Seed Vigor, Soilborne Pathogens, Preemergent Growth, and Soybean Seedling Emergence

Abstract

Emergence of soybean [Glycine max (L.) Merr.] seedlings in the field is frequently less than predicted by standard germination, but the causes of this emergence failure are not well understood. This study explored the influence of soil pathogens and seed vigor on soybean seedling preemergent growth and emergence. Seed from six seedlots, representing a range in seed vigor, were planted as pregerminated and as dry seed into sterile and pathogen‐infested soil maintained at a constant soil water potential (−0.005 MPa). Final emergence (FE) and emergence rates from two planting depths (25 and 60 mm) were recorded under ambient greenhouse conditions. Once the FE stage had been reached, nonemerged seedlings were exhumed, and classified as stunted, abnormal, or dead. The FE of the high‐ and medium‐vigor seedlots was always higher than the low‐vigor seedlots, and the advantage was greatest under stressful conditions (deep planting, nonsterile soil). The FE was always lower in nonsterile than sterile soil. Seedlings emerged more slowly from deep plantings and when pathogens were present, and FE decreased as emergence was delayed in nonsterile soil. This relationship became more pronounced with low vigor seed. Planting pregerminated seeds always resulted in higher FE than dry seeds, but it did not eliminate emergence failure. Abnormal seedlings accounted for most of the emergence failure in sterile soil, but the lack of germination or of growth immediately after germination was also important in nonsterile soil. Lack of germination alone therefore does not account for lack of emergence; postgerminative, preemergent growth may be more important.

Soybean Response to Plant Population at Early and Late Planting Dates in the Mid‐South

“…The higher seeding rates in current recommendations provide protection against low seedling emergence caused by poor seed quality and/or stress after planting, factors that could reduce yield if seeding rates are lower. The use of high‐vigor seed could reduce this risk (Egli and TeKrony, 1995; Egli and TeKrony, 1996; Hamman et al, 2002) when seeding rates are lowered to reduce production costs. Field emergence averaged 70% for plantings in May, June, and July in experiments that included 272 seed lots of commercial cultivars over 10 yr (Egli and TeKrony, 1996).…”

Soybean Seed Yield Response to Planting Date and Seeding Rate in the Upper Midwest

“…Growers have avoided planting in late April due to the perceived risks of cold, wet soil, and exposure to seedling diseases, which in certain years can reduce plant stands, seedling health (Hamman et al, 2002), and yield (Wrather et al, 2003). Planting into cool wet soil delays emergence (Andales et al, 2000), may increase imbibitional injury (Bramlage et al, 1979; Helms et al, 1996), and exposure to late spring frost (Meyer and Badaruddin, 2001).…”

Arbuscular Mycorrhizal Colonization Response to Three Seed‐Applied Fungicides

“…E arly planting of soybean has become more frequent in the upper Midwest since it has been shown to significantly increase yields (Oplinger and Philbrook, 1992; Pedersen and Lauer, 2003). Conversely though, early soybean planting exposes seed to cooler and more saturated soils, leading to slow germination and development (Hatfield and Egli, 1974), thus extending the time that seeds are exposed to pathogens that cause seed root and damping off (Hamman et al, 2002; Thomas et al, 1975).…”