Studies on the Growing Process of Soybean Plant with Stable Manure and Three Nutrient Elements in the Virgin Volcanic Ash Soil.

Abstract

In order to make clear the effect of stable manure and three nutrient elements (nitrogen, phosphorus, potassium) on the growth of soybean plant (Norin No. 4), the growing process was examined for three years rotation system of soybean-potatoes-corn in the virgin volcanic ash soil. The results obtained are as follows: 1) In general, the higher yields were obtained in 2nd and 3rd year than 1st year. 2) Nitrogen deficient plot : 1st year, the nitrogen content of each organ was almost similar to NPK plots in the later stage, but a little lower in the early stage. And also there was not so difference in plant characters and yields. In 2nd and 3rd year, the growth type was almost same as in NPK plots. Phosphorus deficient plot : Throughout three years, the plants had especially higher nitrogen content and lower phosphorus in each organ than the plants in NPK plots. The growth was almost same as the plants in the non-fertilized plots, and each of the plant character has changed to the worse remarkably. Potassium deficient plot : In 1st year, the potassium content in each organ was rather lower and the nitrogen content rather higher compared with NPK plots, but growth and yields were fairly same as in the NPK plots. In 2nd year, the depression of potassium content in each organ was remarkable but that of the yields is smaller. In 3rd year, the response to potassium deficiency was observed remarkably on the plants and the potassium content became furthermore reduced. Some yellowish-white leaves were observed and yields were decreased. 3) The effects of the stable manure were remarkable on the plant growth since 1st year, which resulted in the increase of the phosphorus and potassium contents in the plants, and the yields became higher. In 2nd and 3rd year such tendencies appeared more remarkable, especially the growth became too vigorous and branches were broken in 3rd year. 4) After all, possitive correlations between the yields (20-350 kg/10a) and the leaf length of main stem, maximum LAI, the phosphorus content in leaves, dry matter weight per area and node numbers per area were observed. On the other hand, N/P ratio in leaves had negative correlation with the yields. The leading element influencing these characters is phosphorus from 1st year, and with the lapse of time, the potassium is to be added as an important element in these volcanic ash soil.