生物炭和秸秆还田对紫色土旱坡地土壤团聚体与有机碳的影响

明确生物炭和秸秆还田对未利用的新垦紫色土旱坡地土壤团聚体和有机碳的影响，为三峡库区土壤改良提供科学依据.采用田间试验方法，分析不施肥（CK）、常规施肥（NPK）、优化施肥（GNPK）、化肥减量配施秸秆（RSD）和化肥减量配施生物炭（BC）处理对不同粒径土壤团聚体含量及其有机碳贡献率的影响.结果表明，施肥可提高土壤养分含量水平，尤以RSD和BC处理最为显著；各处理以<0.25 mm粒级团聚体为优势粒级，施肥能显著增加5~0.5 mm粒级团聚体含量，提高平均重量直径（MWD）、几何平均直径（GMD）和R_0.25（>0.25 mm团聚体含量）值，降低分形维数（D）和土壤结构体破坏率（PAD_0.25）值（P<0.05）；施肥能显著提高土壤有机碳含量，其中BC （6.73 g ·kg^-1）和RSD （5.45 g ·kg^-1）效果显著优于NPK （5.05 g ·kg^-1）和GNPK （3.63 g ·kg^-1）；<0.25 mm团聚体有机碳贡献率最高（34.92%~59.49%），>5 mm团聚体有机碳贡献率最低（1.55%~6.01%），BC处理显著提高了5~2 mm和2~1 mm粒级团聚体有机碳贡献率（P<0.05），而NPK、RSD和GNPK在0.5~0.25 mm贡献率提升最为显著（P<0.05）；各施肥处理均能提高油菜和玉米产量，年际间差异较大，但处理间差异不显著；土壤团聚体稳定性和作物产量随土壤有机碳的增加呈上升趋势.生物炭和秸秆还田能促进土壤中，大、中团聚体形成，有效提高土壤团聚体稳定性，增加土壤有机碳含量，促进作物增产，是改良紫色土土壤结构、提升土壤质量的有效措施.

Effects of Biochar and Straw Return on Soil Aggregate and Organic Carbon on Purple Soil Dry Slope Land

The aim of the study was to understand the impact of biochar and straw return on soil aggregates and organic carbon for soil improvement of the newly cultivated purple soil dry slope land in the Three Gorges Reservoir area. In this study, a field test was used to set five treatment pairs with regards to soil aggregate composition and organic carbon distribution:no fertilization(CK), conventional fertilization(NPK), optimized fertilization(GNPK), chemical fertilizer reduction combined with straw(RSD), and chemical fertilizer reduction combined with biochar(BC). The results showed that fertilization can improve the level of soil fertility, especially with the RSD and BC treatments. The soil aggregates of each fertilization treatment were<0.25 mm in size. Compared with the CK, each treatment significantly increased the aggregate content of 0.5-5 mm particles, and the values of MWD, GMD, and R_0.25. Further, the treatments significantly reduced the value of D and PAD_0.25(P<0.05), and each fertilization treatment significantly increased the soil organic carbon content, of which BC(6.73 g·kg^-1) and RSD(5.45 g·kg^-1) were significantly better than NPK(5.05 g·kg^-1) and GNPK(3.63 g·kg^-1). The<0.25 mm aggregates had the highest contribution rate of organic carbon(34.92%-59.49%), while the>5 mm aggregates had the lowest contribution rate of organic carbon(1.55%-6.01%). The BC treatment significantly increased the organic carbon contribution rate of 5-2 mm and 2-1 mm agglomerates(P<0.05), while the contribution rate of NPK, RSD, and GNPK was the most significant for 0.5-0.25 mm(P<0.05). Each fertilization treatment increased the yield of rapeseed and corn, with large inter-annual differences, but the overall difference between treatments was not significant. The stability of soil aggregates and crop yields showed an upward trend with the increase of soil organic carbon. Biochar and straw returning to the field may promote the formation of large and medium aggregates in soil, effectively improve the stability of aggregates, increase organic carbon content, and promote crop yields. It is therefore an effective measure to improve the soil structure of purple soil and improve soil quality.