Predicting Initial Tall Fescue Root Growth Response to Calcium/Aluminum Solution Concentrations

A study was conducted to quantify effects of soluble aluminum (Al) and gypsum (CaSO₄) on initial root growth of three varieties of tall fescue (Festuca arundinacea). Experiments were performed in a growth chamber using hydroponic solutions containing Al from 0 to74 µM in combination with CaSO₄ at 0 to10 mM. Seedlings were grown for 7 d, harvested, air dried, scanned, and weighed for treatment comparisons. Significant differences in root length existed between varieties in Al‐only solutions at low Al concentrations. All varieties showed reduced root growth at concentrations greater than 37 µM Al. Increased calcium (Ca²⁺) and sulfate (SO₄ ^2?) at given concentrations of Al resulted in greater root growth. Relative root growth increased approximately 30% to >80% at 37 µM Al as CaSO₄ increased from 2.5 to 10 mM. A simple logistic model adequately described the effects of Al and CaSO₄ on root growth (r² = 0.86, 0.95, and 0.96 for the three varieties).