Development Of Coated And Urease/Nitrification Inhibitor Bound Controlled-release Urea And Its Effect On The Growth Of Wheat

Nitrogen is a necessary nutrient element for plant growth and development.Application of nitrogen fertilizer is an essential measure to ensure crop yield and food security.There are serious environmental pollution problems caused by low utilization rate and nitrogen loss in the application of nitrogen fertilizer,it have aroused people’s attention.In order to reduce or slow down the release and conversion rate of nitrogen,improve the utilization rate of nitrogen and reduce the environmental pollution caused by nitrogen loss,a new type of nitrogen fertilizer was developed.In this study,a new type of coated controlled-release urea was developed by combining the coating with urease/nitrification inhibitor,the slow-release effect of controlled-release urea combined with coating and urease/nitrification inhibitor on nitrogen and urease/nitrification inhibitor was studied.The effects of controlled-release urea combined with urease/nitrification inhibitor on soil nitrogen supply and wheat growth was studied through field experiments,the biological effect of the new controlled-release urea was determined.The main results are as follows:1.The technology of fertilizer coating was applied to urease inhibitor,and the coated urease inhibitor was prepared to prolong its duration.The inhibition of this kind of fertilizer on urea hydrolysis and its effect on wheat growth were studied by means of indoor simulated culture and outdoor field experiment.The method of capsule coating was used,the urease inhibitor hydroquinone（HQ）was partially or completely mixed with urea.A pot experiment,which including five treatments as control（CK）,common urea（U）,U+common urease inhibitor HQ（SRU1）,U+coated HQ（SRU2）,And U+30%common HQ+70%coated HQ（SRU3）,were conducted to study the effect of 5 different fertilizers on wheat growth,soil nitrogen,and urease activity.The results showed that compared with SRU1,coated HQ can promote wheat growth,improve wheat yield structure,increase wheat yield,and improve nitrogen utilization rate.SRU2 and SRU3respectively increase the yield of wheat by 34.7%and 56.5%.Compared with SRU2,SRU3treatment of common HQ mixed with Coated HQ could effectively inhibit the hydrolysis of urea at the early stage,maintain the appropriate concentration of NH₄⁺-N in soil,and increase the content of NH₄⁺-N at the later stage,so as to ensure the continuous supply of available nitrogen in the soil,reduce the loss of nitrogen,and maintain the urease activity of soil at a low level for a long time in the whole growth period of wheat.The resin coating technology was used to coat HQ,and the resin coating slow-release HQ was developed.The mechanism of reducing urea hydrolysis by HQ with different coating ratio and its effect on wheat growth were studied by indoor culture experiment and field experiment,The results showed that HQ fertilizer with resin coating had complete film formation and inhibitor was completely surrounded by the coating,and the release period was42 days;The addition of HQ can effectively inhibit the hydrolysis of urea and avoid the phenomenon of sharp increase in the hydrolysis process,while the coating HQ can prolong the reaction time of urea hydrolysis.When mixed with HQ,the hydrolysis process of urea was more gentle,the hydrolysis time was extended from 10 days to 30 days,and the maximum hydrolysis rate of common urea was reduced by 62.44%.The field experiment showed that T4treatment significantly promoted the growth of wheat,increased the plant height and tiller number of winter wheat,increased the SPAD value of functional leaves,and had the strongest ability of nitrogen supply,the most significant effect of maintaining the NH₄⁺-N content of soil,the highest nitrogen utilization rate,and the highest yield of wheat was 9902.7kg/hm².2.The resin coating technology was applied to the coating of nitrification inhibitor（DCD）to prepare resin coating DCD,so as to extend the duration of the inhibition of DCD on soil NH₄⁺-N nitrification.The slow-release properties of DCD coated with resin were determined by SEM and static water release test,and the effects of control（CK）,common urea（U）,U+common DCD（SUD1）,U+coated DCD（SUD2）,And U+30%common DCD+70%coated DCD（SUD3）on wheat growth and soil nitrogen supply capacity were studied by field test.The results showed that the resin coated DCD had good slow and controlled release performance and achieved the expected effect.The release period was 7 days.Coated DCD can significantly promote the growth of winter wheat,increase the plant height and stem diameter of winter wheat,increase the SPAD value of functional leaves,improve the yield structure of wheat,increase the yield of wheat,and improve the utilization rate of nitrogen;It can prolong the action time,delay the transformation rate of NH₄⁺,keep the form of NH₄⁺-N in soil for a long time,and reduce the accumulation of NO₃^--N.SUD3 treatment not only effectively inhibited the transformation of ammonium nitrogen to nitrate nitrogen in the early stage,but also prolonged the action time of DCD in the later stage,further reduced the apparent nitrification rate of soil ammonium nitrogen,reduced the leaching loss of NO₃^--N,the treatment significantly promoted the growth of wheat and obtained the highest yield of wheat.3.In this study,the controlled release technology of urea coating was combined with the slow release technology of urease/nitrification inhibitors,four kinds of coated fertilizers were developed.The four kinds of coated fertilizers include resin coated urea（CU）,resin coated urease inhibitors HQ coating urea（CRU1）,resin coated nitrification inhibitor DCD coating urea（CRU2）and resin coated HQ and DCD combined coating urea（CRU3）.The micro structure,nutrient and inhibitor release properties of the self-made double controlled release urea were determined by SEM and hydrostatic release test.And the effects of different fertilizers on wheat growth and soil nitrogen supply capacity were And the effects by field experiments in Weifang and Taian.The coated fertilizer prepared by this technology has complete film formation,uniform film thickness,smooth surface and dense film layer.The resin coated material can completely cover the surface of the fertilizer core.The joint of urea and inhibitor is tightly connected without gap,the inhibitor is completely surrounded by the coating layer.Under the condition of static water release,the release of urea and inhibitor can be controlled simultaneously by co-envelop of urea and inhibitor.Compared with CU,the combination of coating and inhibitor can promote the growth of wheat,increase the amount of dry matter transport after flowering,improve the yield structure of wheat,and improve the yield and nitrogen use efficiency of wheat.CRU1,CRU2 and CRU3 treatment increased the yield of wheat by 23.38%,23.13%and 38.79%respectively in Weifang,and by 6.36%,9.52%and 28.57%respectively in Taian.CRU1 and CRU3 treatment can maintain the soil urease activity at a low level during the growth period of wheat,CRU2 and CRU3 treatment can inhibit the transformation of soil NH₄⁺-N to NO₃^--N,and reduce the apparent nitrification rate of soil NH₄⁺-N.CRU3 treatment had the strongest sustainable nitrogen supply ability,the highest nitrogen utilization rate,the most significant role in promoting the growth of wheat,and the highest yield of wheat.