Tuesday, November 6, 2007
164-4

Cultivar, Planting Date, and Seeding Rate Effects on Soybean Growth and Yield.

Stephen Kyei-Boahen, International Institute of Tropical Agriculture - IITA, Av. Eduardo Mondlane NR 326, Nampula, Mozambique and Lingxiao Zhang, Mississippi State University, Delta Research and Extension Center, PO Box 41, Stoneville, MS 38776.

Cultivar selection, time of planting and the number of plants per unit area are important factors that influence soybean growth and yield variables. The objectives of this study were to evaluate the effects of planting date, seeding rate and their interactions on yield and yield components of indeterminate soybean cultivars. Three indeterminate early soybean cultivars were planted on clay loam soil at Stoneville, MS, on 30 March, 19 April, 9 May and 25 May 2005 using three seeding rates: 12, 18 and 24 seeds m-1 of row to obtain approximately 255,000, 385,000 and 515,000 plants ha-1, respectively. Seeding rate and planting date had significant effects on soybean yield and yield components. Generally, the interaction between planting date and seeding rate, and between planting date and cultivar was significant. However, no interaction occurred between cultivar and seeding rate suggesting that seeding rate affected the cultivars similarly. For the early planting date, higher seeding rate increased yield but the effect of seeding rate was generally not significant when seeding occurred after the first week in May. The yields for the late March and Mid April planting dates were higher than the May planting dates. The number of pods produced by individual plants was consistently higher for the 12 compared with the 24 seeds m-1 of row. The number of seeds per pod did not vary among seeding rates but differences in seed weight occurred when planted on 30 March. Seed weight also decreased consistently as planting date delayed due primarily to the relatively shortened seed filling duration when planting was delayed.