Experiments were conducted to determine the effectiveness of paclobutrazol in solid spike form as compared to foliar spray or medium drench applications for height control of several foliage and flowering plants grown in 8-inch or 10-inch hanging baskets. Paclobutrazol was applied as either a 20 or 40 mg·liter–1 foliar spray, 1 or 2 mg·liter–1 medium drench, or 200 or 400 mg·liter–1 spike insertion per basket. Begonia × tuberhybrida `Nonstop Apricot' and Begonia × hiemalis `Barbara' treated with paclobutrazol were significantly shorter than nontreated controls. Drench applications were more effective than either spray or spike treatments for both species, with Hiemalis begonia showing severe dwarfing at both the 1 and 2 mg·liter–1 drench. Paclobutrazol treatments did not significantly affect flower number for either species. Syngonium podophyllum `White Butterfly' and Epipremnum aureum showed similar trends as the begonias; however, relative reductions in height were not as great. Plants appeared to be slightly less stretched than nontreated plants.
Harvey J. Lang and Don C. Wilkerson
Brad Abrameit, Michael Boyd, and Don C. Wilkerson
Denitrification of irrigation runoff was achieved using a fixedcolony of facultative, heterotrophic bacteria in an anaerobic environment. Ammonium nitrate was used to create three influent nitrate concentrations of 50, 150, and 200 ppm NO– 3, which were passed through two 17.5-gallon upflow bioreactors at 1.0 gallon/minute and yielded effluent concentrations of 1.9, 5.2, and 15.9 ppm NO– 3, respectively. The fate of nitrate, nitrite, and ammonium as they passed up the columns was analyzed at an influent of 100 ppm NO– 3, 29 ppm NH+ 4, 0 ppm NO– 2, and 1.0 gpm at five sample regions along the columns. The majority of the nitrates (76.5%) were removed in the first region of the columns with subsequent regions reducing 4.8% to 7.6%. Nitrite was produced (1.0 ppm) within the first region of the columns, with the majority (21.12%) being removed in the final region. Intermediate regions reduced 5.2% to 16.5% of the nitrites. Ammonium concentrations remained mostly steady, with slight reductions (6.3% to 11.1%) occurring primarily in the first two regions of the columns. Colony equilibration (Transient Response Time) was also recorded at 1.0 gpm with NO– 3 concentration steps from 150 to 100 ppm NO– 3 and 100 to 50 ppm NO– 3. About 2 days passed before the colony adjusted to the change.
Don C. Wilkerson and Tony M. Garza
A survey of five different waste water treatment plants was conducted to identify potential variability in water quality factors. Salinity, pH, and alkalinity varied widely between sites. Mineral content did not differ significantly between sites. Syngonium spp. were subirrigated with four different combinations of treated waste water (TWW) and reverse osmosis (RO) water. Weekly measurements of EC and pH were taken and final height, width, and quality ratings were recorded. Based on these results, a 1 TWW: 1 RO water combination was then used to evaluate four different soluble fertility regimes. Salinity was the most limiting factor in the use of TWW on Syngonium spp. Growth and quality decreased as the percentage of treated waste water increased in each treatment combination. Salable plants were produced using a 1 TWW: 1 RO water combination and 100 ppm (N) fertilizer.
Don C. Wilkerson, Dan R. Lineberger, and Priscilla J. Files
In response to the goals set forth in Target 2000, a long-range environmental plan for the Texas/Floral Industry developed by the TAMU Nursery/Floral Management Team in cooperation with the Texas Association of Nurserymen (TAN), an interactive, World Wide Web-based integrated pest management program (hortIPM) has been developed for commercial nursery and greenhouse growers. The objective of Target 2000 is to assist growers in initiation of innovative cultural and structural practices, which will result in the following changes by the year 2000: 1) reduce water consumption to 1990 levels; 2) reduce current fertilizer and pesticide usage by 50%; 3) lower current energy consumption by 25%; 4) reduce current solid wastes from agricultural plastics by 75%; 5) develop applications for municipal wastes and composted materials for nursery and floral crop production. More so than in any other cropping system, ornamental stock producers apply pesticides on a calendar basis regardless of pest damage to prevent cosmetic injury to their crops, thus reducing their marketability. As justification for this misuse of insecticides, growers cite the extraordinary low damage thresholds associated with their crops. Nursery and floral crops producers that have better access to educational resources and recommendations may be more inclined to follow biologically sound pest management principles. HortIPM is designed as a tool to facilitate access to pest management information and enhance IPM programs already in place. Currently, hortIPM is in the developmental phase, on the cusp of release to a number of sites for preliminary evaluation.
Michael A. Arnold, Bruce Lesikar, Ann Kenimer, Don C. Wilkerson, and Mitchell W. Goyne
The nursery/greenhouse industry is the fastest growing segment of U.S. agriculture. Consumer demand for excellent product quality requires luxury applications of water and agricultural chemicals. These cultural practices tend to yield significant volumes of runoff rich in nutrients and pesticides. A capture and recycle system at the Nursery/Floral Crops Research and Education Center at Texas A&M University was fitted with 12 subsurface flow (SSF) and 12 free-surface flow (FSF) wetland cells. Constructed wetland cells provided substantial reduction of runoff nutrient concentrations without increasing electrical conductivity, an indicator of salinity. Growth of Iris pseudacorus L. and Canna ×generalis L.H. Bailey during spring growth was greater in the FSF wetland cells, while that of Colocasia sp. Fabr. was greater in the SSF wetland cells. Equisetum hyemale L. grew equally well in both cell types. Direct reuse of nursery runoff reduced the number of Ilex vomitoria Ait. `Nana' reaching marketable size in 2.3-L containers. Interactions among irrigation water sources and container media types for growth indices occurred for Juniperus procumbens `Green Mound' and I. vomitoria `Nana', but not for Raphiolepis indica L. `Carmelita'.
Garry V. McDonald, Michael A. Arnold, Bruce J. Lesikar, Larry W. Barnes, and Don C. Wilkerson
An experiment was initiated in June and Aug. 2004 to determine affects of ozonated fertilizer–injected water on plant growth of chrysanthemum (Chrysanthemum× morifoliumT. de Romatuelle `Covington'). Aliquots (20 L) of reverse osmosis water were amended with 0, 50, and 300 mg·L-1 N (21N–3.1P–5.8K) water-soluble fertilizer and exposed to ozone (O3) gas for 0, 30, 60, or 120 s at a flow rate of 300 mL/min. Containers were sealed and allowed to set for 15 min for O3 diffusion. Treated water was used to irrigate plants. Plants were in 10.2-cm pots and grown until floral initiation. Plants were harvested on 12 Aug. 2004 or 24 Nov. 2004. Growth index (height x canopy width × canopy width in a perpendicular direction/3), and shoot and root dry masses were determined. Interactions between fertility concentration and ozone exposure rates were nonsignificant (P≤ 0.05). Significant main effect differences occurred in growth index and shoot/root dry masses in response to fertilizer concentrations, but growth measures were not affected by ozone exposure. Peak ozone concentrations in fertilizer-injected irrigation water averaged 0.21 mg·L-1 O3 (120 s exposure at 300 mL·L-1) after 15 min diffusion time. At 20 min diffusion times, ozone levels dropped to 0 mg·L-1. No gross morphological differences or obvious necrosis typical of ozone damage on chrysanthemum occurred at any O3 exposure level. No observable nutritional deficiencies were noted. Vegetative growth of chrysanthemum was not directly injured by irrigation water that was exposed to ozone gas for 0 to 120 s at a 300 mL/min flow rate.
Michael A. Arnold, Don C. Wilkerson, Bruce J. Lesikar, and Douglas F. Welsh
Studies were conducted using Zea mays L. and Taxodium distichum L. seedlings as model systems to study Cu leaching from Cu(OH)2-treated containers. Initial experiments developed Cu toxicity curves (as CuSO4) in an inorganic (sand) or organic (bark-sand) medium with single (acute) or multiple (chronic) applications. A second pair of experiments investigated short-term (35 days) Cu accumulation and plant responses to irrigation with water (125 mL/plant per day) recycled through a fixed reservoir volume (9.5 L) from 0.7-L Cu(OH)2-treated containers filled with an inorganic or organic medium. Finally, plant responses and Cu leaching were monitored during growth in 2.3-L Cu(OH)2-treated containers filled with two organic media fertigated with high (8.0) or low (6.5) pH solutions. Different Cu(OH)2 concentrations and application methods were tested. Leachate data from the latter studies were used to calculate potential Cu concentrations in nursery runoff using various water application methods and pot spacings. Expression of Cu toxicity symptoms depended on exposure, concentration, and medium for each species. Plants subjected to chronic exposure and grown in an inorganic medium developed toxicity symptoms at lower doses than plants subjected to acute exposure and grown in an organic medium. Several measures of plant growth were greater for both species when grown in 0.7-L Cu(OH)2-treated containers, but not in 2.3-L containers. Plants in Cu(OH)2-treated containers seldom exhibited Cu toxicity symptoms in shoot tissues, even with an inorganic medium. Soluble Cu content of the recycled solution from Spin Out-treated containers increased slightly (<1.2 mg·L-1) during the 35-day experiment. Longer-term studies with nonrecycled leachate from 2.3-L containers indicated that Cu leaching increased after 60 to 90 days. Copper leaching was greater with the combination of applied solution of pH 6.5 and bark-sand-peat medium than with the combination of applied solution of pH 8.0 and bark-sand medium, and increased with greater concentrations of Cu(OH)2 in container wall treatments or when containers were filled before latex carrier was dried. Calculations of potential nursery runoff indicated that the levels of soluble Cu in effluent for most concentrations and spacings projected were below EPA action levels for potable water (1.3 mg·L-1) when overhead irrigation was used.
Rolston St. Hilaire, Michael A. Arnold, Don C. Wilkerson, Dale A. Devitt, Brian H. Hurd, Bruce J. Lesikar, Virginia I. Lohr, Chris A. Martin, Garry V. McDonald, Robert L. Morris, Dennis R. Pittenger, David A. Shaw, and David F. Zoldoske
In the United States, urban population growth, improved living standards, limited development of new water supplies, and dwindling current water supplies are causing the demand for treated municipal water to exceed the supply. Although water used to irrigate the residential urban landscape will vary according to factors such as landscape type, management practices, and region, landscape irrigation can vary from 40% to 70% of household use of water. So, the efficient use of irrigation water in urban landscapes must be the primary focus of water conservation. In addition, plants in a typical residential landscape often are given more water than is required to maintain ecosystem services such as carbon regulation, climate control, and preservation of aesthetic appearance. This implies that improvements in the efficiency of landscape irrigation will yield significant water savings. Urban areas across the United States face different water supply and demand issues and a range of factors will affect how water is used in the urban landscape. The purpose of this review is to summarize how irrigation and water application technologies; landscape design and management strategies; the relationship among people, plants, and the urban landscape; the reuse of water resources; economic and noneconomic incentives; and policy and ordinances impact the efficient use of water in the urban landscape.