Abstract
The quantitative distributions of soil organic matter, free iron oxide, and value of Eh in the plow layer at lotus field, which influence the occurrence of epidermic blackening and browning of lotus rhizome, were measured. Then we considered the effects of hydraulic and soil conditions on Eh, and proposed the conditions of lotus field required for land consolidation works to prevent epidermic blackening and browning.
The results are as follows:
1) The amount of soil organic matter was in proportion to the content of clay, whether organic fertilizer had applied or not.
2) The clayey soil contained a lot of free iron oxide, where accumulated in the rhizosphere soil, especially in the fields which a large amount of organic fertilizer was applied.
3) Eh increased in winter at the sides of the drainage canal or paddy field with no ponding water.
4) The lager quantity of percolation at a side of the field in winter there was, the higher Eh became.
5) Therefore, it is required to restrain percolation.
