Abstract: Using an enclosure growth chamber to collect and determine volatilized ammonia from alfalfa,we attained the results that ammonia evaporation loss,day and night,mounted in a continuous alfalfa cropping plot during the plant ramification and budding periods.The volatilizing rate from a continuous alfalfa cultivation plot,day-and-night,averaged 54.3 μg/(m²·h)in the ramification period,111.6 μg/(m²·h)in the budding stage,and 181.9 μg/(m²·h)in the blooming stage,showing that ammonia loss soars with the advance of the growth periods.Applying 26.2 kg/hm² phosphate fertilizer to a continuous alfalfa plot could reduce the plant ammonia loss.In an alfalfa rotation plot,the ammonia volatilizing rate,day-and-night,averaged 49.2 μg/(m²·h)in the ramification period,346.5 μg/(m²·h)in the budding stage,and 149.1 μg/(m²·h)in the blooming stage,showing that rotation cropping changes alfalfa ammonia loss rate during its different growth periods.Compared to the ammonia loss of the continuous cropping plot during its budding stage,that of the rotation plot in the same growth period is 2.1 times higher,while during the blooming stage,the ammonia loss of the latter is 18.0% less than the former.

Key words: Dry land, Alfalfa, Ammonia volatilization, In situ, Long-term experiment

摘要： 采用密闭通气法研究了紫花苜蓿草地原位氨挥发损失。结果表明,紫花苜蓿(Med icago sativa L)草地分枝期、现蕾期和开花期昼夜都有氨挥发损失;连作苜蓿草地分枝期、现蕾期和开花期的昼夜平均氨挥发速率分别为54.3、111.6和181.9μg/(m²·h);连作苜蓿草地的昼夜氨挥发速率随着生育期的推移迅速增加;施P 26.2 kg/hm²可以降低连作苜蓿草地的氨挥发损失;轮作苜蓿草地分枝期、现蕾期和开花期的昼夜平均氨挥发速率分别为49.2、346.5和149.1μg/(m²·h);轮作改变了氨挥发速率的变化规律,现蕾期比连作高2.1倍,开花期比连作低18.0%。

关键词: 旱地, 紫花苜蓿, 氨挥发原位, 长期试验