Effect of Different Rice-Crab Coculture Modes on Soil Carbohydrates

Abstract

Traditional agricultural systems have contributed to food and livelihood security. Rice-crab coculture (RC) is an important eco-agricultural process in rice production in northern China. Recognizing the soil fertility in RC may help develop novel sustainable agriculture. Soil carbohydrates are important factors in determining soil fertility in different culture modes. In this study, soil carbohydrates were analyzed under three different culture modes including rice monoculture (RM), conventional rice-crab coculture (CRC) and organic rice-crab coculture (ORC). Results showed that the contents of soil organic carbon and carbohydrates were significantly higher in the ORC than those in RM. The increasing effect was greater with increased organic manure. Similar tendency was found in CRC, but the overall effect was less pronounced compared with ORC. Carbohydrates were more sensitive to RC mode and manure amendment than soil organic carbon. Compare to RM, the (Gal+Man)/(Ara+Xyl) ratio decreased in all the RC modes, indicating a relative enrichment in plant-derived carbohydrates due to the input of crab feed and manure. While the increasing (Gal+Man)/(Ara+Xyl) ratio in ORC modes with increased organic manure suggested that crab activity and metabolism induced microbially derived carbohydrates accumulation. The lower GluN/MurA ratio in ORC indicated an enhancement of bacteria contribution to SOM turnover in a short term. The findings reveal that the ORC mode could improve the quantity and composition of soil carbohydrates, effectively, to ensure a sustainable use of paddy soil.