1998 Volume 69 Issue 6 Pages 590-597
The applicability of a kinetic method for estimation of the progress of nitrogen (N) mineralization in soil was examined in Tokachi District, Hokkaido, which had a lower amount of rainfall than other districts in Japan. Also, the rates of N absorption of spring wheat (Triticurn aestivum L. cv. Haruyutaka) plant were compared with the rates of N mineralization in soils to evaluate the efficiency of mineralized N for plant absorption. The estimated progress of N mineralization by the zero-order kinetic method nearly agreed with the change in the sum of spring wheat plant N and inorganic N in surface (0-30 cm) soils in plots without N fertilizer in 1990 and 1991. The facts suggested that the kinetic method was effective to estimate the N absorption of spring wheat plant in a district with less rainfall like Tokachi. The amount of N absorbed by the spring wheat plants (y) in plots without N fertilizer in 1991 was closely related to the days transformed at standard temperature (x) proposed by Konno and Sugihara (1986). The relationships were consisting of an exponential equation for the early growth stage and a linear one (y=ax+b) for the middle and late growth stages. As the rate of N absorption of spring wheat plant at standard temperature, value "a" could be used. The rates of N absorption of spring wheat plants were 82-98% of the rates of N mineralization in soil layers with the accumulation of soil organic matter.
