稻田养萍(满江红)是工本省而效果显著的增肥途径。但是在浙北有些冬天(例如1962—1963年冬)最低气温接近-10℃,如在河塘或由间露天放养越冬,就有大部分或全部冻死的危险。因而种萍越冬问题是当地大面积养萍的关键性问题之一,也是继续进行“南萍北移”工作的限制因子之一。以往各地虽找到了很多比较好的越冬途径,例如温泉越冬、田间复盖玻璃或塑料薄膜越冬、活动草扇复盖越冬 Rice Paddock (Azolla) is the province of the province and the effect of significant ways to increase fat. However, some winters in northern Zhejiang (such as the winter of 1962-1963) have temperatures approaching -10 ° C. Most of them, or all of them, are at risk of freezing from death if they are kept in wintering houses or wintering from the open air. Therefore, the over-wintering problem is one of the key issues for keeping a large area in a local area and one of the limiting factors for continuing the “southward migration to the north”. In the past, although we have found quite a lot of ways to winters in the past, such as hot spring overwintering, field covered glass or plastic film overwintering, active grass fan covering winter