Different responses of preemergence and early seedling growth to planting depth between vegetable soybean and grain soybeans

Planting depth can cause nonuniform emergence and poor field stands. There have been no investigations to compare the planting depth on field emergence between vegetable soybean and grain soybean [Glycine max (L.) Merr.]. This study examined the effect of planting depth on preemergence and seedling emergence in growth chamber conditions using one vegetable soybean and one grain soybean cultivar. The hypocotyl and radicle length in the vegetable soybean were significantly longer than that of the grain soybean at emergence, while the hypocotyl and radicle diameter in the vegetable soybean were significantly larger than that of the grain soybean during emergence period irrespective of planting depth. The weight of hypocotyl + radicle in the vegetable soybean was significantly greater than that ofthe grain soybean during emergence period irrespective of planting depth and days after planting, but deeper planting depth reduced cotyledon weight in the vegetable soybean strongly at emergence. As planting depth increased from shallow (1-cm) to deep (5-cm), emergence declined. However, the grain soybean seed consistently emerged better than the vegetable soybean seed. Emergence of both the grain soybean seed and the vegetable soybean was > 65% until planting depth increased to 3-cm, while the vegetable soybean seed had the lowest emergence (< 30%) at the deepest (5-cm) level. The 3-cm planting depth had no effect on the emergence of both the grain soybean and the vegetable soybean. The vegetable soybean was more susceptible to deeper planting depth than the grain soybean.