PURPOSE: To effectively apply a phosphoric acid by using a coated phosphate fertilizer and contact applying this fertilizer to crop roots in soil having high fixation power of the phosphoric acid, such as volcanic ash soil.
CONSTITUTION: Release of nourishment meeting the growth stage of the objective crops is important to improve absorption of the phosphoric acid and to enhance the rate of utilization. Such release is attained by combining a fertilizer adjustable in the effect of fertilization of the phosphoric acid and the fertilization position meeting the kinds of crops when the shortage of the transfer distance of the applied phosphoric acid and the highness of the fixation power like that of the volcanic ash soil are taken into consideration. An ammonium primary phosphate and ammonium secondary phosphate having a high content of components are preferable as the coated phosphate fertilizers 1. The coating materials may be thermosetting and thermoplastic resins, etc., and the resins which permit control of the elution rate of the nourishment in compliance with the fertilizer absorption characteristics of the crops suffice. As to fertilization positions, the contact fertilization to the root areas is basically effective when the substantial absence of the transfer of the phosphoric acid applied in the soil is taken into consideration. The elongation form, etc., of the roots by differences in crop kinds are taken into consideration.
YAMADA NORIAKI
YAMAMOTO KAZUO
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