PLANTING SPEED EFFECTS ON STAND ESTABLISHMENT AND GRAIN-YIELD OF CORN

Planting speed can affect a planter's ability to uniformly singulate and deliver seed to the seed furrow. A replicated on-farm strip trial was conducted in 1993 on 22 farms in three states to evaluate the effect of planting speed (4, 5, 6, and 7 mph) on plant population, plant spacing variability, and grain yield of corn (Zea mays L.). Increased planting speed significantly decreased plant population at one site (-527 plants/acre per mph increase in speed) and increased plant population at nine other sites (207 to 1912 plants/acre per mph). Among the 10 sites where increased planting speed influenced plant population, plant spacing variability significantly increased at four sites and was unaffected at the six other sites. Among the remaining 12 sites where plant population was unaffected by planting speed, plant spacing variability (PSV) significantly increased with increased planting speed at five sites and was unaffected at the seven other sites. Where observed, standard deviation of plant-to-plant spacing increased from 0.22 to 0.37 in./mph increase in planting speed. Grain yield was significantly influenced by increased planting speed at only five of 22 sites. Among the five responsive sites, grain yield decreased linearly from 1.9 to 4.7 bu/acre per mph increase in planting speed. There was no clear relationship between occurrence of grain yield loss and changes in either plant population or plant spacing variability. The possibility for significant grain yield loss with excessive planting speed must be considered when growers contemplate changes in their standard planting speed practices.