Postemergence Wheel‐Traffic Effects on Plant Population and Yield in Solid‐Seeded Soybean

Some soybean [ Glycine max (L.) Merr.] producers have been hesitant to use postemergence herbicides in solid‐seeded soybean for fear of yield loss from wheel‐traffic damage to plants. The objective of this study was to quantify the loss in plant population and seed yield due to postemergence tractor‐wheel traffic at various times during vegetative and early reproductive growth. A field study was conducted in 1985 and 1986 near West Lafayette, IN, on a Chalmers silt loam (fine, loamy mixed mesic Typic Argiaquoll). A split‐plot design was used with the factorial combinations of nine wheel‐traffic treatments and two cultivars, ‘Asgrow 3127’ and ‘Hobbit’, as whole‐unit treatments arranged in a randomized complete block design with four replications, and three soybean row types, designated center, wheel‐track, and adjacent as subunit treatments. The nine wheel‐traffic treatments consisted of no wheel traffic, single passes at 2, 3, 4, 5, and 6 wk, and double passes at 2 and 4, 3 and 5, and 4 and 6 wk after planting. Plant population in wheel‐track rows decreased linearly as number of passes increased and as wheel traffic was delayed. Seed yield in wheel‐track rows decreased linearly as number of passes increased and quadratically as wheel traffic was delayed. Rows adjacent to wheel‐track rows partially compensated for the yield loss in wheel‐track rows. When yield loss was calculated on a total field basis, the loss due to postemergence wheel traffic was no more than 1.0 bu/acre. A soybean producer should not hesitate to drive on solid‐seeded soybean in order to apply postemergence materials.