Influence of Drainage Improvement on Soybean Dry Matter and Seed Production in Poorly Drained Fields in the Hokuriku Region of Japan

Abstract

We grew soybean using ridge-cultivation in a poorly drained field in the Hokuriku region of Japan for 3 years after drainage-improvement treatment. The soil moisture content of the plow layer in the improved plot was equal to or less than that in a non-treated control plot. Ponding on the plow pan during the rainy season was improved for 1–2 years after the treatment, but not in the third year. Plants grown in the treated field had more pre-flowering branch nodes per plant, heavier dry weight of top, larger leaf area index, higher nitrogen uptake during the seed filling mid-stage of growth and higher root activity after flowering than the control plants. The yield was increased by drainage-improvement treatment in the year of low yield, but not in the three-year average.