Study On Quantitative Evaluation Of Nitrogen Losses From Different Controlled Nitrogen Fertilizersapplied To Ecology System Of Turf

Field plot and lysimeter experiments with tall fescue turf were conducted in Beijingsuburbs to investigate transformation and fate of applied difference slow/controlledrelease nitrogen fertilizer in turf systems. Effects of various slow/controlled-releasenitrogen fertilizers on plant growth, N uptake and N losses were studied during turfgrowth period. Ammonia volatilization was measured by the enclosure chamber method.Denitrification loss was measured by the acetylene inhibition-intact soil core technique,and N2O emission was also measured in the absence of acetylene. Soil auger dynamicsampling and lysimeter techniques were combined to study nitrate movement andleaching in soil profile. Main results of this study were summarized as follows:1. The application of nitrogen fertilizer significantly increased clipping yields of turf.The treatments of PCU60which nitrogen release period was60days could significantlyimprove growth of turfgrasses, clipping yields and nitrogen absorption. Two yearsexperimental data showed that the nitrogen use efficiency (NUE) of treatments whichapplied nitrogen were11.03%-23.07%in2011and24.29%-45.28%in2012whichchanged the fertilization period. It is worth noting that the NUE of PCU60was45.28%in2012. In the experiments, PCU60with single basal application in spring and autumncould significantly increased clipping yields of turf compared with urea with splitapplication of four times a year.2. Soil pH and ammonical N concentration in surface soil are the primary affectingfactors for ammonia volatilization of turf. The application of nitrogen fertilizers couldchange the soil pH in the small range within a short period of time.In the test site, pH of0-30cm soil was more than7.10which was beneficial to the volatilization of ammonia.Rainfall (or irrigation) following application of nitrogen fertilizer greatly reduced ammonia volatilization because rainfall reduces nitrogen concentration in the surface soil.The ammonia volatilization loss of applied nitrogen treatments of PCU30, PCU60, SCU,UI, U were17.67kg/hm2,13.59kg/hm2,18.54kg/hm2,44.42kg/hm2,39.53kg/hm2in2011and4.63kg/hm2,19.51kg/hm2,28.26kg/hm2,55.74kg/hm2,53.96kg/hm2in2012respectively. The results show that coated slow/controlled release nitrogen fertilizer couldreduce ammonia loss, and treatment of UI which mixed Nitrification inhibitors(Dicyandiamide, DCD) could improve ammonia loss.3. The results show that denitrification losses of nitrogen applied treatments rangedfrom1.79%to4.53%in2011and1.94%to4.66%in2012respectively, and N2Oemissions ranged from0.89%to2.89%in2011and0.80%to2.69%in2012respectively.Application of slow/controlled release nitrogen fertilizer could significantly decreasedenitrification losses and N2O emissions in comparison with urea, especially treatmentsof PCU60and UI. The denitrification losses and N2O emissions increased with theincrease of temperature.4. Application of nitrogen fertilizer could significantly increase concentration ofnitrate nitrogen and ammonium nitrogen in0-30cm soil. For example, the highest nitratecontent in applied nitrogen treatments was PCU30which reached29.10kg/hm2in2011.The situation has changed in2012. The highest nitrate content was U which reached36.31kg/hm2.There was little nitrogen loss by leaching in lysimeter experiments during2011and2012.In addition to soil nitrogen residues and rainfall(or irrigation), soil textureis the determined factor for nitrogen leaching. Although irrigation after fertilizing everytime and rainfall frequently, for example heavy rain in July21,2012, the solubilitynitrogen loss by leaching of applied nitrogen treatments of PCU30, PCU60, SCU, UI, Uwere1.54kg/hm2,0.94kg/hm2,2.07kg/hm2,2.10kg/hm2,1.73kg/hm2in2012respectively. This may be related to clay soil of field. It seems that leaching loss from turfwas low in the condition of climate and clay soil of southwest Beijing.But there is anegative influence risk of soil and groundwater negative effects.5. In the experiment, total N loss ranged from40.74kg/hm2to82.03kg/hm2in2011and from45.75kg/hm2to94.45kg/hm2in2012. The ammonia volatilization and denitrification were the most important N loss pathway.The leaching loss was lowest.The rate of nitrogen loss by ammonia volatilization of PCU30, PCU60, SCU, UI, U were6.80%,5.23%,7.13%,17.08%,15.20%in2011and8.21%,6.50%,9.42%,18.58%,17.99%in2012respectively. Compared with2011, the nitrogen loss by ammoniavolatilization and denitrification was increased significantly in2012.The rate of nitrogenloss by denitrification were2.75%,2.09%,3.25%,1.79%,4.53%in2011and2.49%,1.94%,3.71%,2.37%,4.66%in2012respectively. The nitrogen loss pathways of allnitrogen applied treatments are in order ammonia volatilization>denitrification>leaching.