Masters Theses

Date of Award

8-1978

Degree Type

Thesis

Degree Name

Master of Science

Major

Plant, Soil and Environmental Sciences

Major Professor

John H. Reynolds

Committee Members

Vernon Reich, M. C. Bell

Abstract

A two-year experiment was conducted to determine the effects of fall stockpiling and date of removal of the stockpiled forage on the yield and quality of tall fescue stockpiled forage and winter regrowth forage. Tall fescue was stockpiled from August to December, August to January, and August to February, during 1975-1976 and 1976-1977. The forage was removed at the end of these three periods during both years and dry matter yields were determined. Samples were taken for forage quality analyses during October, 1975 and October and November, 1976 without harvesting by mowing and also immediately prior to harvesting the stockpiled forage during December, January, and February of both years. Estimates of the digestibility of the forage were obtained through the in vitro dry matter digestibility (IVDMD) method of Tilley and Terry. Analyses for crude protein (CP), neutral detergent fiber (NDF), water-soluble carbohydrates, K, Mg, Ca, and P provided additional information on the quality of this forage. At the end of the stock-piling periods in which the forage was harvested for yield, two rates of nitrogen fertilization, 0 and 56 kg/ha, were imposed. Crude protein concentrations and dry matter yields declined as the length of the stockpiling period increased. Water-soluble carbohydrate concentrations in the stockpiled forage increased with the onset of freezing temperatures in the fall and decreased thereafter. In vitro dry matter digestibility percentages declined after December, 1975 and November, 1976, while NDF percentages in this forage increased after these dates. Increases in water-soluble carbohydrate concentrations were associated with decreases in NDF concentrations and increases in IVDMD percentages. Mineral concentrations were, in general, decreased by increasing the duration of fall stockpiling. Crude protein and Ca concentrations of the stockpiled forage were adequate for a 450 kg dry, pregnant beef cow during both years, as was K during 1975-1976. Potassium levels that were below the NRG requirement for this type of animal occurred in the forage after mid-January, 1977. Phosphorus levels in the forage below the NRG minimum requirement for a 450 kg dry, pregnant beef cow occurred after October, 1975 and November, 1976. Magnesium concentrations of the forage dropped below 0.18 percent after December, 1975 and January, 1977. The quality of stockpiled tall fescue declined earlier in the fall and to a greater extent during the winter of 1976-1977 due to harsher temperature conditions during this period. Nitrogen fertilizer applications after forage removal significantly increased the GP concentration of the winter regrowth forage. The greatest yield increases due to nitrogen fertilization were noted when the nitrogen was applied at later stockpiled forage removal dates. No significant differences were evident in NDF concentrations during 1976-1977 or IVDMD percentages in either year's winter regrowth due to forage removal dates or nitrogen fertilization. During 1975-1976, neutral detergent fiber percentages were significantly decreased due to nitrogen fertilization. Neutral detergent fiber percentages were significantly lower in the regrowth forage when the stockpiled forage was removed during February of the 1975-1976 season. Nitrogen fertilization did not significantly affect water-soluble carbohydrate concentrations during either year. Removing the stockpiled forage during December, 1975 significantly decreased the water-soluble carbohydrate concentration of the winter regrowth forage as compared to removing this growth in January or February. Potassium percentages were significantly increased by nitrogen fertilization during both years. Calcium concentrations were significantly decreased by nitrogen fertilization during 1975-1976. Forage removal dates did not significantly affect the mineral concentrations in either year, except K during 1975-1976. Crude protein, Mg, K, and Ca concentrations of the winter regrowth were adequate for a 450 kg lactating beef cow on the harvest date of both years. Phosphorus concentrations of the regrowth forage were slightly below the NRC minimum requirement for this type of animal in both years. It is suggested that fall-stockpiled tall fescue forage be utilized before January to avoid sizeable reductions in quality, although quality may decline extensively before this time if unfavorable weather conditions occur early in the fall. Nitrogen applications to promote winter regrowth should be made during the late winter in order to avoid losses of nitrogen.

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