Abstract:

Ammonia emissions from farmlands are closely related to the surface ammonia concentration near the ground. However, there is still a lack of systematic research on whether these can be converted to each other. This study used the near-surface ammonia concentration (passive method) as the main application method and the traditional sponge method as the control method. A correlation study was conducted on the relationship between ammonia emissions and near-surface ammonia concentration during the base fertilizer period of the maize season under five typical fertilization treatments in lime concretion black soils in Southern Henan. The results showed that the peak value of ammonia volatilization under different fertilization treatments appeared 2−4 d after fertilization and significantly decreased from the 5th day. After the 8th day, there was no significant difference compared with the control. The cumulative emissions of ammonia from the different treatments varied greatly, in the order TR>OPT>SOPT>HK>CK. The cumulative emissions were 7.68 kg∙hm⁻², 5.48 kg∙hm⁻², 3.37 kg∙hm⁻², 2.78 kg∙hm⁻², and 0.2 kg∙hm⁻², respectively. At the same time, it was found that there was a similar trend in the near surface ammonia concentration under different fertilization treatments, with a peak occurring 2-4 days after fertilization and a significant decrease starting from the 5th day. The average ammonia concentration ranked as TR>OPT>SOPT>HK>CK, with an average of 17.5 μg∙m⁻³, 11.6 μg∙m⁻³, 10.7 μg∙m⁻³, 8.21 μg∙m⁻³ and 1.70 μg∙m⁻³, respectively. Linear correlation analysis showed that the linear correlation between ammonia volatilization and near-surface ammonia concentration was stronger in the first eight days after fertilization. However, the correlation between these two factors was weak after 8 days. This indicates that the correlation between the near-surface ammonia concentration and cropland ammonia volatilization is related to the level of cropland ammonia volatilization. In addition, the passive method had better estimation values for low nitrogen application and slow fertilizer control than the emission factor method, whereas the emission factor method had a better estimation of ammonia volatilization under high fertilization conditions than the passive method. However, the overall relative error of the passive method in estimating ammonia volatilization was between 15.9% and 17.5%, whereas the relative error of the emission factor method was between 54.3% and 81.8%. The passive method clearly had a higher estimation accuracy, which was particularly evident in the low-nitrogen application and slow-release treatments. Based on the above results, it is suggested that the passive method can replace traditional ammonia monitoring methods to estimate ammonia volatilization in large-scale croplands. However, the estimation accuracy mainly focuses on the high ammonia emission period after nitrogen fertilizer application.

Key words: ammonia volatilization, passive method, near-surface ammonia concentration, correlation, emission factor method, corn season

摘要：

农田氨排放量与近地表氨浓度密切相关，但两者能否相互转换还缺乏系统研究。基于此，以近地表氨浓度经典方法（被动法）为主要使用方法，以传统海绵法为对照方法，在豫南砂姜黑土开展5种典型施肥处理玉米季基肥期氨排放量与近地表氨浓度的相关性研究。结果发现，不同施肥处理的氨挥发峰值均出现在施肥后的2－4 d，第5天开始显著降低，第8天之后基本与对照无明显差异；不同处理的氨累计排放量差别较大，排序为TR>OPT>SOPT>HK>CK，累计排放量分别为7.68、5.48、3.37、2.78和0.22 kg∙hm⁻²；同时发现，不同施肥处理近地表氨浓度也有相同趋势，峰值同样出现在施肥后的2－4 d，第5天开始显著降低，平均氨质量浓度排序为TR>OPT>SOPT>HK>CK，均值分别为17.5、11.6、10.7、8.21和1.70 μg∙m⁻³。线性相关性分析表明，施肥后前8 d不同施肥处理的氨挥发量与近地表氨浓度的线性相关性较强，而8 d之后两者的相关性较弱，说明近地表氨浓度和农田氨挥发量的相关性与农田氨挥发量的高低有关。除此之外，不同方法中被动法对低施氮量和缓释肥的估算优于排放因子法，而排放因子法对高施肥条件下氨挥发量的估算优于被动法。整体而言，被动方法估算氨挥发量的相对误差介于−15.9%－17.5%之间，排放因子法相对误差介于−54.3%－81.8%之间，被动方法明显具备更高的估算精度。以上结果说明，被动方法可以潜在替代传统氨监测方法估算大区域农田氨挥发量，但估算精度主要集中在高氨排放期。

关键词: 氨挥发, 被动法, 近地表氨浓度, 相关性, 排放因子法, 玉米季