IRTA Institute of Agrifood Research and Technology, Aquatic Ecosystems, Sant Carles de la Ràpita, Spain.
IRTA Institute of Agrifood Research and Technology, GIRO, Torre Marimon, Caldes de Montbui, Spain.
PLoS One. 2018 May 31;13(5):e0198081. doi: 10.1371/journal.pone.0198081. eCollection 2018.
Paddy rice fields are one of the most important sources of anthropogenic methane. Improving the accuracy in the CH4 budget is fundamental to identify strategies to mitigate climate change. Such improvement requires a mechanistic understanding of the complex interactions between environmental and agronomic factors determining CH4 emissions, and also the characterization of the annual temporal CH4 emissions pattern in the whole crop cycle. Hence, both the growing and fallow seasons must be included. However, most of the previous research has been based on single-factor analyses that are focused on the growing season. In order to fill this gap, a study was conducted in a Mediterranean rice agrosystem (Ebre Delta, Catalonia) following a farm-to-farm approach with the purpose of 1) evaluating the cumulative and temporal pattern of CH4 emission, and 2) conducting a multi-variate analyses to assess the associative pattern, relative contribution and temporal variation of the main explanatory variables concerning the observed CH4 emissions. Measurements of CH4 emissions and agronomic and environmental parameters in 15 commercial rice fields were monitored monthly, during a whole crop field cycle. The temporal pattern of CH4 emission followed a bi-modal distribution peaking in August and October. The cumulative annual CH4 emissions from rice fields amounted 314 kg CH4 kg ha-1, of which ca. 70% were emitted during the fallow season. The main controlling factors of the CH4 emission rate in the growing season were positive related to water level and plant cover, while soil redox was negatively related. The main controlling factors in the fallow season were water level (negatively related, conversely to the growing season), as well as straw incorporation and soil temperature (positively related). The results of this study highlight the importance of the often neglected fallow season in the accurate estimation of CH4 emissions and, thus, the necessity of measurement programs that cover the whole crop field cycle. This information is the first step for setting effective mitigation strategies based on straw and water management.
水稻田是人为甲烷的最重要来源之一。提高 CH4 收支平衡的准确性对于确定缓解气候变化的策略至关重要。这种改进需要对确定 CH4 排放的环境和农业因素之间复杂相互作用的机制有深入的了解，还需要对整个作物周期的年度时间 CH4 排放模式进行特征描述。因此，必须包括生长季和休耕季。然而，大多数先前的研究都基于侧重于生长季的单因素分析。为了填补这一空白，在一个地中海水稻农业系统（加泰罗尼亚的埃布罗三角洲）中进行了一项研究，采用从农场到农场的方法，目的是 1）评估 CH4 排放的累积和时间模式，2）进行多元分析，以评估与观察到的 CH4 排放有关的主要解释变量的关联模式、相对贡献和时间变化。在整个作物田间周期中，每月监测 15 个商业水稻田的 CH4 排放和农业及环境参数的测量值。CH4 排放的时间模式呈双峰分布，峰值出现在 8 月和 10 月。来自水稻田的累积年 CH4 排放量为 314 kg CH4 kg ha-1，其中约 70%在休耕季排放。生长季 CH4 排放率的主要控制因素与水位和植物覆盖呈正相关，而土壤氧化还原与水位呈负相关。休耕季的主要控制因素是水位（与生长季相反，呈负相关），以及秸秆还田和土壤温度（呈正相关）。这项研究的结果强调了往往被忽视的休耕季在准确估计 CH4 排放中的重要性，因此，需要测量方案涵盖整个作物田间周期。这一信息是基于秸秆和水管理制定有效缓解策略的第一步。
