Effects of two rice-shrimp co-cultural models on soil organic nitrogen mineralization

【Objective】To analyze the effects of rice-shrimp co-cultural model on lower arable stratum of paddy soil nitrogen mineralization and microbial response mechanism，so as to provide a theoretical reference for study on mechanism of shrimp on soil nitrogen fertility and formulation of nitrogen fertilizer application scheme.【Method】Comparison experiment was conducted to determine the parameters related to arable stratum（10-20 cm），soil organic nitrogen mineralization，soil nitrogen content and microbial community structure under rice-Cherax quadricarinatus co-cultural model （RC）and rice-Macrobrachium rosenbergii（RM）co-cultural model. Meanwhile，the correlation between microbial community and mineralization parameters was analyzed.【Result】Compared with the beginning period，contents of soil total nitrogen and ammonium nitrogen decreased at final stage，and no significant difference in total nitrogen content between the two models at beginning period（P>0.05）had been found，while the total nitrogen content of RC was significantly lower than RM，at final period（P<0.05，the same below）. The results showed that the cumulative mineralization，mineralization potential，and nitrogen mineralization ratio［131.21±2.12 mg/kg，242.62±5.18 mg/kg，（0.31±0.01）%］in RC were significantly higher than those in RM［119.85±1.36 mg/kg，217.51±1.83 mg/kg，（0.28±0.01）%］at the end of the experiment，respectively. Meanwhile，microbial community data showed that Shannon index of RC was significantly lower than that of RM at final period，and there were significant differences in community structure between RC and RM. In addition，the relative abundance of Actinobacteriota in RC was significantly higher than that in the RM，while the relative abundances of Desulfobacterota，Myxococcota，and Nitrospirota were significantly lower than that in the RM. Moreover，the correlation analysis showed that the cumulative nitrogen mineralization，mineralization potential，and the nitrogen mineralization rate were extremely positive corelated with the Actinobacteriota，Chloroflexi，and Proteobacteria（P< 0.01，the same below），but were extremely negative correlated with Bacteroidota，Desulfobacterota，Myxococcota，and Nitrospirota.【Conclusion】Different living habits of shrimp affect the composition of soil microbial community and create differences in arable stratum（10-20 cm）soil microbial community structure. Hence，In Jingjiang，Jiangsu Province，compared with the RM，there is stronger mineralization and higher values of the mineralization potential and other related parameters in RC，which is more beneficial to the growth of rice.