Effects of Mixed Coating of Oxygen Generating Chemicals and Several Kinds of clay on Seedling Emergence in Direct Sowing of Paddy Rice

The effects of mixed coating of seed with oxygen-generating chemicals containing 16% calcium peroxide (CaO2) and clay on the seedling emergence of rice (Oryza sativa L.) from flooded soil were examined. The emergence of seedlings was improved by coating seeds with oxygen-generating chemicals and clay mixed coating compared with only a single coating of oxygen-generating chemicals. However, the effect of mixed coating was different with clay. Diatomaceous earth 1 and Japanese acid clay 1 of the montmorillonite group showed a larger effect on emergence than clay of the kaolinite group. From the observation of flooded soil mixed with 0.3% methylen b1ue, where the oxidized area becomes blue, the size of the oxidized area around the seed was found to be larger for the mixed coating than for the single coating. The size was related to the collapse of the mixed coating meterials in water. The mixed coating of the oxygen-generating chemicals and diatomaceous earth 1 or Japanese acid clay 1 showed a large effect on the maintenance of the oxidized area around the seed. It was found that the intensity of staining of the oxidized area around the seed with methylene blue was more closely associated with emergence than was the size of the oxidized area. In particular, diatomaceous earth 1 showed a large effect on the inhibition of the soil reduction around the seed. Additionally, a small amount (from 25 to 50%) of diatomaceous earth 1 showed a large effect on the emergence of seedlings.