| Different straw returning methods and fertilization types and other farmland management measures have an important impact on soil organic carbon and components,soil fertility and crop yield.This study conducted field straw return positioning experiments in two experimental plots of Anhui Agricultural University Experimental Base in the Chaohu Basin.Experiment 1: 8-year soil cover return and reduced fertilization experiment,with six treatments set up: no straw return+no fertilization(CK),traditional fertilization(F),straw return+traditional fertilization(SF1),straw return+traditional fertilization reduction by 20%(SF2)Straw mulching and returning to the field+optimized fertilization reduction of 20%(NPK)and optimized fertilization(NPK+).Experiment 2: 1-year soil cover or cover return and reduced fertilization experiment,with six treatments set up: no straw return+no fertilization(CK),straw cover return+no fertilization(JF-),traditional fertilization(F),straw cover return+traditional fertilization(JF+),straw cover return+traditional fertilization reduction 15%(JFR),and straw cover return+traditional fertilization(SFR).The effects of two different straw returning methods and reduced fertilization on total soil organic carbon(SOC),dissolved organic carbon(DOC),particulate organic carbon(POC),labile organic carbon(LOC),carbon pool management index(CPMI)and rice yield in the farmland soil profile(0～20,20～50,50～80 cm)of the Chaohu Lake Basin were investigated.The specific research results are as follows:(1)The 8-year experiment of soil mulching and soil returning with reduced fertilization,and the 1-year experiment of soil mulching or soil mulching and soil returning with reduced fertilization had an increasing effect on the content of Total organic carbon and its components in the profile soil,and the content of each index showed a downward trend as the soil layer deepened.Compared with CK,the content of SOC,DOC,POC,and LOC in other treatments increased to varying degrees in different soil layers(0～20,20～50,50～80 cm)during the 8-year experiment of soil cover and reduced fertilization.In the 0～20 cm soil layer,compared with the F treatment,straw mulching and different fertilization treatments(SF1,SF2,and NPK)significantly increased the content of SOC,DOC,POC,and LOC,with each index increasing by 3.36%～21.74%,10.47%～26.74%,12.34%～38.34%,and 6.09%～17.29%(P < 0.05);In a soil layer of 20-50 cm,straw mulching and different fertilization treatments(SF1,SF2,and NPK)significantly increased the content of SOC and POC,with an increase of 4.16%～23.64% and20.00%～28.83%,respectively(P < 0.05).NPK treatment had the highest DOC content,which was significantly increased by 56.55% compared to F treatment(P < 0.05);The LOC content of SF1 treatment significantly increased by 17.62% compared to F treatment(P < 0.05);In a soil layer of 50～80 cm,the content of SOC,DOC,and POC in SF1 treatment significantly increased by 80.56%,25.81%,and 87.68% compared to F treatment(P < 0.05).The 1-year experiment on covering soil or returning farmland with mulch and reduced fertilization showed that compared to CK treatment,straw covering soil or returning farmland with mulch and traditional fertilization treatment(JF+,SFR)both increased the content of soil organic carbon and components in the profile.In the0～20 cm soil layer,JF+ and SFR treatments increased the content of SOC,POC,DOC,and LOC,with increases of 19.36%～28.00%,85.41%～127.45%,92.44%～127.45%,and42.44%～75.20%,respectively;In a soil layer of 20～50 cm,the content of SOC,POC,and DOC significantly increased by 36.55%,132.21%,and 56.55%(P < 0.05)after JF+treatment;In a soil layer of 50～80 cm,the content of DOC significantly increased by118.73%(P < 0.05)after JF+ treatment.(2)Returning straw to the field can change the soil carbon pool management index(CPMI),and CPMI can provide a good indicator of the dynamic changes of soil carbon pool.The 8-year experiment of soil cover and reduced fertilization showed that compared to CK treatment,other treatments significantly improved the soil carbon pool management index of 0～50 cm soil layer,and the CPMI value of SF1 treatment was the highest in different soil layers;The CPMI values of different treatments showed a trend of first increasing and then decreasing with the increase of soil depth,among which the CPMI values of each treatment in the 20～50cm soil layer were the highest.The 1-year experiment of covering soil or returning soil with mulch and reducing fertilization showed that compared to CK treatment,other treatments all improved the soil carbon pool management index,and the CPMI value of JF+ treatment was the highest in different soil layers;The CPMI of different treatments shows an overall upward trend with the increase of soil depth.(3)The correlation analysis of soil organic carbon and components showed that in the8-year experiment of soil cover and reduced fertilization,SOC had a very significant or significant correlation with POC and LOC in the 0～80 cm soil layer,while DOC had a significant correlation with POC and LOC in the 0～50 cm soil layer.In the 1-year experiment of covering soil or returning soil with mulch and reducing fertilization,there was a significant correlation between SOC and DOC,POC,and LOC in the 0～20 cm soil layer,and DOC showed a highly significant positive correlation with LOC and POC.Comprehensive analysis shows that the correlation between SOC,POC,and LOC in the0～20 cm soil layer indicates that the content of POC and LOC in the topsoil is closely related to SOC,indicating that POC and LOC can be important factors for evaluating soil quality and fertility changes.(4)Both the 8-year soil cover and reduced fertilization experiment and the 1-year soil cover or soil cover and reduced fertilization experiment can improve crop yield.Compared with the blank treatment,other treatments significantly increase rice yield.Compared with the F treatment,the rice yield increased by 6.78%～9.25% with straw mulching and different fertilization treatments(SF1,SF2,and NPK+)in the 8-year experiment of soil mulching and reduced fertilization,and the SF1 treatment had the highest rice yield.The 1-year experiment of covering soil or returning soil with mulching and reducing fertilization showed that compared with the F treatment,the rice yield of SFR and JF+ treatments increased by 3.38% and 7.74%,respectively,with the highest rice yield of JF+ treatment.To sum up,straw mulching+traditional fertilization(SF1 and JF+)treatment has the best effect on improving soil carbon pool and crop yield,which can be used as one of the farmland management measures to improve farmland soil fertility,soil carbon pool and rice yield in the Chaohu Lake Basin. |
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