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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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R. Scott Johnson, Rich Rosecrance, Steve Weinbaum, Harry Andris, and Jinzheng Wang

The suspected contributory role of soil fertilization to nitrate pollution of groundwater has encouraged exploration of novel fertilizer management strategies. Foliar-applied urea has long been used to supplement soil N applications, but there have been no apparent attempts to replace soil N applications completely in deciduous orchard culture. Two experiments were conducted to study the effect of foliar-applied low biuret urea on productivity and fruit growth of the early maturing peach [Prunus persica L. Batsch (Peach Group)] cultivar, Early Maycrest. In a 3-year experiment, a total foliar urea regime was compared to an equivalent amount of N applied to the soil. The foliar treatment supplied adequate amounts of N to the various organs of the tree including the roots, shoots, and fruit buds, but mean fruit weights were lower than in the soil-fertilized treatment. In a 2-year experiment, a 50%-50% combination treatment of soil-applied N in late summer with foliar-applied N in October, maintained yields and fruit weight equal to the soil-fertilized control. Some soil-applied N appears necessary for optimum fruit growth. Soil N application may be needed to support root proliferation and associated processes, but we did not determine a threshold amount of soil-applied N needed. The combination treatment also reduced excessive vegetative growth which is characteristic of early maturing peach cultivars. Therefore, this combination treatment offers promise as a viable commercial practice for maintaining tree productivity and controlling excessive vegetative growth in peach trees.

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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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Harrison Hughes

Colorado State Univ. recently underwent the development of a new all university core curriculum. All faculty were encouraged to submit proposals for new courses or revised courses, which would be reviewed for inclusion under specified categories. Basic Horticulture was redesigned te emphasize the scientific method, the understanding between science and society, and the use of handson and inquiry-based instruction in the laboratory. Horticultural Science is now an applied science course that includes the use of hypothesis formulation, experimentation, observation, data collection, summation and presentation in scientific format of reports of at least three laboratory exercises, as well as extensive general observation and presentation in both written and oral format. It teaches science in the context of everyday interaction with the environment in which the student lives, the interior and exterior plants that surrounds the student at CSU, and the controversies as well as the health aspects that surround the production of foods derived from plants that require intensive cultivation. Examples of such issues include sustainability, the organic movement, genetically modified organisms, ground water pollution form overfertilization, and water usage for landscaping and golf courses in a water short region. A review of the revisions as noted above and the use of technology in teaching the course will be presented.

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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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C.M. Geraldson

The gradient concept is designed with a soluble source of N–K banded on the soil bed surface in conjunction with a continuing source of water that synchronizes the nutrient–water input with rate of removal by the root. By placing the N–K on the surface rather than conventionally in the bed, nutrient movement to the root shifts from mass flow to diffusion. Nutrients that move by mass flow are a function of water requirement and potentially a source of nutritional instability. With the shift to movement by diffusion, nutrients move independently of the water to replace those removed from the gradient by the root. The gradient with a continuing nutritional stability replaces the variable and limited stability potential of the soil. Commercial tomato yields in Florida more than doubled with the shift to the gradient-mulch procedure. A containerized version of the concept (The EarthBox™) has been most successful for the home gardener and substantiates the validity of the gradient. Most innovative procedures with the gradient as the buffer component minimize pollution, require minimal management, and use minimal water with microirrigation or an enclosed system. To better understand the gradient concept and utilize the procedure, it may be necessary to consider the procedure as a nutritional paradigm shift.

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C.M. Geraldson

The Earth Box is made of recycled plastic and designed to maintain a water table. A nutritional gradient is initiated with N–K fertilizer applied on the surface of the soil or media contained in the box. The box is designed to facilitate the functioning of a nutritional procedure known as the gradient concept. Basically, the concept synchronizes the nutrient/water input with removal, providing stability and nutritional predictability to the ionic composition of the soil solution. Crop response (yields and, especially, quality) with the Earth Box has been most positive, indicative of an optimal nutritional precision. The positive response is also evident in the field—average tomato yields in Florida more than doubled with the inception of the gradient-mulch system (1970s). the gradient as the dominant nutritional component eliminates the soil (type and/or quantity)–plant–season as nutritional variables. The Earth Box with minimal water, minimal pollution, minimal management, and the potential for a minimal unit cost could be the basis of a globally sustainable production 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.