| Agricultural activities such as tillage,fertilization and Straw returning have a great influence on soil organic carbon.Some studies have shown that Straw returning is the leading factor for increasing soil carbon fixation rate in China,field experiments were conducted in Tongyang town,Chaohu,to study the effects of balanced fertilization of rice straw with N,P and K on rape yield,soil organic carbon components and their contents,the results reveal the process of Straw decomposition and soil property change,and contribute to the exploration of suitable fertilization measures for local production,the improvement of Straw returning technology in this area and the maintenance of global carbon balance.The field plot experiment was divided into six treatments,which were repeated three times: Treatment 1(CK)Straw return to field + No Fertilization;Treatment 2(SF)Straw return to field + optimized fertilization 20%;treatment 3(NPK)conventional fertilization;treatment 4(SF1)Straw return to field + conventional fertilization;Treatment 5(SF2)Straw returned to the field + 20% conventional fertilizer reduction;treatment 6(NPK +)optimized fertilization.The main results were as follows:1)the vertical distribution of soil SOC(soil organic carbon),POC(soil particulate organic carbon),DOC(soil dissolved organic carbon),LOC(soil active organic carbon),LFOC(soil light fraction organic carbon)and HFOC(soil reconstituted organic carbon)were significantly affected by applying fertilizer.Compared with blank treatment,the other five treatments all increased soil organic carbon components in different degrees,among which SF1 treatment significantly increased SOC,LOC,FLOC and HFOC contents,and SF2 treatment significantly increased POC and DOC contents.Compared with CK,SF1 increased by 42.11%,30.39%,105% and 36.94% in 0～20cm soil layer,increased by 14.55%,32.78%,197% and 6.54% in 20～50cm soil layer,and increased by 23.16%,13.2%,125% and 22.62% in 50～80cm soil layer.The POC and DOC contents of SF2 treatment increased by 33.59% and 42.26% in 0～20cm soil layer,by 27.98% and 100% in 20～50cm soil layer,and by 22.2% and 36.36% in 50～80cm soil layer.With the increase of soil depth,the content of each treatment also decreased.2)CPMI could be a good indicator of soil carbon pool dynamics.Compared with CK,all the other five treatments significantly increased CPMI values in topsoil(0 ～ 20cm)by20.33%,34.16%,22.64%,32.66% and 15.93%,respectively,with NPK and SF2 treatments increasing the most.SF1,SF and NPK treatments significantly increased CPMI values in soil(20 ～ 50 cm),and the Carbon Pool Management Index of SF and SF1 treatments increased by 49.34% and 51.71%,respectively,while SF treatments significantly increased CPMI values in soil(50 ～ 80 cm),and SF treatments increased by 34.24%.The results showed that the CPMI value of soil was significantly increased with the application of Straw and chemical fertilizer,and NPK treatment was the best.3)compared with CK,the yield of rape in the field increased significantly after 4A combined application of Straw return and chemical fertilizer,in which NPK + and SF1 increased the most,because NPK + and SF1 could improve the soil fertility(SOC content)of tillage layer,and thus improve the nutrient use efficiency of crops.It is an important agricultural management measure to optimize fertilization and Straw returning combined with conventional fertilization to improve the farmland productivity in this area.4)The sensitivity index of soil LFOC was much higher than that of POC,LOC,SOC and DOC.The range of LFOC in three soil layers was 19.13% ～104.94%,56% ～197.3%and 34.07% ～125.81%,respectively.Soil LFOC could sensitively reflect the change of soil quality under different fertilization measures.SOC and soil organic carbon components(LFOC and HFOC)were significantly correlated in 0 ～ 80 cm soil layer.The content of LFOC and HFOC in soil was related to the content of SOC,which could be used as an indicator of soil quality change.Based on comprehensive analysis,LFOC can be used as a variable factor of soil quality in Chao Lake experimental field.SF1(Straw return + conventional fertilization)is an effective management mode to improve soil carbon pool,rape yield,soil fertility,water storage and soil moisture conservation in Chao hu. |
