Damages to Rice Crops Caused by a Wind Storm, with Special Reference to a Typhoon that Visited Kansai District, Japan. Part II. External Characteristics of the Damage to Plant and Grain

[摘要] The wind damage to plants and the grains they bore varied in extent with certain ecological factors, of which the important ones were distance of the locality from the sea coast, earliness in the heading of the plant, the fertilizers used, and the existence of drought damage at the same time. (1) In localities about 12 kilometers from the coast, only slight damage was done to the rice grains, brown discolored spots appearing on their surfaces (Fig. 3). About 8 kilometers distant, the damage slightly increased, about 4 kilometers away it became more conspicuous, while in fields only 1 kilometer from the coast, none of the grains completely developed. In fields continuous to the sea some of the plants were totally ruined by the brine (Fig. 4 :1), while in others that barely survived the panicles were very poor and mostly empty of grain, or their development was abnormal, the dormant buds on the nodes following the terminal ones growing into small axillary panicles, consequently forming together with the primary panicles at the terminals the so-calles "two-stepped" panicles (Figs. 4 : 2 & 3). There was also delayed tillering without maturation. These gradations in the extent of damage suffered seem to accord with the amount of brine held by the wind, and also to be due in part to the velocity of the wind. (2) The time of heading of the plant was another imporatnt factor that determined the severity of the damage. Grain damage was most severe on panicles that were hit by the storm from three to five days after heading, while on panicles that had headed earlire or later, the damage was decidedly less intense. The heading time of the plants differed with the variety, the time it was transplanted, the amount of fertilizer used, etc. and these factors caused differences in the damage suffered (Fig 5). (3) As to the effect of the fertilizer used, a notable fact is that the damage was markedly slighter in the case of plants grown in fields that had been continuously supplied with compost, when compared with those grown with such fertilizers as green manure, soybean oil cake and ammonium sulphate (Fig. 6). The writer concludes from this, that compost, owing partly to its own silica content and partly to the effect of free CO2 decomposed from it, which transforms the insoluble silica compounds in the soil into soluble and available forms, thus naturally enriching the plant body in its silica components, accelerating especially the silicification of the epidermal tissues of the plant, resulting in healthy growth and in consequent resistance to damage. (4) The damage done by violent wind on rice grains that were suffering from drought during their development were strikinglt severe (Fig. 7). In some parts of the district, the soil, which was of diluvial origin, was poor in both humus and in silica, with the result that the plant and the grain grown in such places suffered considerably from water shortage and silica deficiency, so that the damage was consquently most severe.

[学科分类] 农业科学（综合）