The Effect of Plant Spacing Variability on Corn Yield in the Southeastern US.
Ronnie Heiniger, North Carolina State Univ., 200 Lakeside Drive, Edenton, NC 27932-2060 and Joni Williamson, North Carolina State University, 658 E. Main St, Belhaven, NC 27810.
Increases in plant populations and high planter speed often result in variability in the spacing between corn plants. Unfortunately, there have been conflicting studies describing the impact of plant spacing variability (PSV), measured as the standard deviation of plant-to-plant spacing in a row, on corn yield. The objective of this research was to document the PSV found in corn fields in North Carolina and to determine the impact of non-uniform spacing on corn yield. A statewide survey was conducted of over 40 fields in 10 counties representing all areas of the state. In addition, two test plots were established in Hyde County and PasquotankCounty to measure the yield impacts from non-uniform plant spacing. In these tests a range of PSV was achieved by the use of a cone seeder in which the various slots were covered to created different spacings. The statewide survey found that PSV ranged from 17.87 to 42.18 cm2. Based on earlier research in the midwest this would indicate that North Carolina corn growers are losing 0.4 to 0.8 Mg ha-1 in yield due to non-uniform plant spacing. In the replicated experiments there were significant differences in PSV among the treatments with PSV ranging from 12.70 to 58.50 cm2. Yield results from the replicated plots indicated that North Carolina corn growers are actually losing 0.9 to 2.2 Mg ha-1 bu/acre in yield. This study found that corn growers in the southeastern US need to pay careful attention to planter maintenance and planting speed to avoid yield loss due to variability in plant-to-plant spacing. More data is needed to determine if the large losses found in 2005 are typical or if they only occur in years with above-average yield.