灌溉和缓释尿素对水稻全生育期冠层氨通量的调控机制

Ammonia emissions from paddy fields lead to nitrogen losses and environmental problems. Research on the mechanisms and regulation methods of ammonia emissions in paddy fields has scientific significances for improving nitrogen use efficiency and environmental effects. Ammonia emissions in paddy fields are dependent on canopy ammonia fluxes, a bidirectional and dynamic process involving ammonia absorption and release in the canopy during rice growing seasons. Canopy ammonia flux is affected by soil moisture and fertilizer management. Our previous work showed that application of slow-release urea, along with rational irrigation, affected the variations of soil available nitrogen and rice morphological and physiological characteristics, and thus had potential effects on controlling canopy ammonia fluxes. However, little information is available about the effects of irrigation and slow-release urea on canopy ammonia fluxes during rice growing seasons. The experiments will be conducted following a split-plot design, where, the main plots will consist of flooding irrigation, intermittent irrigation, and controlled irrigation; while the subplots will consist of common urea, slow-release urea, and no-urea (as the control). The variations of canopy ammonia fluxes during rice growing seasons will be studied, using real time measuring devices. The key physiological characteristics and growth stages affecting canopy ammonia fluxes will be identified. The results are expected to reveal the mechanisms of irrigation and slow-release urea on controlling canopy ammonia fluxes, clarify the key controlling periods and strategies, and then guide the water and fertilizer management and reduce ammonia emissions in paddy fields.

稻田氨排放量大，造成氮肥损失和环境危害。研究稻田氨排放的过程机制和调控方法，对改善水稻氮肥利用效率和环境效益具有重要的科学意义。冠层氨通量表示叶片吸收氨或释放氨的双向、动态过程，贯穿水稻全生育期，是决定稻田氨排放量的重要参数。农田水肥运筹可影响冠层氨通量。项目前期研究表明，缓释尿素配合灌溉可调节土壤速效氮素含量和水稻形态生理特征，对冠层氨通量具有潜在调控作用，但具体机制尚不明确。项目拟设置不同的灌溉(常规灌溉、间歇灌溉、控制灌溉)和尿素(普通尿素、缓释尿素、无尿素对照)组合，借助密闭抽气实时测定装置，研究水稻全生育期的冠层氨通量变化；分析决定冠层氨通量的关键生理特征和生长阶段。研究结果将揭示灌溉和缓释尿素对水稻冠层氨通量的效应机制，探讨冠层氨通量的关键调控时期和调控策略，为指导水稻水肥运筹、降低稻田氨排放提供科学依据。

【背景】氨挥发是稻田氮素损失的重要途径，造成肥料资源浪费和环境污染。通过合理的水肥管理措施，有望降低稻田氨挥发。目前有关灌溉模式和氮肥类型对水稻冠层氨通量的调控机制尚不明确。.【研究内容】构建3种灌溉模式(浅水、中水、深水)和3种施肥处理(无氮对照、常规尿素、缓释尿素)的完全组合，探究不同水肥管理组合对水稻全生育期氨挥发参数的影响；基于地表水和土壤因素、水稻形态生理特征等解析稻田氨挥发的变化机制；揭示影响稻田氨挥发的关键因素和关键时期。.【重要结果与数据】①田面氨挥发是影响稻田氨排放的主要因素，而冠层氨通量对稻田氨排放的影响较弱。②冠层氨通量与水稻籽粒产量存在负效应关系，当冠层氨通量超过一定临界值以后，水稻籽粒产量急剧下降，因此冠层氨通量可能是反映水稻生产力的一个潜在指标，在水稻育种和高效田间管理措施筛选中具有应用前景。③根据冠层氨通量的数值，可以将水稻全生育期划分为4个阶段，在时期1 (移栽期~分蘖期)和时期3 (抽穗中后期)，水稻冠层氨通量多为负值(表明冠层对空气氨存在净吸收)；在时期2 (拔节期~抽穗前期)和时期4 (灌浆期~成熟期)，水稻冠层氨通量多为正值(表明冠层存在氨的净排放)。④地表水铵态氮浓度和pH是影响稻田氨挥发的重要因素，当其数值超过一定临界值以后，稻田氨挥发会急剧增加。⑤冠层顶部氨挥发与土壤温度、地表水温度呈负相关关系，与其他15个田间参数呈正相关关系(平均相关系数变化范围为0.066 ~ 0.992)。⑥深水灌溉对田间因素的稀释效应和缓释尿素对田间因素的缓释效应，两者可能是降低稻田氨挥发的关键机制。⑦本研究中，深水灌溉配合缓释尿素是减少氨挥发、提高水稻产量和水氮利用率的最优模式。.【科学意义】通过3年的试验，系统解析水稻全生育期氨挥发参数和田间因素的变化特征，阐明其相互关系，探究影响稻田氨挥发的关键因素和关键阶段，为水稻水氮管理和氮肥高效利用提供理论借鉴和应用指导。