Effects Of Different Phosphate Fertilization Regulations On Crops And Soil Phosphorus Pool

The Guanzhong area is an important grain producing area in northwest of China,and winter wheat-summer maize is an important agricultural planting system in the region.In recent years,phosphorus utilization efficiency has decreased and soil phosphorus has accumulated in large quantities because of the excessive application of phosphorus fertilizer by farmers,which further increasing the risk of environmental pollution.The field experiment was conducted to study the effects of different fertilization methods,phosphorus reduction and regulation measures on crop yield,fertilizer phosphorus efficiency and soil phosphorus pool.Some results and conclusions were drawn as follow:（1）Compared with no phosphorus application（CK）,the maize yield of JFT1（15%reduction of phosphorus rate on the basis of recommended phosphorus rate（RF）combined with straw coating）was significantly higher than that of CK,but there was no significant difference in wheat yield.In the wheat season,compared to conventional fertilization（CF）and RF,the 15%reduction of phosphorus rate on the basis of RF（JF,from broadcast application to localized application）has a downward trend which is not significantly different,while the phosphorus recovery rate and partial productivity of it were significantly higher than that of CF.Compared with JF,the 15%reduction of phosphorus rate on the basis of RF combined with ammonium sulfate instead of urea treatment（JFT2）and the 30%reduction of phosphorus on the basis of RF combined with comprehensive regulation measure of straw enwrapping and ammonium sulfate instead of urea（JFT3）could significantly increase the grain yield of wheat,and the P recovery and partial productivity of JFT1,JFT2 and JFT3 were improved,in which JFT3 was significantly improved.The recovery rate of phosphate fertilizer for each phosphorus treatment ranged from 7.3%to 24.9%,of which JFT3 treatment was up to 24.9%;except for JF,the recovery rate of phosphorus reduction treatments of JFT1,JFT2 and JFT3 were significantly higher than that of CF（P<0.05）.（2）After a rotation year,the grain yield of RF and JFT1 treatments in the 2018 maize season was significantly higher than that of CK and JF treatments.The phosphorus recovery rate and partial productivity of JFT3 were improved compared with JF treatment,and its partial productivity was significantly higher than that of JF treatment.Therefore,reducing the application of phosphate fertilizer did not reduce the crop yield,and the phosphorus fertilizer reduction treatment combined with the regulation measures（straw enwrapping or ammonium sulfate instead of urea）could also improve the utilization rate of phosphorus fertilizer and partial productivity.（3）Compared with CK,the soil available phosphorus（Olsen-P）content of JFT1 and JFT2 were improved at the filling stage,and the soil available phosphorus content of JFT1treatment was significantly improved.Soil phosphorus extracted by calcium chloride（CaCl₂-P）was the highest in JFT1 at jointing stage.Soil microbial biomass phosphorus（MBP）in RF was higher than that in CF,but the difference was not significant.In the wheat season,JFT1,JFT2 and JFT3 also increased soil Olsen-P and MBP during harvesting,and the MBP of JFT1 and JFT2 was significantly higher than that of JF treatment.After a rotation year,in the 2018 maize season,compared with CK,the Olsen-P and CaCl₂-P were increased in each treatment;the CaCl₂-P in RF treatment at jointing stage was significantly higher than that in CF treatment,and CaCl₂-P was significantly improved in each treatment at the maize filling stage.Reducing the application of phosphate fertilizer did not reduce the soil Olsen-P,and soil Olsen-P level could be improved by the combination of strip application and regulation measures（straw enwrapping or ammonium sulfate instead of urea）.In summary,compared to the conventional fertilization practiced by farmers,the phosphorus application rate of recommended fertilization（157.5 kg P₂O₅/hm² per year）can achieve high yield,improve the utilization rate of phosphorus fertilizer and basically maintain the stability of soil phosphorus level under the premise of reducing the amount of phosphate fertilizer.Considering that the current soil phosphorus level is relatively high,15%reduction of phosphorus application rate on the basis of the recommended fertilization combined with straw enwrapping or ammonium sulfate instead of urea is the most preferable phosphorus fertilizer reduction and regulation scheme to be recommended.However,its long-term feasibility needs be further verified with the continuous reduction of phosphate fertilizer and the change of soil phosphorus level.