南京两种菜地土壤氨挥发的研究

在南京雨花区武警农场和栖霞区东阳科技站先后进行了秋季小青菜和秋冬季大白菜田间试验,研究菜地土壤施用氮肥后的氨挥发及其影响因素,氨挥发采用密闭室间歇密闭通气法测定。结果表明,小青菜试验地的pH为5 .4 ,施肥后土壤pH值也未高于6 .0 ,故氨挥发损失低(<0 .4 % ) ;而在pH为7.7的大白菜试验地上,控释尿素、低氮和高氮3个处理(施氮量分别为N 180、30 0和6 0 0kghm-2 )氨挥发率分别为0 .97%、12 .1%和17 1%。以上结果表明,土壤pH是影响菜地土壤氨挥发的主要因素,降低氮肥用量能明显减少氨挥发,而施用控释尿素是一种有效控制氨挥发损失的措施。大白菜不同施肥期的结果还表明,施尿素后降雨通过降低表层土壤氮的浓度而影响氨挥发,降雨离施肥期越近,雨量越大,氨挥发越小

AMMONIA VOLATILIZATION FROM UREA APPLIED TO TWO VEGETABLE FIELDS IN NANJING SUBURBS

Field experiments were conducted to investigate ammonia volatilization from urea applied to green cabbage (Xiao Qing Cai) in 2002 and Chinese cabbage in 2003 in the suburbs of Nanjing.Ammonia volatilization was measured with the enclosure method.Results obtained were as follows: ammonia volatilization was low (<0 4%) after urea applied to the green cabbage due to the low pH value of the soil.In the Chinese cabbage field, of which the soil pH was 7 7, ammonia volatilization from the treatments of controlled release urea (N 180 kg hm -2 ), low rate N (300 kg hm -2 ) and high rate N (600 kg hm -2 ) as urea was 0 97%, 12 1% and 17 1%, respectively, of the total N applied.The results show that soil pH is an important factor affecting ammonia volatilization, reducing N application rate can reduce ammonia loss, and the use of controlled release urea is an effective way to reduce ammonia loss.Results of the experiment on timing of N application to Chinese cabbage show that rainfall following application of urea greatly affects ammonia volatilization because rain water reduces N concentration in the surface soil.The heavier and the closer the rain following the application, the less ammonia lost through volatilization.