2018 Volume 87 Issue 2 Pages 176-182
The Kumamoto Earthquake in 2016 caused severe roughness of paddy fields in Kumamoto-city, However, leveling of the soil surface was not performed before planting soybean seeds. Thus, it was anticipated that soybean plants grown in concave positions were exposed to wet injury. In this study, we examined the effect of the roughness of the soil surface on the growth and yield of soybean. The seed yield in the concave position was decreased 50% by the reduction in the number of pods m–2 compared with seed yield in the convex position. The reason for the reduction in yield was that soybean root in the concave position was damaged by wet injury, which depressed nodule activity and water uptake ability. Therefore, leveling of the soil surface should be performed for succeeding sustainable crop production in such fields. If leveling is not practical, planting seeds which were disinfected and regulated in moisture content should be used for reducing the damage by wet injury in the concave position. Furthermore, it might be effective for enhancing the drainage from the field to dig an open ditch in the concave position.
