Effects Of Phosphate Fertilizer Rates And Types On Crop Yield And Soil Phosphrous Pool On Eum-Orthic Anthrosols

Phosphorus is the second largest nutrient element necessary for plant growth and development,and the low utilization rate of phosphate fertilizer in the current season is the main limiting factor restricting agricultural development and increasing environmental risks.Excessive and unreasonable application of phosphate fertilizer has caused a large amount of phosphorus accumulation in the farmland soil and waste of phosphate fertilizer resources,and phosphate ore resources are limited.The rational and effective use of phosphate fertilizer resources and the improvement of phosphate fertilizer utilization rate through a variety of ways are of great significance for guiding the rational application of phosphate fertilizer and achieving sustainable development.In view of the problems of the accumulation of large amounts of phosphorus in the farmland,the low utilization rate of phosphorus fertilizer and the high risk of soil phosphorus leaching in the Guanzhong area,field experiments were conducted to study the effects of the phosphorus fertilizer application rates and the phosphate fertilizer varieties on crop yield,phosphorus use efficiency and soil phosphorus pool in the crop system of"winter wheat-summer corn".Phosphate fertilizer rates were set as 0,30,60,90,120 kg P₂O₅·ha^-1 for single-season crops on the basis of the same amount of nitrogen fertilizer.Phosphate fertilizer varieties were tested with no phosphorus?CK?,single superphosphate?SSP?,calcium magnesium phosphate?CMP?,monoammonium phosphate?MAP?,diammonium phosphate?DAP?,25%CMP+75%SSP,50%CMP+50%SSP,75%CMP+25%SSP,in which the same amounts of nitrogen were applied for all treatments and the same amounts of phosphorus were applied except for CK.Field trials were conducted for two consecutive years from 2017 to 2019,and the crop?winter wheat and summer maize?yields,grain and straw phosphorus contents were measured during the crop harvest period,and soil samples were collected to determine the available phosphorus?Olsen-P?and water-soluble phosphorus?Ca Cl₂-P?and microbial biomass phosphorus?SMBP?etc.The following main results and conclusions have been achieved:On the Eum-Orthic Anthrosols soil with high phosphorus,the total crop grain yields(33748?34993 kg·ha^-1)were not significantly different under different phosphorus application rates,and the cumulative utilization efficiency of phosphorus,partial productivity and production-investment ratio were significantly?P<0.05?declined with the increase of phosphorus application rate.The soil total phosphorus,available phosphorus,and water-soluble phosphorus contents were not significantly different between different phosphorus application rates.The SMBP content could be significantly improved by the Phosphate fertilizer application,but it didn't increase anymore after single-season application rate is higher than 60 kg P₂O₅·ha^-1.When the amount of phosphorus applied was 60kg P₂O₅·ha^-1 in a single season,the apparent soil phosphorus balance was in a surplus state with an average of 7.1 kg P·ha^-1 in the maize season,was in a deficit state with an average of6.9 kg P·ha^-1 in the wheat season,and was surplus with an average of 0.3 kg P·ha^-1 in total of 2years.The cumulative phosphorus utilization efficiency of CMP and MAP was better than that of DAP and SSP in maize season,and that of SSP was the highest in wheat season.The cumulative phosphorus utilization efficiency was proportional to the proportion of CMP in the maize season,while the opposite was in the wheat season.Soil microbial biomass was higher under the water-soluble phosphate fertilizers?SSP>MAP>DAP?than under citrate-soluble phosphate fertilizer?CMP?,and all were significantly higher than CK regardless of the maize season or the wheat season.The apparent soil phosphorus balance was deficit in 118.7kg P·ha^-1 for no phosphorus application?CK?,while it was surplus for all phosphorus application treatments that were significantly higher than CK,and in which it was closest to"0"for SSP treatment in 2 years.The apparent balance of the soil phosphorus had a linear positive correlation with the annual phosphorus fertilizer?P₂O₅?input,and the change of soil available phosphorus was linearly correlated with the apparent balance?P<0.5?.For every surplus of 100 kg P·ha^-1,the increase of soil available phosphorus was 4.9 mg P·kg^-1.On soils rich in phosphorus,when the annual phosphorus application rate was 120 kg P₂O₅·ha^-1,the phosphorus balance was closest to"0",and the phosphorus supply level of the soil within 13 years could be maintained at 17?40 mg P·kg^-1.In summary,it is recommended to use single superphosphate as the main phosphorus source in the wheat season and calcium magnesium phosphate as the main phosphorus source in the corn season under the"winter wheat-summer corn"crop system in the farmland with high soil available phosphorus content in the Guanzhong area.The annual phosphorus application rate recommended is 120 kg P₂O₅·ha^-1.It can not only ensure crop grain yield,but also avoid the depletion of the soil phosphorus pool and maintain the soil phosphorus supply level and soil microbial biomass that achieve the purpose of saving phosphate fertilizer resources and reducing planting costs and the risk of eutrophication of water bodies.The conclusions are only obtained through two years of field trials,and the field verification needs to be done further.