Ammonia Volatilization Of Urea From Summer Maize-winter Wheat Rotation System In Dryland

Urea is the most common form of nitrogen fertilizer in China and even worldwide,which plays an important role in guaranteeing the high production of crop.However,the utilization rate of nitrogen fertilizer in China is extremely low,leading to serious waste of nitrogen fertilizer and ecological environment pollution,among which Ammonia?NH₃?volatilization is one of the main means of loss.How to accurately evaluate the ammonia volatilization and determine the reasonable amount of nitrogen fertilizer is a hot issue for agricultural technologists.In this study,therefore,field experiment of summer maize-winter wheat rotation system?two crops?with five nitrogen supply levels?without urea and applied urea 100,200,300,400kg N/ha,and it was respectively abbreviated as N0,N1,N2,N3,N4?was conducted to evaluate the ammonia volatilization of urea by using the calibrated Dr?ger-Tube Method?DTM?.The main results of this study were concluded as follows:1.In the summer maize-winter wheat rotation system,the ammonia volatilization rate from five nitrogen treatments showed similar tread.The ammonia volatilization rate increased with time at first,peaked at 2-4days after fertilization,and then decreased until volatilization could not be detected.In addition,with the application of nitrogen fertilizer,the rate of ammonia volatilization increased significantly with the increase of nitrogen supply rate.In summer maize season,after the topdressing at trefoil stage,the highest ammonia volatilization rate of each treatment was detected at the fourth day after fertilization,and the values were 5.45?5.99?24.10?33.92?22.83 g N ha^-11 h^-1,respectively.After the topdressing at ten-leaf stage,the highest ammonia volatilization rate of each treatmentwas detected at the second day after fertilization,and the corresponding values were 35.65?61.31?97.73?115.49 and 139.29 g N ha^-11 h^-1,respectively.In winter wheat season,after basal fertilization in,the highest ammonia volatilization rate of each treatment was detected at the second day after fertilization,and the corresponding values of treatment from N0 to N4 were 8.15?20.67?38.88?51.30?62.92 g N ha^-11 h^-1,respectively.2.In summer maize season,after the topdressing at trefoil stage fertilization,the cumulative emissionamounts of ammonia volatilization from each treatments were 0.89,1.06,3.15,3.64,3.07kg N ha^-1,respectively.From which,around 0.16,2.26,2.75,2.18kg N ha^-1were come from nitrogen fertilizer,and it accounts for 0.41%?2.82%?2.29%?1.36%of applied nitrogen fertilization,respectively.After the topdressing at ten-leaf stage,the cumulative emission amounts of ammonia volatilization from each treatment were 3.74?5.84?9.03?9.91?10.87kg N ha^-1,respectively.From which,around 2.10?5.29?6.17?7.13kg N ha^-1were come from nitrogen fertilizer,and it accounts for 3.50%?4.41%?3.43%?2.97%of applied nitrogen fertilization.It is obviously that the amount of ammonia volatilization after ten-leaf fertilization is higher than that of trefoil,and the reason for this difference was mainly due to the high temperature,soil moisture content,and the fertilization rate.3.In winter wheat season,after basal fertilization,the cumulative emission amounts of ammonia volatilization of treatments from N0 to N4 were 1.21?1.99?3.54?4.19?4.79kg N ha^-1,from which,around 0.78?2.33?2.98?3.58kg N ha^-11 were come from nitrogen fertilizer,and it accounts for 0.78%?1.16%?0.99%?0.90%of applied nitrogen fertilization,and the treatment N2,N3,N4 were significantly higher than N0 and N1 treatment.4.After the topdressing at ten-leaf stage in summer maize,there was about 90%of ammonia volatilization occurred in the first seven days,and just about 10%of total loss after the seventh day,as well as the same after basal fertilization in winter wheat,which indicating that the first week after fertilization was the main period to control the loss of ammonia volatilization.In the summer maize-winter wheat rotation system,the cumulative emission amounts of ammonia volatilization of treatments from N0 to N4 were 5.84?8.88?15.72?17.73?18.74kg N ha^-1,from which,around 3.04?9.88?11.89?12.90kg N ha^-11 were come from nitrogen fertilizer,obtained by subtraction method,and it accounts for 1.53%?2.47%?1.98%?1.61%of applied nitrogen fertilization.There was significant difference between different nitrogen levels and no nitrogen treatments,and the cumulative loss of ammonia volatilization increased with the increase of nitrogen application amounts.5.The fertilizer ammonia volatilization of nitrogen in summer maize season accounted for the proportion of 3-5%,which is much higher in winter wheat season?about1%?.Under the same nitrogen treatment,the ammonia volatilization loss in the summer maize season accounted for about 70%of the total loss in the whole rotation system,which was significantly higher than the loss in the winter wheat season.This is related to the method of fertilization application,air temperature and other factors,which shows that the summer maize season is the important period for ammonia volatilization loss.It is the key that how to avoid the ammonia volatilization in summer maize season fertilization under high temperature and high humidity conditions to reducing the loss of ammonia volatilization in the summer maize-winter wheat rotation system.