Effect of Farming Systems on Soil Organic Carbon Mineralization of Rhizosphere and Non-rhizosphere in Purple Paddy Fields

Based on a 20-year-long fertilization experiment in paddy field,effects of farming systems on soil organic carbon(SOC) mineralization of rhizosphere and non-rhizosphere in paddy were studied.This experiment included four cultivation treatments: plain-cultivation(rice),ridge-cultivation without tillage(rice),ridge-cultivation without tillage(rice-rape) and plain-cultivation(rice-rape).The results showed that the daily mineralization of SOC declined rapidly in the first seven days and then gradually became more and more stable under different farming systems.At the end of incubation,the daily mineralization of SOC was only 3.1%～6.7% of the first day.Plus,the mineralization rates of SOC was decreased effectively when practiced the rotation of rice and rape.The daily and cumulative mineralization of SOC and mineralization intensity under the treatment of the rhizosphere of ridge-cultivation without tillage(rice-rape) were higher than those of non-rhizosphere,but other treatments were opposite.The daily mineralization of SOC of rhizosphere and non-rhizosphere fitted with a power-function with incubation time.The daily mineralization of SOC of non-rhizosphere was higher than rhizosphere in the whole incubation period of 62 days except the first day in all treatment.And discrepancy rate was between 67.0% and 98.7%.The daily and cumulative mineralization of SOC and mineralization intensity of rhizosphere and non-rhizosphere were significant correlation with pH.The discrepancy between rhizosphere and non-rhizosphere of daily and cumulative mineralization of SOC were evident correlation with microbial biomass carbon and nitrogen.