Abstract
ABSTRACT The self-sufficiency ratio and national average yield of wheat are low in Japan. Reducing the yield gap and receiving the government subsidy for grain quality are vital strategies for profitability. Elucidating optimum nitrogen application scheme is awaited to attain both higher yield and appropriate grain protein content (GPC) for wheat cultivation in Japan. Such decision support can be realized by integrating field experimental knowledge to crop growth models, although they have scarcely been utilized for wheat production in Japan. Therefore, the purposes of this study were to apply a widely used crop growth model (APSIM) to wheat growth on an Andosol in the Kanto region in Japan by calibration and validation. Selected model parameters of APSIM-wheat for phenology, leaf growth, and grain formation were readjusted based on the phenology and growth data of soft and hard wheat cultivars. Then the model was validated by using similar variables obtained in an independent experiment. For the simulation of the optimum sowing for winter wheat in the Kanto area (November), the root mean square error for grain yield was 23 and 48 g m−2 for Ayahikari and Yumeshiho varieties, respectively, and that for GPC was 1.9 and 1.4%. Thus, the overall model performance was acceptable for optimum sowing. However, grain yield and dry matter production were significantly overestimated when the data of late sowing groups were included. Therefore, further model improvement was suggested to add an algorithm to reduce the number of emerged plants under cold temperature in late sowing conditions.
Highlights
Understanding the complicated interactions between crop, soil and climate is vital to make decisions on agro nomic practices including nitrogen fertilizer manage ment towards achieving higher yield and appropriate grain protein concentration for wheat in Japan. Japan is endowed with favourable wheatgrowing conditions with sufficient annual precipitation (840–2800 mm), the national average yield (4.1 t ha−1) is lower than that in other major wheat-producing coun tries in Europe, such as France, Germany, and the United Kingdom (7.4, 8.6, and 8.6 t ha−1, respectively)
The results of the calibration for both phenological and plant growth parameters are listed in Tables 3 and 4
After the calibration, simulated dry matter at flower ing, that at maturity, grain yield, Leaf area index (LAI) and grain protein content (GPC) were comparable to the observed values and were in the range of 787.1–1046, 778.9–1201, 324.2–608.6, 2.1–3.3 and 10–15.8 for Yumeshiho and 765–973, 764–1191, 318.8–636.3, 1.8–2.8, 10.5–15.3 for Ayahikari respec tively. (Supplementary Table 1)
Summary
Understanding the complicated interactions between crop, soil and climate is vital to make decisions on agro nomic practices including nitrogen fertilizer manage ment towards achieving higher yield and appropriate grain protein concentration for wheat in Japan. Japan is endowed with favourable wheatgrowing conditions with sufficient annual precipitation (840–2800 mm), the national average yield (4.1 t ha−1) is lower than that in other major wheat-producing coun tries in Europe, such as France, Germany, and the United Kingdom (7.4, 8.6, and 8.6 t ha−1, respectively). (Food and Agriculture Organization of the United Nations, 2014), wheat is the second most important cereal in Japan following rice. Wheat varieties in Japan are classified into two groups – hard wheat (used for bread) and soft wheat (used for Japanese noodle), depending on the grain quality (mainly protein content) (Nakano et al, 2008). The required grain protein content (GPC) for hard and soft wheat are 11.5–14% and 9.7–11.3%, respectively (Ministry of Agriculture, Forestry and Fisheries, Japan, MAFF, 2014). Wheat producers in Japan can obtain the highest quality bonus when GPC falls into these ranges. In other countries such as the United States the premium price for wheat is deter mined based on GPC (Olmos et al, 2003)
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