Effects Of Different Fertilization Patterns,Planting Duration And Straw Addition On Phosphorus Availability Of Vegetable-grown Soil

Phosphorus（P）is one of the essential nutrient elements for the normal growth and development of vegetables.Phosphorus fertilizer is likely overused and greatly exceeds the requirement of vegetable production,resulting in increased soil P surplus and P loss posing a threat to the environment.Combined application of organic and inorganic P fertilizer（OIPF）has been widely used in vegetable production in China,yet the effect on yield is affected by many factors.Rationally combined application should be carried out on the basis of comprehensive understanding of the influencing factors.China,as a large agricultural country,annually produces tremendouse crop straw and returning the straw to the field in farmland management can enhance the retention ability of soil nutrients,improve soil microenvironment and soil aggregate structure,achieve the effect of carbon fixation and emission reduction,and play an irreplaceable role in regulating soil P.Therefore,this study firstly collected the literature of vegetable field experiment and used meta-analysis to explore the changes and influencing factors of vegetable yield under different fertilization methods,and comprehensively evaluate the effects of OIPF on vegetable yield and soil available P accumulation.The study used an on-farm survey to investigate the basic situation of vegetable planting in the Hexian County,"the hometown of vegetables".Meanwhile,it collected the representive soil in typical vegetable production areas to examine the characteristics of the soil P adsorption-desorption,the influence of adding straw on the soil of different planting years,and the changes of soil P pool and aggregates.This study aimed to provide theoretical basis for the rational application of P fertilizer for facility vegetables.The main results are as follows:（1）In China’s vegetable production,the OIPF is an effective method to ensure vegetable yield and reduce soil available P accumulation.The results of meta-analysis show that the OIPF in spring and autumn was the best in the greenhouse soil rich in organic matter.Under the OIPF or single application of inorganic P fertilizer（IPF）,the vegetable yield was similar,which was 5.73×10⁴ kg ha^-1 and 5.61×10⁴ kg ha^-1,respectively.The former could reduce the soil available P accumulation by 24%.Effects of different P fertilizations on vegetable yield depended on soil texture,soil fertility,vegetable species,season and cultivation method.The OIPF was the best in the soil with organic matter content>30 g kg^-1.Compared with IPF,OIPF could increase the yield by 12%and reduce the soil available P accumulation by 76%.Compared with IPF,the OIPF significantly increased the yield by 53%in spring,and the soil available P accumulation decreased by 36.8%.OIPF increased leaf vegetable yield by 28%compared with IPF.In addition,the OIPF significantly reduced the accumulation of available P and the content of organic matter in sandy soil and loam soil by more than 30g kg^-1compared with the IPF in greenhouse cultivation.In conclusion,OIPF was an effective way to increase vegetable yield while reducing soil P accumulation in China’s vegetable production system.（2）Soil nutrient content of the treated vegetables with long-term fertilization was significantly higher than that of the adjacent paddy soil and the natural soil without any planting,and it increased with planting years.The contents of total P and available P in the topsoil（0-20 cm）of 28-year planting vegetables were 4.16 g kg^-1 and 380.22 mg kg^-1,respectively,which were 232-253%%and 138%-181%higher than those in the topsoil of 5and 13-year planting vegetables.With the extension of planting years,the soil phosphorus adsorption capacity decreased while it’s desorption capacity increasing,and the soil phosphorus supply capacity of greenhouse vegetables increased significantly,causing the increased phosphorus movement to the deep soil.（3）With the increase of planting years,the soil microbial biomass phosphorus（MBP）content increased,and soil large particle size（>0.25mm）aggregates in the 28-year greenhouse vegetable significantly decreased by 43%and the small particle size（<0.25mm）aggregates significantly increased by 40%compared with that in the 5-year case.Straw addition increased the content of soil microbial biomass P,while increased the proportion of labile P and moderately labile P,ang decreased the proportion of non-labile P;it also increased the large particle size aggregate（>0.25mm）,and decrease the micro-particle size aggregate（<0.25mm）.At 120 days of cultivation,the MBP content of the soil increased by37%after 28 years of continuous planting compared with the control.The contents of H₂O-P fraction in soil P pool increased by 5.6%and 22.3%for 5-year and 13-year planting duration,respectively.The contents of Na HCO₃-Po fraction increased by 35.4%,9.9%and59%for 5-year,13-year and 28-year planting duration,respectively.The proportion of large aggregate（>0.25mm）increased by 44%,while the proportion of small aggregate（<0.25mm）decreased by 11%.Therefore,adding straw to the soil with long planting years was beneficial to improve soil phosphorus conversion and soil aggregate structure.