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 7d, 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 10mM. 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).