| Horqin sandy land lies in the agropastoral transitional zone in Northeast of China.The desertification and degradation of farmland in this region is serious,which restrict and hinder the local agriculture and animal husbandry development.How to improve sandy soil quality and productivity is the most urgent ecological environment problem that needs to be solved.In this study,the modified bentonite(B-HA)was used as a soil amendment.This study was conducted to study the effect and long-term mechanism of 1-7 years after B-HA addition on soil physical-chemical properties,soil microecology,maize growth and yield.The objectives of this research are to provide theoretical basis and technical support for using the B-HA toimprove the degraded soils.Main results are as follows:1.Addition of B-HA improved soil structure,and significantly(P<0.05)decreased soil bulk density,enhanced soil water fill-pore space and increased all different soil aggregate classes(>0.25mm).It also increased soil water content,water storage and water holding capacity,and improved the sandy soil water retention and supply capacity.Meanwhile,it significantly(P<0.05)increased soil cation exchange capacity,soil organic matter,soil nitrogen,phosphorous and potassium content,and improved sandy soil fertility.2.Addition of B-HA promoted soil microbial activities,and significantly(P<0.05)increased soil microbial biomass and enzyme activities.The highest activities appeared in 90 days after maize sowing.Compared to CK,soil microbial biomass carbon,nitrogen and phosphorous size increased by 5.50%-22.03%,17.48%-57.73%and 11.48%-41.06%,respectively.Soil urease,invertase,phosphatase and catalase activity increased by 10.81%-43.23%,6.78%-23.00%,4.9%-17.03%and 9.05%-36.87%5 respectively.3.Addition of B-HA enhanced soil microbial communities functional diversity.It significantly(P<0.05)increased average well color development(AWCD),Shannon-Wiener index(H),Substrate richness(S),but showed no significant effect on evenness(E).It significantly(P<0.05)increased the soil microorganisms utilization of phenols and amines,but decreased carbohydrates utilization.The soil microbial communities functional diversity did not significant change in 1st year after B-HA addition,it improved as the B-HA application year increasing,the functional diversity reached the highest in 5th year after B-HA addition.4.Addition of B-HA significantly(P<0.05)increased soil bacterial community diversity,it increased the diversity of eutrophic bacteria,the Finnicutcs increases by 44.2V-34I.39%compared to CK,and Bacteroidetes was 1.73-3.7 times higher than CK.It decreased the diversity of oligotrophic and autotrophic bacteria,the Acdiobacteria and Chloroflexi decreased by 20.88%-66.68%and 35.98%-75.33%compared to CK,respectively,but showed no significant effect on bacterial community richness.The UniFrac analysis indicated that soil bacterial community of 1st year after B-HA addition clustered with CK,it showed that B-HA application has minor change on bacterial community in the 1st year after B-HA addition.The greatest change appeared in 3th year after B-HA addition,the community was similar between 5th and 7th year after B-HA addition,it showed that the soil bacterial community tended to be stable after 5 years B-HA addition.The RDA analysis indicated that soil available phosphorous(R2=0.84,P<0.001)was the most important environment factor driving the change in soil bacterial community diversity.5.Addition of B-HA significantly(P<0.05)reduced the soil fungal community diversity and richness.As the B-HA addition year increasing,it gradually decreased the Fusarium and Gibberella diversity by 27.01%-79.56%and 43.54%-63.31%compared to CK,which favors to the control of sandy soil-bome diseases.The UniFrac analysis indicated that the fungal community had a major change in the presence of B-HA.The community was similar between 3 and 7 years after B_HA addition.However,the community was similar between CK,1 and 5 years after B-HA addition.The RDA analysis indicated that soil available nitrogen(R2=0.785,?<0.001)was the most important environment factor driving the change in soil fugal community diversity.6.Addition B-HA significantly(P<0.05)enhanced maize height,leaf area index,above?ground dry biomass and root biomass.It also significantly(P<0.05)increased maize yield,grain nutrient content,water use efficiency(WUE)and economic benefits.The highest grain nitrogen,phosphorous and potassium content appears in 3 to 4 years after B-HA addition,averagely increased by 5.36%-21.89%,18.07%-54.14%and 6.21%-38.57%compared to CK,respectively.Maize yield,WUE and economic benefits reached the highest in 5 years after B-HA addition,the grain yield,above-ground biomass yield and WUE averagely increased by 65.65%,52.06%and 67.24%compared to CK,respectively,then remained steady thereafter.Addition of B-HA strengthen the correlations between maize grain yield,soil physical-chemical properties and microbial properties,it also increased the correlation coefficient and mutual relationship between the properties mentioned earlier.7.The effect of B-HA addition on soil structure,fertility,microbial biomass and enzyme activities showed that the best influence in 5trh to 6trh year after B-HA addition,then remained steady thereafter.Addition of B-HA had a major influence on the indicators mentioned earlier in 0-40cm depth,specially on 10-20cm depth.As the B-HA application years increasing,it showed an increasing influence on soil depth below 40cm. |
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