Date of Award
Master of Science
John H. Reynolds
Horace C. Smith, Laurence N. Skold
The effect of high nitrogen fertilization and intensive manage-ment 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 condi-tions 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.
Lewis, Charles Ramsey, "Nitrate and protein concentration in orchardgrass (Dactylis glomerata L.) forage produced under several cutting management and nitrogen fertilization regimes. " Master's Thesis, University of Tennessee, 1970.