Recommendation of nitrogen fertilizer application for winter wheat [Triticum aestivum] based on using diagnosis of soil nitrate-N in early spring in Hokkaido [Japan]
2008
Sato, K.(Hokkaido. Tokachi Agricultural Experiment Station, Memuro (Japan)) | Nakatsu, S. | Miki, N. | Nakamura, R. | Fueki, N. | Shiga, H.
Application levels of Nitrogen (N) fertilizer has a great influence on grain yields and grain protein content of winter wheat ( Triticum aestivum L.). A higher rate of N fertilizer application in recent years has caused damage during lodging and excess protein content in wheat grain. In order to determine the adequate rate of N topdressing in early spring, a diagnosis method of measuring soil mineral N was examined. Soil mineral N accumulated more in the Abashiri district than the Tokachi district, and this difference could probably have been influenced by rainfall and soil freezing periods. In addition, rainfall also greatly affected the vertical distribution of soil mineral N. NH4-N of soil mineral N was at the same low level in almost every field in both, the Tokachi and Abashiri districts. On the other hand, NO3-N varied widely among fields. According to a field experiment using sup(15)N, it was apparent that winter wheat mainly used NO3-N available in the 0-80 cm depth layer. However, NO3-N in the 0-60 cm layer significantly correlated (p0.01) with that in the 0-80 cm layer. Therefore, NO3-N in the 0-60 cm layer was measured for soil diagnosis. The total amount of NO3-N available in the 0-60 cm layer in early spring and the rate of N fertilizer topdressing after early spring showed a significant correlation with N uptake by winter wheat. High correlation coefficients between grain yields and N uptake in winter wheat were observed in common levels of grain protein content (100 mg/g). Consequently, setting a targeted grain yield can be the basis for calculating the required N uptake, and measuring soil NO3-N enables us to recommend an optimum rate of N topdressing for winter wheat to obtain a targeted grain yield.
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