Effects Of Tillage Practices On Soil Carbon Sequestration And Crop Growth Under A Wheat-maize Cropping System In The North China Plain

In order to identify the effects of straw returning and tillage practices on the soil organic carbon(SOC)sequestration and crop production in the wheat-maize two-cropping area of North China Plain,a long-term site experiment was established at the Wuqiao Experimental Station of China Agricultural University in 2008.The experiment included 5 treatments,no tillage with straw returning(NTS),sub-soiling with straw returning(STS),rotary tillage with straw returning(RTS),ploughing tillage with straw returning(CTS)and ploughing tillage without straw returning(CT).In this study,the soil physical properties,SOC pool and crop production of crop harvest period during the growing period of winter wheat-summer maize cropping system were analyzed.In addition,the carbon footprint(CF)and correlation between organic carbon and crop yield were assessed to identify the effects induced by tillage and residue managements.The data in this study were data from 2013 to 2015.The main results are as follows:(1)The effects of different tillage on soil physical were different among the treatments.The treatment of NTS significantly increased the bulk density at 0-20 cm soil depth,while the differences at subsoil among the treatments were not significant(P<0.05).The total soil porosity and capillary porosity of NTS were lower than those of the other four treatments.On the contrast,the treatments of CTS and RTS decreased the bulk density of 0-20 cm soil layer and increased the soil total porosity and capillary porosity of 0-30 cm soil layer.In addition,NTS increased the proportion 2 mm aggregates at 5-20 cm soil depth and significantly increased the average geometric diameter of soil aggregates at 0-20 cm soil depth(P<0.05).(2)The effect of interaction between straw returning and tillage practices on SOC was mainly concentrated in 0-30 cm soil layer.The SOC concentration at 0-5 cm soil depth were significantly increased with the reduction of tillage intensity.The NTS significantly increased SOC concentration and storage in the 0-10 cm soil layer,but also increased the stratification ratio of SOC(P<0.05).The differences of SOC concentration and storage between RTS and other treatments were relatively small.CTS and STS treatments enhanced the distribution of SOC concentrations in the 0-20 cm soil layer,and the CTS treatment increased the SOC concentration at the 10-20 cm soil depth,while decreased the stratification rate of SOC in the 0-30 cm soil layer.The SOC concentrations of all water-stable aggregates at the 0-5 cm soil depth was the highest under NTS,significantly higher than the other treatment(P<0.05).However,the SOC concentrations of 0.25-2 mm water-stable aggregates at the 10-20 cm soil depth was the highest under CTS and lowest under CT,but the differences among the other treatment was not significant,significantly higher than the other treatment(P<0.05).(3)The differences of SOC fractions induced by tillage were mainly in 0-30 cm soil layer,but not significant in the subsoil(>30 cm).The NTS increased in particulate organic carbon(POC)and light organic carbon(LOC)at the 0-5 cm soil depth,but decreased the content of liable organic carbon,but they are all higher than CT treatment(P<0.05).RTS treatment increased the organic carbon composition of 0-10 cm soil layer,and the content of liable organic carbon was higher than other treatments.Besides,the content of soil organic carbon in 10-20 cm soil layer was raised and the uniform distribution of organic carbon components was promoted in the treatment of STS and CTS.The treatment of CT witnessed a smallest composition of organic carbon in all soil layers.(4)Compared with CT,NTS prolonged the growth period of winter wheat,but the effect on the growth period of summer maize was similar with othrer treatments.Compared with NTS,STS and CTS treatments increased the emergence rate of wintr wheat(P<005),but there was no significant difference in the emergence rate of summer maize.The NTS and STS increased the net photosynthetic rate of winter wheat and decreased the photosynthetic lunch break.The yield of winter wheat and summer maize under CTS and STS treatments were higher than other treatments.The water use efficiency was highest under CTS but lowest under CT.(5)Including or not including the SOC storage changes,the CF of NTS treatment was the lowest(-0.03-0.63 kg CO2-eq ha-1 year-1),but CT was highest(0.22-0.75 kg C02-eq ha year-1).The differences of CF among the other 3 treatments were not significant whatever SOC changes included or not,in the order of RTS>STS>CTS.When SOC included,the CF under CT was increased mainly due to the decrease of SOC.The correlation analysis of various indicators indicated that SOC positively corretated with water-stable aggregates SOC and SOC fractions(P<0.01).