Tillage systems impact early season growth and development; but do they also impact plant spacing uniformity? University of Nebraska research in 2001 investigated this along with the effect of crop rotation (continuous corn and corn-soybean).
Seed spacing may vary due to planter errors, poor planter maintenance, or seed germination problems. Average plant spacing and standard deviation of plant spacing are often used to determine plant spacing accuracy. Having only an average of plant to plant spacing is not a good measure of what is present in the field, because spacing between plants is not normally distributed (not uniform). The standard deviation is not a very good measurement either since it is based on squared deviations of the mean and is therefore influenced by a few very large spacings (skips or misses).
How critical is plant to plant spacing for corn? Past research has shown variable results, with some results showing that for every 1 inch in variation from the targeted spacing, yields were reduced 2.5 bushels per acre. Other researchers report even higher losses, while others report less. National yield contest winners often state that slow planter speeds improve plant spacing uniformity and are part of their formula for success.
