Submitted to: Agronomy Journal
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 12/10/2007
Publication Date: 3/1/2008
Citation: Sharratt, B.S., Gesch, R.W. 2008. Emergence of polymer-coated corn and soybean influenced by tillage and sowing date. Agronomy Journal. 100:585-590. Interpretive Summary: Polymer-coated seed has been promoted as a technology that delays germination and allows crops to be sown earlier in the spring in the Northern US Corn Belt. Since soils are typically cold and wet in early spring, polymer-coated seed could potentially reside in the soil for a longer time without compromising seed viability. We found that germination and emergence of corn and soybean was delayed by sowing polymer-coated versus non-coated seed. This delay did not affect plant populations, except when sowing soybean very late in the spring which resulted in exposure of the emerging plant to lethal soil temperatures. Our data indicates that polymer-coated seed is a viable technology for delaying germination and emergence of seeds in the spring.
Technical Abstract: Early establishment of crops is vital for maximizing production in the northern US Corn Belt. No tillage often delays soil warming, thus sowing too early may compromise seed viability due to prolonged exposure to cold soil. Coating seed with a temperature-activated polymer may circumvent the adverse effects of sowing into cold soils. Tillage, sowing date, and seed-coat treatments were applied in a split-split plot experimental design near Morris, MN. Near-surface soil water content and temperature, seed germination, and seedling emergence were monitored in 2000, 2001, and 2002. Although tillage did not influence soil water content, soil temperatures were more than 0.5°C higher for conventional tillage than for no tillage. Germination of corn and soybean was delayed as a result of sowing polymer-coated versus non-coated seed; germination of polymer-coated corn seed was delayed by 6, 4, and 2 days while germination of polymer-coated soybean seed was delayed by 11, 10, and 9 days in successive years. This delay was also evidenced by polymer-coated seed requiring more thermal time to germinate and emerge than non-coated 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 two out of three years of this study. While the effect of sowing date on plant population was not consistent between years, soybean population was smaller for the polymer-coated seed treatment when planted in late spring. 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.