Effects Of Combined Application Of Organic And Inorganic Fertilizers On Yield,Photosynthetic Characteristics And Nitrogen Utilization Efficiency Of Different Soybean Summer Soybeans

The experiment was conducted in the Water and Fertilizer Coupling Research Experimental Station of Shandong Agricultural University and the Agricultural Research Station of Shandong Agricultural University in 2017 and 2018 respectively.In this study,soybean was used as researchmaterial.In 2017,9different soybean varieties screening conducted,the summer soybean variety Qi Huang 34（QH34）obtained the maximum yield.In2018,the photosynthetic performance and nitrogen use efficiency of QH34 were studied by different planting density and organic and inorganic fertilizer application.The effects of organic and inorganic fertilizer application and cultivation density were combined to analyze the changes of nitrogen nutrient,nitrogen accumulation,nitrogen distribution,dry matter mass accumulation and distribution in soybean.To reveal the changes of photosynthesis and chlorophyll fluorescence performance of summer soybean after flowering,and to explore the optimal cultivation management mode of organic and inorganic fertilizer application and different planting density,through rational close planting and optimized fertilization,in order to give full play to the nitrogen utilization efficiency of soybean after flowering.Provide scientific basis for potential photosynthetic production capacity and increase crop yield.Based on scientific evidence,it provides scientific guidance for the optimal summer soybean cultivation model in the Huang-Huai-Hai area.The main findings are as follows:1.Effects of planting density and organic and inorganic fertilizers on dry matter distribution and yield formation of soybeanAppropriate cultivation density and organic and inorganic fertilizer application can increase the accumulation of dry matter in various organs of soybean,enhance the distribution ratio of dry matter in pods after flowering,and promote the accumulation of dry matter in pods.The treatment of U,M and UM at the same planting density could increase the yield of soybean,and the effect of um yield was significant;UM-D2 increased yield by 28.95% and 26.77%,respectively,compared with U-D2 and M-D2.Under the same fertilizer application conditions,the yield will increase with the increase of planting density in the range of reasonable density,which is D3>D2>D1.The application of organic and inorganic fertilizers combined with simple application of chemical fertilizers or simple application of organic fertilizers can significantly increase the number of effective pods,100-grain weight and grain weight per plant.The yield of UM-D3 is the highest,and the number of effective pods of UM-D1 is the highest.2.Effects of planting density and organic and inorganic fertilizers on photosynthetic fluorescence of soybeanThe net photosynthetic rate（P_n）and leaf stomatal conductance（G_s）of soybeans increased first and then decreased,and the blast stage reached the highest value.The mature stage leaves began to turn from green to yellow.The net photosynthetic rate decreases rapidly,and the intercellular CO₂entration（C_i）tends to be opposite.The combination of organic and inorganic fertilizers significantly increased the net photosynthetic rate（P_n）and leaf stomatal conductance（G_s）of soybean leaves at different stages after flowering,and the difference was significantly different with the extension of flowering time.Under the same planting density,the net photosynthetic rate（P_n）of UM-D2 was increased by 34.77% and 24.52%,and the stomatal conductance（G_s）of leaves increased more than U-D2 and M-D2.At the 31.07% and 21.68%,the intercellular CO₂ concentration（C_i）decreased by 6.30%and 3.21%.Under the same fertilizer treatment,the net photosynthetic rate of UM-D1 was the highest,and there was no significant difference between UM-D1 and UM-D2,which was significantly different from um-D3.The pn of UM-D1 increased by 8.29% on the average of UM-D3 at the flowering,pod-forming and granulation stages,and G_s increased by 6.55% on average.The combination of organic and inorganic fertilizers at different densities can increase the net photosynthetic rate and stomatal conductance of soybean leaves,and effectively reduce the intercellular CO₂concentration,which can prolong the photosynthetic high value duration of post-anthesis soybean leaves.Under the same planting density,the performance index(PI_ABS)based on the absorbed light energy of soybean leaves was UM>U>M>N0.Under the condition of D2,the UM treatment increased evenly after U and M.68.48%and 37.74%.In the combined application of organic and inorganic fertilizers,D2 increased by 83.38%and 46.35%compared with D1 and D3 in each period after flowering.The post-anthesisV_jand W_k values of the combined application of organic and inorganic fertilizers were lower than those of other treatments,indicating that the donor side and acceptor side properties of soybean photosystem Ⅱ（PSII）could be significantly improved under the combined application conditions.The degree of openness of the active reaction center（Ψ_o）,the maximum photochemical efficiency(φ_po),and the light energy absorbed by the reaction center were used for electron transfer in different treatments of post-flowering leaf photosystem Ⅱ（PSII）illumination for 2 ms.The quantum yield(φ_Eo)is UM>M>U>N0,which indicates that the application of organic and inorganic fertilizers enhances the absorption of light energy and subsequent electron transfer performance of PSII in post-flowering leaves,and improves the light energy utilization efficiency of the leaves.3.Effects of planting density and organic and inorganic fertilizers on nitrogen use efficiency of soybeanThe nitrogen content of leaves and stems treated with um was significantly higher than that of N0 treatment during the growth period of soybean flower.Under the condition of D2,the nitrogen content of the um treated pods increased by 19.28%and 10.55%on average,and the difference reached a significant level.The combination of organic and inorganic fertilizers can promote the nitrogen uptake of soybean plants and significantly increase the nitrogen accumulation of leaves,stems,pods and other organs.The nitrogen accumulation of various organs treated by um is always higher than the other treatments.It indicated that the combination of organic and inorganic fertilizers was very beneficial to the accumulation of nitrogen in soybeans and could effectively improve the nitrogen use efficiency of soybean.In summary,the results of this experiment show that the fertilizer application type of Qihuang 34 summer soybean variety combined with organic and inorganic fertilizers in Huanghuaihai area is the highest under D3 conditions.