Final soil manipulation before seed germination occurs during the planting operation. Contact force of depth-gauge wheels adjacent to the seed opener potentially alters the environment for corn seed germination and early plant growth. A field experiment was conducted measuring seed spacing, spacing variability, seed depth, emergence rate, plant dry matter, final stand, crop growth stage, and extended leaf height with different soil contact loads (light, 18 to 50 kg (40 to 110 lb); medium, 50 to 91 kg (110 to 200 lb); and heavy, over 91 kg (200 lb)) and a range of three soil moistures (dry, moist, wet). A treatment with randomly variable contact load similar to that of a conventional planter (control) was also included.
Emergence rate of corn plants was affected by load level and soil moisture conditions. With moist soil or in wet conditions, corn emerged more rapidly with a low load. In dry soil conditions, corn emerged more rapidly with a heavy load. Corn planted in the control treatment did not emerge as rapidly as the optimal loading for a given soil condition. Even though planter depth settings were set at the same position, seeds were planted deeper (8 to 13 mm (0.3 to 0.5 in.)) when load was heavier on depth-gauging wheels. Average seed spacing, standard deviation of seed spacing, final stand, growth stage, and extended leaf height were not statistically different across load levels. Plant dry matter weight was slightly increased at the V3 growth stage with low load levels in moist soils, but only at a reduced 85% confidence level.
Available at: http://works.bepress.com/mark_hanna/213/