山形県庄内地域(グライ土壌)の地力窒素の無機化について

概要

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Soil N mineralization of paddy soils in Shonai district under field condition were investigated mainly by the kinetic method, and the parameters obtained were discussed. The results obtained are summarized as follows: 1) A double exponential model consisting of two components [N_<t_a>, t_b=A{1-exp(-k_a×t_a)}+B{1-exp(-k_b×t_b)}+C] was as follows: the first component is all the mineralizable organic N, where A is the potentially mineralizable N, k_a is the mineralization rate, and t_a is the time required for N mineralization, respectively, and the second component is denitrification or immobilization of labile mineralized organic N. 2) From middle growth stage to maturity stage, the amount of soil N absorbed by rice plant correlated to the amount of mineralized N derived from all the mineralizable organic N (r=0.799***). 3) More than 50% of all the mineralizable organic N was mineralized by the latter part of June. 4) Coefficient of variation of the amount of mineralized N within a given period of time correlated to the apparent activation energy (r=0.764***). Furthermore, the amounts of mineralized N correlated to the potentially mineralizable N (A) (r=0.631***).
1989-02-05