Utilization of Azolla in rice cultivation for environmental conservation and adaptation to climate change

在试验开始时，红萍与水稻一起沿着种植，作为双季作物（覆盖）或作为绿色肥料加双季作物（在此为AGM +覆盖）。与对照（化肥; NPK）相比，NPK +覆盖和AGM +覆盖处理没有影响整个水稻生长期的累积CH 4排放量。但是，与NPK + Cover处理相比，AGM + Cover处理对水稻生育前期、中期和后期CH 4排放的影响显著，分别为NPK + Cover处理的141%、25%和33%。这些排放归因于红萍作为绿色肥料掺入后，产甲烷菌容易获得的碳底物。与NPK相比，NPK +覆盖和AGM +覆盖显著增加了中稻生育期N2 O排放量，分别增加了646%和816%。在水稻生长前期和后期，三种处理的N2 O排放量差异均不显著。水稻生长中期N2 O排放量的增加主要是由于夏季气温升高导致满江红死亡后基质有效性增加。AGM +覆盖显著降低水稻产量38%（NPK）和35%（NPK +覆盖），NPK和NPK +覆盖之间差异不显著。这种减少是由于氮固定从合并满江红在早期阶段。因此，为了确定红萍在稻田中的潜力，以解决环境安全，同时保持产量，强调不同的应用方法与各种管理措施的相互作用是必要的。

Azolla was either grown as a dual crop (Cover) or incorporated as green manure plus dual cropping (herein AGM + Cover) at the beginning of the experiment along with rice. Compared with the control (chemical fertilizer; NPK), NPK + Cover and AGM + Cover treatments did not influence cumulative CH4 emissions throughout the rice growth period. However, AGM + Cover treatment affected significant CH4 emissions at early, middle, and later rice growth stages by 141%, 25%, and 33%, respectively, compared with NPK + Cover treatment. These emissions were attributed to the readily available carbon substrate for methanogens following the incorporation of Azolla as green manure. Compared with NPK, NPK + Cover and AGM + Cover significantly increased N2O emissions by 646% and 816%, respectively, during the middle rice growth stage. No significant N2O emission differences were observed in the three treatments in the early or later rice growth stages. The higher N2O emissions from the middle rice growth stage were ascribed to high substrate availability from the dead Azolla by higher summer air temperature. AGM + Cover significantly decreased rice yield by 38% (NPK) and 35% (NPK + Cover), with no significant differences between NPK and NPK + Cover. This reduction was attributed to nitrogen immobilization from the incorporated Azolla during the early stage. Therefore, to ascertain the potential of Azolla in paddy fields to address environmental safety while sustaining yield, emphasis on the interaction of different application methods with various management practices is necessary.