在实验室和晚稻田间研究了铵态氮对我国稻田中应用的几种固氮蓝藻固氮活力的影响,同时对湖北省圻春县和浠水县不同肥力的76块晚稻田水层铵态氮含量进行了测定,获得了下列结果。在实验室条件下,铵态氮浓度为1ppm时,对蓝藻固氮活力有抑制,不同种类之间抑制程度有差别。当溶液中铵被耗尽后,固氮活力上升,并在9小时后可恢复到原来水平, 在小区实验的晚稻中,施硫酸铵40斤/亩和碳酸氢铵50—70斤/亩作底肥,插秧后放蓝藻,固氮酶活力的变动与实验室情况相近,在稻田水中铵态氮浓度降低或消失时,固氮活力恢复,一般施肥后1—3天,稻田水中铵态氮可以完全消失。晚稻田施底肥1—4天后,稻田水层中铵态氮含量很低,79%田块中检测不出。由此可见,湖北现阶段晚稻底肥水平下,插秧后放蓝藻对蓝藻固氮活力影响甚微或不会有影响。 The effects of ammonium nitrogen on the nitrogen fixation activities of several nitrogen-fixing cyanobacteria in paddy fields in China were studied in laboratory and late rice fields. Meanwhile, the contents of ammonium nitrogen in 76 late rice fields with different fertility in Qichun County and Xishui County, Hubei Province, The measurement was carried out and the following results were obtained. Under laboratory conditions, ammonium nitrogen concentration of 1ppm inhibited the nitrogen-fixing activity of cyanobacteria, and the inhibition degree of different species was different. When the ammonium in the solution was exhausted, the nitrogen fixation activity increased and returned to its original level after 9 hours. In the plot experiment, 40 kg / mu ammonium sulfate and 50-70 kg ammonium bicarbonate were used as base fertilizer After transplanting, the change of cyanobacteria and nitrogenase activity was similar to that in laboratory. When ammonium nitrogen concentration in paddy water decreased or disappeared, nitrogen fixation activity was restored. Generally, NH4 + -N in rice water could disappear 1-3 days after fertilization. After 1-4 days of late rice paddy application, the content of ammonium nitrogen in rice paddy water layer is very low, and it can not be detected in 79% of the paddy field. Thus, Hubei at the present stage of late rice under the level of fertilizer, after planting transplanting cyanobacteria on the blue-green algae nitrogen activity little or no effect.