Humectants as Post-Plant Soil Amendments: Effects on the Wilting Cycle of Drought-Stressed, Container-Grown Tree Seedlings

Abstract

To test the potential effectiveness of humectant-containing compounds for improving soil moisture availability in the rhizosphere of newly transplanted trees, one-year-old Jiffy Plug™ and bare-root seedlings of red maple (Acer rubrum L.) and red oak (Quercus rubra L.) and one-year-old bare-root seedlings of yellow-poplar (Liriodendron tulipifera L.) were treated with Hydretain ES™ (HydES) and EcoSential™ (EcoS) in greenhouse studies. Both products were applied as a root drench to seedlings in 3.8 L plastic pots containing soilless substrate. Following treatment, water was withheld and days to wilt (DTW) recorded for each seedling. For red maple, HydES at the recommended rate (16 mL/L, X), as well as at 0.75X and 0.5X, was effective in increasing DTW, as was EcoS at 16 mL/L (the recommended rate, X) and at 0.75X. For red oak, the lowest concentration of HydES (0.5X) was ineffective, but the two higher levels (X and 0.75X) increased DTW significantly when compared to untreated controls. For yellow-poplar, DTW was consistently greater in treated than in untreated seedlings, but the differences were not always statistically significant. The data also indicate that for certain species (e.g. red maple), production type (Jiffy Plug or bare root) may influence the degree to which seedlings respond to humectant treatment.