Study On The Application Pattern Of Phosphorus Fertilizer To Apple Trees Under The Condition Of Water And Fertilizer Integration

Phosphorus is one of the indispensable nutrients for plant growth,and the metabolic process of plant growth and the synthesis of important compounds in the body cannot be achieved without the participation of phosphorus.Phosphorus has low mobility in the soil,and the way phosphorus fertilizer is applied determines how easily phosphorus is absorbed by plant roots.Water-fertilizer integration can improve fertilizer utilization,but it is still necessary to optimize nutrient supply in time and space.The demand for nutrients varies among different fertility stages of apple trees,so it is also important to have the right proportion of phosphorus applied to each fertility stage.A reasonable water and fertilizer supply pattern,phosphorus fertilizer application method and fertility phosphorus fertilizer distribution ratio can not only improve yield based on the utilization of water and fertilizer resources,but also improve fruit quality and reduce the incidence of physiological diseases,which is conducive to water conservation,abundant yield,high quality and efficient production.In this study,field trials of different phosphorus fertilizer management for apple trees were conducted in Luochuan,Shaanxi,including three trials of water and fertilizer supply modes,phosphorus fertilizer application modes,and allocation ratios of follow-up phosphorus fertilizer.A three-factor,two-level complete combination test was conducted with the drip line layout（one pipe in a row and two pipes in a row）,fertilization cycle（15 d and 30 d）and dripper spacing（30 cm and 50 cm）as test factors.Three treatments of integrated phosphorus application with water and fertilizer（M₁）and phosphate fertilizer ditch application（M₂）under three methods of two pipes in one row and 30 d fertilizer application cycle,one pipe in one row and 15 d and 30 d fertilizer application cycle（both with a 30 cm dripper spacing）,respectively.Two phosphorus fertilizer allocation ratios were set up under one pipe in a row,30 d fertilizer application cycle and 30 cm dripper spacing.By analyzing the spring tip,leaf area index,leaf and fruit mineral element content,fruit quality,yield and soil available phosphorus content of apple trees,the influence of different phosphorus fertilizer distribution methods was investigated to provide a theoretical basis for optimizing the phosphorus fertilizer management methods in apple orchards.The main conclusions are as follows:（1）The effect of different phosphorus fertilizer management on the growth of apple trees was revealed.One pipe in a row significantly promoted new shoot growth and leaf area index in2021 compared to two pipes in a row,and the method of drip line layout had no significant effect on new shoot growth and leaf area index in 2022.The effect of fertilizer application cycle on new shoot growth and leaf area index was basically insignificant.The combination of one pipe in a row with 15 d fertilization cycle was more favorable than other treatments for leaf area index.Under the one pipe in a row condition,the integrated fertilizer application of phosphorus was more beneficial to the growth of new shoots and leaf area index.There was no significant effect of different phosphorus fertilizer allocation rates on new shoot length during the growing period.For leaf area index,increasing the proportion of phosphorus fertilizer application during the expansion period could increase the leaf area index to some extent.（2）The effect of different phosphorus fertilizer management on the mineral element content of apple tree leaves was revealed.With the extension of fertility period,the overall trend of leaf N,P,K and Mg contents of different treatments decreased,and the overall trend of leaf Ca and Zn contents increased.Two pipes in a row will effectively increase the leaf P and Zn content and decrease the leaf Ca and Mg content.Fertilizer application cycle 15 d can effectively increase the leaf Zn content.Integrated fertilizer application of phosphorus was more effective than ditch application of phosphorus fertilizer treatment to increase leaf N and K content,but the effect on P and Zn content was basically insignificant.For leaf Ca and Mg contents,they varied with the sampling year.Overall,increasing the proportion of phosphorus fertilizer applied during the expansion period increased the leaf N,K,Ca,Mg,and Zn contents and facilitated the accumulation of leaf mineral elements.（3）The effect of different phosphorus fertilizer management on the mineral element content of apple fruit was revealed.Different water and fertilizer supply patterns have different effects on fruit mineral element content.Two pipes in a row were effective in increasing fruit N,P,K,Ca,Mg and Zn contents.Fertilizer cycle of 15 d resulted in high levels of N,P,K,Ca and Zn.The combination of two pipes in one row and 15 d fertilization cycle was beneficial to fruit mineral accumulation.The integrated fertilizer application of phosphorus and increasing the proportion of phosphorus fertilizer applied during expansion was beneficial to the accumulation of N,P,K,Ca,Mg and Zn in fruits.（4）The effects of different phosphorus fertilizer management on apple quality and yield were revealed.Two pipes in a row increased apple yield.15 d fertilization cycle increasing fruit soluble sugar,VC content,and decreasing fruit shape index.Integrated phosphorus application with water and fertilizer increased fruit soluble solids content,VC content,solid-acid ratio,sugar-acid ratio and yield;reduced fruit hardness and titratable acid content.Increasing the proportion of phosphorus fertilizer applied during the expansion period significantly increased soluble sugar,titratable acid,VC content and yield.（5）The effect of technical parameters of drip irrigation fertilization parameters on the spatial and temporal distribution of soil available phosphorus in apple orchards was revealed.Two pipes in one row can increase the horizontal distribution of soil available phosphorus.With the increase of phosphorus application years,the distribution range of soil available phosphorus level at 30 d of fertilization cycle was wider.Soil available phosphorus was mainly concentrated in the 0-20 cm soil layer and showed a pattern of decreasing with increasing soil depth.With the increase of fertilizer application years,the dripper spacing of 50 cm increased the soil available phosphorus content of soil in all layers compared with 30 cm.Fertilizer application cycle of 15 d increased soil available phosphorus content in all soil layers from 20-100 cm compared to 30 d.Compared with2018,the percentage of soil available phosphorus in the 0-20 cm soil layer decreased and the percentage of soil available phosphorus in the 20-100 cm soil layer increased in 2021,indicating a downward trend of soil available phosphorus in four consecutive years of fertilization.After four years of drip irrigation application,the percentage of soil available phosphorus in the 0-100 cm soil layer increased in the range of 0-60 cm from both sides of the tree row in all treatments.