A review on improvement and utilization of southern cold-waterlogged paddy fields in China

Cold-waterlogged (CW) paddy fields are the main low-yield paddy fields in South China. CW paddy fields have attracted close attention as they belong to common derelict lands with huge potential for crop productivity and good ecological conditions. CW paddy fields are the products of the complex interaction of climate, topography, hydrology and anthropogenic activity. Influenced by years of surface water and groundwater dip, soil physicochemical and biological properties of CW paddy fields have shown huge variations in the degree of coldness, rottenness, toxicity and infertility. CW paddy fields have low-temperature waters, soils and immersed bulk density, excessive reducing substances and soil organic carbon, but also low active organic carbon, microflora and available nutrients or unbalanced nutrients. Soil quality of CW paddy fields can be diagnosed and assessed by gley horizons, soil reducing substances and groundwater levels. This study summarized the integrated management and utilization of CW paddy fields, including engineering, agronomic and biological measures. This included open ditch and hidden drainage tubes, suitable rice varieties, paddy-upland crop rotation, ridge cultivation, balanced fertilization, soil conditioning, etc. In addition to traditional rice cultivation, it was an effective measure to comprehensively improve production capacity by adapting local conditions to the utilization of CW paddy fields. Finally, there was clear need to put future research emphasis on the administration and utilization of CW paddy fields based on sustainable agricultural development. This include 1) studying the differences in soil structure and the composition of organic matter under different gleyic states and the alternation of drying and wetting; 2) Strengthening research on methane emission characteristics under long-term gleyic state in CW paddy fields; 3) Strengthening research on ecological processes of anaerobic microbes and production enzymes and regulating and improving CW paddy fields using micro-organisms; 4) There was also need to strengthen technological integration and policy support based on different ecological types and production conditions in CW paddy fields.