To elucidate the trend of the recent soybean production in the upland field converted from the paddy field of Hokkaido, we performed the field study and questionnaire survey at Shinsinotsu, and Shibetsu-Kenbuchi region in Hokkaido. Recent soybean yield in Hokkaido over the past couple of decades (1994 – 2013) did not increase. In the study regions, Shinsinotsu, and Shibetsu-Kenbuchi regions, yield of soybean decreased over the past couple of decades. Especially, the yield of soybean in Shinshinotsu decreased considerably. The “yield reduction fields” and the “yield maintenance fields” of soybean were responded by the agricultural producers via the regional farming organization before the field study and questionnaire survey. Following the results of questionnaire survey, it was suggested that pest and weed damages might be caused as the problems in soybean fields. The soybean yield is lower in the “yield reduction fields” than in the “yield maintenance fields” obtained by the response of the agricultural producers. The number of plant, 100-seed weight and node number were also lower in in the “yield reduction fields” than in the “yield maintenance fields”. Soil pH and exchangeable-K were positively related to the yield of soybean. Also, the planting times of soybean and wheat over the past 5 years related to soil pH and soil exchangeable-K and the planting times of wheat over the past 5 years related to soil exchangeable-K.
北海道道央地域の水田転換畑における大豆生産性と 栽培管理および土壌理化学性の実態
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