6 Roberts et al.: Humectants as Post-plant Soil Amendments Arboriculture & Urban Forestry 2012. 38(1): 6–12 Humectants as Post-plant Soil Amendments: Effects on Growth and Physiological Activity of Drought-stressed, Container-grown Tree Seedlings Bruce R. Roberts, R. Scott Linder, Charles R. Krause, and Ryan Harmanis Abstract. One-year-old seedlings of red maple (Acer rubrum L.) and yellow poplar (Liriodendron tulipifera L.) were treated with Hydretain ES™ or EcoSential™ (HydES) (EcoS) applied as a soil drench. A progressive drought cycle was imposed after treatment, and as each seedling wilted, the leaves and roots Red Maple; River Birch; Root Zone Moisture Management; Yellow Poplar. were harvested. Foliar growth was unaffected by HydES or EcoS, but root growth (roots < 1 mm diameter) was significantly less for seedlings grown in the humectant-treated media. These data, along with measurements of substrate moisture content taken during a similar dry down period, suggest that drought- induced fine root growth in humectant-treated media was slower because there was less need for these roots to extend and proliferate in search of addition- al soil moisture supplies. In studies conducted the following year, HydES or EcoS were applied as a soil drench to one-year-old seedlings of red maple and river birch (Betula nigra L.) prior to withholding irrigation. In these studies, measurements of chlorophyll fluorescence, leaf gas exchange, and xylem wa- ter potential indicate that physiological activity was greater for drought-stressed seedlings grown in HydES-treated media compared to similar seedlings grown in EcoS-treated media, a condition attributed to lower levels of plant-water stress (higher xylem water potentials) in the HydES-treated seedlings. Key Words. Acer rubrum; Betula nigra; Chlorophyll Fluorescence; CO2 Exchange; Liriodendron tulipifera; Organic Amendments; Production Type; While transplant success and tree establishment depend on the suc- cessful completion of a chain of events ranging from propagation to aftercare (Struve 2009), reduced post-plant growth is primarily the result of plant water stress caused by root loss at harvest (Hasse and Rose 1993). It is widely recognized that adequate moisture is an important factor affecting the physiological well-being of trees in the urban environment (Wiseman 2004), and transplants of- ten undergo massive physiological shock because of disruptions in the soil-plant-air continuum that occur during transplanting (Kramer and Boyer 1995). Since substantial portions of the root system may be removed during harvest, the presence of sufficient functional root tissue and the existence of adequate soil moisture resources are critical factors in the successful post-plant estab- lishment of newly planted trees (Watson and Himelick 1997). To help ameliorate the effects of transplant shock and to stimulate post-plant growth and development, numerous non- traditional soil additives have been studied as possible backfill amendments. These additives have met only limited success, partly because they don’t adequately address the problem of root zone soil moisture management (Abbey and Rathier 2005). More recent technology has resulted in the development of cer- tain organic substances, including polyhydric alcohols, such as glycerol and sorbitol, which function as humectants. Humec- tants are hygroscopic substances containing several hydrophilic groups, often hydroxyl groups, which have a strong affinity to form hydrogen bonds with water molecules. Aqueous solutions ©2012 International Society of Arboriculture of these organic compounds have specific humidity equilibrium points that inhibit evaporation to, and absorb moisture from, the atmosphere at relative humidities above their equilibrium point (Hanson 1999). Thus, when applied to the growing media around plant material, humectants have the potential to enhance the pro- portion of water available for plant growth by extracting moisture from air spaces within the soil matrix and in certain instances, by inhibiting the evaporative loss of water from porous soils. While humectant-containing compounds have gained wide- spread acceptance in pharmaceutical, food, and personal care products, their use in agriculture is less well documented. A re- view of existing literature suggests that the primary use of hu- mectants in agriculture has been as carriers for water-soluble herbicides (Matsumoto et al. 1992; Marzouk et al. 1998; Ramsey et al. 2005; Ramsey et al. 2006). Proprietary products contain- ing humectants have also been used to improve the drought resistance of bedding plants (Barrett 1991) and to increase the yield of tomato plants (Ciardi et al. 1998). With the exception of an agricultural extension report from Clemson University (Arena 2001), in which the stem caliber of Hydretain™ -treated and untreated live oaks was compared, no scientific studies could be found that involve the use of humectant-containing com- pounds for improving the drought tolerance of woody plants. The present investigation is the continuation of an earlier study (Roberts and Linder 2010), which was undertaken to de- termine if commercially available humectant products might
January 2012
| Title Name |
Pages |
Delete |
Url |
| Empty |
Search Text Block
Page #page_num
#doc_title
Hi $receivername|$receiveremail,
$sendername|$senderemail wrote these comments for you:
$message
$sendername|$senderemail would like for you to view the following digital edition.
Please click on the page below to be directed to the digital edition:
$thumbnail$pagenum
$link$pagenum
Your form submission was a success. You will be contacted by Washington Gas with follow-up information regarding your request.
This process might take longer please wait
