead to soil deterioration. Tillage practices have a major effect on distribution of C and N, and the rates of organic matter decomposition and N mineralization. Proper adoption of tillage and residue can increase or maintain the quantity and quality of soil organic matter, and improve soil chemical and physical properties.

Tillage significantly reduced the proportion of macro-aggregate fractions (>2.00 mm) and thus aggregate stability was reduced by 35% compared with (ridge with no tillage) RNT, indicating that tillage practices led to soil structural change for this subtropical soil. The highest SOC was in the 1.00-0.25 mm fraction (35.7 and 30.4 mgkg-1for RNT and CT, respectively), while the lowest SOC was in micro-aggregate (<0.025mm) and silt +clay (<0.053mm) fractions (19.5 and 15.7 mgkg-1 for RNT and CT, respectively). Labile C fractions: particulate organic C (POC), microbial biomass C (MBC) and dissolved organic C (DOC) were all significantly higher in NT and ST than in CT in the upper 15 cm. Higher SOC content of 19.44 gkg-1 of soil was found in zero tilled residue retained plots followed by 18.53 g kg-1 in permanently raised bed with residue retained plots. Whereas, the lowest level of SOC content of 15.86 g kg-1 of soil were found in puddled transplanted rice followed by wheat planted under conventionally tilled plots.

Rice transplanted on wide raised beds and transplanted rice under reduced tillage plots consumed more moisture from the deeper profile layer than conventional tillage practice. The wide raised beds plots increased the water use efficiency of 15.12 and 15.78kg grain ha-1 mm. The per cent increased in water use efficiency under wide raised beds over conventional tillage was 38.67 and 39.23. The wide raised beds plots increased the water use efficiency of 15.12 and 15.78 kg ha-3 and water productivity (1.28 and 1.18kg ha-3). Inland configuration systems, B90–4 and 4 cm irrigation at IW/CPE 1.2 displayed significantly higher water use efficiency (2.53; 2.51 and 2.19; 2.18 kg m-3) compared with other treatments. These collected review demonstrated that tillage and straw retention is crucial for improving soil health and sustainability of irrigated farming systems in rice-wheat cropping system.