Sustainability of the rice–crayfish farming model in waterlogged land: A case study in Qianjiang County, Hubei Province, China

The rice–crayfish farming model has been rapidly developed and become an economically viable method to supply food in China in recent years. However, its environmental and economic sustainability has not been thoroughly investigated. This study uses a survey in 2016 and a field experiment in 2017 in Qianjiang, Hubei Province, China to assess the relative economics of concurrent rice–wheat (RW), rice–crayfish (RC), and crayfish monoculture (CM) models in waterlogged land areas. The field survey indicated that the RC model had a higher benefit–cost ratio (3.5:1) than the RW (2.0:1) and CM (3.1:1) models and the RC model protected farmers’ enthusiasm for grain production facing unfavourable weather conditions. The field experiment aimed to explore nitrogen management strategies in RC fields. In the experiment, four levels of nitrogen concentration gradient - 0 kg N ha−1 (0 N), 75 kg N ha−1 (75 N), 150 kg N ha−1 (150 N) and 225 kg N ha−1 (225 N), were set in a 2-year-old rice–crayfish (RC2) field, an 8-year-old rice–crayfish (RC8) field, and a RW field as a control. The field experiment results suggested that the peak rice yield in RW, RC2, and RC8 occurred when 225 N, 150 N and 75 N were used, respectively. In RC2 and RC8, however, residual feed-nitrogen that was not used by crayfish was utilized by rice plants. Thus, an optimal amount of nitrogen in RC fields was proposed to improve the nitrogen use efficiency and reduce environmental pollution by nitrogen fertilizer. Farmers use less nitrogen but have higher net income in RC than in RW and CM. It is necessary to sustainably develop integrated farming technologies (i.e., proper field configurations for rice fields) to effectively sustain rice production. The results also showed that the RC farming model was a viable diversification option for rice farmers in waterlogged land.