Effects of long-term rice-crayfish farming on soil CNP storage and stoichiometry

In recent years, traditional rice monoculture (RM) has led to agricultural intensification, resulting in loss of soil nutrients and the low fertility. Rice-crayfish (RC) integrated farming, as a sustainable agricultural system, could significantly enhance accumulation of soil C (carbon), N (nitrogen) and P (phosphorus) while improve soil fertility. However, it is still unknown how the characteristics of soil CNP stoichiometry and storage are influ-enced by long-term RC farming. This study examined the patterns of soil CNP storage and stoichiometry at 0-30 cm soil layers in RM and RC systems (1, 6, 10, and 15 years) scattered in Nanxian County, Hunan Province, China. Compared to RM system, soil C, N, and P storage increased by 4.1-10.9, 0.1-0.9, and 0.03-0.4 Mg ha-1 in 6, 10, and 15-year rice-crayfish (RC6, RC10 and RC15) systems, respectively. Meanwhile, compared to RM system, soil C:N, C:P and N:P ratio increased significantly in RC6, RC10 and RC15 systems. Besides, the principal component, redundancy analysis and structural equation model revealed that soil BD, pH, aggregates and nutrient altered by agricultural practices (no-tillage, feed and flooding) of RC system significantly affected CNP stoichiometry and storage of paddy soil. Although the accumulation of soil nutrient were showed in long-term rice-crayfish farming system, it is also necessary to pay attention to the negative impact of nutrient surplus on the environment. Based on these results, it is necessary to regulate input of fertilizer and improve efficient utilization of feed for guaranteeing soil nutrient balance and retention, so as to ensure sustainable development of rice crayfish farming system.