Wednesday, November 15, 2006
262-4
Tall Fescue Root Growth and Clipping Yield Response to Gypsum in Highly Weathered Acid Soils.
John Kruse, Georgia Pacific Corporation, 194 Snyder Rd. NE, 194 Snyder Rd. NE, Milledgeville, GA 31061, William P. Miller, University of Georgia, 3111 Miller Plant Sciences, Athens, GA 30602, and M.J. Schlossberg, Penn State University, 116 Asi Bldg, University Park, PA 16802.
Factorial experiments using repacked soil columns were conducted to determine the effects of surface-applied gypsum on the chemical properties of various acid subsoils, and subsequent tall fescue (TF) root growth and clipping yield. Turf-type TF was grown over 85- or 800-d periods, on acid subsoils with similar chemical characteristics but varying texture. The 85-d study treatments included a control, surface-applied CaSO4·2H2O, and soil-incorporated CaCO3. Columns were established under lights in a container that maintained soil temperature at 15o C. After an initial growth period, TF was physiologically stressed by allowing the columns to dry down, followed by rewetting, then dried down again. Upon experiment termination, columns were divided into sections for soil chemical analysis and root density determination by depth. Lime and gypsum significantly increased soil extractable Ca through the column profile, indicating surface-applied gypsum moved well through the soil. Gypsum significantly reduced Mg, had little effect on exchangeable K, and had some effect on CEC and exchangeable acidity, depending on soil and depth. Lime-treated soils produced a significantly higher 59% root-density growth response over control treatments, but gypsum had less effect (32% growth response). Root distribution by depth and gypsum treatment varied by soil type, as significant differences were observed between soils averaged across all treatments. The 800-d study treatments of CaSO4·2H2O, CaCl2·2H2O, or CaCO3 were surface-applied at rates of 15.5, 13.3, or 4.9 Mg ha-1, respectively. Shoot growth of CaSO4-treated TF showed a significant increase of 15 or 18% compared to the respective CaCO3 or untreated columns. All treatments increased leaf Ca compared to the control, while CaSO4 and CaCl2 applications increased leaf S 71% compared to the CaCO3 and untreated columns. Moreover, rooting and water use (soil depths >38 cm) data show high rates of surface-applied CaSO4 may ameliorate subsoil acidity and improve TF stress tolerance.