Autumn‐Accumulated Tall Fescue and Orchardgrass. I. Growth and Quality as Influenced by Nitrogen and Soil Temperature1

Abstract In many situations autumn‐saved pastures offers an excellent alternative to more traditional and expensive livestock programs where hay or silage are the main winter feeds. Environmental conditions during the period of fall forage accumulation are markedly different from those of the spring and summer months and both forage yield and quality were affected. The objective of this research was to study the effects of temperature and nitrogen fertilization on the growth and quality of autumn‐accumulated forage. Two field experiments were conducted during 1970–71 on a Beltsville silt loam soil (Typic Fragiudults) to measure the influence of N rates and soil temperatures on the growth and quality of autumn‐saved ‘Ky‐31’ tall fescue (Festuca arundinacea Schreb.) and ‘Potomac’ orchardgrass (Dactylis glomerata L.). Nitrogen was applied at either 0, 50 (1970 only), or 100 kg N/ha in late September. In 1971 soil temperatures were maintained at ambient and approximately 12, 20, and 27 C during the autumn using specially designed field equipment. Forage samples were collected from randomly‐selected, previously unharvested areas. These were separated into green, dead, and miscellaneous fractions for yield and quality evaluation. Tall fescue was a more suitable species for autumn‐saved pasture primarily due to its superior growth compared with orchardgrass. Differences in quality were not consistently found between the species. In November of each year, dry matter availability reached a maximum of approximately 4,000 and 3,300 kg/ha for tall fescue and orchardgrass, respectively. During December under ambient conditions net loss of dry matter occurred in both species, presumably due to a greater rate of leaf death and decay than leaf growth. Digestibility and protein percentages decreased only slightly during autumn. The minimum IVDMD and crude protein levels measured during approximately 100 days of accumulation in either year were 80 and 13.5% for tall fescue and 73.0 and 15.2% for orchardgrass, respectively. Nitrogen fertilization stimulated growth of the autumn‐saved pastures and also tended to increase crude protein percentages. An application of 100 kg N/ha in late summer produced up to 50% more dry matter by early winter than zero N. IVDMD of the forage was not affected by N fertilization. Growth of the grasses during fall was stimulated by increasing the soil temperature. This effect was greater for tall fescue than orchardgrass. Plant quality was only slightly affected. However, the relative effects of the soil temperature treatments in relation to air temperatures and light parameters were not determined.