Effect Of Different Tillage Methods On Annual Greenhouse Gas Emissions And Soil Nutrients From A Farmland Ecosystem In A Rice-oilseed Rape Cropping System

To research the function and influence of different tillage methods on the carbon sequestration and mitigation from rice field system, and evaluate the southern rice-oilseed rape cropping system in different tillage, we chose the long-term different tillage methods experiments ?focusing on no-tillage ?NT? and conventional tillage ?CT?? in the rice-oilseed rape cropping system, measured the net ecosystem exchange ?NEE? of CO₂ and CH₄ fluxes in different tillage methods in daytime from a rice field ecosystem by using an Ultraportable Greenhouse Gas Analyzer, analyzed the dynamic change of labile carbon and nitrogen ?soil microbial biomass carbon ?SMBC? and soil microbial biomass nitrogen ?SMBN?, etc.? in different periods, and studied the effect of different methods on soil nutrients in temporal and spatial distribution. Main results are as follows:In a rice-oilseed rape cropping system, the trend of total CO₂ NEE and CH₄ NEE from a rice paddy ecosystem and its distribution between crops had different performance. During rice-oilseed rape cropping period, the CO₂ NEE was net uptake, and the CH₄ NEE was net emission. The CO₂ NEE of NT ?net uptake? was higher than that of CT by 11.75%, and the CH₄ NEE of NT ?net emission? was higher than that of CT by 16.55%. CO₂ NEE almost accounted for 70% of the total CO₂ NEE and CH₄ NEE accounted for more than 99% during the rice growing stage. Our results suggest that during rice-oilseed rape cropping period, most CO₂ and CH₄ NEE occur during rice growing stage. Compared with CT, the annual CO₂ net absorption of NT and CH₄ net emissions were higher in daytime from a rice field ecosystem.In a rice-oilseed rape cropping system, the dynamic trend of SMBC and SMBN content in paddy layer?0-20 cm?had different performance. The SMBC and SMBN content of CT were higher than that of NT. The SMBC content of CT was obviously higher than that of NT at flowering and maturity stage in oilseed rape. The SMBN content of CT was obviously higher than that of NT in late tillering stage, booting stage, yellow ripening stage, and after harvesting during the rice growing season and in emergence and budding stage during the rape growing time ?p<0.05?. It shows that compared to NT, the content of SMBC and SMBN of CT were higher.Tillage methods can affect the vertical distribution of soil nutrient in paddy field ?0?60 cm?. There was no obvious difference of the content of SOM, total nitrogen and available potassium between CT and NT in each soil layer. The content of SOM, total nitrogen, total phosphorus, alkaline hydrolysis nitrogen, available phosphorus and available potassium declined with the increasing depth of soil profile, but the content of total potassium was increasing with the increasing depth of soil profile. Except total potassium, these soil nutrients mainly concentrated in 0?20 cm soil layer. From the content averages of SOM, total nitrogen, total phosphorus, total potassium, alkaline hydrolysis nitrogen and available phosphorus, these content averages of NT were higher than that of CT.