| Given the soil degradation in farmland black soil of Northeast China such as seriously destroyed soil structure,increasing bulk density,thicker plow layer and degraded soil fertility caused by long-term single agricultural management system such as continuous rotary tillage and excessive application of chemical fertilizers,which poses a threat to the growth and development of crops,we conducted a field experiment to improve the problems mentioned above.The experiment was established with two rotation modes: consecutive rotary tillage(R)and deep ploughing--rotary tillage(D),combined with four fertilization modes: straw returning to the field(T),straw returning to the field + organic fertilizer(M),straw returning to the field + straw decomposing agent(C),straw returning to the field + organic fertilizer + straw decomposing agent(CM).The aim of this study is to elucidate the coupled effect of different rotation modes and fertilization modes on soil physical properties,biological properties,and corn growth condition,which could provide an insight for investigating a promising tillage strategy in improving soil structure,activating soil nutrients,constructing a reasonable plough layer,so that realizing the sustainable utilization of black soil.The study conclusions are as followed:(1)Compared with the consecutive rotary tillage,the deep plowing-rotary tillage treatment could increase the soil temperature at the depth of 20 cm and 30 cm at the seedling and jointing stage of corn by 0.80℃ and 0.15℃,0.90℃ and 0.95℃,respectively.Deep plowing-rotary tillage and rotation treatment could increase the soil moisture content and field water holding capacity of15-45 cm soil layer at each growth period of corn,and the effect was strengthened by the application of organic fertilizer and straw decomposing agent.(2)Deep plowing-rotary tillage significantly reduced the soil bulk density and compactness of 15-45 cm soil depth during each growth period of corn,and the combined application of organic fertilizer and straw decomposing agent significantly reduced the soil bulk density of 0-45 cm soil,while the combined application of organic fertilizer and straw decomposing agent in consecutive rotary tillage only improved the bulk density of the 0-15 cm soil depth.Deep plowing-rotary tillage could promote the formation of macro-aggregate at 15-45 cm soil depth,and the mean weight diameter of soil aggregates were significantly increased in response to the application of organic fertilizer and straw decomposing agent.The deep plowing-rotary tillage treatment decreased the soil solid phase proportion but increased the soil liquid phase and gas phase proportion.The application of organic fertilizer has a better effect on improving the three-phase ratio of soil than the application of straw decomposing agent.(3)Deep ploughing-rotray tillage increased soil urease,acid phosphatase,and amylase activity,but decreased soil invertase activity.The application of organic fertilizer boosted soil invertase activity,amylase activity,urease activity,and acid phosphatase activity,but the boosting effect is weaker than that of straw decomposing agent.Deep ploughing-rotary tillage enhanced AM fungal root infection rate and spore density,but reduced mycelial density.Compared with single organic fertilizer,organic fertilizer combined with straw decomposing agent enhanced AM fungal root infection rate and alleviate the negative impact on the extra-root hyphae density caused by the application of straw decomposing agent.(4)Deep ploughing-rotary tillage significantly enhanced corn stem height and above-ground biomass at the seedling stage and jointing stage,additionally,ear width,100-kernel weight,and yield were increased by 2.83%,4.25%,and 8.18%,respectively.The application of organic fertilizer and straw decomposing agent could increase corn yield,but the increasing effect appeared to be different in two rotation modes with a higher yield in consecutive rotary tillage and a lower yield in deep ploughing-rotary tillage.In summary,among all treatments,we recommend deep plowing-rotary tillage with the straw returning to the field and the addition of organic fertilizer and straw decomposing agent to be a promising strategy in constructing a reasonable plough layer,activating soil nutrients and maintaining the stability of corn yield in northeast China and similar regions around the world. |
