TALL FESCUE (FESTUCA ARUNDINACEA SCHREB.) ROOT RELATIONSHIPS

Tall fescue (Festuca arundinacea Schreb.) growing under field conditions, was sampled periodically during 1979 and 1980 in order to determine the seasonal trend in root length when the tall fescue was subjected to several cutting and fertility treatments. The effect of harvest date on the seasonal root length trend was determined by sampling plots harvested according to four cutting schedules. The four cutting schedules were; harvests on 22 May, 1 July, and 9 September; harvests on 22 May and 9 September; harvests on 1 July and 9 September; and a harvest on 9 September. The effect of nitrogen fertilizer on root length was assessed by sampling roots from tall fescue growing on unfertilized plots and from plots fertilized with 392 kg/ha nitrogen. Phosphorus and potassium effects on root length were determined by sampling the roots of tall fescue growing under conditions of; low phosphorus (\u3c 5 kg/ha) - low potassium (\u3c 112 kg/ha), low phosphorus - high potassium (\u3e 168 kg/ha), high phosphorus (\u3e 17 kg/ha) - low potassium, or high phosphorus - high potassium. During 1979 tall fescue root length decreased from 51 km/m(\u272) on 19 June to 25 km/m(\u272) on 17 July. Root length then increased to 72 km/m(\u272) by 19 September. During 1980 root length increased from 84 km/m(\u272) on 25 March to 107 km/m(\u272) on 22 May. Root length did not decrease appreciably until early August. The minimum root length was 69 km/m(\u272) and occurred on 4 November. Root length in the upper soil profile was inversely related to soil moisture and directly related to the average daily low temperature between sampling dates in 1979. Sampling date, soil fertility level, and cutting management all influenced root length, but the relationship between root length and the log of soil depth was linear in all cases. The root length of tall fescue harvested initially on 22 May was approximately 10% greater during the remainder of the growing season than the root length of tall fescue not cut on 22 May. Cutting nitrogen fertilized tall fescue initially 1 July greatly reduced stand density. Ethanol soluble sugar and fructosan percentages in stem bases of tall fescue harvested on 22 May averaged 5.02 and 21.45%, respectively. Ethanol soluble sugar and fructosan concentrations in stem bases of tall fescue not harvested on 22 May averaged only 4.49 and 16.48%, respectively. Nitrogen fertilized tall fescue averaged 5.02 and 21.45% ethanol soluble sugar and fructosan in the stem bases, respectively, while unfertilized tall fescue averaged 6.98 and 28.72%, respectively. There was no apparent relationship between root length and carbohydrate percentage in stem bases. Nitrogen fertilized and unfertilized tall fescue had a dry matter yield of 7700 and 2240 kg/ha, respectively. Nitrogen fertilized tall fescue averaged 8% less root length during October through December than unfertilized tall fescue. Nitrogen fertilization had no effect (P \u3e .10) on root length prior to October. Soil potassium level had no effect on dry matter yield. Plots with a soil phosphorus level \u3e 17 kg/ha yielded one and one-half times more dry matter than plots with \u3c 5 kg/ha available phosphorus. Root length averaged 90, 86, 90, and 105 km/m(\u272) for the low phosphorus - low potassium, low phosphorus - high potassium, high phosphorus - low potassium, and high phosphorus - high potassium treatments, respectively. When soil phosphorus was \u3c 5 kg/ha the ratio of root length:dry matter yield averaged 1159, 1253, and 1175 km root/kg dry matter for the first, second, and third harvests, respectively. At a soil phosphorus level \u3e 17 kg/ha the root length:dry matter yield ratio averaged 296, 808, and 983 km/kg for the first, second, and third harvests, respectively. These differences reflected the effect of phosphorus on dry matter yield. Root length was relatively unaffected by soil phosphorus level