| In order to reveal the influencing mechanism of soil hydro-thermal,soybean growth and development,yield and yield composition factors caused by different straw mulching period and amount of straw mulching in northeast black soil area.In the field exp eriment,2 straw mulching periods(after sowing and in the three-leaf period)and 3 straw mulching amounts(0.4 kg/m~2,0.8kg/m~2,1.2 kg/m~2)were set,and no straw mulching treatment was used as the control treatment.To explore the influence mechanism of straw mulching period and straw mulching amount on soil hydro-thermal,soybean growth,yield formation and yield effect.A structural equation model was established to analyze the causal relationship between yield and yield components under straw mulching treatment and the causal relationship between soil hydro-thermal,soybean growth and yield components.Based on the factors of soil hydro-thermal,soybean growth,yield and yield components,the matrix evaluation method and the improved TOPSIS model were u sed to comprehensively evaluate each treatment.In order to provide theoretical basis and technical support for straw mulching technology in northeast black soil area,the appropriate straw mulching period and straw mulching amount were put forward.The ma in conclusions are as follows:(1)Postponing the straw mulching period to the three leaf period can significantly increase the soil moisture content and soil moisture storage.Postponing the straw mulching period to the three leaf period can reduce the moisture consumption from seedling stage to flowering and pod stage,and increase the moisture consumption from flowering and pod stage to maturity stage.No matter whether the straw mulching period is delayed or not,the soil moisture content and soil moisture storage capacity show a gradually increasing trend with the increase of straw mulching amount.No matter whether the straw mulching period is delayed or not,the moisture consumption from seedling stage to flowering and pod stage decreases gradually with t he increase of straw mulching amount with the increase of straw mulching amount.With the progress of growth,the difference of soil moisture content between early stage of flowering and pod setting and early stage of pellet formation was greater than that between seedling stage and branching stage and middle stage of pellet formation and maturity stage.(2)The soil temperature under straw mulching has a significant cooling effect.Delaying the straw mulching period to the three leaf period can significantly alleviate the cooling effect and increase the soil effective accumulated temperature.Under the condition of three leaf period,soil temperature and soil effective accumulated temperature decreased gradually with the increase of straw mulching.Under the condition of straw mulching after sowing,soil temperature from seedling stage to early stage of pelleting gradually decreased with the increase of straw mulching,while soil temperature from middle stage of pelleting to maturity stage increased with the inc rease of straw mulching.Under straw mulching after sowing,soil effective accumulated temperature decreased gradually from seedling stage to flowering and pod stage,but increased gradually during other growth stages and the whole growth period.With the progress of growth,the soil temperature in flowering and pod setting stage was not significantly different from that in other growth stages.No matter whether the straw mulching period was changed or not,the soil temperature and effective accumulated temperature in the whole growth period significantly decreased under the straw mulching amount of 0.8 kg/m~2 and 1.2 kg/m~2,but the difference between the two was not significant.(3)Postponing the straw mulching period to the three leaf period can significantly promote soybean seedling emergence,growth and yield formation,and thus increase soybean yield.With the increase of straw mulching amount in different straw mulching periods,the emergence rate of soybean decreased gradually.With the increase of straw mulching amount in different straw mulching periods plant height,leaf area,chlorophyll content,dry matter accumulation,yield and yield components of soybean increased first and then decreased.Under different straw mulching conditions,the growth and development of soybean were most vigorous under the straw mulching amount of 0.8 kg/m~2.No matter whether the straw mulching period was delayed or not,the growth and development index of soybean under the straw mulching amount of 1.2 kg/m~2 was the lowest.(4)The simulation results of structural equation model show that,pod number per plant of soybean affects grain number and grain weight,and then affects grain yield and biological yield.Pod number per plant was positively correlated with seed number per plan t and grain weight per plant.Pod number per plant had a significant effect on seed number per plant,and the standardized path coefficient was 1.011.The grain number and weight per plant were positively correlated with grain yield and biological yield.The grain number and weight per plant had significant effects on grain yield,and the standardized path coefficients were 0.940 and 0.839 respectively.Soil moisture and soil temperature were negatively correlated under straw mulching treatment,The effect of soybean plant height on seed weight was greater than that of leaf area,and the effect of soybean leaf area on seed number and pod number per plant was greater than that of plant height on seed number and pod number per plant.The effect of soil moistur e and soil temperature on yield formation was greater than that on crop growth,and the effect on soybean growth and yield formation basically comes from direct effect.(5)Based on the 15 evaluation indexes of soil moisture content,soil temperature and soybe an plant height,the comprehensive evaluation of each straw mulching treatment was conducted by using the matrix evaluation method and the improved TOPSIS model.The evaluation results show that the suitable straw mulching period is the three leaf straw mulching period,and the suitable straw mulching amount is 0.8 kg/m~2. |
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