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Zhiguo Ju, Yousheng Duan, and Zhiqiang Ju

In China, one of the most serious problems to fruit growers is too much vegetative growth and too many pests and diseases during the growing season. Therefore, a large number of growth regulators, pesticides, and fungicides are used each year, which increases production costs and causes environmental pollution. To reduce the usage of agrochemicals, a device was invented to confine the treated area. Instead of applying chemicals directly to leaves, which may have reduced the efficiency by washing or UV degradation, the chemicals were injected directly to the truck of trees and transported through the xylem to the target organ, the leaf. Results showed that, to reach the same level of control, using plant regulators such as paclobutrazol, gibberellins, and ascorbic acid, the amount used could be reduced by 50% to 80%. The use of fungicides such as captan and diazinon could be reduced by 35% to 60%, and the use of pesticides such as vendex could be reduced by as much as 50%. Compared with the conventional method, the injection method showed three advantages: 1) It is economical in that production costs were reduced by about 40%, 2) It is efficient in that the same level of control was achieved using less chemicals (Due to the small acreage cultivated by family growers in China, the device could be installed within days and chemicals could be applied within hours.), 3) It is environmentally friendly because chemicals were not released throughout the orchard.

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Michael D. Frost, Janet C. Cole, and John M. Dole

Improving the quality of water released from containerized production nurseries and greenhouse operations is an increasing concern in many areas of the United States. The potential pollution threat to our ground and potable water reservoirs via the horticultural industry needs to receive attention from growers and researchers alike. `Orbit Red' geraniums were grown in 3:1 peat:perlite medium with microtube irrigation to study the effect of fertilizer source on geranium growth, micronutrient leaching, and nutrient distribution. Manufacturer's recommended rates of controlled-release (CRF) and water-soluble fertilizers (WSF) were used to fulfill the micronutrient requirement of the plants. Minimal differences in all growth parameters measured between WSF and CRF were determined. A greater percentage of Fe was leached from the WSF than CRF. In contrast, CRF had a greater percentage of Mn leached from the system than WRF during the experiment. Also, regardless of treatment, the upper and middle regions of the growing medium had a higher nutrient concentration than the lower region of medium.

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Zhongchun Jiang, W. Michael Sullivan, Carl D. Sawyer, and Richard J. Hull

Turfgrass cultivars that have superior nitrate uptake ability are needed for the protection of ground water from pollution by excess nitrate. Information on temporal variation of nitrate absorption is also needed to enhance the environmental safety of turfgrass N fertilization programs. Our objectives were to evaluate Kentucky bluegrass (Poa pratensis L.) cultivars for their differences in nitrate uptake rate (NUR) and temporal variation in NUR. Six cultivars (Barzan, Blacksburg, Connie, Dawn, Eclipse, and Gnome) were propagated from individual tillers and six plants of each cultivar were generated from one mother plant. Plants were grown in silica sand, mowed weekly, and watered daily with half-strength modified Hoagland's nutrient solution containing 1 mM nitrate. When 5 months old, the plants were excavated, the roots were washed to remove sand, and the plants were transferred to 120-mL black bottles. After 24 hours in tap water, the plants were supplied with half-strength nutrient solution containing 0.5 mM nitrate, and the solutions were replaced daily for 8 days. NURs expressed as micromoles per plant per hour were calculated from solution nitrate depletion data. Significant genotypic differences in NUR were found: `Blacksburg' > `Connie' > `Dawn' > `Barzan' = `Eclipse' > `Gnome'. Significant temporal variation in NUR was also found, with NUR on the second day more than the first day after tap water. A significant interaction was noted between genotype and time. Temporal variation was greatest in `Blacksburg', while none noted in `Connie' and `Eclipse'. In `Barzan' and `Gnome', NUR on the last day was higher than the first day.

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Jonathan Lynch and Kathleen Brown

We have developed solid-phase P buffers capable of maintaining P concentrations in soiless media much lower than conventional fertilizers, in the range of available P levels found in natural soil. In addition to substantially reducing PGH reaching into the environment, these buffers can have a number of useful effects on crop growth. Using various floriculture and ornamental species, plants grown in media buffered at low P levels have stimulated root branching and growth, increased drought resistance, better transplant establishment, better shoot form, better vegetative growth, increased flowering, and continued development of buds in the postharvest environment. Phosphorus availability regulates many aspects of root architecture including adventitious rooting, lateral branch density, root gravitropism, and root hair formation. It appears that many of the effects of P on root growth may be mediated by ethylene. We hypothesize that the high P concentrations used in many horticultural systems are detrimental to optimal plant growth, and that buffered media represent an opportunity to improve production systems while also reducing environmental pollution from nutrient effluents.

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Clayton L. Rugh, Scott A. Merkle, and Richard B. Meagher

The use of plants to stabilize, reduce, or detoxify aquatic and terrestrial pollution is known as phytoremediation. We have employed a molecular genetic approach for the development of potentially phytoremediative species using a bacterial gene for ionic mercury detoxification. One gene of the bacterial mercury resistance operon, merA, codes for mercuric ion reductase. This enzyme catalyzes the reduction of toxic, ionic mercury to volatile, elemental mercury having far lower toxicity. Early attempts to confer Hg++ resistance to plants using the wildtype merA gene were unsuccessful. We hypothesized the highly GC-skewed codon usage was ineffective for efficient plant gene expression, and sequence modification would be necessary to confer merA gene activity and ionic mercury resistance in plants. A directed mutagenesis strategy is being used to develop modified merA gene constructs for transformation and analysis in plants species. Transgenic Arabidopsis and yellow-poplar plants having modified merA codon usage display Hg++-resistance. Arabidopsis plants with modified merA were observed to evolve ≈4 times the quantity of Hg0 from aqueous Hg++ in controlled experiments. In contrast, plants with unaltered merA coding sequences display unstable and inactivated gene expression. Our progress towards further merA modification and transgenic plant development will be reported. Additionally, the theoretical phytoremediative benefits and potential advantages of merA-expressing plant species will be discussed as part of our long-term goals.

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Marsha Ann Bower, David H. Trinklein, and John M. Brown

Recent trends in greenhouse container production suggest using ebb and flow irrigation for water conservation and pollution control. A major problem in this system is management of soil borne pathogens. Some species of Trichoderma, a beneficial fungi, are known to control Pythium and Phytopthora in container production. This study investigates the potential of applying a Trichoderma conidial spore suspension in an ebb and flow irrigation system. Trichoderma conidia were collected from culture and placed in 101 l stock solution tanks at 10-2 and 10-4 colony forming units (CFU) per ml. Six inch container grown Dendranthema grandiflora `Delano', were irrigated as needed. To determine Trichoderma density in the root environment, soil samples were acquired from the container at 7 day intervals. Results showed that initial population densities of 10-4 CFU/ml were required to achieve adequate container populations to control disease after one irrigation. This study successfully demonstrated that Trichoderma could be dispersed through irrigation water into container plants in an ebb and flow system.

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Michael A. Schnelle, Sharon L. von Broembsen, and Michael D. Smolen

A comprehensive educational program focusing on water quality protection was developed for the Oklahoma nursery industry. The program focused on best management practices to limit pesticides and nutrients in irrigation runoff and on capture and recycle technology as a pollution prevention strategy. Key professionals from the departments of entomology and plant pathology, biosystems and agricultural engineering, and horticulture formed a multidisciplinary team within the Oklahoma Cooperative Extension Service (OCES). During 1998, water quality workshops were conducted on-site throughout Oklahoma at leading nursery operations. These workshops were designed to highlight best management practices (BMPs) that were already in place as a foundation on which to implement additional BMPs with the assistance of the OCES team. Training workshops were augmented by written publications, by web-based information, and by videotape instruction. These provided for ongoing education beyond the formal grant period. The written materials included a water quality handbook for nurseries and a fact sheet on capturing and recycling irrigation runoff. The water quality handbook was also made available on the web and a website on disease management for nurseries using recycling irrigation was provided. The water quality video, highlighting successful growers, was designed to show aspects of both best management practices and capture and recycle technology. Results of these 3-year extension efforts will be discussed.

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Renee Keydoszius and Mary Haque

During the fall semester of 2003, a Clemson University introductory landscape design class collaborated with South Carolina Botanical Gardens staff and coordinators of Sprouting Wings, an after school gardening program for at risk children, to design an exploratory Children's Garden within the Botanical Gardens. Project methodology included site selection, research, site analysis, conceptual diagrams, preliminary designs, and full color renderings of final designs. Students periodically presented their progress on the project to the clients in order to receive feedback and advice. One of the thirteen themed gardens designed is the Wonders of Water Garden. Project goals were to create a center for environmental education addressing current issues in water quality such as pollution from industries and runoff, erosion, stream degradation, and sedimentation resulting from land clearing and development. Visitors will be able to observe and learn about various environmental factors affecting native plant and animal life. The garden will help to teach environmental stewardship and understanding of general aquatic ecology. An observation deck, serpentine bridge through a bog garden, and a bridge crossing a waterfall stream will allow close observation of native aquatic plant and animal life. The Wonders of Water Garden design includes the bog garden and carnivorous garden that border two pools connected by a stream of small waterfalls which may be used to create awareness of current water quality issues and serve as a model to teach visitors the importance of water and aquatic plants in the environment.

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S.B. Sterrett, C.P. Savage Jr., and H.E. Hohlt

Tomatoes (Lycopersicon esculentum Mill.) were grown under plastic culture on a Bojac sandy loam soil in 1991, 1992, and 1994 to determine influence of nitrogen rate at planting and water application scheduling by pan evaporation (PAN) on crop yield and fruit size. Marketable yield and percentage of large fruit was significantly increased in 1991, 1992, and 1994 as irrigation application increased from 0.5 to 1.0 or 1.5 PAN (one application per day). Nitrogen applications exceeding 168 kgha–1 resulted in lower yield and reduced fruit size in 1992. In 1994 (late planting followed by hot, dry growing season), yield was increased with increasing N to 213 kgha–1 with 1.0 PAN, but not influenced by N at 1.5 PAN. Residual soil nitrate concentration was increased with reduced irrigation or increased nitrogen application. Nutrient management plans to address non-point source pollution concerns of EPA will need to reflect crop irrigation needs to maintain yield and fruit size while minimizing nitrate accumulation within the soil profile.

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Shumin Li, Nihal C. Rajapakse, and Ryu Oi

Growth chamber experiments were conducted to investigate the effectiveness of several photoselective plastic films in controlling height of `Sweet Success' cucumber, `Mt. Pride' tomato, and `Capistrano' bell pepper transplants. Four types of treatment films; a control, two far-red light intercepting films (YXE-1 and YXE-10), and a red light intercepting film (SXE-1), with R: FR ratios of 1.0, 2.0, 1.6, and 0.8, respectively, were used as the covering materials of experimental chambers. Photosynthetic photon flux (PPF) was adjusted to be the same in all chambers with cheese cloth. Treatment period for cucumber and tomato was 15 days and that for bell pepper was 20 days. At the end of the treatment, significantly shorter plants were found in both YXE-1 and YXE-10 chambers for all the three tested crops. However, YXE-10 was more effective than YXE-1 in producing compact cucumber, tomato and bell pepper transplants. SXE-4 film produced taller plants than control film. Magnitude of response to filtered light varied with the crop species. Number of leaves was not significantly affected by the light transmitted through photoselective filters, indicating that the height reduction was mainly caused by the reduction in internode length. With the commercial development of photoselective greenhouse covers or shade material in the near future, nursery and greenhouse industry could potentially reduce the cost for growth regulating chemicals, reduce the health risks to their workers and consumers, and reduce environmental pollution.