Abstract
These experiments were made to probe the effects of the composition of soil air on the growth of crops in their different stages of growth. Upland rice, soybean, sweet potato and maize were tested. The authors examined the effects of the decrease of the O2 concentration in soil air on the growth of crops in their early stage (from June 20 to July 10), in their middle growth stage (from July 10 to July 29), in their late growth stage (from July 29 to August 19), and in the ripening period of upland rice alone (from August 27 to October 7). In any crop, the check of dry matter production due to the decrease of O2 concentration in the soil air was found to be larger in its late growth stage when its growth was remarkable. However, when the rate of the increase of dry weight in the managing period in N gas injection treatment compared with that of standard treatment, the growth periods were different depending on the kinds of crops. The results according to the kinds of crops was as follows. (a) As to upland rice, its early stage of growth was largely affected by the decrease of O2 Concentration, and its growth in the managing period was liable to be hampered. Its ripening period was less affected than any other growth stage and the weight of grains was 98% of that of the standard treatment. (b) As to soybean, as the effects of treatment among its different growth stages was not so great, it was evident that the effects of O2 concentration was somewhat larger in later growth. (c) As to sweet potato, its late stage of growth was most largely affected by the decrease of O2 concentration and its growth was checked. Its early stage of growth was next to it, and its middle stage of growth was little affected. The effects of the composition of soil air on the weight of its tuberous roots was especially large. (d) As to maize, its late stage of growth was most largely affected by the decrease of O2 concentration, and its growth was checked. Its early stage of growth was next to it, and its middle stage of growth.
