Preparation Of Diammonium Phosphate Coated With Polyurethane And Its Application Effect On Soybean And Maize

Phosphorus is indispensable to the growth and development of crops by participating in important metabolic processes such as carbohydrate in crops in various ways.Phosphorus fertilizer is easily fixed when applied directly into soil,resulting in low availability and utilization rate of phosphorus in soil.The coating layer of coated fertilizer can avoid the direct contact between phosphate and soil after fertilizer application,regulate the slow release of phosphorus,improve the utilization rate of phosphorus fertilizer,and reduce the risk of water eutrophication.However,there are relatively few researches on coated phosphorus fertilizer at present,and most of them are on preparation of coated slow-controlled release phosphorus fertilizer or simple application effect verification,while there are few reports on its application in obstructed soil or its effect in combination with synergists.In this study,castor oil bio-based polyurethane coated phosphate fertilizer was prepared by in situ film forming technology.Firstly,the key process of preparation of coated phosphate fertilizer was optimized by waterbased rounding technology,and then the effect was verified on soybean in saline-alkali land.In addition,growth enhancing coated phosphate extracts(ZNC)were prepared by combining water and fertilizer table modification techniques with fertilizer enhancer Paecilomyces variotii extracts,which were used on maize and their mechanism of increasing yield and efficiency was explored.The main research results are as follows:(1)The key process of the nutrient release and stability of polyurethane coated diammonium phosphate was optimized.Four commercially available diammonium phosphate(DAP)types(WF,KP,JFR and SH)were selected.It was found that the ratio of 3-5 mm particles of diammonium WF and KP were 83.38% and 85.46%,respectively,which had obvious advantages over diammonium SH and JFR.Measured the Angle of repose,the particle fluidity of WF is relatively good.The results show that the quality of WF diammonium phosphate is relatively good.DAP was modified under different water and temperature conditions,it was found that the roundness of DAP could be improved.At the same time,DAP particles were heated in a water bath to simulate the preheating process of the envelop.It was found that the ammonia yield was 0.049 mol/h when the preheating temperature was 70℃,which was 15.2% lower than the fertilizer loss rate at 80℃.The release period of diammonium phosphate in the modified polyurethane envelope with the addition of water becomes longer with the increase of the membrane thickness.When the membrane thickness is 4%,the release period can reach 70 days.When the coating thickness was 4%,the release time of wax modified coated ammonium diammonium phosphate(CDAP)was 10 d longer than that of wax sprayed once and twice,and the average release time was 80 d.(2)The application effect and yield increase mechanism of coated phosphorus fertilizer in saline-alkali soil were clarified.Compared with CF treatment,plant height,pod number per plant,seed number per plant and weight per plant increased by 24.1%,22.2%,16.4% and 9.3%under 100 mm CRP treatment,respectively.When the plant spacing was 85 mm and 70 mm,the plant height of CRP treatment was increased by 47.3% and 8.2% compared with CF treatment,respectively.In addition,when the plant spacing was 100 mm,the average yield of soybean per mu under CRP treatment was 248 kg,9.3% higher than that of CF treatment.Under the conditions of this experiment,the treatment of coated phosphorus fertilizer has a better effect on soybean plant height,pod number per plant,seed number and other yield related indicators,so as to further improve the soybean yield.(3)The effects of ZNC application on maize physiological characteristics and soil supply intensity were discussed.Compared with the application of total ordinary diammonium phosphate,total application of coated diammonium phosphate(CP100%)significantly enhanced the activities of adenosine triphosphate synthetase and plant pyruvate phosphate dual kinase,which were the key enzymes in photosynthesis,increased by 28.6% and 46.9%,increased the yield of maize by 14.6%,and increased the utilization rate of phosphate fertilizer by 20.3 percentage points.Stable yield after 20% phosphorus reduction;Compared with single coating and ZNC spraying(P100%Z),coated diammonium phosphate combined with ZNC significantly increased the net photosynthetic rate by 23.1% and 32.0%,respectively,and increased ADP-glucose pyrophosphorylase by 37.3% and 4.5%,respectively.In the first season,compared with CP100% and P100%Z treatment,the grain yield increased by 9.6% and 14.3%,and the utilization rate of phosphorus fertilizer increased by 11.3% and 51.6%,respectively,showing a significant synergistic effect.Under the conditions of this study,the surface roundness and fluidity of polyurethane coated diammonium phosphate fertilizer modified by adding water and wax were improved,and the controlled release performance was also significantly improved.The application of polyurethane coated diammonium phosphate on soybean in saline-alkali soil showed a good yield increase.The application of polyurethane coated diammonium phosphate and synergist ZNC on maize showed that the coating of diammonium phosphate or the combination of ZNC could increase the yield and utilization rate of phosphate fertilizer,and the coating treatment effect was the best.The combination of ZNC with diammonium phosphate coating could significantly improve the photosynthesis and glycolytic pathway related enzyme activities,but did not show a stable synergistic stimulation effect.The research can provide reference for the preparation process innovation of coated diammonium phosphate and the scientific application of coated diammonium phosphate and ZNC,and provide a reference for the research and development of special fertilizer products for summer soybean and summer maize.