Seed Grade Effect on Corn Performance1

Abstract

AbstractSmall‐sized or ungraded corn (Zea mays.) seed usually costs less than large‐graded seed. Since planters can now uniformly plant ungraded and/or small seed, we conducted trials at Waseca and Lamberton, Minn., in 1973 and 1974 to determine the effect of seed size and shape on performance of early compared to late‐planted corn.Four seed grades — large round (LR), large flat (LF), small round (SR), small flat (SF), and mixed (M) — were evaluated each year. The M category was an equal mixture of the four grades. In 1973, the single cross hybrid ‘A639 × A638’ was used; in 1974 we used ‘DeKalb XL45A’ and ‘DeKalb XL43.’ Early plant height, early plant dry weight, and tassel dates were recorded at the Waseca location and grain yield was measured at both locations.Seed grades did not affect corn yields when data were averaged over years, locations, and hybrids. In only one of 12 comparisons was there a seed grade effect with higher yields from graded vs. ungraded seed, from large vs. small seed, and from round vs. flat seed. Seed grade did not affect early plant height or tassel dates. Early plant dry weight for plots seeded with SR and SF seeds was lower than that of plots seeded with LR or LF seeds in 1973; only very small plant dry weight differences occurred in 1974.Grain yields from the early May planting were higher than from late May planting for all location‐years except Waseca in 1973. Interactions of seed grade with planting dates or hybrids were not statistically significant for three of the four location‐years of the study. Soil temperature at the 10‐cm depth for the 2 weeks post planting was 8 to 10 C colder for early vs. late planting dates, yet yields from SR and SF seed were equal to those from LR or LF.