Soil labile organic carbon and carbon pool management index as affected by different years no-tilling with straw mulching

A field experiment(2000-2010) was conducted at the Heyang Dryland Farming Experimental Station in Shaanxi Province of China to study the effects of no-tillage with straw mulching on soil labile organic carbon(LOC) and carbon management index(CMI) ,and further,to search the appropriate years for no-tillage with straw mulching.Five treatments of different years no-tillage with straw mulching,i.e.,1 year(S1) ,3 years(S3) ,5 years(S5) ,8 years(S8) ,and 10 years(S10) ,and two treatments of conventional cultivation(CK) and 10 years no-tillage with zero straw mulch(CK0) were installed.In treatments S1,S3,S5,S8,and S10,the organic carbon(TOC) content in 0-10 cm soil layer increased by 7.6%,13.5%,25.4%,48.6%,and 79.0%,LOC content increased by 40.1%,51.5%,102.4%,78.4%,and 75.3%,and CMI increased by 49.4%,61.2%,126.8%,85.4% and 75.3%,respectively,compared with CK.The spring maize grain yield,total nitrogen,total phosphorus,and available phosphorus had significant correlations with soil LOC and CMI(P 0.01) ,but less correlation with soil TOC.As compared to soil TOC,soil LOC and CMI could more rapidly and objectively reflect the effects of no-tillage with straw mulching on soil carbon pool and maize grain yield,and be used as the indices to assess the ecological effects of no-tillage with straw mulching.The appropriate years for no-tillage with straw mulching in Weibei dryland area of China could be 5-8 years.