Optimum redox potential in flooded paddy soil: managing rice (Oryza sativa L.) straw and irrigation for sustainable enhancement of productivity

摘要: Incorporation of rice straw into flooded paddy soil is one strategy for sustainable nutrient cycling as it improves soil fertility and provides an environmentally sound alternative to the burning of crop residues. However, anaerobic straw decomposition also has potentially negative agronomic and environmental effects on nutrient dynamics and greenhouse gas emissions. The objective of this study was to combine straw incorporation with the water-saving technique of alternate wetting and drying (AWD) irrigation to optimize soil redox potential, thus maximizing nutrient availability while minimizing emissions of methane and nitrous oxide. Several water regimes (continuous flooding vs. several variations of AWD) were tested with multiple rates of straw incorporation in a pot experiment using a heavy clay soil. Results showed that short drying periods caused by a small increase in soil redox potential, which caused an increase in nitrous oxide production but resulted in no measurable decrease in methane production. With straw incorporation, methane production increased and nitrous oxide production decreased. Longer soil drying periods caused a large increase in soil redox potential, which minimized methane emission, but decrease availability of some nutrients, such as P. With higher amount of straw incorporation, soil redox potential responded more slowly to water treatments. The AWD irrigation technique has greater positive environmental and agronomic benefits with straw-incorporation than without straw.