长期不同施肥和耕作对坡耕地黄壤团聚体组成及有机碳的影响

Effect of long-term different tillage and fertilization measures on aggregates composition and organic carbon in yellow soil slope cultivated land

为探究不同施肥和耕作对坡耕地黄壤团聚体组成及有机碳的影响,本文以贵州省农业面源污染长期定位监测为试验平台,对比研究不施肥+顺坡平作(T1)、常规施肥+顺坡平作(T2)、优化施肥+顺坡平作(T3)、优化施肥+横坡垄作(T4)、优化施肥+横坡垄作+秸秆覆盖(T5)和优化施肥+横坡垄作+秸秆覆盖+等高植物篱(T6)对黄壤团聚体组成及有机碳含量的影响。结果表明:各处理机械稳定性团聚体和水稳性团聚体组成均以>0.25 mm大团聚体为主;同等耕作条件下,T3较T2水稳性团聚体的平均质量直径、几何平均直径、>0.25 mm的团聚体分别提高14.22%、25.74%、5.24%;T6的土壤团聚体破坏率、不稳定团粒指数和分形维数与其他处理相比均为最低;不同粒级水稳性团聚体中均以T1有机碳含量最低,同等耕作条件下,>5、5~2、0.5~0.25、<0.25 mm团聚体中T3较T2的有机碳含量提升1.88%~26.32%,同等施肥条件下,>5、5~2、2~1、1~0.5 mm团聚体中T5和T6较T4的有机碳含量分别提升3.21%~17.20%和0.26%~10.19%;土壤团聚体有机碳主要集中在>0.25 mm的大团聚体中,T2、T3、T4、T5、T6中>5 mm团聚体的有机碳贡献率均最高,分别为27.04%、31.51%、30.89%、33.61%、31.63%。长期优化施肥结合保护性耕作可改善土壤团聚体,提高团聚体稳定性和土壤有机碳含量,可作为喀斯特地区坡耕地较佳的施肥与耕作组合。

[Background]The findings demonstrated the suitable tillage measures and rational application of fertilizer could effectively prevent and control regional soil erosion.Soil properties that affect soil erosion are mainly anti-erodibility and impact resistance,and soil aggregates are their characteristic form.Stabilization of soil aggregation is considered to be the most important mechanism for soil carbon sequestration.The effects of conservation tillage and optimized fertilization on the soil aggregates composition and soil organic carbon were compared in this paper,and it can be used as a better combination of farm and fertilization for slope land in karst area.[Methods]The long-term positioning monitoring of agricultural non-point source pollution in Guizhou province was taken as the experimental platform.The dry sieve method(mechanically stable aggregates)and the wet sieve method(water stable aggregate)were used to compare and study the effects of 6 treatments on the aggregate composition and organic carbon content of yellow soil,6 treatments referred to no fertilization+downslope conventional tillage(T1),conventional fertilization+downslope conventional tillage(T2)as the control,optimized fertilization+downslope conventional tillage(T3),optimized fertilization+cross ridge tillage(T4),optimized fertilization+cross ridge tillage+straw mulching(T5),and optimized fertilization+cross ridge tillage+straw mulching+contour hedgerow(T6).[Results]1)The compositions of mechanically stable and water stable aggregates by each treatment were mainly composed of large aggregates of>0.25 mm.Under the same tillage conditions,the mean weight diameter(MWD),geometric mean diameter(GMD)and aggregates size of>0.25 mm(R0.25)of T3 increased by 14.22%,25.74%and 5.24%compared to T2,respectively.2)Compared with other treatments,the soil of percentage of aggregate destruction(PAD),unstable aggregate index(ELT)and fractal dimension(D)of T6 were the lowest,the organic carbon content of T1 was the lowest in water stable aggregates of different particle sizes.The organic carbon content of T3 increased by 1.88%-26.32%compared to T2 in the aggregate sizes of>5.00,5.00-2.00,0.50-0.25,and<0.25 mm under the same tillage conditions.The organic carbon content of T5 and T6 increased by 3.21%-17.20%and 0.26%-10.19%compared to T4 in the aggregate sizes of>5.0,5.0-2.0,2.0-1.0,and 1.0-0.5 mm,respectively under the same fertilization conditions.The contents of soil aggregate organic carbon was mainly in the size of>0.25 mm,and the>5.00 mm aggregates were the highest contribution rate of organic carbon in T2,T3,T4,T5 and T6,which were 27.04%,31.51%,30.89%,33.61%and 31.63%,respectively.Furthermore,soil aggregate organic carbon showed a positive correlation with soil total organic carbon.[Conclusions]Long-term optimized fertilization and conservation tillage may effectively improve the aggregates and its stability and soil organic carbon content,and can be used as a better combination of tillage and fertilization for slope land in karst areas of China.