| In order to investigate the emission loss characteristics of soil ammonia volatilization in the Yellow River Irrigation Region of Ningxia, a field experiment was conducted under the rotation system of open field broccoli and Chinese cabbage from May to September, 2013 to have studied the effects of different combined applications of organic-inorganic fertilizers on rate of soil ammonia volatilization, accumulative loss by ammonia volatilization, and loss ratio of N applied. The results indicated that the peak rates of ammonia volatilization after base fertilization in open field broccoli and Chinese cabbage appeared generally within 1～4 days, whereas the peak rates anticipated 1~2 days after top dressing. Soil ammonia volatilization could sustain more than 10 days with high N application rates. Soil ammonia volatilization happened mostly during top dressing fertilizers treatments in broccoli season (accounted for the total ammonia volatilization by 50.2%～60.3%, except for treatments with only manure and low N rate application). However, ammonia primarily became lost during base fertilization in Chinese cabbage season (accounted for the total ammonia volatilization by 57.0%～73.6%). The maximal rates of ammonia volatilization after base and top dressing fertilizations in open field broccoli ranged from 0.79～4.56 and 1.00～5.34 kg·hm-2·d-1, respectively, and the corresponding maximal rates in Chinese cabbage ranged from 3.49～13.09 and 1.54～7.03 kg·hm-2·d-1, respectively. In different combined applications of organic-inorganic fertilizer treatments, accumulative losses by ammonia volatilization during the total growing periods of broccoli and Chinese cabbage ranged from 5.15～35.82 and 11.11～70.60 kg·hm-2, respectively, which were always elevated with the increase of total N application. The loss ratios of N applied in different fertilization treatments ranged from 4.02%～4.87% and 2.54%～10.55% in broccoli and Chinese cabbage seasons, respectively, and the corresponding contribution ratios of chemical fertilizers were 62.0%～100.0% and 85.5%～100.0%, respectively. The contribution ratios of chemical fertilizers were upraised with the increase of chemical N application. Therefore, with the application of organic manure at the same level, it is important to decrease chemical N application, reducing emission loss by soil ammonia volatilization in the open vegetables field in this region. |