Japanese Journal of Soil Science and Plant Nutrition

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In the previous report, the writers pointed out that the climatic condition at transplanting has important meaning in respect to the growth processes of rice plants thereafter. In the case of the cool area, transplanting is made under rather cold condition, so it is difficult for seedlings to revive from damage by transplanting. In the case of the warm area, transplanting is made under arther hot condition, so rice plants can revive easliy from damage by transplanting and absorb their nutrients vigorusly at early stage of growth, but they suffer from shortage of nutrients at later stage of growth. For these reasons, characteristic transplanting techniques have been developed correspondingly in different localities. In the present report, these techniques were analyzed from the standpoint of nutrio-physiology. Using the seedlings which were cultured by standard methods of each locality, their chemical characters were studied. Density of transplanting in different localities was also compared. Following are the results obtained. Following are the results obtained. 1) In the case of cool area type, nitrogen level of seedlings is high (about 4% of dry matter), phosphorus and potassium level are also rather high and the carbon-nitrogen ratio is abut 10. These suggest that power of revival of seedlings after transplanting is strong. In the case of transplanting, number of hills per unit area and number of plants per hill are large. This high density of transplanting results to intensify the growth of early stage in comparison to the growth of later stage. 2) In the case of warm area, nitrogen level of seedlings is low (lower than 1%) and the carbon-nitrogen ratio is about 20. So, regenerating power of seedlings is very week. Number of hills per unit area and number of plants per hill are small. This low density of transplanting results to intensify the growth of later stage in relation to the growth of earlier stage. These nutrio-physiological characters of seedlings and transplanting density are favorable for the whole process of growth of rice plant in the respective area.

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The object of the present studies were to find method of paddy fertilization in fields damaged by flood. The studies are classfied into the following, 1) The establishment of experiment plots on paddy field. 2) Growth survey of rice plants. 3) Research on the farm-management of farmers whose field were damaged by flood. 4) Soil survey and physico-chemical analysis of paddy soil just after rice-harvest. The results obtained were as follows, 1) In the early growth at ages, root initiation was belated in flood-damaged fields, and accordingly, leaves were light green in colour. But the lodging was very frequent due to excess of nitrogen liberated thereafter. 2) The muds accumlated by flood were mostly fertile heavy clay or clay loam. At the accumlated layers from 5 to 10 inches nitrogenous fertilizers must not be used. When NH_4-N by ammonification are more than 10 mg per 100 g of air dried soil. 3) Effect on rice yield of phosphorus and potassium fertilizers was little. 4) If the amounts of NH_4-N by ammonification were less than 7〜8 mg per 100 g of soil, from 1 to 1.5 kans of ammonium sulfate must be applied as base-fertilizers. 5) At the accumlated layers from 2 to 3 inches when the amounts of NH_4-N are more than 10 mgs per 100 g of soil, 50% of normal dressings of nitrogenous fertilizers may be applied.

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The influence of percolating velocity of water stagnated in a paddy soil during a period of paddy planting, on the amount of NH_4 produced in or leached out from a cultivated surface layer was investigated. The greater the percolating velocity, in a certain range, the more the NH_4 was formed or leached out. We consider that there may be the most suitable percolating velocity for the best growth of paddy plants, at which the total amount of produced NH_4 is as enough as the concentration of NH_4 in a percolating water is always higher than a constant concentration caused by the increased percolation to a certain limit. In reference to the above consideration, the concentration of NH_4 seems not to be less than 10 ppm, otherwise the tellering of the plant may be injured. It may be said that a best percolating velocity may be such that water decreases its depth in the range between 2.5 cm and 3.0 cm a day. From the amount of NH_4 leached out from a surface layer to the subsoil and the concentration of NH_4 in the percolating water, we can realize that the significance of permeability or the condition of porosity of soils for the utilization of nutrient in a percolating water by the paddy roots.

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Wheat seedlings were grown with the technique similar to NEUBAUER but under artificially controlled light and temprature. To each beaker was added a quuantity of labelled fused magnesium phosphate, quartz sand and increasing quantities of natural soil differing in the exchange acidity and phosphate fixation. The results are show in Table 1,2 and Fig. 1. Similar experiments were conducted with artficially base unsaturated soils, the bases being washed out by 0.1 N HCl. The results are shown in Table 3,4 (a) (b) and Fig. 2. It can be concluded that the hydrogen ion of soil colloids which can enter into exchange reaction in KCl solution is of primary importance positive contributing to the "Contact solutional uptake" of phosphoric acid from fused magnesium phosphate, a kind of water hardly soluble but 2% citric acid soluble phosphatic fertilizers. Of second importance as negative factor was the power of phosphate fixation of the pertinent soils. As shown in Table 5 and 6,this mecanism was also proved to hold good over the whole growth period of millet in a pot experiment. The results might well suggest a new method of dressing for such kinds of phosphatic fertilizer i.e. if the soil is acid, to preliminarily mix the fertilizer with some dose of soil, as contrasted to the normal recommendation for superphosphate of lime as far as not mix it with soil.

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