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SEEDS

Emergence of Polymer-Coated Corn and Soybean Influenced by Tillage and Sowing Date

^a USDA-ARS, 213 LJ Smith Hall, Washington State Univ., Pullman, WA 99164
^b USDA-ARS, 803 Iowa Ave., Morris, MN 56267

^* Corresponding author (sharratt{at}wsu.edu).

No tillage often delays soil warming and drying, thus sowing too early in the spring may compromise seed viability due to prolonged exposure to cold and wet soil in the northern Corn Belt. Coating seed with a temperature-activated polymer may circumvent the adverse effects of exposing seeds to cold and wet soil. Germination and emergence of noncoated and polymer-coated corn (Zea mays L.) and soybean [Glycine max (L.) Merr.] seed as influenced by tillage and sowing date was examined near Morris, MN. Conventional and no tillage plots were split to accommodate early and late sowing-date treatments while sowing-date plots were split to accommodate seed coat treatments. Near-surface soil water content and temperature, seed germination, and seedling emergence were monitored in 2000, 2001, and 2002. Germination of corn and soybean was delayed by as much as 6 and 11 d, respectively, as a result of sowing polymer-coated vs. noncoated seed. This delay was also evidenced by polymer-coated seed requiring more thermal time (>200°C h for corn and >1000°C h for soybean) to germinate and emerge than noncoated seed. Tillage, sowing date, and seed coating had little influence on plant population of corn. Sowing date and seed coating, however, influenced plant population of soybean in 2 out of 3 yr of this study. We surmise that polymer-coated soybean seed produced a poorer stand as a result of exposure of the hypocotyl to lethal soil temperatures during emergence. This study suggests that temperature-activated polymer coatings delay germination and emergence of corn and soybean.

Abbreviations: T_b, base temperature • TDR, time domain reflectometry • TT, soil thermal time

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Received for publication May 9, 2007.