Nitrogen Release Characteristics Of Slow/controlled Release Fertilizers With Different Production Processes

Slow/controlled release fertilizers can effectively control the release rate of nitrogen,reduce the loss of nitrogen fertilizer caused by volatilization,leaching,etc.,thereby increasing the utilization of fertilizers and reducing the pollution caused by fertilization to the environment;and after a one-time application,it can basically meet the crops.Nutrient demand throughout the growth period has therefore a good application prospect in agricultural production.In this study,UF-UF6(UF1-UF6)was produced under different membrane material dosages of coated urea(CRU1;CRU2),different production temperatures and reaction times,and the effects of coated urea on water and soil were investigated through indoor culture experiments.The law of nitrogen release,the solubility and activity index of urea-formaldehyde fertilizer and its release in soil were used to investigate the effects of production process,membrane material dosage and soil type on nitrogen release characteristics of slow/controlled release fertilizers.The main findings are as follows:1.According to the national standard measurement method and regulations,the initial nutrient dissolution rates of CRU1 and CRU2 were 15.61% and 0.64%,respectively,and the release periods were 30 days and 100 days,respectively,at 25±0.5°C.2.The soil type and membrane dosage significantly affected the release of nitrogen from the coated urea.The maximum nitrogen release rates of CRU1 in albic,black and chernozeic were 111.76%,113.66%,and 115.54%,respectively.The periods were 37 days,36 days and 34 days,respectively;the maximum nitrogen release rates of CRU2 in white soil,black soil and chernozem were 96.87%,93.39% and 93.14%,respectively,and the release periods were 182 days and 209 days respectively.At 213 days,the release rate of CRU1 and CRU2 in albic soil was highest,followed by black soil and lowest in chernozem.3.The production temperature and reaction time all significantly affect the solubility and activity index of urea-formaldehyde fertilizer nitrogen in water.Among them,when the reaction temperature rises from 60°C to 70°C,the content of cold water-soluble nitrogen,cold water insoluble nitrogen,and hot water insoluble nitrogen Both decreased from 20.70%,20.00%,10.50% to 18.40%,19.50%,and 8.40%,respectively,and only the hot water-soluble nitrogen content and nitrogen activity index increased from 9.50% and 47.70% to 10.60% and 54.00%,respectively.When the reaction time increased,the contents of cold water-soluble nitrogen,cold water-insoluble nitrogen,and hot-water insoluble nitrogen all decreased.They decreased from 19.40%,19.80%,and 10.60% to 19.10%,19.50%,and 9.60%,respectively.The nitrogen activity index increased from 9.20% and 46.50% to 10.00% and 50.70%,respectively.4.The soil type,urea-formaldehyde fertilizer production temperature and reaction time all significantly affected the nitrogen accumulation and release rate of the tested urea-formaldehyde fertilizers,among which,the white soil was the highest(82.05%),followed by black soil(76.66%);The lowest soil(74.50%).