Impact of Spring Planting Date on Germination of Fall-harvested Soybean Seed.
Andrew Robinson1, Shawn Conley2, and Jeffrey Volenec1. (1) Purdue University-Agronomy Dept., Purdue University, 915 W State St., West Lafayette, IN 47907, (2) 915 West State St, Purdue University-Agronomy Dept., Purdue University, Department of Agronomy, West Lafayette, IN 47907-2054
Although planting soybean [Glycine max (L.) Merrill] earlier in the Upper Midwest has shown to increase yield, little information has been published on the impact this has on seed germination and vigor. Our objective was to evaluate the impact of planting date (PD) and maturity group (MG) on soybean seed quality. Our hypothesis was soybean planted in March and April will have decreased germination and vigor as compared to May and June planted soybean. Three cultivars differing in MG (2.6, 3.2, and 3.7) and six planting dates (planted in approximately two week intervals starting the last week in March) were seeded at West Lafayette, Indiana in 2006 and 2007. The experimental design was a randomized complete block split-plot design with main plots as PD and maturity groups as sub-plots. Soybean was planted with a no-till drill in 38-cm rows at 370,000 plants ha-1. Seed viability was assessed via warm germination and accelerated germination tests. Results from year one indicated that percent germination increased progressively for warm germination tests at each PD from 78% (in late March) to 96% (in early June). Percent germination varied notably by MG with 83% germination for MG 2.6, 88% germination in MG 3.2, and 92% germination in MG 3.7 when averaged across PD. Genotype by planting date interaction was significant. Germination of seeds from the MG 2.6 cultivar was lower when it was planted in early spring, while germination of seeds from the MG 3.7 cultivar was less affected by planting date. Our results indicated that percent germination was greatest for the 3.7 MG soybean and the best time to plant soybean for seed purposes was late May through early June.