Comparison between both rates of nitrogen mineralization in soils and nitrogen absorption of spring wheat plant using the days transformed at standard temperature

摘要

The applicability of a kinetic method for estimation of N mineralization in soil was examined in Tokachi District, Hokkaido, which had less rainfall than other districts in Japan. The rates of N absorption of spring wheat cv. Haruyutaka were compared with the rates of N mineralization in soils to evaluate the efficiency of mineralized N for plant absorption. The estimated N mineralization by the zero-order kinetic method nearly agreed with the change in the sum of spring wheat plant N and inorganicN in surface (0-30 cm) soils in plots without N fertilizer in 1990 and 1991. The kinetic method was effective in estimating the N absorption of spring wheat in a low rainfall district. The amount of N absorbed by the spring wheat (y) in plots without Nfertilizer in 1991 was closely related to the days transformed at standard temperature (x) proposed by Konno and Sugihara (1986). The relationships consisted 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 was at a standard temperature, the 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.