| This experiment was conducted at the agricultural experiment station of Shandong agricultural university from October 2016 to October 2017.Jimai 22 and zhengdan 958 were selected as Winter wheat cultivars and summer maize cultivars,respectively.Based on the test platform for straw returning to the field with long-term positioning,we set four trial treatments,including NN(both summer maize straw and winter wheat straw were removed),MS(winter wheat straw was returned in summer maize season,but summer maize straw was not returned in winter wheat season),WS(summer maize straw was returned in winter wheat season,but winter wheat straw was not returned in summer maize season),SS(summer maize straw ws returned in winter wheat season,and winter wheat straw was returned in summer maize season).The objective of this experiment was to investigate the effects of straw returning methods on the annual soil nutrient,the accumulation and distribution of nutrients in aboveground plants,as well as the yield and its constituent elements,aiming at rationally utilizing straw resource in Huanghuaihai grain-producing areas and achieving a synergistic increase in soil quality and yield.The main findings were as follows: 1.Effects of annual straw returning methodson soil nutrientCompared with the treatment without straw returning,straw returning could improve soil nutrient content to different extent.After jointing stage of summer maize and swinter wheat,the effect of straw returning gradually emerged.Soil total nitrogen,available potassium,and available nitrogen content under the treatment of straw returning was higher than that without straw returning to some extent.Soil total nitrogen and available nitrogen content were increased by 0.05 to 0.84 g/kg and 5.50 to 64.36 mg/kg,respectively.Meanwhile,Soil available potassium content was increased by 4.26% to 34.13%.Straw returning both in summer maize season and winter wheat season(namely annual straw returning)had greater impact on soil nutrient content than that in summer maize season or winter wheat seasonalonely.In addition,the annual straw returningcould reduce the content of available potassium and available nitrogen in the soil layer of 100-160 cm,decreasing the risk of available nitrogen and available potassium leaching in the deeper soil,thereby reducing the loss of nutrients.Annual straw returning had not significant influence on soil available phosphorus content in wheat season,but increased available phosphorus content in 0 to 40 cm soil layer in maize season by 6.8 mg/kg.2.Effects of annual straw returning on crop productionThe treatment of straw returning could significantly improve the biological accumulation of winter wheat and summer maize.Compared with the treatment without straw returning,the biological accumulation of winter wheat and summer maize under the treatment of straw returning increased 5.83% to 27.15% and 4.39% to 10.50%,respectively,and the effect of annual straw returning was superior to other straw returning treatments.Meanwhile,both the accumulation of stem,leaf and grain of winter wheat and the accumulation of stem,grain and cob of summer maize with annual returning significantly increased.The harvest index of winter wheat was ranked as: straw was not returned in winter wheat and summer maize season > straw was returned in summer maize season > straw was returned in winter wheat season > straw ws returned both in winter wheat and summer maize season,and the harvest index of summer maize was ranked as: straw ws returned both in winter wheat and summer maize season > straw was returned in summer maize season > straw was returned in winter wheat season > straw was not returned in winter wheat and summer maize season.Apparently,annua straw returning had distinct influence on harvest index of winter wheat and summer maize.3.Effects of annual straw returning on crop nutrients absorption and utilizationThe biomass of straw returning treatments was significantly increased,and we found that the accumulation of pant's nitrogen,phosphorus and potassium was also significantly increased.The accumulation of phosphorus under the treatment of straw returning in winter wheat season was the highest,and the accumulation of nitrogen and potassium was ranked as: straw returned both in winter wheat and summer maize season > straw returned in summer maize season > straw returned in winter wheat season > straw removed in winter wheat and summer maize season.Compared with the treatment without straw returned,the accumulation of nitrogen,phosphorus and potassium under the treatment of annual straw returning increased by 25.87%,49.64% and 28.25% in winter wheat season,respectively,owning to more nitrogen,phosphorus and potassium accumulation in grain,leaf and stem.Annual straw returning increases the nitrogen and phosphorus accumulation in the grains and leaves of summer maize and the accumulation of potassium in the stems,resulting in the increase of the total accumulation in nitrogen,phosphorus,and potassium by 20.64%,9.88%,and 21.12%,respectively.Therefore,annual straw returning significantly increased the amount of nutrient accumulation in aboveround plant,and transported more nutrients to the stem,leaves and grains.4.Effect of annual straw returning on crop yield and its componentsCompared with the treatment without straw returning,annual straw returning increased the yield of winter wheat by 24.29%,owning to 9.98% and 3.94% higher in the number of effective panicles and grains per panicle,respectively.Meanwhile,annual straw returning increased the grain yield of summer maize by 13.32%,due to the number of rows per ear and grain weight increasing by 4.00% and 2.98%,respectively.Ultimately,the annual straw returning increased the annual yield by 18.55%.In summary,straw returning both in winter wheat and summer maize season could significantly improve soil fertility,and markedly increase the annual grain yield with more nutrition accumulation. |
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