Adoption of no-tillage in the northern Corn Belt has lagged behind other regions because of slow warming
and drying of soils early in the spring coupled with a short growing season. Cold, wet soil can lead to
seed damage resulting in poor stand establishment. Because of slow warming and drying, no-tilled soils
are typically sown later than conventionally tilled systems thus often requiring the use of early maturing
crop cultivars. Temperature-activated polymer seed coatings might allow soybean [Glycine max (L.)
Merr.] to be sown earlier than normal under no-tillage while protecting seed against damage caused
by cold, wet soil and perhaps allow the use of later maturing cultivars. These ideas were tested during
2005 and 2006 in west central MN on a Barnes loam no-tilled soil previously cropped in corn (Zea
mays L.). Polymer-coated seed of a maturity group (MG) 0 and I soybean were sown as early as possible
(early- to mid-April) and at an average recommended time (mid-May) for the study site. Only in 2005 did
the polymer coating significantly increase emergence (p < 0.0001), where maximum emergence of early
sown polymer-coated seed of the MG 0 and I cultivars was 51 and 35% greater than their uncoated counterparts.
Conversely, for the average sowing date in 2006, under unusually dry conditions, the polymer
coating slowed seedling emergence and reduced maximum emergence, although yield was not affected.
Laboratory incubations confirmed that the germination delay of soybean caused by the polymer-coating
increased by decreasing initial osmotic moisture potentials. The MG I soybean out yielded the earlier
maturing cultivar in both years, but sowing date did not have a significant effect either year. Results indicate
that temperature-activated polymer-coated seed may reduce the risk of poor stand establishment
in no-tilled soil in instances where low soil temperatures cause seed to remain in the soil for an extended
time before emerging.
Adoption of no-tillage in the northern Corn Belt has lagged behind other regions because of slow warmingand drying of soils early in the spring coupled with a short growing season. Cold, wet soil can lead toseed damage resulting in poor stand establishment. Because of slow warming and drying, no-tilled soilsare typically sown later than conventionally tilled systems thus often requiring the use of early maturingcrop cultivars. Temperature-activated polymer seed coatings might allow soybean [Glycine max (L.)Merr.] to be sown earlier than normal under no-tillage while protecting seed against damage causedby cold, wet soil and perhaps allow the use of later maturing cultivars. These ideas were tested during2005 and 2006 in west central MN on a Barnes loam no-tilled soil previously cropped in corn (Zeamays L.). Polymer-coated seed of a maturity group (MG) 0 and I soybean were sown as early as possible(early- to mid-April) and at an average recommended time (mid-May) for the study site. Only in 2005 didthe polymer coating significantly increase emergence (p < 0.0001), where maximum emergence of earlysown polymer-coated seed of the MG 0 and I cultivars was 51 and 35% greater than their uncoated counterparts.Conversely, for the average sowing date in 2006, under unusually dry conditions, the polymercoating slowed seedling emergence and reduced maximum emergence, although yield was not affected.Laboratory incubations confirmed that the germination delay of soybean caused by the polymer-coating
increased by decreasing initial osmotic moisture potentials. The MG I soybean out yielded the earlier
maturing cultivar in both years, but sowing date did not have a significant effect either year. Results indicate
that temperature-activated polymer-coated seed may reduce the risk of poor stand establishment
in no-tilled soil in instances where low soil temperatures cause seed to remain in the soil for an extended
time before emerging.
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