Effects Of Long-term Application Of Phosphorus And Organic Fertilizer On Organic Phosphorus Forms And Related Properties In Vegetable Soil

Long-term application of phosphorus fertilizer has led some problems in agricultural production,such as the accumulation of phosphorus in the soil year by year,the decrease of phosphorus fertilizer utilization rate and the increase of phosphorus loss risk.In this study,a research method combining long-term fertilizer positioning experiment and indoor analysis was adopted.There were 11 fertilization treatments were set up to measure the content of different forms of organic phosphorus and organic matter in the soil,and analyze the effects of each phosphorus index on the content of available phosphorus,and the correlation between different active organic matter and phosphorus related indicators.The effects of long-term application of phosphorus and organic fertilizer on the organic phosphorus forms and availability phosphorus in vegetable soil were discussed,which provided a theoretical basis for efficient utilization of phosphorus in farmland soil.The main results were as follows:(1)The content of total phosphorus and available phosphorus in vegetable fields without fertilization for a long time was significantly reduced.After 16 years,the total phosphorus in the soil decreased by 0.12 g/kg(20.00%),and available phosphorus also decreased by 12.30 mg/kg(61.19%).Compared with non-fertilization treatment,single application of phosphorus fertilizer,organic fertilizer or combined application of phosphorus and organic fertilizer significantly all increased the content of soil total phosphorus and available phosphorus,and the contribution rate of organic fertilizer to the accumulation of available phosphorus was greater than that of phosphorus fertilizer.For example,when 100 kg/hm2 P2O5 phosphorus or organic fertilizer were applied,the content of soil available phosphorus increased by 2.64 rng/kg or 3.53 mg/kg,respectively.Similarly,the application of phosphorus or organic fertilizer significantly also increased the soil phosphorus activation coefficients,which increased by 0.23-2.23 percentage points,and the soil phosphorus activation coefficients increased significantly with the increase of organic fertilizer.(2)The proportions composition of the organic phosphorus in each treatment was as follows:moderately labile organic phosphorus>moderately stable organic phosphorus>highly stable organic phosphorus>labile organic phosphorus.Long-term application of phosphorus or organic fertilizer could increase the content of each component of soil organic phosphorus.Among them,single application of organic fertilizer or organic fertilizer combined with application of phosphorus fertilizer has a significant effect on increasing the content of each component of organic phosphorus,while single application of phosphorus fertilizer significantly increased the content of moderately labile organic phosphorus.And the contribution rate of organic fertilizer to the accumulation of various forms of organic phosphorus was greater than that of phosphorus fertilizer.For example,when 100 kg/hm2 P2O5 organic fertilizer were applied,the total amount of soil organic phosphorus,labile organic phosphorus and moderately labile organic phosphorus,moderately stable organic phosphorus and highly stable organic phosphorus were increased by 18.00 mg/kg,0.60 mg/kg,15.35 mg/kg,1.38 mg/kg,and 0.68 mg/kg respectively.However,the ratio of the two labile organic phosphorus was increased,and the ratio of the two stable organic phosphorus was reduced by applying phosphorus fertilizer alone,organic fertilizer alone or organic fertilizer combined with phosphorus fertilizer.(3)Long-term application of phosphorus fertilizer,organic fertilizer or organic fertilizer combined with phosphorus fertilizer significantly increased the soil microbial biomass phosphorus,alkaline phosphatase and readily desorbed phosphorus content,with average increases of 169.36%,58.38%and 827.48%,respectively.And the alkaline phosphatase increased slowly with the increase of fertilization year,the average annual increase was 0.19-0.63[P mg/(100g·2h)].The contribution rate of organic fertilizer to the accumulation of soil microbial biomass phosphorus and alkaline phosphatase was higher than that of phosphorus fertilizer,while the readily desorbed phosphorus was the opposite.For example,when 100 kg/hm2 P2O5 phosphorus fertilizer or organic fertilizer were applied,the microbial biomass phosphorus,alkaline phosphatase and readily desorbed phosphorus were increased by 0.80 mg/kg or 1.76 mg/kg,0.07[P mg/(100g·2h)]or 0.70[Pmg/(100g·2h)],0.19 mg/kg or 0.15 mg/kg respectively.Similarly,single application of phosphorus fertilizer,organic fertilizer,or organic fertilizer combined with application of phosphorus fertilizer increased the degree of phosphorus sorption saturation and reduced the maximum phosphorus absorption capacity of soil,and the decrease of the maximum phosphorus absorption capacity of soil by organic fertilizer was greater than that of phosphate fertilizer.(4)Compared with the soil before the experiment,the long-term non-fertilization and single application of phosphorus fertilizer reduced the content of soil organic matter and each component of labile organic matter.Among them,the content of soil organic matter,high labile organic matter,middle labile organic matter and labile organic matter decreased by 9.55%,35.15%,22.84%and 41.76%respectively,after I 6 years of non-fertilizer.While,the content of soil organic matter and each component of labile organic matter were significantly increased by applying organic fertilizer alone or organic fertilizer combined with phosphorus fertilizer.Compared with the non-fertilization treatment,single application of organic fertilizer or organic fertilizer combined with phosphorus fertilizer could significantly increase the content of soil organic matter,high labile organic matter,middle labile organic matter and labile organic matter,and their growth rates were 44.78%-78.69%,90.65%-120.56%,166.37%-240.36%,122.04%-191.45%respectively,and each component of soil labile organic matter increased slowly with the increase of fertilization years.(5)The correlation analysis between soil available phosphorus and other phosphorus indicators showed that total phosphorus,total organic phosphorus,microbial biomass phosphorus and readily desorbed phosphorus were significantly positive correlated with available phosphorus,and the correlation coefficients were 0.968,0.634,0.724 and 0.946,respectively.While,the direct path coefficient of total phosphorus to available phosphorus was larger.All forms of organic phosphorus also have a very significant positive correlation with available phosphorus,and the moderately labile organic phosphorus has a greater direct effect on available phosphorus,and its direct path coefficient to available phosphorus was 0.658.The correlation analysis of the factors affecting the transformation of available phosphorus and phosphorus showed that soil alkaline phosphatase,maximum phosphorus absorption capacity,organic matter and each component labile organic matter all have an extremely significant correlations with available phosphorus,among which the maximum phosphorus absorption capacity and available phosphorus were extremely significant negative correlated.The path analysis also shows that the direct path coefficient of the maximum phosphorus absorption capacity to the available phosphorus was-0.841.Moreover,each component of labile organic matter also has a very significant positive correlation with the labile organic phosphorus,alkaline phosphatase and microbial biomass phosphorus,among which the high labile organic matter has a greater direct impact on the content of these three indicators.In summary,long-term application of phosphorus fertilizer or organic fertilizer has increased the content of soil organic phosphorus and alkaline phosphatase,and the effect of application of organic fertilizer,organic fertilizer combined with phosphorus fertilizer was higher than that of single application of phosphorus fertilizer,which improved the availability of phosphorus by affecting the indicators of organic matter and organic phosphorus.