| As the main by-product of agricultural production,returning straw to farmland scientifically and reasonably is beneficial to alleviate the environmental pollution caused by straw abandonment and open burning.Thus,the agricultural and rural ecological environment could be improved,and the purpose of soil fertility and crop yield increase could be achieved.However,the effects of straw returning on soil water,fertility and crop yield are different due to soil types,returning methods,returning amount and crop types.Therefore,it is of great theoretical and practical significance to explore scientific and reasonable straw returning methods and amounts for the efficient utilization of straw resources,the promotion of crop yield increase and stable yield,and the sustainable development of agriculture.Based on this,this study takes the typical winter wheat-summer maize rotation system in North China Plain as the research object.The single-season returning mode of maize straw returning in winter wheat season and wheat straw not returning in summer maize season was adopted.The effects of corn stalk and corn stalk biochar on soil water and fertility and crop yield of winter wheat-summer maize rotation system in the tidal soil region of North China Plain were studied.Multiple application was conducted according to the actual average dry matter weight of maize straw in the field-located plot.The maize straw returning amount was 0.5 times(S0.5,3.80 t/hm~2),1.0 times(S1.0,7.60 t/hm~2),1.5times(S1.5,11.40 t/hm~2)and 2.0 times(S2.0,15.20 t/hm~2).Biochar was applied by converting equal amount of maize straw into biochar(conversion rate was 30%),and the returning amount was 0.5 times(B0.5,1.14 t/hm~2),1.0 times(B1.0,2.28 t/hm~2),1.5 times(B1.5,3.42 t/hm~2)and 2.0 times(B2.0,4.56 t/hm~2).The treatments without straw and straw biochar were used as control(CK,0 t/hm~2).There were 9 treatments in this experiment.Through the combination of field positioning observation and indoor analysis,the effects of different straw biochar amounts and straw returning amount on the vertical soil moisture at 0-100 cm in each main growth period of winter wheat-summer maize,the vertical soil nutrients at 0-100 cm after harvest,grain yield and water use efficiency were analyzed.The main conclusions are as follows:(1)In the 0-100 cm soil layer,straw returning could better promote the increase of soil water content at tillering stage of winter wheat.In the winter wheat overwintering stage,mature stage and summer maize growth stages,biochar treatment showed a better soil moisture retention effect.Compared with the control,the average soil water content in 0-20cm and 0-100 cm soil layers of winter wheat-summer maize under biochar and straw returning treatments showed no significant difference.B1.5,S1.5 and S2.0 treatments could simultaneously increase the average soil water content of 0-20 cm and 0-100 cm in each growth period of winter wheat.Only B1.5 treatment in the summer maize season could simultaneously promote the increase of average soil moisture at 0-20 cm and 0-100cm in each growth period.(2)Biochar and straw could promote soil nutrients after the harvest of winter wheat and summer maize after returning to the field in the winter wheat season.The promotion effect on soil nutrients in the winter wheat season was better than that in summer maize season,and the promotion effect on soil nutrient content in 0-20 cm layer was greater.Compared with the control,biochar and straw returning treatments could promote the accumulation of nitrate nitrogen,ammonium nitrogen,available phosphorus,available potassium,total phosphorus and total potassium in 0-20 cm soil layer of winter wheat season,and also help to increase the accumulation of nitrate nitrogen and total potassium in 0-100 cm soil.Compared with the control,biochar and straw returning treatments could promote the accumulation of nitrate nitrogen,total phosphorus and total potassium in 0-20cm soil layer of summer maize in different degrees.The biochar and straw returning treatments had the best promotion effect on soil total potassium in summer maize season,and the soil total potassium accumulation at 0-20 cm and 0-100 cm in each treatment were higher than that in the control.(3)Compared with the control,biochar and straw returning could increase the aboveground dry matter mass of winter wheat by 3.71%-16.12%,and B2.0 treatment had the largest increase.Compared with the control,biochar application significantly increased the yield of winter wheat by 9.04%-21.76%,and straw returning significantly increased the yield of winter wheat by 15.31%-22.96%.The grain yield of winter wheat was significantly correlated with 1000-grain weight.Compared with the control,S1.5 and S2.0treatments significantly increased summer maize aboveground dry matter by 10.96%and13.15%,respectively.B0.5,S1.0,S1.5 and S2.0 treatments significantly increased summer maize aboveground dry matter by 10.86%,8.72%,10.89%and 12.22%,respectively.Grain yield of summer maize was significantly correlated with grain number per spike and1000-grain weight.(4)Compared with the control,the application of biochar increased the water use efficiency of winter wheat by 6.35%-28.34%,and straw returning increased the water use efficiency of winter wheat by 9.30%-17.64%,of which B2.0 treatment had the best promotion effect.Except for B1.5 and B2.0 treatments,the water use efficiency of biochar and straw returning treatments were higher than that of the control,and the B0.5 treatment had the best promotion effect on water use efficiency of summer maize,which was higher than 12.14%of the control.Based on normal fertilization in calcareous fluvo-aquic soil area,the application of biochar and straw in single season has a certain promoting effect on soil water and fertility and crop yield in wheat-maize rotation system.The application of 0.5 times of biochar carbonized by maize straw and 1.0 times of maize straw in the winter wheat season is conducive to improving soil fertility,and at the same time it could improve the grain yield and water use efficiency of winter wheat and summer maize. |
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