PRELIMINARY STUDY ON THE EFFECT OF ROOT ZONE TEMPERATURES ON VEGETATIVE GROWTH AND LEAF MINERAL NUTRIENTS OF `GULF COAST' BLUEBERRY PLANTS

Abstract

The effect of root zone temperature (temp.) on 18-month-old plants of `Gulf Coast' blueberries (predominantly Vaccinium corymbosum L.) grown in temperature-controlled water tanks during Summer 1993 were determined for plant growth and leaf nutrient status. Soil medium (1 sand: 1 peat, v/v) was maintained at or above –20 k Pa. Six singleplant replicates were placed in either a 24 or 31C tank. After 60 days, plants grown at 24C had more leaves, greater total leaf area, and higher leaf and stem fresh weight. Leaf moisture (P < 0.09) and stem dry wt (P < 0.07) were greater at the lower root temp. Root: shoot ratio and total root dry weight were not affected by root temp. Leaf S and Cu levels were higher and NO3 levels lower in plants grown at the 24C root temp. compared to those grown in the 31C root temp. Nitrogen, K, Na, Ca, Mg, P, Fe, Mn, and Zn (order of decreasing concentration) were not affected by root temp. The total N: NO3-N ratio was higher at the lower root zone temp.