Effects Of Compound Microbial Fertilizer Combined With Chemical Fertilizer On Soil Characteristics And Soybean Growth

In order to clarify the response of soil fertility to composite microbial fertilizer in northern Northeast China,the effects of different fertilizer dosages combined with composite microbial fertilizer on soil physical and chemical properties of soybean fields were studied,and related indexes such as soybean growth and development,nutrient accumulation and yield formation under different fertilization treatments were compared and analyzed,so as to provide theoretical and practical basis for the stable growth of soybean yield in main soybean producing areas in Northeast China.The experiment will be conducted in 2021 and 2022 in Heshan Farm experimental field of Heihe City,Heilongjiang Province.Jinyuan 55(P1)and Keshan No.1(P2)were selected as the soybean varieties tested.Three treatments were set up: T1(conventional fertilization),T2(50% nitrogen fertilizer +complex microbial fertilizer)and T3(0 nitrogen fertilizer + complex microbial fertilizer).The effects of application amount of compound microbial fertilizer on soybean growth morphology,photosynthetic characteristics,nutrients in different parts of the plant,grain quality,soil physical and chemical properties,soil enzyme activity and yield formation were comprehensively analyzed.The results show that:(1)Compared with(conventional fertilization)T1 treatment,application of complex microbial fertilizer(T2,T3)reduced soil bulk density and increased soil porosity,and(0 nitrogen fertilizer +complex microbial fertilizer)T3 treatment had the best effect.Compared with T1 treatment,the clay volume fraction in T2 and T3 treatment decreased,while the sand volume fraction increased,and the change range in T3 treatment was the most obvious.In the 0-20 cm layer,the aggregate content of > 5mm was the highest in each treatment.Compared with T1 treatment,the application of complex microbial fertilizer(T2 and T3)promoted the formation of soil large aggregates and reduced the microaggregates < 0.25 mm,and the effect of T3 treatment was the most obvious.(2)Under the same cultivation and hydrothermal conditions for two years,the activities of sucrase,urease,catalase and alkaline phosphatase in(50% nitrogen fertilizer + complex microbial fertilizer)T2 and(0 nitrogen fertilizer + complex microbial fertilizer)T3 treatments showed a tendency to increase compared with(conventional fertilization)T1 treatment.The results showed that the application of compound microbial fertilizer could improve soil enzyme activity,and the activity of soil enzyme increased with the increase of fertilizer application amount.(3)Compared with(conventional fertilization)T1 treatment,the content of total soil nutrients in the two compound microbial fertilizer treatments(T2 and T3)showed an increasing trend with the increase of fertilizer application rate,but there was no significant change among treatments.The p H of T3 treatment was significantly lower than that of T1 treatment.Compared with T1 treatment,the organic matter content of composite microbial fertilizer replacement treatment(T2 and T3)had a certain improvement effect,but it was not significant.After two years of experiment in which compound microbial fertilizer replaced fertilizer(T2 and T3),soil available K,available P and alkalihydrolyzed N were significantly increased compared with that in control T1 treatment with chemical fertilizer alone.The contents of nitrate nitrogen and ammonium nitrogen in soil showed a decreasing trend,but the application of complex microbial fertilizer(T2 and T3)could effectively prevent the downward leaching of nitrate nitrogen and ammonium nitrogen.(4)Compared with(conventional fertilization)T1 treatment,the growth and morphological indexes of soybean increased in different degrees under T2 treatment(50% nitrogen fertilizer +complex microbial fertilizer),indicating that complex microbial fertilizer could provide sufficient nutrients instead of chemical fertilizer to promote the growth of soybean plants.Compared with T1 treatment,the growth and morphological indexes of soybean were decreased by T3 treatment(0nitrogen fertilizer + complex microbial fertilizer).Compared with T1 treatment,T2 treatment increased the nutrient uptake of crops and nitrogen,phosphorus and potassium,and T2 treatment had the highest nutrient utilization efficiency among the two varieties.The photosynthetic indices of T2 treatment were significantly higher than that of T1 treatment after additional application of complex microbial fertilizer.However,T3 treatment showed that the photosynthetic rate,stomatal conductance and transpiration rate of soybean leaves decreased,indicating that excessive fertilizer reduction would lead to the decrease of photosynthetic characteristics of plant leaves.Instead of chemical fertilizer treatment(T2 and T3),compound microbial fertilizer significantly improved the protein quality of soybean,but significantly inhibited the fat content of soybean,and the fat content of T1 treatment was significantly higher than that of T2 and T3 treatment.(5)In 2021,the yield components of all treatments of Jinyuan 55(P1)showed T2>T1>T3,with soybean yield increased by 13.02% in(50% N fertilizer + compound microbial fertilizer)T2 treatment compared to(conventional fertilizer)T1 treatment,and soybean yield decreased by 9.34% in(0 N fertilizer + compound microbial fertilizer)T3 treatment compared to(conventional fertilizer)T1treatment.All yield components of Keshan 1(P2),except 100 grain weight,were T2>T1>T3,with soybean yield in the T2 treatment increasing by 5.34% and soybean yield in the T3 treatment decreasing by 9.26% compared to the T1 treatment.In 2022,the yield components of each treatment at Jinyuan 55(P1),except for 100 grain weight,were T2 > T1 > T3,with soybean yield in the T2 treatment increasing by 12.60% compared to the T1 treatment and soybean yield in the T3 treatment decreasing by 17.23% compared to the T1 treatment.All yield components of Keshan 1(P2)except100 grain weight were T2>T1>T3,with soybean yield in the T2 treatment increasing by 20.43%compared to the T1 treatment and soybean yield in the T3 treatment decreasing by 11.41% compared to the T1 treatment.