Masters Theses

Date of Award

3-1970

Degree Type

Thesis

Degree Name

Master of Science

Major

Agronomy

Major Professor

John H. Reynolds

Committee Members

Horace C. Smith, Laurence N. Skold

Abstract

The effect of high nitrogen fertilization and intensive management on the dry matter production, nitrate nitrogen concentration and protein nitrogen concentration of orchardgrass (Dactylis glomerata L.) was studied at Knoxville, Tennessee during 1969. Twelve combinations of three factors were incorporated in the experiment. The orchardgrass was harvested either four or eight times at stubble heights of 4 cm or 10 cm, and with nitrogen applications of 224, 448, or 672 kg/ha applied in two equal applications. Dry matter yields of forage ranged from 3.82 to 8.46 metric tons per hectare. Nitrogen levels did not significantly affect yield, however management levels were highly significant. The highest yielding treatment was 448 kg/ha of nitrogen, 4-cutting frequency and 4-cm height. Lowest yields occurred at 448 kg/ha, 8-cutting frequency and 4-cm height. The difference in total yields indicates the detrimental effect of frequent harvests on stand persistence and the effect of periods of adverse environmental conditions during the months of May, June, and August. Nitrate nitrogen concentrations were found to be affected significantly, on harvest dates analyzed, by nitrogen application but usually not by cutting management. The highest concentration was accumulated at 672 kg/ha followed by 448 kg/ha and 224 kg/ha, respectively. Nitrate nitrogen concentrations for the three nitrogen rates were high early in the season (April 29), .43, .41, and .13 percent respectively, reaching toxic levels at the 672 and 448 kg/ha rates. Concentrations then declined until June 6 when values were .11, .05, and .01 percent. Following this date the second half of the nitrogen was applied and resulted in a slight increase in the nitrate nitrogen concentration in the forage which remained below toxic levels. Concentrations of samples taken on July 22 were .24, .16, and .07 percent, respectively. By September 1, values had again declined with concentrations of .16, .06, and .00 percent. Protein nitrogen concentrations were affected by both nitrogen levels and management levels. Concentrations ranged from 2.55 to 5.33 percent during 1969. Concentrations were high, approximately 5 percent, for all treatments during the early part of April. Following this period, values dropped to approximately 3 percent and remained at that concentration for the remainder of the growing season. The highest concentration for the season occurred at the 672 kg/ha nitrogen level, 8-cutting frequency, and 4-cm stubble height. The lowest concentration occurred at the 224 kg/ha nitrogen level, 4-cutting frequency, and 10-cm stubble height. The highest protein nitrogen concentrations at all nitrogen rates were found at the 8-cutting frequency.

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