Abstract

Winter flooding of paddy rice production is characterized by flooding of paddy fields during the winter fallow season. It has attracted attention in terms of its ecological function, supporting the biodiversity of paddy field ecosystems. Therefore, recent winter flooding in Japan has been conducted by organic farming. However, it is not well documented how organic farming with winter flooding affect the productivity of rice. We conducted field experiments to examine changes in rice yield in organic farming with winter flooding compared with those in conventional and organic farming over the period of 5 and 9 years. The yields in organic farming with winter flooding were lower than those in conventional farming but were almost the same as those in organic farming. We found a trend that shows the relative yield of organic farming with winter flooding compared to that of conventional farming increased during the first several years after the conversion from conventional farming to organic farming with winter flooding, but that it decreased after several years. This trend may be caused by the flourishing of weeds during continuous organic farming with winter flooding. Therefore, we tested four weed control methods: rice bran application, mechanical weeding, repeated puddling, and side-row fertilizer application. Although each method suppressed weeds to certain extents, some combinations of different weeding methods more effectively suppressed weed growth, thereby resulting in enhanced rice yields. We found a trend in rice yield and a possibility of combining several weed control methods in organic farming with winter flooding.

摘要

水稻生产的冬季洪灾的特点是冬季休耕季节水田泛滥。它的生态功能吸引了人们的注意，支持了稻田生态系统的生物多样性。因此，日本最近的冬季洪水是通过有机农业进行的。但是，尚无充分文献证明冬季洪水下的有机农业如何影响水稻的生产力。我们进行了田间试验，以调查在5年和9年的时间里，冬季洪水与常规和有机农业相比，有机农业的水稻产量变化。冬季泛滥的有机农业的产量低于常规农业，但几乎与有机农业相同。我们发现了一种趋势，表明在从常规农业转换为带冬季洪水的有机农业后的最初几年中，冬季灌溉与常规农业相比的有机农业的相对产量有所增加，但几年后却有所下降。这种趋势可能是由于在连续的有机耕作和冬季洪水期间杂草的繁盛引起的。因此，我们测试了四种杂草控制方法：米糠施用，机械除草，反复水浸和侧排施肥。尽管每种方法都能在一定程度上抑制杂草，但不同除草方法的某些组合可以更有效地抑制杂草的生长，从而提高水稻产量。我们发现水稻产量有趋势，并且有可能将有机农业中的几种杂草控制方法与冬季洪水相结合。