Effect of Row-Width and Planting Density on Podding and Yield Performance of Early Soybean Cultivar ‘Enrei’ with Reference to Raceme Order

Abstract

To elucidate the effect of planting patterns on yield performance of soybean, we cultivated early cv. ‘Enrei’ with 80 and 30 cm row-spacing, and 11.1 and 22.2 plants m^-2 in 2001 and 2002. The number of nodes on main stem, racemes with compound leaves and total number of nodes, were larger in dense planting than in normal planting in both years. The number of branches, nodes on branches, racemes with compound leaves, and total number of nodes per m² were larger in narrow-row planting than in wide-row planting. The length of main stem was longer in dense planting than in normal, and in wide-row planting than in narrow-row planting. The weight, diameter and cross section area of stem were longer(greater)in normal than in dense planting and in narrow-row than in wide-row planting. Seed yield was higher in 2001 than in 2002, in dense planting than in normal planting, and in narrow-row than in wide-row planting. The highest seed yield, 668g m^-2, was obtained in 2001 with dense and narrow-row planting. The yield was mainly determined by the pod number in 2001, and by both pod number and seed size in 2002. In dense planting, a large proportion of pods were occupied by those on the main stem and racemes with compound leaves, and in narrow-row planting, a large proportion of pods were occupied by those on branches and racemes with compound leaves. Seed yield was closely correlated with pod number on the racemes with compound leaves, especially in 2001. In narrow-row planting, the upper layer of canopy had a large leaf area but it had low light extinction coefficients, and the canopy exhibited good light intercepting characteristics. Although the solar radiation in canopy differed between the spaces on the furrows and ridges in wide-row planting, the radiation in canopy was uniform in narrow-row planting. The yield in narrow-row planting with dense planting was higher than that in wide-row planting. This is due to the reduction of competitions with neighbor plants resulting from the suppression of elongation growth and increased development of branches. It was also due to the increased development of the racemes with compound leaves and increased pod number resulting from the efficient use of solar radiation in the upper layer of the canopy. Improvement of lodging tolerance and establishment of weed control at earlier stage is needed for the narrow-row and dense planting of soybean.