Study On Soil Phosphorus Status, Leaching Threshold And Repression Technology In Apple Main Production Area

Phosphorus is an indispensable element in the process of growth and yield formation of apple.The suitable phosphorus content in soil is the basis of high quality and high yield of apple.However,phosphorus is easily fixed in soil and easy to bring about surplus of phosphorus,thus bring environmental risks.Therefore,the investigation data of soil and farmers'survey data in 115 apple orchards in 12 typical regions of Bohai Bay and Loess Plateau apple production area were analyzed in 2012 and 2016.To understand the fertilizer input and soil fertility status of orchard in the two major apple producing areas in China.The soils of Shandong and Shaanxi apple orchard,the two major apple producing areas in China,were selected as the test materials.The soil phosphorus efficiency and the leaching risk of phosphorus in soil were studied under the simulated annual average rainfall conditions under the simulated annual rainfall conditions.This provides a basis for rational management of soil phosphorus and reducing soil phosphorus leaching risk in apple orchard.The effect of fulvic acid and activated carbon on phosphorus loss in potted T337 rootstocks were studied.The major results were as follows:1.The change trend of soil phosphorus nutrient status in the main apple producing area and the relationship with fertilization in the last 5 years:the input of phosphate fertilizer in the apple orchard of Bohai Bay and the Loess Plateau in China was at a high level in 5 years.The average phosphorus input?P₂O₅?of apple orchard in Bohai Bay area was 936.48 kg·hm^-22 in2012,and increased to 1094.99 kg·hm^-22 after 5 years,an increase of 16.93%.The average phosphorus input?P₂O₅?of apple orchard was 986.43 kg·hm^-22 in the Loess Plateau area in2012,and increased to 1032.73 kg·hm^-22 after 5 years,an increase of 4.69%.The contents of available phosphorus in apple orchard in two major producing areas were all high,and phosphorus surplus was present.The average phosphorus surplus was 733.20 kg·hm^-22 in Bohai Bay in 2012,and increased to 867.78 kg·hm^-22 by 2016.In 2012,the average phosphorus surplus in the Loess Plateau area increased from 844.77 kg·hm^-2,and increased to892.92 kg·hm^-22 by 2016.There was a significant linear positive correlation between the available phosphorus and the total input of phosphorus fertilizer in the two big apple orchard,and the change in soil available phosphorus was in a very significant linear correlation with the amount of phosphorus profit and loss.The phosphorus content in the Bohai Bay area and the Loess Plateau production area increased by 0.38 mg·kg^-11 and 0.21 mg·kg^-11 respectively,with phosphorus input of 100 kg·hm^-2.2.Phosphorus leaching threshold and leaching risk assessment of apple orchards in Shandong and Shaanxi:Taking apple orchard soil in Shandong province and Shaanxi Province as experimental materials,indoor soil column leaching simulation method was adopted.The results showed that:There was a significant positive correlation between soil Olsen-P content and phosphorus application in 0¹0 cm,10²0 cm,20³0 cm,30⁴0 cm soil in Shandong and Shaanxi.The critical values of phosphorus leaching in 0¹0 cm,10²0 cm,20³0 cm and 30⁴0 cm soil are respectively 41.38 mg·kg^-1,45.59 mg·kg^-1,53.14 mg·kg^-1and 61.44 mg·kg^-11 in Shandong.The critical values of phosphorus leaching in 0¹0 cm,10²0 cm,20³0 cm and 30⁴0 cm are respectively 39.94 mg·kg^-1,37.62 mg·kg^-1,45.48mg·kg^-11 and 39.03 mg·kg^-11 in Shaanxi.The critical value of no phosphorus leaching in 40⁵0cm and 50⁶0 cm soil layers was present.The risk of phosphorus leaching from soil 0¹0 cm and 10²0 cm soil layer was higher than that in 20³0 cm and 30⁴0 cm soil layers in the two producing areas.The critical value of soil in Shaanxi was lower than that in Shandong Province,and the risk of leaching was greater.3.Effects of fulvic acid on phosphorus utilization and phosphorus repression in T337seedlings:The effects of different fulvic acid treatments on T337 growth,phosphorus uptake and loss were studied in T337 seedlings.The results showed that:The growth of T337seedlings was promoted by fulvic acid.The biomass and total biomass of root,stem,leaf and total biomass of T337 increased and then decreased with the increase of the concentration of fulvic acid,of which H2(100 kg·hm^-2)was the highest.The T337 phosphorus accumulation of H2 treatment increased by 32.33%.The phosphorus accumulation of the rootstock treated by HH2 was 18.42%higher than that of HCK.Fulvic acid can activate and maintain phosphorus in soil.The content of available phosphorus in rhizosphere soil by H2 treatment was 36.04%higher than that of CK,and the content of available phosphorus in rhizosphere soil by HH2 treatment was 32.90%higher than that of HCK.The residual rate of phosphate fertilizer treated by H2 was 53.44%,which was 36.05%higher than that of CK,the loss rate was 40.24%,and 28.07%was lower than that of CK.The utilization ratio of phosphate fertilizer was 32.22%higher than that of CK.The residual rate of phosphate fertilizer treated by HH2 was 39.11%and the loss rate increased by 60.71%.Appropriate amount of fulvic acid can significantly promote the growth of T337 seedlings,activate and maintain phosphorus in soil,and reduce phosphorus loss,with 100 kg·hm^-22 as the best.4.Effects of biological carbon on phosphorus utilization and phosphorus repression in T337 seedlings:The effects of different biochar treatments on T337 growth,phosphorus absorption and loss were studied in T337 seedlings.The results showed that:The biomass and total biomass of roots,stems and leaves of T337 increased first and then decreased with the increase of biochar application,of which T2(600 kg·hm^-2)was the highest.The phosphorus accumulation of T337 increased by 24.61%than that of CK.The phosphorus accumulation of the rootstock treated by HT2 was 21.79%higher than that of HCK.Biochar can activate and maintain phosphorus in soil.The content of available phosphorus in rhizosphere soil by T2treatment was 38.37%higher than that of CK,and the content of available phosphorus in rhizosphere soil by HT2 treatment was 35.11%higher than that of HCK.The residual rate of phosphate fertilizer treated by T2 was 54.36%,which was 38.39%higher than that of CK,the loss rate was 39.69%,and 29.05%was lower than that of CK.The utilization ratio of phosphate fertilizer was 24.69%higher than that of CK.The residual rate of phosphate fertilizer treated by HT2 was 39.15%and the loss rate increased by 61.38%.Proper amount of biochar(600 kg·hm^-2)can significantly promote the growth of T337 seedlings,activate and maintain phosphorus in soil,and reduce phosphorus losses.