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| Improving dynamic chamber method to accurate determine ammonia volatilization from upland soils |
| Received:April 28, 2024 |
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| KeyWord:dynamic chamber method;atmospheric ammonia;soil ammonia volatilization;north China plain;winter wheat-summer maize rotation |
| Author Name | Affiliation | E-mail | | ZHONG Guangdi | School of Tropical Agriculture and Forestry, Hainan University, Haikou 570228, China | | | REN Xian | School of Tropical Agriculture and Forestry, Hainan University, Haikou 570228, China | | | PAN Shanshan | School of Tropical Agriculture and Forestry, Hainan University, Haikou 570228, China | | | ZHANG Chong | School of Tropical Agriculture and Forestry, Hainan University, Haikou 570228, China | zhangchong@hainanu.edu.cn | | JU Xiaotang | School of Tropical Agriculture and Forestry, Hainan University, Haikou 570228, China | |
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| Abstract: |
| The dynamic chamber method is considered a reliable approach to quantify soil ammonia（NH3） volatilization, with the advantages of high sensitivity and low cost. However, most researchers often ignore the atmospheric NH 3 concentration from the inlet of the chamber, which may overestimate soil NH3 volatilization. However, the relevant quantitative studies are still lacking. This study took the winter wheat-summer maize rotation system in the North China Plain as an objective, compared NH3 volatilization measured before and after improvements of the dynamic chamber method using the data of seven fertilization events, which included basal fertilization and topdressing in winter wheat and four-and ten-leaf fertilization in summer maize. Before improvements, the obtained NH 3 fluxes include atmospheric NH3 concentration, representing the conventional approach. After improvements, the atmospheric NH3 was excluded from the NH3 fluxes by installing three sets of devices for atmospheric collection at a height of 2.5 meters above ground. The results showed that the improved method had 0-0.23 kg·hm-2·d-1 （0%-100%）lower NH3 fluxes（calculated on nitrogen）than before, with an average of 0.06 kg·hm-2·d-1 （33%）, and 37% of the samples showed significant differences（P<0.05, n=931）. Moreover, the improved method had 0.53-2.66 kg·hm-2（3%-53%）lower cumulative NH3 emissions than before, with an average of 1.15 kg·hm-2·d-1（29%）, and 47% of the samples showed significant differences（P<0.05, n=49）. The proportion of samples with significant differences in NH3 emissions between before and after improvements increased as NH3 emissions decreased. Regression analysis revealed that the cumulative NH3 emissions before improvements could be calibrated by the equation of y=0.94x-0.78（R2=0.99, P<0.01, n=49）, thus to obtain the real NH3 cumulative emissions, where y and x represent the cumulative NH3 emissions after and before calibration, respectively. This equation could be applied to the soil-crop systems in the North China Plain. In conclusion, we must exclude the atmospheric NH3 when using the dynamic chamber method to quantify soil NH3 volatilization. For cumulative NH3 emissions including the atmospheric NH3, the equation derived from this study can be used for calibration. |
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