Abstract
The fertilizer ratio, which is understand as the ratio existing between the percentage of nitrogen, phosphorus and potash in a fertilizer is a most important factor in manuring practice, as it determines the efficiency of the fertilizer used. The growth of plant being affected by the condition of soil and climate, the fertilizer ratio suitable for a plant is not the same everywhere the plant is cultivated. The determining factors of this ratio of a fertilizer seem, therefore, to be the following : 1) Kind of crop. 2) Climatic conditions. 3) Soil character. It is, then, desirable, if possible, to find a fundamental relation of these factors to the fertilizer ratio in the form of an equation, as we have not heretofore known anything about the deduction of such an equation. As the first step of an investigation the writers intended to study the relation of temperature to that ratio in the fertilizer given to wheat plants. Calculating out the ratios of P_2O_5 and K_2O to N respectively from the amounts of the ingredients in a manure generally used by farmers, in 191 districts in Japan from north to south, examination was made of their relation to the annual mean temperature and also to the mean temperature of the growth period in each district. The following equation in the case of P_2O_5 to N was found to denote clearly the relation existing between the ratio and temperature. [numerical formula] [numerical formula] where T_1 : mean annual temperature T_2 : mean temperature of growth period This indicates that the ratio of P_2O_5 to N is high at the districts of low temperature, decreasing linearly as the temperature increases regardless of the annual temperature or that of the growth period. In the case of K_2O to N, the following equation was obtained : [numerical formula] [numerical formula] This represents also that the same tendency of temperature relation to the ratio as in the case of P_2O_5 to N can be seen even in the case of K_2O to N.
