Evaluation of Tall Fescue Pasture under Different Fertilization Treatments1

Abstract

AbstractThe influence of fertilizer treatment and growth stage on the composition and nutritive value of tall fescue grazed or fed as cut herbage to sheep was examined in first growth and regrowth pasture. Analysis of clipped herbage showed effects of growth stage and fertilizer treatment on plant content of protein, fiber fractions, soluble carbohydrate and certain macro elements, but little consistent effect on trace minerals. With clipped herbage, fertilizer and growth stage altered dry matter and protein digestibility. Fertilizer had little effect on ad lib. intake; intake declined with advancing maturity in the first growth herbage, but there was no effect of date of cutting on intake in the regrowth trials. The dry matter digestibility of grazed herbage was calculated by use of fecal N as an indicator in “local” regressions. The relationship between digestibility and fecal N was found to be affected by growth phase (first cuttings vs regrowth), but not by fertilizer treatment. Calculated dry matter digestibility coefficients averaged 2% higher for grazed than for clipped herbage. Estimated intake values for grazing sheep indicated that cutting date had no effect on intake within first growth or regrowth trials, but that herbage fertilized with higher levels of nitrogen, or nitrogen plus phosphorus, was consumed in greater amount than nonfertilized grass, or grass treated with phosphorus or potassium alone. Grazing sheep in palatability trials showed a marked preference for fescue fertilized with nitrogen, or nitrogen plus phosphorus. Correlation analyses of nutritive criteria with plant composition showed significant relationships between the dry matter digestibility of clipped or grazed herbage and the content of dry matter, crude protein or fiber fractions, but little apparent effect of most plant components on intake.