Effects of different peanut rotations modes on carbon fractions in soil aggregates
To better evaluate planting mode,effects of different peanut rotation patterns were explored on parti-cle size distribution and carbon content in soil aggregates.From 2017 to 2021,studies were carried out in Yantai,Shandong Province,by using local typical crop modes as contols,including winter wheat-summer maize(WM)and spring peanut(CP).Other peanut rotation patterns were set up,namely,WP(winter wheat-summer peanut rotation),PWM(spring peanut → winter wheat-summer maize rotation),and WPWM(winter wheat-summer peanut → winter wheat-summer maize rotation).Effects of planting patterns were investigated on soil aggregate composition and soil organic carbon content,dissolved organic carbon content,and microbial biomass carbon in the aggregates.Results showed that compared with CP mode,the percentage content of 1-2 mm aggregates in 0-40 cm soil layer under PWM and WPWM modes was significantly increased by 14.75-21.25 and 12.47-16.17 percentage points,respec-tively,and WPWM mode was more conducive to increase average weight diameter of soil aggregates.Soil organic carbon content of aggregates in 0-40 cm soil layer under WPWM mode was significantly higher than that under CP mode,except for the particle size of 0.25-0.5 mm.The contribution rate of soil organic carbon in 0-20 cm soil layer of 1-2 mm and<1 mm in WP and WPWM mode was significantly higher than those in CP.Under WPWM mode,dissolved organic carbon content of>5 mm,0.5-1 mm and<0.25 mm aggregates in 0-20 cm soil layer were signifi-cantly increased by 50.75%-81.18%,100.12%-120.12%and 69.44%-90.07%compared with the 2 controls(CP and WM),respectively.In WPWM mode,microbial biomass carbon content of 0-40 cm soil layer aggregates in-creased the most than those of the controls(CP and WM).Compared with the controls in 20-40 cm soil layer,the contribution rate of microbial biomass carbon in 1-2 mm aggregates was significantly increased under PWM,WP and WPWM modes.Soil organic carbon was significantly correlated with dissolved organic carbon,microbial bio-mass carbon,and dissolved organic carbon with microbial biomass carbon in aggregates of 2-5 mm,1-2 mm,and 0.5-1 mm.In general,WPWM increased mean weight diameter in 0-40 cm soil layer,the content of fine and large aggregates(1-2 mm),and the content and contribution rate of soil organic carbon,dissolved organic carbon and mi-crobial biomass carbon in 1-2 mm aggregates,which would improve soil structure and be more in line with the needs of green and low-carbon development.
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