The fate of fertilizer nitrogen applied to the paddy field and its absorption by rice plant part 6 influence of a thermal factor on the soil ammonium nitrogen and the absorption of nitrogen by the rice plant
Takahashi, J.; Wada, G.; Shoji, S.
Japanese Journal of Crop Science 45(2): 213-219
The absorption of N by rice plants was closely related to the accumulated effective thermal index (AETI). The amount of N per unit area absorbed by the plants (y) grown in the field was closely related to the AETI, consisting of an exponential equation (y = cdx) for the early growth stage and a linear one (y = ax + b) [x is the integrated effective temperature index] for the middle and late growth stages. The crossing point of these equations was the AETI of about 400. Similar equations, excepting the b parameter were obtained for both low and high dosages of basal N. The crossing point of these equations was varied due to cultural conditions, especially plant density and fertilizer placement. Soil NH4-N decreased exponentially after transplanting. Almost all of the N disappeared at the AETI of about 400, or at the beginning of ear primodia formation. The rate of N absorption of the rice plants was the limiting factor in the exponential part. The rate of supply of soil NH4-N, or the rate of mineralization of soil organic N was assumed to be the limiting factor in the linear part.