Effect Of Different Intertillage Measures On Soil Physical And Chemical Properties And Soybean Growth

Heilongjiang Province is the main soybean producing area in China.Low temperatures in early spring and poor soil moisture retention capacity are the main limiting factors leading to low soybean yields.In order to improve land productivity,the effects of different intertillage measures on soil physical and chemical properties of soybean fields and related indicators of soybean growth and development and yield formation under the yudou rotation pattern were studied with a view to providing strong support for stable soybean yield improvement.Adopting scientific and reasonable intertillage measures can increase temperature and soil moisture,loosen soil and weed,effectively improve land productivity,and provide favorable conditions for high and stable yield of soybean.Therefore,in order to explore the effects of different intertillage measures on soil physical and chemical properties,soil aggregate stability and related indicators of soybean yield formation in soybean field under rice-soybean rotation mode,the Heshan Farm Science and Technology Park of Jiusan Company of Beidahuang Group in Heilongjiang Province was taken as the experimental base.Based on the long-term fixed-point test of rice-soybean rotation,the field plot test method was used from 2019 to 2021.The local main cultivar Heihe 43 was used as the experimental material.Four different intertillage treatments were set up in 2020 : conventional intertillage(T1),early intertillage(T2),conventional subsoiling(T3)and early subsoiling(T4).In2021,T5 treatment(subsoiling in V4-V5 stage)and T6 treatment(soil culture in V4-V5stage)were supplemented on the basis of early subsoiling.A total of six different medium intertillage measures were used to systematically analyze the effects of medium intertillage on soil properties,microbial characteristics,soybean morphology,photosynthetic characteristics,plant nutrients and yield formation.The experimental results show that :(1)The adjustment of intertillage time and depth can improve soil hydrothermal conditions and soil physical properties,and the intertillage depth is the main factor affecting soil physical structure.Under the same intertillage depth,early intertillage can rapidly increase soil temperature,and promote the generation and preservation of fine silt and clay particles in soil.On the basis of the same medium intertillage time,subsoiling had more obvious effect on soil temperature and moisture conservation,which significantly reduced soil bulk density,increased soil porosity,soil aggregate stability and soil clay content.Compared with T1 treatment,soil temperature and humidity of T3 treatment increased by 5.51 %-6.52 % and 4.86 %-6.85 %,respectively,and bulk density decreased by 16.67 %(P<0.05).Soil temperature,humidity and porosity of early subsoiling(T4,T5,T6)were significantly higher than those of T2.In the early subsoiling treatment,the combination of subsoiling and soil cultivation was the best in the V4-V5 period.Compared with soil cultivation,subsoiling had a greater impact on soil physical properties.(2)Early intertillage and subsoiling could improve the content and stability of soil water-stable aggregates.Among different intertillage treatments,the number and stability of soil water-stable aggregates in T4 treatment were the best.Under the same intertillage depth,compared with T1 treatment,T2 treatment significantly increased the MWD index of V5-R2 period,the GMD index of R2-R6 period and the content of soil water-stable aggregates of R8 period.Compared with T3 treatment,T4 treatment significantly increased the MWD index of V5 period,the GMD index of V5-R6 period and the number of soil water-stable aggregates of R6-R8 period.On the basis of the same intertillage time,subsoiling could significantly increase the number of soil > 0.25 mm aggregates and the proportion of 0.25-2mm water-stable aggregates.The aggregate stability indexes(MWD and GMD index)of different treatments in R6 stage were as follows : T3 > T1,T4 > T5 > T6 > T2,in which T3 treatment increased by 17.43 % compared with T1 treatment,and T4 treatment increased by13.60 % compared with T2 treatment.(3)Deep loosening in advance can improve soil chemical properties,soil nutrient content and availability.Compared with T1 treatment,early subsoiling(T4,T5,T6)significantly reduced soil electrical conductivity,increased soil cation exchange capacity,organic carbon,nitrogen,inorganic nitrogen,available phosphorus and potassium,and significantly improved soil organic nitrogen mineralization ability.Among them,the soil organic carbon and nitrogen contents of T4 treatment increased rapidly and lasted for the longest time at V5 stage,maintaining a high mineralization rate constant and the highest nitrogen mineralization potential.The ammonium nitrogen content and nitrate nitrogen content of T4 treatment were 2.97 mg / kg and 3.09 mg / kg higher than those of T1 treatment,and the increase rates of available phosphorus and potassium reached 18.48 %-22.98 % and10.49 %-10.77 %,respectively.By comparing the effects of intertillage time and intertillage depth on soil chemical properties,it was found that intertillage depth had a greater impact on soil chemical properties and soil nutrients.(4)Nine bacterial dominant species and eight fungal dominant species were detected in soybean field soil under different intertillage measures.Protepbacteria and Acidobacteria were the main dominant bacterial populations,Ascomycota,Basidiomycota and Mortierellomycota were the main fungal dominant species.Medium intertillage time and depth had great influence on soil microbial characteristics.Early medium intertillage could significantly increase the species abundance of bacteria and fungi in soil,while subsoiling could increase the relative abundance ratio and uniformity of dominant species.The alpha diversity analysis and Beta diversity analysis showed that the diversity of bacterial and fungal communities in T4 treatment was the highest,and the microbial diversity in different intertillage treatments was T4 > T3 > T2 > T1,and subsoiling had a greater impact on the diversity of fungal populations.In particular,the early intertillage time on the basis of subsoiling made the response of fungal populations more sensitive,thereby reducing the similarity of fungal population abundance.Different medium intertillage measures had significant effects on soybean growth and yield formation.Early medium intertillage and subsoiling increased the nutrient content of soybean plants,and subsoiling was more conducive to the migration of plant nutrients to grain in reproductive growth stage.Under the same medium intertillage depth,the plant height,leaf area,stem diameter and SPAD value of T2 treatment at R6 stage were 5.06 %-0.57 %,16.86 %-21.93 % and 2.39 %-6.81 % higher than those of T1 treatment,respectively.Compared with T3 treatment,T4,T5 and T6 treatments significantly increased leaf area index,plant height,net photosynthetic rate(Pn),grain dry matter accumulation and soybean yield at R6 stage to varying degrees.Under the same medium intertillage time,compared with T1 treatment,the plant height,leaf area index and root length of T3 treatment at R6 stage increased by5.02 %-6.42 %,8.97 %-13.19 % and 19.95 %-27.28 %,respectively,and the dry matter accumulation and assimilation contribution rate after R5 stage increased by 34.38 %-49.75 %and 7.70 %-32.95 %,respectively.Compared with T2,leaf area index,net photosynthetic rate(Pn),dry matter accumulation after R5,assimilation contribution rate and yield of T4,T5 and T6 increased significantly.Compared with T1 treatment,the morphological indexes,dry matter accumulation and soybean yield of T4 treatment at R6 stage were significantly increased compared with those of T1 treatment,the net photosynthetic rate(Pn)of T4 treatment increased by 29.68 %-34.15 %,and the yield increased by 18.71 %-19.36 %.