Masters Theses

Date of Award

12-1979

Degree Type

Thesis

Degree Name

Master of Science

Major

Plant, Soil and Environmental Sciences

Major Professor

Gary M. Lessman

Committee Members

Vernon H. Reich, Charles R. Graves

Abstract

The primary objective of this study was to determine the effects of three Nitrogen (N) rates, 112, 168, and 224 kg per hectare, and three plant populations, 39,540, 49,420, and 59,300 plants per hectare on the protein content and yield of a medium season (Pioneer brand 3184) and a full season (DeKalb XL-394) corn hybrid (Zea mays L.) at Milan and Cross-ville, Tennessee. Other characteristics measured were lodging, prolifi-cacy, and mineral composition of the ear leaf at silking. Ear leaf samples were collected at silking and analyzed for their N, P, K, Mg, and Ca content. At harvest, yields were determined and sub-samples were taken for protein analysis. Soil samples were taken to establish if plant nutrient levels were related to the soil fertility. In general, increasing the N rate from 112 kg to 168 kg of N per hectare significantly increased the yield and protein content of the corn grain. Increasing N to 224 kg per hectare had no influence on increasing the yield or protein content. Yields were increased when the plant population was increased from 39540 to 59300 plants per hectare, despite small increases in lodging. The plant population had little effect on the percent protein found in the grain, or in the total protein produced per hectare. The one exception being the lowest population at Milan which had a significantly higher protein content than at the two higher populations. At Milan, Pioneer brand 3184 produced the same yield and total protein as KeKalb XL-394. At Crossville, where the growing season is shorter. Pioneer brand 3184 out performed DeKalb XL-394. There were minor differences in percent P, K, Mg, and Ca in the ear leaves at different N rates, Hybrids, or populations. Differences did exist in nutrient composition between locations. The most obvious difference was noted with ear leaf Mg. Corn at Milan contained three times greater Mg concentrations than did the corn at Crossville. This effect was also noted in the amount of extractable Mg in the soil profile, where six times more Mg was found in the soil at Milan.

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