In a series of pots of following dimentions, with following depthes of soil, fertilizer and silica supply, rice plants were raised, and the effects of silica were studied. Dimensions of pots, depths and weights of soil, and fertilizer supplied.[table]The results can be summarized as follows; 1. The yields of grain and straw increased with soil depth. 2. The ratio of fertility, the ratio of the numbers of perfect grains to those of the total grains, and the silica contents in the plants increased and the brown spots on the surface of hulld grains decreased with soil depth. 3. The yields of grain and straw, both from the silica supplied and unsupplied pots, inercased with soil depth, but for the same depth of soil the yield of grains from the former was greater than that from the latter. 4. As the result of silica supply, the ratio of fertility, the ratio of the numbers of perfect grains to those of the total grains, and the silica contents in the plants, greatly increased, and the brown spots on the surface of hulld grains decreased. 5. Above effects of silica on the growth of rice plants decreased with soil depth. The yield and its increment due to silica supply were as follows. Effect of silica supply on the crop yield of rice plant.[table]