| Soybean is an important grain and oil crop in China,which plays an important role in the national economy.Soil tillage can improve soil structure and create suitable soil environment for soybean growth.Deep tillage can decrease the soil bulk density and increase the depth of the topsoil,but it will also increase the operation cost of agricultural machinery and cause the waste of resources.Therefore,to promote the efficient production and high yield of soybean,it is important to define the suitable bulk density and topsoil depth.This test used pot experiment,and the height of soil is 40 cm,with Jiyu 79 and Heinong 44 as test materials.This test set up 4 soil bulk densities: 1.00,1.15,1.30 and 1.45 g·cm-3;and 5 topsoil depth treatments: 0 cm(40 cm soil bulk density is 1.45 g·cm-3.),10 cm(The upper 10 cm soil bulk density was 1.15 g·cm-3,the lower 30 cm soil bulk density was 1.45g·cm-3.),20 cm(The upper 20 cm soil bulk density was 1.15 g·cm-3,the lower 20 cm soil bulk density was 1.45g·cm-3.),30 cm(The upper 30 cm soil bulk density was 1.15 g·cm-3,the lower 10 cm soil bulk density was 1.45g·cm-3.),and 40 cm(40 cm soil bulk density is 1.15 g·cm-3.),this experiment studied the effects of soil bulk density and topsoil depth on plant dry matter accumulation and distribution,absorption of nitrogen,phosphorus,potassium and soybean yield in R1,R5 and R8 stages.The results showed:1.Soil bulk density significantly affected dry matter accumulation and distribution in soybean.The dry matter accumulation of two soybean varieties was increased first and then decreased with the increase of soil bulk density.The dry matter accumulation of soybean reached the maximum under 1.30 g·cm-3 treatment.The 1.00 g·cm-3and 1.45 g·cm-3treatments could significantly inhibit the dry matter accumulation of soybean plant,and1.45 g·cm-3 treatment had the most abvious inhibitory effect.In the three sampling periods,when the soil bulk density was up to 1.45 g·cm-3,the proportion of dry matter distribution in soybean root was the largest.2.Soil bulk density significantly affected the absorption and accumulationof nitrogen,phosphorus and potassium in soybean.The content of nitrogen,phosphorus and potassium in two varieties of soybean plants showed a single peak curvewith soil bulk density,the maximum value appeared at the 1.15-1.30 g·cm-3 soil bulk density,and 1.45 g·cm-3treatment had significant inhibition on absorption ofnitrogen,phosphorus and potassium.Thenitrogen,phosphorus and potassium accumulation of two soybean varieties showed a single peak curve with the increase ofsoil bulk densityin the three sampling periods.The accumulations of nitrogen,phosphorus and potassium in soybean plants was 1.30 g·cm-3>1.15 g·cm-3>1.00 g·cm-3>1.45 g·cm-3,and there was significant difference among treatments.3.The topsoil depth also significantly affected the accumulation and distribution of dry matter in soybean.During the three sampling periods,the dry matter accumulation of soybean increased significantly with the increase of topsoil depth.During the period of R1,R5 and R8,the dry matter accumulation of the whole plant of Jiyu79 was 40 cm>30 cm>20 cm>10 cm>0 cm,and the difference was significant between different treatments.In R1 and R5 stages,whole plant dry matter accumulation of Heinong44 under 40 cm treatment reached the maximum.The whole plant dry matter accumulation reached maximum under 30 cm treatment in R8,and the difference between the topsoil depth 30 cm treatment and 40 cm treatment was not significant.During the three sampling periods,the proportion of dry matter distribution in root was the highest under 0 cm treatment.When the soybean was grown to R5 stage,the dry matter in the stem and leaf was transferred to the pod.When the soybean was grown to R8 stage,the dry matter of soybean was mainly transferred to the pod,and the topsoil was too deep or too shallow was conducive to the transportation of dry matter to the pod.4.The topsoil depthalso significantly affected the absorption and accumulation of nitrogen,phosphorus and potassium.The content of nitrogen,phosphorus and potassium increased with the increase of topsoil depth,and the maximum value was in the range of 30-40 cm.The depth of 0 cm treatment had obvious inhibitory effect on the absorption of nitrogen,phosphorus and potassium in soybean plants.The nitrogen,phosphorus and potassium accumulations of 2 soybean varieties increased with the increase of soil depth.The 0 cm treatment had obvious inhibitory effect on the accumulation of nitrogen,phosphorus and potassium in soybean plants.5.The effect of soil bulk density and topsoil depth had significant effect on soybean yield.When the soil bulk density was 1.30 g·cm-3,the indexes of soybean yield and its components were the highest.In the production process,the soil bulk density of 1.15-1.30 g·cm-3 is appropriate,which should be controlled in this range,to avoid excessive loose and too tight and to provide a good environment for soybean growth.If the topsoil depth is too shallow or too deep,it will reduce the yield of soybean.When the topsoil depth depth was 30 cm,it can meet the requirement of high yield of soybean. |
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