Effects Of Different Fertilization Patterns On Soil Nematode Community In Greenhouse Vegetable Production

As a highly intensive cultivation system with high input and high output,there are several common phenomena such as excessive input of chemical fertilizers,and imbalance application of nutrients in greenhouse vegetable production systems(GVPs)in China.These phenomena results in a series of issues in soils,such as excessive accumulation of nutrients,and loss of biological diversity,which seriously restrict the development of GVPs in China.Nematodes,the most abundant metazoans in soil ecosystems,participate in the matter cycling,as well as energy flow in soils,and play an important role in indicating soil health conditions,and maintaining the stability of agricultural ecosystems,etc.Healthy soil is an important guarantee for the production of greenhouse vegetable,and soil disinfection is an effective means to solve obstacles to continuous cropping,and farmers are accustomed to disinfection of facility greenhouses once or twice a year.Based on a nine-year fixed-site fertilization experiment in a greenhouse vegetable field in Xiqing District,Tianjin City,this study explore the effects of different fertilization patterns on the total number of soil nematode,nematode community structure and nematode ecological indices after soil disinfection,the dissertation preliminarily explore the response of soil nematode community and ecological function to different fertilization patterns.The main findings are summarized as follows:1.Partial substitution of chemical fertilizer with organic amendments,especially medium and high quantities organic substitution patterns,promote the growth of beneficial nematodes and inhibit the growth of harmful herbivores.In comparison with the 4/4CN treatment,1/4CN+3/4MN and strawamended treatments increase the number and relative abundance of beneficial nematodes by average of 12.8% and 2.7% in the 0-5 cm layer,and 30.3% and 13.5% in the 5-10 cm layer,respectively,after soil disinfection(for 1 year and 2 year).Whereas the relative abundance of harmful nematodes is lower in 1/4CN+3/4MN and straw-amended treatments than those in 4/4CN treatment by average of 11.2% and 25.0% in the 0-5 cm and 5-10 cm layers,respectively,after soil disinfection(for 1 year and 2 year).2.Partial substitution of chemical fertilizer with organic amendments increase soil nematode diversity,enhance the advantages of mineralization pathway of bacterivore and fungivore,and optimize nematode community structure;however,with the increase of planting years after soil disinfection,soil herbivorous nematodes' proliferation are accelerated,the diversity of nematodes species are decreased,and soil quality are deteriorated.The values of H',WI,and SI are higher in organic-amended soils than those in 4/4CN-treated soil by respective average of 6.8%,13.2%,and 111.7% in the 0-5 cm soil layer,and 10.9%,39.9%,and 105.8% in the 5-10 cm soil layer,after soil disinfection(for 1 year and 2 year).The relative abundance of herbivorous nematodes and the values of PPI are higher after soil disinfection for 2 year than that after soil disinfection for 1 year(average increase of 61.2% and 21.4%,respectively).Moreover,the values of H',WI,and EI after soil disinfection for 2 year are lower by average of 7.7%,47.0%,and 12.3%,than those after soil disinfection for 1 year.3.Partial substitution of chemical fertilizer with organic amendments strongly improve soil nematode community structure;meanwhile,soil physicochemical properties,e.g.,pH,AP contents,and soil water contents,have significant effects on the structure of nematode communities.The key factors that affect soil nematode community structure are different after 1 and 2 years of soil disinfection.After 1 year of soil disinfection,nematode community in the 0-5 cm layer is mainly regulated by available P content and pH;meanwhile,nematode community in the 5-10 cm layer is largely controlled by soil pH.After 2 year of soil disinfection,nematode community in the 0-5 cm layer is mainly regulated by soil water content;meanwhile,nematode community in the 5-10 cm layer is largely controlled by soil water content and EC.4.Nematodes,as the biological indictors of soil ecosystems,are closely related to the yields of vegetables.The increase of beneficial nematodes is conducive to increase the yields of greenhouse vegetables,whereas herbivore nematodes,as harmful nematodes,their relative abundance increases reduce the yields of vegetables.Combination of vegetable yields,nematode-related indicators and physicochemical properties in soils,and practical operability,the 2/4CN+1/4MN+1/4SN treatment is recommended as continuous high-yield fertilization patterns in GVPs.