Analysis Of Common Factors Contributing To Soil Degradation In Facilities And Research On Microbial Remediation

Facility agriculture is a modern production method that boasts high yields and efficiency.However,the unique facility environment and intensive production methods can lead to severe soil degradation.This degradation ultimately hinders the sustainable development of facility agriculture.To ensure sustainability,it is essential to identify the common key factors of soil degradation in facilities and to propose remediation technologies to address them.This study focused on three major facility vegetable growing areas in Hebei Province and investigated three types of facility soils with varying growing years.The study aimed to identify common factors of soil degradation by systematically analyzing physical,chemical,and biological indicators.Additionally,the study aimed to determine the composition of degraded soil amendments and their remediation effects.The main findings of the study are as follows:1)The study found that after several years of cultivation,the soil capacity in the three planting areas decreased by 1.77%-16.84%.However,the maximum water holding capacity increased by 2.77%-18.68%,indicating that the soil physical properties are still favorable.On the other hand,the soil total salt content and EC values increased by65.19%-65.77%and 77.38%-103.40%,respectively.Notably,there were significant differences observed in the p H levels,which decreased by 0.06-0.21 units with each planting year.The soils in the facility areas exhibited secondary salinization and acidification trends that varied with the number of years of planting.Organic matter,total nitrogen,total phosphorus,fast-acting nitrogen,fast-acting phosphorus and fast-acting potassium showed a cumulative trend over the years of planting.The results of the principal component analysis indicated that p H,electrical conductivity（EC）and total salt are common physicochemical factors contributing to soil degradation in the facilities.2)In this study,the culturable microorganisms from three different growing areas were analyzed over a period of three years.The results showed that the number of soil bacteria in the 5-7 a facility planting increased significantly compared to the 1-3 a facility planting,by 7.24%-59.99%,59.99%and 5.24%.However,the number of fungi decreased by 5.63%-43.55%,leading to an elevated bacterial/fungal ratio.Overall,these findings suggest that the soil microbial status of the 5-7 a facility planting was good.On the other hand,the condition of culturable microorganisms in areas above 10 a showed a deterioration.The study found that there was no significant decrease in Urease,sucrase,alkaline phosphatase and peroxidase activities with planting age.However,bacterial diversity indices such as Chao1 index,Pielou’s evenness index,Shannon index,and Simpson index showed a decreasing trend.On the other hand,all fungi showed an elevated trend.The results of the redundancy analysis revealed a positive and significant correlation between fast-acting phosphorus,bacterial population,organic matter and changes in the microbial structure of the facility soil.3)In facilities with soil degradation caused by chemical and microbial factors,a combination of biochar and bacteria has shown to be effective in remediation.Biochar,in particular,has been found to have a positive impact on the soil.However,the optimal amount of biochar required for remediation varies depending on the planting years of the facility.For facilities with more than 10 years of planting,a suitable amount of 10 t·hm^-2of biochar is recommended.The study aimed to screen for combinations of strains that could improve degraded facility soils.Among the tested combinations,the one consisting of Bacillus amyloliquefaciens K9-4 and Bacillus methylotrophicus BH21 was found to be the most effective.4)This study analyzed the impact of a composite microbial amendment,consisting of biochar and bacteria on soil remediation at a facility plot.The results were compared to a control group.The dosage of the complex microbial improver used was 150 kg·hm^-2.The study found that the EC and total salt content were reduced by 22.50%-41.87%and56.81%-64.51%,respectively.Additionally,there was a p H increase of 0.08-0.11 units and a bacterial population increase of 270.41%during the peak growth period of cucumber.During the vigorous growth period of cucumber,a dose of 75 kg·hm^-2 was found to significantly reduce the fungal population.Moreover,the application of 75-150 kg·hm^-2resulted in a better improvement of soil degradation and cucumber quality in facilities.