Gas transport enhancement under windy condition in poorly tilled seedbed of clayey rotational paddy field
Gas transport enhancement under windy condition in poorly tilled seedbed of clayey rotational paddy field
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大风条件下粘土质轮作稻田欠耕苗床气体输送增强
DOI：
10.1080/00380768.2021.2015236
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发表时间：
2021
影响因子：
2
通讯作者：
Nishida Kazuhiro
中科院分区：
文献类型：
--
作者：
Matsumoto Yoshihiro;Yoshida Shuichiro;Sekiya Hiroyuki;Nishida Kazuhiro
土壤和大气之间的气体交换控制着植物的生长和空气中气体成分的全球循环。据报道，在大孔介质中，风可以增强气体交换。在粘质稻田，耕作容易形成大团聚体(块)和团粒间孔隙。然而，在这些领域中还没有考虑风对天然气运输的影响。这项研究量化了风致气体通过由大块土块组成的水稻土层的移动。利用气体扩散方程对平均冰块大小和风况进行了分析，验证了分析的适用性。未受干扰的土柱取自种植大豆的“耕作不良”和“耕作相当”的稻田。土块的平均直径分别为3.4厘米和1.9厘米的“差”和“相当”的分耕柱。还制备了重新填充的硅砂柱作为参考。以CO2为吹扫气体，大气氧气为示踪气体，在野外自然风条件下和实验室平静条件下对柱子进行了扩散试验。气体传输效率的评价指标为和，即野外氧气浓度达到大气中氧气浓度的50%和90%的时间与实验室氧气浓度的比率。结果表明，在自然风条件下，气体通过由几厘米厚的土块组成的水稻土层的传输速度比在平静条件下快11倍。在低耕土壤上，当风速超过1.2m S−1时，地表以上20 cm处的风致气体交换最大。在平耕土壤中，随着风速的增加，风的作用逐渐增强，当风速在2.0m S−1左右时，风的作用逐渐接近于弱耕土壤。气体扩散方程的适用性随着风速从1.2m S−1增加到2.6m S或团聚体平均粒径从1.9cm1增加到3.4cm时变差。
Gas exchange between soil and atmosphere governs the growth of plants and global circulation of the gaseous component of air. Enhancement of gas exchange by wind has been reported in media with large pores. In clayey paddy fields, large aggregates (clods) and inter-aggregate pores are prone to be formed by tillage. However, the effect of wind on gas transport has not been considered in such fields. This study quantified the wind-induced gas movement through the paddy soil layer composed of large clods. The applicability of the analysis using the gas diffusion equation was also verified regarding the mean clod size and wind condition. Undisturbed soil columns were taken from the ‘poorly tilled’ and ‘fairly tilled’ paddy field under the cultivation of soybean. The mean diameters of the clods were 3.4 and 1.9 cm for the ‘poorly’ and ‘fairly’ tilled columns, respectively. A repacked silica sand column was also prepared as a reference. Diffusion tests were conducted for the columns in the field under natural wind and in the laboratory under calm conditions, with CO2as a purge gas and atmospheric oxygen as a tracer gas. The gas transfer efficiency was evaluated byand, which is the ratio of the time until the oxygen concentration reaches 50% and 90% of that in the atmosphere in the field to that in the laboratory, respectively. The results showed that gas transfer through the paddy soil layers, comprised a few centimeters of clods, under natural wind was up to 11 times quicker than under the calm conditions. The wind-induced gas exchange remained at maximum under the wind speed of more than 1.2 m s−1at 20 cm above the soil surface in the poorly tilled soil. In contrast, in the fairly tilled soil, the effect of wind gradually increased with wind speed and finally became close to that in the poorly tilled soil at the wind speed around 2.0 m s−1. The applicability of the gas diffusion equation deteriorated as the wind speed increased from 1.2 to 2.6 m s−1or the mean aggregate size increased from 1.9 to 3.4 cm.