Effects Of Fertilization On The Accumulation Characteristics Of Nitrogen And Phosphorus In Purple Soil Under Different Utilization Patterns

The application of chemical fertilizers has made a great contribution to the development of China's agriculture.However,long-term excessive fertilization leads to the accumulation of N and P in the soil.Under the process of precipitation or irrigation,N and P enter the water body through runoff,lateral seepage and leaching.Which will not only cause N pollution,but also cause eutrophication.Purple soil is an erosive high-productivity and lithological soil that is widely distributed in Sichuan Basin.It has high silicon-aluminum-iron ratio,rich in salt-based ions,potassium,and thus possess high agricultural utilization value.However,purple soil is easily been weathered under steep terrain area,and is prone to be washed away.The land use patterns of purple soil are diverse,but the research on the accumulation of nitrogen and phosphorus in purple soil are mostly under single planting system,research of different utilization modes is scarce.This study focus on purple soil of long-term stationary base under different land use patterns,taking the Flooded Paddy Field?FPF?,the rice Field-upland Field Rotation?FFR?and the dry slope land?DS?as target samples,collecting purple soil of 0⁵0 cm and0⁶0 cm depth under different land use modes.The soil samples are analyzed with the indoor test methods to attain the N and P content of different compounds.The main findings are as follows:?1?The contents of total nitrogen and alkali nitrogen in three different utilization patterns of purple soil under NPK fertilization treatment were FPF>FFR>DS,and the total phosphorus content was DS>FPF>FFR,the effective phosphorus content is FPF>DS>FFR,indicating that total nitrogen,alkali nitrogen and available phosphorus are more likely to accumulate in the surface layer of purple-soil in the flooded paddy field,and all phosphorus is more likely to be in the dry slope land.The total nitrogen and total phosphorus reserves in the flooded paddy field utilization pattern are mainly accumulated in the 20⁴0cm soil layer,while the total nitrogen and total phosphorus reserves in the field-upland field rotation and the dry slope land use mode are mainly accumulated in the 0²0cm surface soil.?2?For FPF group,among the four fertilization treatments,the total nitrogen,total phosphorus and available phosphorus in the surface soil of NPK treatment were the highest,1.81 g·kg^-1,0.44g·kg^-1 and 29.78 mg·kg^-1,respectively,which were better than other fertilization treatments.Increased by 1.12%⁵.23%,2.33%²2.22%and 18.50%¹59.86%.For the whole section,the contents of total nitrogen,total phosphorus and available phosphorus in rice-winter paddy soil under different fertilization treatments showed significant surface aggregation.The total nitrogen content of each soil layer was the highest with NPK treatment,and the content of alkali nitrogen in the treatment with NP was the highest,and the total phosphorus and available phosphorus content were the highest in NPK treatment in the range of 0⁴0 cm soil layer.In terms of reserves,the total nitrogen and total phosphorus reserves of different fertilization treatments were the highest in the20⁴0 cm soil layer,which were 2814.47³485.78 kg·hm^-2 and 541.54⁷83.31 kg·hm^-2,respectively,of which NPK treatment The total nitrogen and total phosphorus reserves are the highest in all soil layers.The cumulative rates of total nitrogen and total phosphorus in the topsoil were highest by NPK,which were 22.16 kg·hm-2·a^-1 and 9.98 kg·hm^-2·a^-1,respectively.?3?For FFR group,total nitrogen,alkali nitrogen,total phosphorus,available phosphorus content of surface soil the High-input fertilization?HNPK?treatment were the highest,of which total nitrogen was 5.56%higher than PK treatment,alkali nitrogen was 17.29%higher than PK treatment,total phosphorus ratio NK treatment is 30%higher and effective phosphorus is 149.6%higher than NK treatment.After the flooded paddy field utilization mode was converted into the field-upland field rotation utilization mode,the total nitrogen and alkali nitrogen content of the topsoil were lower than the initial total nitrogen and alkali nitrogen content,and the content of the total phosphorus increased in the three phosphorus applied soils compared with the initial total phosphorus content.For the whole section,the contents of total nitrogen,alkali nitrogen,total phosphorus and available phosphorus decreased with the increase of soil depth.The total nitrogen and alkali nitrogen content of each soil layer were the highest with NPK treatment.The total phosphorus content of different treatments varied from 0 to 30 cm,and the available phosphorus content varied from 0 to 20 cm,and both were treated with HNPK.In terms of reserves,the total nitrogen storage of each treatment is mainly concentrated in the range of 0²0 cm soil layer,which is 1484.15¹570.82 kg·hm^-2.The total phosphorus reserves of NPK treatment and PK treatment showed a decreasing trend with the increase of soil depth,reaching the highest value in 0¹0 cm soil layer,which were 426.80 kg·hm^-2and 424.74 kg·hm^-2,respectively.The HNPK treatment and NK treatment reached the maximum values in the 10-20 cm soil layer,which were 474.32 kg·hm^-22 and 378.58 kg·hm^-2,respectively.The total nitrogen accumulation rate was the highest with NPK treatment,which was-68.43 kg·hm^-2·a^-1,which was less than the total nitrogen loss of 14.44 kg·hm^-2 per year compared with the PK treatment without nitrogen application.The total phosphorus accumulation rate was the highest with HNPK treatment,which was 18.37 kg·hm^-2·a^-1,accumulating 17.86 kg·hm^-2 of total phosphorus per year compared with NK treatment without phosphate fertilizer.?4?For DS group,the total nitrogen,alkali nitrogen and ammonium nitrogen in the topsoil of the four fertilization treatments were the highest by M+NPK,which were 0.65 g·kg^-1,52.37 mg·kg^-1and 32.83 mg·kg^-1,respectively,increasing 47.73%,36.53%and 246.51%compared with CK.The total phosphorus and available phosphorus content in the topsoil of the four fertilization treatments were the highest in HNPK,1.16 g·kg^-1 and 19.24 mg·kg^-1,and the water-soluble phosphorus was the highest in M+NPK,which was 15.86 mg·kg^-1.They were increased by 103.51%,1080.37%and2133.80%,respectively,than CK treatment.For the whole section,the total nitrogen content of each treatment decreased with the increase of soil depth.The whole profile showed M+NPK>HNPK>NPK and CK.The difference of alkali nitrogen in each treatment was mainly 0²0cm.It is expressed in the soil layer and is expressed as M+NPK>HNPK>CK>NPK.The total phosphorus content in the whole section was significantly higher than that of other fertilization treatments in HNPK treatment,and the trend of NPK-treated total phosphorus in the profile was consistent with HNPK treatment,and the total phosphorus content increased with the increase of fertilization concentration.M+NPK treatment can promote the downward movement of phosphorus.In terms of reserves,the total nitrogen storage of different treatments was the highest in the 0¹0 cm soil layer,which was 651.59⁸97.54 kg·hm^-2,and the highest M+NPK in each soil layer was865.71¹380.01 kg·hm^-2.The total phosphorus reserves of each treatment were inconsistent with the increase of soil depth,and were highest with HNPK,which was 1513.42²898.92 kg·hm^-2.The total nitrogen accumulation rate in the topsoil of each treatment was the highest with M+NPK treatment,which was 10.78 kg·hm^-2·a^-1,and the cumulative total nitrogen was 24.59 kg·hm^-2 per year compared with CK treatment.The cumulative rate was highest in HNPK,which was 83.77kg·hm^-2·a^-1,which accumulated more than 100.44 kg·hm-² of total phosphorus per year compared with CK treatment.