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Thesis (M.S.)—University of Nebraska—Lincoln, 1970. Department of Agronomy.


Copyright 1970, the author. Used by permission.


Field experiments were conducted at Mead, Nebraska, on a Sharpsburg silty clay loam in 1968 and 1969 to determine the effects of date of planting, time of N application, and rate of N fertilization on a medium-season corn hybrid, DeKalb XL45.Each of the three factors was studied at seven levels.A randomized complete block design with a composite treatment arrangement was used.A secondary objective of this experiment was to demonstrate the use of the composite treatment arrangement to study management factors other than fertilizer rates.The most economical optimum treatment combination was calculated for each year.

Results obtained included grain yield, grain moisture, ear population, number of days from planting to tasseling, nutrient content of leaves, and residual soil NO-3-N accumulation.There was no significant effect of planting date in 1968, but there was a trend toward lower yields with late planting dates at high rates of N application.The linear date effect in 1969 was highly significant and positive.

Yields increased with later plantings.Differences in air temperature, soil temperature, and precipitation at different points in the season were the most tangible reasons for the difference in date of planting response between the years.There was relatively little yield difference between the two years averaged over all treatments.

The writer is of the opinion that this 2-year study was not adequate to make a specific statement on date of planting for this variety in this location.However, it can be concluded that early plantings as advocated by many persons are not always advisable, as was demonstrated in 1969.Extremely early planting and extremely late planting seldom gave high yields.Proper timing of N fertilization was found to be very important and not entirely independent of date of planting.A proper combination of all management factors was necessary to obtain the greatest economic returns.

Advisor: Gary A. Peterson