Planting Depth and Tillage Interactions on Corn Emergence

Surface crop residues lower soil temperatures delaying emergence of corn (Zea mays L.) under no-till tillage systems in the northern Corn Belt. This study evaluates the use of planting depth as a management tool to overcome the disadvantages of cool temperature under residue covered soils. Growth chamber experiments evaluated the effects of planting depths, ranges of soil temperatures, and soil matric potentials on corn emergence. The seeding medium was aggregates of Webster clay loam (fine-loamy, mixed, mesic Typic Haplaquolls). Deep planting (75 mm) delayed emergence from 2.8 to 18 d as the soil temperatures decreased from ranges of 15 to 25 °C and 5 to 15 ° C. Seed zone growing degree days (GDD) needed to achieve 75% emergence increased with an increase in planting depth and a decrease in soil matric potential. Relationships of corn emergence vs. seed zone GDD needed to achieve 75% corn emergence at various planting depths were tested in the field for three planting depths, three tillage and three surface residue conditions during 1984 and 1985. Predicted time to 75% corn emergence was within 2 d of the field-measured values for three planting depths, and seven tillage and surface residue conditions, over two seasons. Simulation studies were conducted to predict the effects of tillage, planting depth, and planting date on the probability of obtaining 75% corn emergence within 14 d of planting. Input data for simulation studies included 10 to 20 yr of daily maximum and minimum air temperatures from Morris, MN and Lexington, KY. Tillage treatments included moldboard plow, no surface residue, and no-till surface residues. Reducing the planting depth from 50 to 25 mm advanced the planting date from 2 d to several weeks, depending on the weather, soil matric potential, and tillage-surface residue conditions. When soil water is nonlimiting, the effect of cooler temperatures on corn emergence under a no-till tillage system (with surface residues) can be compensated for by reducing the planting depth by 25 mm or less from that of average planting depth under conventional tillage systems. Contribution from the Dep. of Soil Science and the Minnesota Agric. Exp. Stn., Univ. of Minnesota. Paper no. 15637, Science Journal Series. Laboratory and field research were completed when the senior author was with the Soil and Water Management Res. Unit, USDA-ARS, St. Paul, MN.