Research was conducted at three locations in North Carolina in 2012 and 2013: the Tidewater Research Station in Plymouth, NC, the Piedmont Research Station in Salisbury, NC, and at a private farm near Hertford, NC. Six treatments were included to examine kernel set and grain fill rate. The first treatment is an untreated control with a standard seeding rate of 25 seeds/row ft. and an application of 10 gal 11-37-0 at planting. In the second treatment, the fungicide Quilt was applied at 14 oz/a at GS70 to examine the role of fungicide in keeping leaves healthy and increasing seed weight. Treatment three involves applying 10 lbs. of N at GS70 to examine the role of nutrition in plant health and seed weight. Shading was applied from pollination to harvest in treatment 4 to examine the effect of light interception on grain weight. Treatment five was a low seeding rate thinned. Plots were planted at a low seeding rate of 10 seeds/row ft., and tillers were trimmed from main plants. Treatment six involved a high seeding rate of 35 seeds/row ft. with an additional 60 lbs. of N applied in late December. Samples consisting of 30 plants per plot were taken at weekly intervals from GS70 to maturity. Plant weight, kernel number, and individual kernel weight were measured.
Across all locations and years, the shaded treatment had the lowest rate of grain fill and therefore the lowest kernel weight. Both the shaded and low seeding rate treatments resulted in significant reductions in yield. None of the remaining treatments were significantly different from the untreated control. The significant yield loss in shaded plots demonstrates the critical importance of light interception in determining kernel weight. In comparison, the seeding rate in the low population treatment was so low that plants could not compensate through tillering.