Study On The Ammonia Volatilization Law Of Dairy Cattle Manure And Its Emission Prediction

The volatilization of NH₃ in dairy cattle manure is affected by many factors,including temperature and manure physicochemic properties but there are few studies on NH₃ volatilization under controlled conditions.The emission of NH₃ from the dairy cattle manure is mainly due to the decomposition and volatilization of urea,Urea is released into the bloods after liver synthesis,and is expressed by plasma urea nitrogen（PUN）.The urea in the plasma can be filtered through the kidneys to form urine urea nitrogen（UUN）.When lactating,it spreads through the mammary epithelial cells.Entering the milk to form milk urea nitrogen（MUN）.Therefore,there is a certain correlation among PUN,MUN and UUN,which are related to the volatilization of NH₃ in manure.However,it is not reported whether PUN,MUN and UUN of dairy cattle at different production levels can predict the amount of NH₃ volatilization in manure.Therefore,based on the investigation of NH₃ volatilization law from dairy cattle manure under different temperatures and production levels,the regression analysis was carried out between PUN,MUN,UUN at different production levels and the NH₃ volatilization of manure.Experiment 1 Study on the law of volatilization of NH₃ in dairy cattle manureThe feces and urine of 20 cows were thoroughly mixed according to different production levels,The p H,total nitrogen,total ammonia nitrogen,urea nitrogen and dry matter were measured and then the NH₃ volatilization was measured at 20,30 and 40℃ for 72 h.The results showed that the total nitrogen and urea nitrogen in urine of high yield dairy cattle were significantly higher than that of low yield dairy cattle（P<0.05）;The maximum volatilization rate of NH₃ in high yield and low yield dairy cattle group at 30℃ and 40℃ was about 12 hours,while the maximum volatilization rate of NH₃ was delayed at 20℃.For low yield dairy cattle in the first 48 h,the volatilization rate increased with the increase of temperature,and the rate try to same in 48 h until the end of the experiment.In the high yield dairy cattle group,the volatilization rate increased with the increase of temperature from the beginning to 24 h.Except the high yield 30℃ group after 24 h,the NH₃ volatilization rate of the high yield group was higher than that of the low yield group at the same temperature and time point.In addition to the high yield dairy cattle in the 30℃ group,cumulative emissions and cumulative emissions as a percentage of total nitrogen and total urea nitrogen increased with increasing temperature and production levels for others.The proportion of cumulative volatilization of NH₃ at 72 h accounted for urea nitrogen in the substrate in all groups more than 100%.The above results show that with the increase of temperature and production levels,the rate of dairy cattle manure NH₃ volatilization,cumulative total amount and the proportion of cumulative account for total nitrogen and urea nitrogen will increase overall.Other nitrogenous substances in the manure are also important sources of NH₃ volatilization,especially in high temperature environments.Experiment 2 Prediction on the amount of NH₃ volatilization in manure by urea nitrogen in blood,milk and urine of dairy cattleThe urea nitrogen content of plasma,urine and milk from dairy cattle of different production levels was determined by a urea nitrogen kit and milk component analyzer.The NH₃ volatilization measuring device was used to measure the emission rate of NH₃ in each dairy cattle manure and calculate the total amount of emissions within 24 hours.The results showed that high yield dairy cattle had higher urea nitrogen content in blood,urine and milk than low yield dairy cattle（P<0.05）;There were linear positive correlation among PUN,UUN and MUN（P<0.01）,and the correlation coefficients were r=0.80,r=0.88,r=0.89 respective;PUN,UUN and MUN were linear positive correlation with NH₃ emission（P<0.01）.The regression equation of MUN and NH₃ volatilization is NH₃(mg·m^-2)=0.67× MUN（mg/d L）-9.24（R²=0.605）,and the regression equation of PUN、UUN and NH₃ volatilizationis is NH₃(mg·m^-2)=0.77×PUN（mg/d L）+0.373（R²=0.591）,NH₃(mg·m^-2)=0.12× UUN（mg/d L）+4.35（R²=0.426）respective.The above results indicate that there is a linear positive correlation among PUN,UUN and MUN which is a linear correlation with volatilization of manure NH₃..In summary,as the temperature and production levels increase,the rate of dairy cattle manure NH₃ volatilization and cumulative total amount will increase overall.Other nitrogenous substances in the manure are also important sources of NH₃ volatilization,especially in high temperature environments.PUN,UUN and MUN is a linear correlation with volatilization of manure NH₃,MUN is most suitable as a predictor of NH₃ volatilization.