Effect Of Remediation Measures On Degraded Soil Of Aging Orchards In Weibei Dryland

Most of the old orchards with an age of 20-30 years used excessive chemical fertilizers,resulting in an imbalance of nutrient ratios and a decline in microbial diversity.As a result,pests and diseases occurred frequently,tree senescence was premature,fruit quality deteriorated,and economic benefits decreased.The application of exogenous amendments improved soil physicochemical properties,biological properties,fruit quality and fruit yield,as well as increased soil microbial species richness and altered soil microbial community structure.The effects of chemical fertilizers with different organic amendments on soil characteristics of apple orchards have been widely studied,but the comprehensive improvement effect on orchards’ soil is not clear.Applying of exogenous amendments could improve soil physicochemical and biological properties,increase soil microbial species richness and change soil microbial community structure,thereby reducing the occurrence of diseases,prolonging the life of fruit trees,improving fruit quality and increasing fruit yield.The experiment was conducted to determine soil physicochemical properties,CNP acquisition enzymes,MBC,MBN and microbial community.The extracellular enzyme stoichiometry model was applied to explore the metabolic limitations of microbial communities in soils treated with different fertilizers,and investigated the effect of fertilizer reduction with different organic amendments on soil improvement in old orchards of Weibei dry land.This provided a theoretical basis for extending the fruiting period of the orchard,constructing a healthy ecosystem in the orchard,and maintaining and coordinating the relationship between fruit tree production and the environment.The main conclusions of this study are as follows:(1)Based on reducing the application of chemical fertilizers,with the application of organic fertilizers,biochar,organic fertilizers plus bacterial agent could effectively improve the yield of apples.The yields of MCF,MYR+CF and BCF treatments were significantly increased by 22.65%,22.51% and 21.18% compared with chemical fertilizer reduction treatment,respectively.These yields were higher than the farmers’ accustomed usage.Moreover,compared with the farmers’ customary dosage,the income per hectare of MYR+CF treatment and the MCF treatment increased by 17.1 thousand yuan and 19.2thousand yuan respectively.(2)Based on reducing the application of chemical fertilizers,with the application of organic fertilizers,biochar,organic fertilizers plus bacterial agent could significantly increase the soil TN,SOC,available K and available P,microbial carbon and nitrogen contents.During different growth stages,the SOC and TN contents of the topsoil(0-20 cm),biochar application increased to varying degrees,compared with the farmers’ customary dosage and chemical fertilizer reduction treatments.Compared with chemical fertilizer reduction treatment,the content of available P and available K in the soil surface of MCF,MYR+CF and BCF treatments under different growth periods were increased by 22.4-43.2%,3.6-38.8%,reaching the level of farmers’ habitual usage.The MBC and MBN contents of the three treatments in the 0-40 cm soil layer at different growth periods were increased by22.2-126.1% and 1.0-46.4% respectively,compared with the farmers’ habitual usage.(3)MCF,MYR+CF,BCF treatments could increase the enzyme activities in 0-40 cm soil to varying degrees.Furthermore,according to the enzyme stoichiometry,the three treatments alleviated soil microbial phosphorus limitation,and the microbial phosphorus limitation of0-40 cm soil of AP,AK was negatively correlated.(4)The combination of chemical fertilizer reduction and application of different organic amendments affected soil microbial community structure.The application of organic amendments increased the relative abundance of beneficial bacteria in the soil.Compared with the farmers’ habitual dosage,the relative abundance of Proteobacteria increased by15.1-25.8% of organic fertilizer + bacterial agent + chemical fertilizer reduction and biochar+ chemical fertilizer reduction.The microbial community composition of old orchard was different from that of healthy orchard,and the BCF and MYR+CF treatments changed the microbial community structure in the soil of old orchard.In summary,the reduction of chemical fertilizers with different organic amendments improved soil fertility to varying degrees,alleviated the limitation of soil microbial phosphorus,increased bacterial and fungal OTUs in soil,and further improved fruit tree growth and microbial communities.However,considering the economic benefits,organic fertilizer + bacterial agent + chemical fertilizer reduction application and Organic fertilizer +chemical fertilizer reduction application are the most recommended fertilization methods.