准动态箱法测定农田NH3挥发初探

提出了能够原位测定农田土壤-植物体系NH3排放的准动态箱法,并开展了一系列实验对其进行评估。该方法的回收率为89.0%±4.9%,与风洞法一致;对农田裸地施肥后的NH3挥发测定结果与有限流通密闭室法具有显著一致性(r<0.05);休闲裸地1日内的NH3挥发与气温呈显著指数相关(r<0.05)。根据NH3挥发的日变化和逐日动态规律,准动态箱法测定农田日NH3挥发的最佳时间为9时(北京时间,下同)左右或16时左右,对单次施肥引起的NH3挥发最佳观测周期为施肥后1～2星期。且实验表明,山西冬小麦拔节期追施(撒施)尿素后,采用准动态箱法测定的NH3挥发N损失率为3%～5%。

A Preliminary Study of Measurement of NH3 Volatilization from Cropland Using Quasi-Dynamic Chamber

The authors proposed a quasi-dynamic chamber method for measurement of NH_3 emission from a soil-plant system. This method showed that the recovery rate is 89. 0%± 4.9% for measurement of NH_3 volatilization, which is in agreement with the recovery rate of a wind-tunnel method. It can also yield results consistent with those measured by a limitedly ventilated close chamber method. There is a significant exponential correlation between diurnal NH_3 emissions and temperature (r<0.05). The optimum time for an intermittent measurement using the quasi-dynamic chamber method was proposed at around 0900LST or 1600LST. The NH_3 emission caused by an N fertilization event could be best captured after 1-2 weeks using the quasi-dynamic chamber method. Using the quasi-dynamic chamber method, the NH_3-N losses from the applied urea into a wheat field in Shanxi Province during the wheat jointing stage were observed at 3% - 5%.