Effects Of Interaction Between Tillage Patterns And Nitrogen Fertilizer Treatments On Soil Physicochemical Property And Yield Of Winter Wheat

The objective of this study was to better facilitate the production of winter wheat and application of nitrogen fertilizer in Shan dong province. A three-year field experiment from October 2012 to June 2015 was conducted with three tillage patterns(three-year rotary tillage without maize straw returning, RT; three-year rotary tillage with maize straw returning, RTS; and two-year rotary tillage plus one-year deep tillage with maize straw returning, RTS-DTS.) and four nitrogen application levels(165kg/ha, Nr; 225kg/ha, Nm; 300kg/ha, Ni; 360kg/ha, Nl). Compared to rotary tillage, deep tillage facilitated decomposition of the maize straw and high N level accelerated the decomposition speed. Correlation analysis showed that soil physical properties were significantly correlated with soil organic matter content. Under non-straw-return condition, continuous rotary tillage reduced the organic matter content in 0-30 cm soil layer, leading to increased bulk density and decreased soil porosity. Under straw-return condition, continuous rotary tillage increased the organic matter content in 0-10 cm soil layer and soil porosity and decreased bulk density. Moreover, RTS-DTS showed positive effects on tilth soil structure. For example, compared to RTS, RTS-DTS had the effect on increasing organic matter content in 10-30 cm soil layer, decreasing bulk density in 0-20 cm soil layer, and increasing the total porosity and capillary porosity in 0-20 cm and 10-30 cm soil layer, respectively.Under continuous rotary tillage, straw returning increased the mass proportion of large macro-aggregate in 0-10 cm layers by 9.1-33.3%, small macro-aggregate in 10-20 cm and 20-30 cm layers by 5.1-18.8% and 3.3-22.6% than that without straw returning, respectively. Straw returning with 225kg/ha nitrogen fertilizer had higher mass proportion of large macro-aggregate and small macro-aggregate. When conversion from rotary tillage to deep tillage in the third year, the mass proportion of macro-aggregate in 10-20 cm layers was markedly enhanced by 55.6-78.9%, meanwhile, it increased the macro-aggregate in 10-20 cm and 20-30 cm by 5.7% and 3.1%, respectively. Under continuous rotary tillage, the organic carbon stock of surface soil and organic carbon stock in aggregates(except large macro-aggregate in 20-30 cm layers) were significantly increased with straw incorporation compared to that without straw returning. RTS-DTS balanced nutrients distribution of topsoil, and markedly enhanced the organic carbon stock of macro-aggregate in 10-30 cm layers. The stability of aggregate was positively correlated with the mass proportion of large macro-aggregate, namely, continuous rotary tillage with straw returning and RTS-DTS increased the stability of aggregate in 0-10 cm and 10-20 cm layers, respectively. The rule also applied to the relative contribution of aggregates to soil organic stock. Nitrogen application amount had little significant effects on soil aggregates than tillage patterns. When the nitrogen fertilizer applied was 225kg/ha or 300kg/ha, the mass proportion of macro-aggregate, the stability, organic carbon stock etc often had better performance. In consideration of tillage methods coupled with nitrogen fertilizer, two years for rotary tillage plus one year for deep tillage with straw returning and 225kg/ha nitrogen fertilizer applied could be selected as an approach for promoting soil quality.Without straw returning, the yield decreased markedly with each passing year under continuous rotary tillage, the grain yield of the third year reduced by 5.0-8.7% compared with the first year. Although the yield of RTS was 7.3-8.9% higher than that of RT, it also showed obvious decline in the third year.With straw returning, the third year under deep tillage increased spike number and grain number by 14.5% and 5.7%, respectively, indicating better performance in producing more grain yield, meanwhile, it increased PFPn and NUE by 5.3% and 1.8%, respectively. More nitrogen(300kg/ha, Ni; 360kg/ha, Nl) applied could not significantly increase the grain yield, and the PFPn and NUE decreased with more nitrogen applied. Taken together, with maize straw returning, deep tillage following two years rotary tillage with 225kg/ha nitrogen fertilizer is a sustainable soil carbon enhancement method and it provided guarantee for the sustainable agriculture.