Date of Award
Master of Science
Plant, Soil and Environmental Sciences
John H. Reynolds
Jeff Wolt, M. C. Bell
Field experiments were initiated on established stands of tall fescue (Festuca arundinacea Schreb.) located on soils subject to flooding at Knoxville and Chapel Hill, Tennessee. Treatments were imposed to determine effects on K, Mg, Ca, and A1 concentrations in tall fescue forage. Fertilizer treatments consisted of 112 kg Mg/ha, 181 kg K/ha, or a combination of both applied as Epsom salts, potassium sulfate, Sul-Po-Mag, or Epsom salts + potassium sulfate. Concen trations of K, Mg, Ca, and A1 in tall fescue forage were related to fertilizer treatments and variations in mean monthly air tem perature at each location. Potassium fertilization often resulted in higher K concentrations in the forage, while Mg fertilization had little effect on plant Mg concentration. At Chapel Hill fertilization with Mg or K had little effect on plant Ca concentration, while at Knoxville, Ca results were somewhat inconsistent. Aluminum concentration of plants was usually unaffected by fertilizer treatments. Equivalent ratios of K/(Ca + Mg) were sometimes in creased by K fertilization. Plant K concentrations were associated with increasing mean air temperature up to 12 or 13° C, when K concentrations declined. Magnesium concentrations in tall fescue declined through late fall and early winter, and then either declined or remained at low levels through spring. Calcium concentrations in the forage were somewhat ivV erratic in relation to mean air temperature. Aluminum concentration of the forage dropped considerably when temperatures rose above 10° C. Equivalent ratios of K/(Ca + Mg) closely followed trends of K in plant tissue as associated with temperature. Squares of sod were removed from a soil fertility field experiment for a greenhouse study in Knoxville. Epsom salts had been applied in the field at the rate of 0, 84, and 168 kg Mg/ha/year for 5 years. Half of the squares of sod were placed in trays that allowed drainage of water. The other half were placed in trays lined with polyethylene to prevent drainage and to approximate flooded field conditions. Equal numbers of sod trays were placed inside and outside the greenhouse to vary the temperature regime. In only one instance was K concentration in tall fescue affected by soil moisture, and in no instance was it affected by level of Mg fertilization. Magnesium concentration in forage was sometimes affected by soil moisture and was often increased by the highest level of Mg fertilization. Calcium concentration was not affected by soil moisture, but was often highest at 0 kg Mg/ha, indicating possible Mg-Ca competition. Aluminum was unaffected and equivalent ratios of K/(Ca + Mg) were not consistently affected by either soil moisture or Mg fertilization. Potassium, Mg, and Ca concentrations in tall fescue were usually higher at warmer temperatures while A1 concentrations were higher at cooler temper atures. Ratios of K/(Ca + Mg) were mostly unchanged between temperature regimes.VI In general, fertilization with Mg fertilizers had little consistent effect on increasing tall fescue Mg concentrations, while K fertilizers increased plant K content and the potential for tetany. Fertilization had no effect on decreasing plant Al. Mean air temperatures appeared to have a considerable influence on cation composition of tall fescue, and along with K fertilization may cause the greatest changes in potential for tetany.
West, Joe W., "Cation composition of tall fescue as affected by potassium and magnesium fertilization, temperature, and soil moisture. " Master's Thesis, University of Tennessee, 1982.