Study On The Effect Of Organic Fertilizer Application On The Environment And Vegetable Growth In Vegetable Field Systems

At present,excessive fertilizer application and irrational irrigation in greenhouse vegetable production are one of the main causes of agricultural non-point source pollution,soil property deterioration,and vegetable quality reduction.Therefore,in this study,the sandy loam soil of typical greenhouse vegetable fields in suburban Wuhan was used as the test soil,and tomato and cabbage were used as the test vegetables.From the perspective of optimizing fertilizer application,Set up 6 fertilization treatments in the plastic greenhouse:no fertilization（CK）,conventional chemical fertilizer（CF）,optimized fertilization（bio-organic fertilizer replaced 30%of chemical fertilizer nitrogen,OF）,combined application of straw and conventional chemical fertilizer（CFS）,combined application of straw and optimized fertilization（OFS）,30%reduction in irrigation at the combined level of straw and optimized fertilization（OFSW）.The effects of different fertilization treatments on the migration of nitrogen and phosphorus,subsurface leaching losses,soil properties,microbial communities and vegetable growth in the soil of the greenhouse vegetable field were systematically investigated from the macro level to the micro level through field experiments,with the aim of explored environmentally friendly fertilization patterns and providing a theoretical basis for sustainable green production of greenhouse vegetables.The main results are as follows:（1）Through the in-situ leaching monitoring platform in the field,the subsurface leaching losses of soil nitrogen and phosphorus were dynamically monitored.The results showed that NO₃^--N was the main form of nitrogen loss in the subsurface leaching solution,followed by dissolved organic nitrogen（DON）.The leaching losses in the tomato season were 16.77%to 50.02%and 22.34%to 43.52%of total dissolved nitrogen（TDN）,and the leaching losses in the cabbage season were 25.58%to 62.76%and 18.96%to 43.48%,respectively.Compared with the CF treatment,the OF,CFS,OFS and OFSW treatments all reduced the amount of TDN leaching,with the OFSW treatment showed the least amount of leaching,but the continuous application of straw and organic fertilizer increased the risk of DON leaching.The leaching amount of NH₄⁺-N and total phosphorus（TP）is low,and the migration characteristics in soil profile fluctuate greatly,and the law is not obvious.Through the soil isothermal adsorption test,it was found that the soil treated with OF,CFS and OFS increased the adsorption of NH₄⁺-N and weakened the adsorption of TP.（2）The response of soil physical and chemical properties,quality and agglomerate structure to fertilizer application in greenhouse vegetable fields was explored at a macro level.The results showed that,after three seasons of tomato and cabbage rotation,compared with CF treatment,OF treatment significantly increased soil NO₃^--N content and p H,while CFS treatment significantly increased soil total nitrogen（TN）,total phosphorus（TP）,available phosphorus（AP）content and p H,and significantly decreased soil bulk density（BD）.Evaluation of soil quality based on soil quality index（SQI）.The results showed that continuous application of straw and organic fertilizer improved the soil quality index,and the soil quality of OFS treatment was the highest.Different fertilization treatments changed soil aggregate structure,under wet sieving,OF,CFS,OFS and OFSW treatments increased WR_0.25,MWD,GMD,and decreased PAD.The OFS treatment was the best.（3）By measured the soil enzyme activities of different fertilization treatments after three seasons of tomato and cabbage rotation.The results showed that,CFS,OFS and OFSW treatments significantly increased the activities of soil acid phosphatase（S-ACP）and soil sucrase（S-SC）.The results of 16s high-throughput sequencing and Alpha diversity index analysis showed that optimized fertilization treatments increased the abundance and diversity of bacteria,and the community structure analysis showed that the dominant bacterial phylum was similar among treatments,but the abundance was different,the relative abundance of Proteobacteria,Acidobacter,Bacteroides and Chloroflexi in the soil samples of each treatment accounted for more than half.In addition,OF,CFS and OFS treatments reduced the abundance of nitrification（Nitrification,Aerobic ammonia oxidation and Aerobic nitrate oxidation）related bacteria,and increased the abundance of Nitrogen reduction and Ureolysis related bacteria.（4）The investigation of growth traits of tomato and cabbage before harvest showed that the combination of straw and organic fertilizer significantly increased the leaf length and stem diameter of the first node spike of tomato,and significantly increased the aboveground biomass of cabbage.The yield of tomato and cabbage were improved to varying degrees,and the nitrogen and phosphorus use efficiency were improved.Tomato yield was highest with OFSW treatment and cabbage yield was highest with OFS treatment.The nutritional quality of tomato and cabbage was improved,and the application of straw and organic fertilizer reduced the titratable acid content of tomato,increased the soluble protein content,and increased the soluble solids,vitamin C and soluble sugar content of cabbage.