By Dennis Egli
It’s that time of the year – producers are done tinkering with their planters and are ready to hit the field, hoping to get that perfect ‘picket fence’ stand where every plant is equally spaced and all the seedings emerge at the same time. Producers are also planting earlier these days which means that they are probably planting into colder soils.
Is there a conflict between planting early and uniform stands? Does planting early result in less uniform seedling emergence?
We investigated the uniformity of emergence in a series of greenhouse and growth chamber experiments with corn and soybean. We used 19 corn seed lots (9 were treated with fungicides, 7 with insecticides and 3 were un-treated) and 5 soybean seed lots (all untreated). Germination of the corn seed lots were all, except one, greater than 95%. All soybean seed lots germinated above 90%. We planted the seeds by hand and carefully controlled soil water levels to create near ideal conditions for emergence. We counted emerged seedlings every 6 to 8 hours until emergence was complete to evaluate uniformity. Temperatures in the greenhouse and growth chambers were adjusted to create variation in the time from planting to seedling emergence.
When corn seeds were planted 1.5 inches deep in warm soil (~75F), the first seed lots emerged 96 hours (4 days) after planting and emergence was very uniform (most of the seedlings emerged in a 24-hour window). Lowering the soil temperature (~60F) delayed emergence with some seed lots not emerging until 288 hours (12 days) after planting. The window when most seeds emerged increased to 96 hours (4 days). Reducing the temperature delayed emergence of corn seedlings and significantly decreased the uniformity of emergence.
Source : uky.edu