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John D. Lea-Cox*

Environmental and human safety regulations are now an inevitable part of horticultural crop production. For most businesses, worker training and the subsequent collection and administration of data required for reporting purposes is often regarded as an economic burden. There are few systematic models that firstly provide an ecompassing approach to this business requirement, but more importantly which provide resources that simplify and perhaps automate the reporting of data to any significant degree. A good environmental management system (EMS) should provide a framework to systematically plan, control, measure and improve an organization's environmental performance and assessment. Significant environmental improvements (and cost savings) can be achieved by assessing and improving management and production processes, but only if the data are collected and analyzed quickly and easily. Many times, growers do not realize the relationship between their improved environmental performance and other key EMS benefits, such as reduced liability, better credit ratings, enhanced employee performance, improved customer relations, marketing advantages together with improved regulatory compliance. The International organization for Standardization (ISO) 14001 series is the most widely accepted international standard for EMS. Growers in most states in the US are required to document their use of pesticides and other agrochemicals that can impact human health, and in some states are also required to to document and monitor their applications of water and nutrients, in an effort to environmental pollution. This paper will illustrate the key elements of environmental management systems and how this can be integrated into production management using process management software.

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John D. Lea-Cox

In 1998, the state of Maryland adopted some of the toughest nutrient management planning regulations in the Nation, requiring virtually all agricultural operations plan and implement nitrogen and phosphorus-based management plans by Dec. 2002. The nursery and greenhouse industry is faced with a far more complicated nutrient management planning process than traditional agronomic planning scenarios. Factors include a large number (>500) of plant species, various fertilization and irrigation strategies, with crop cycles ranging from 6 weeks (bedding plants) to upwards of 15 years for some tree species in field production, often with a lack of knowledge of specific nutrient uptake rates and utilization. In addition, unique infrastructural and site characteristics that contribute to water and nutrient runoff from each nursery contribute to a multitude of variables that should be considered in the planning process. The challenge was to identify a simple, effective process for nutrient management planning that would a) provide an accurate assessment of nutrient loss potential from this wide variety of production scenarios, b) identify those specific factors that contribute most to nutrient leaching and runoff, and c) provide a mechanism to economically assess the various risk management (mitigation) scenarios. This risk assessment process provides information on a number of fixed (site) and dynamic (management) variables for soils/substrates, irrigation and fertilization practices, together with any surface water management systems (e.g. containment ponds, riparian buffers). When all the risk factors for a nursery are evaluated and scored, the complete picture of risk assessment then emerges. By identifying higher risk factors and evaluating different risk management options, the grower and/or nutrient management planner can then choose economic alternatives to reduce the potential for nutrient runoff.

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John C. Majsztrik and John D. Lea-Cox

Restoration efforts in the Chesapeake Bay recently intensified with the 2010 introduction of federal total maximum daily load (TMDL) limits for all 92 bay watershed segments. These regulations have specific, binding consequences if any of the six states or the District of Columbia fail to meet interim goals, including loss of federal dollars for various programs and increasing regulation of point sources, if non-point source (agricultural and urban) nutrient reduction goals are not met in the watershed. As part of the effort to better understand and account for non-point sources of pollution in the watershed, a team of agricultural experts from across the bay region was recently assembled, including the nursery industry. The goal of this panel was to inform stakeholders and policymakers about the inputs and management practices used across all Bay states. To increase both the precision and accuracy of loading rate estimates, more precise information should guide future iterations of the Chesapeake Bay model. A more accurate accounting of land area by operation type (e.g., greenhouse, container, and field) is a primary issue for the nursery and greenhouse industry, because the current Chesapeake Bay model relies on USDA agricultural census data, which does not separate container and field production, which have very different nutrient and irrigation practices. Field operations also typically account for a higher percentage of production area in each state, which may skew model results. This is very important because the type of operation (field, container-nursery, or greenhouse operation) has a significant impact on plant density, types of fertilizer used, and application rates, which combine with irrigation and water management practices to affect potential nutrient runoff. It is also important to represent a variety of implemented best management practices (BMPs) in the Chesapeake Bay model such as vegetated buffer strips, sediment ponds, controlled-release fertilizer, and accurately assess how these mitigate both nutrient and sediment runoff from individual operations. There may also be opportunities for growers who have implemented BMPs such as low-phosphorus slow-release fertilizers (SRF), precision irrigation, etc., to gain additional revenue through nutrient trading. Although there are currently some questions about how nutrient trading will work, this could provide additional incentives for further implementation of BMPs by both ornamental and other agricultural growers. It is possible that the TMDL process currently being implemented throughout the Chesapeake Bay will be used as a remediation process for other impaired estuarine water bodies, which have similar water-use regulations and issues. The lessons learned about the Chesapeake Bay model in general, and for the nursery and greenhouse industry in particular, will likely provide guidance for how we can be proactive in reducing environmental impacts and protect the economic viability of ornamental growers in the future.

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Tamela D. Michaels and John D. Lea-Cox

Electronic information systems that take advantage of new technological developments on the Web are a key towards fulfilling the mission of the extension educator; i.e., to help individuals, families and communities put research-based knowledge to work in improving their lives. Webpages are one key to achieving this goal, but vertical searches using search engines are tedious and inefficient. There is a need for a) rapid and easy access to verifiable information databases and b) the coordination of good information resources that are already available on the Web in an horizontal format. NurseryWeb was developed as an open information resource within a frames environment that enables users to gather information about a variety of nursery-related material; e.g., cultural information, diagnostic criteria for disease and pest identification, data on integrated pest management and marketing data. In addition, a password-protected communication resource within the page provides nurserymen with conferencing and direct email connections to nursery extension specialists through WebChat, as well as providing time-sensitive data, alerts, and links to professional organizations. A number of critical issues remain unresolved—e.g., the integrity of information links, data and picture copyright issues, and software support. Nonetheless, the ease of use, availability of information in remote areas at relatively low cost, and 24-hr access assures that this type of information provision will become dominant in the future.

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John D. Lea-Cox and James P. Syvertsen

Eighteen, 4-year-old Grapefruit (Citrus paradisi) cv. `Redblush' trees on either Volkamer lemon (C. volkameriana = VL) or Sour orange (C. aurantium = SO) rootstocks were grown in 7.6 kiloliter drainage lysimeters in a Candler fine sand (Typic Quartzipsamments), and fertilized with nitrogen (N) in 40 split applications at 76, 140 and 336 g N year-1 (= 0.2, 0.4 and 0.9 x the recommended annual rate). Labelled 15N was substituted for the N in a single fertigation at each rate at the time of fruit set the following year, to determine N uptake, allocation and leaching losses. “Nitrogen-uptake and allocation were primarily determined by the sink demand of fruit and vegetative growth, which in turn were strongly influenced by rootstock species. Larger trees on VL required at least 336 g N yr-1 to maintain high growth rates whereas smaller trees on SO of the same age only required 140 g N year-1. Of the 15N applied at the 336 g N rate to the SO trees, 39% still remained in the soil profile after 29 days. With optimally scheduled irrigations, 15N leached below the root zone was less than 3% of that applied after 29 days, regardless of rate. However, 17% of the applied 15N was recovered from a blank (no tree) lysimeter tank. Total 15N recovery ranged from 55-84% of that applied, indicating that a sizeable fraction of the 15N applied may have been lost through denitrification.

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John D. Lea-Cox and I.E. Smith

Pine bark and peat-based substrates have been shown to have low-phosphorus (P) fixation capacity and high leach-potential, similar to that occurring in high-organic soils lacking in inorganic colloids. A long-term greenhouse experiment was conducted where three rootstock species of varying growth rate, Citrus jambhiri Lush.(RL), Citrus reshni Hort. ex Tan. (CM), and Poncirus trifoliata L. × Citrus sinensis L. (Osbeck) (CC), were grown in 3-L containers in composted pine bark, amended with three forms of P. Two slowly soluble forms (Calmafos and MagAmp) and soluble single superphosphate were incorporated at 0 (control), 200, 400, and 800 g P/m3, in a completely randomized block design (n = six plants). A split fertigation treatment of P at 50 mg·L–1 vs. No P was superimposed on the design (n = 3). Despite significant (P > 0.01) differences in P availability in the substrate after 380 days, particularly between liquid P (μ = 65 mg·L–1) vs. no liquid P (μ = 15 mg·L–1), differences in leaf analysis of seedlings after 235 days showed little significance (2.2 vs. 2.7 mg·g–1). To avoid excessive leaching of P from pine bark substrates, it therefore appears that slow-release forms of P are adequate to maintain relatively high growth rates of citrus stock without supplemental P fertigation.

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John D. Lea-Cox and Irwin E. Smith

Pine bark is utilized as a substrate in citrus nurseries in South Africa. The Nitrogen (N) content of pine bark is inherently low, and due to the volubility of N, must be supplied on a continual basis to ensure optimum growth rates of young citrus nursery stock. Three citrus rootstock (rough lemon, carrizo citrange and cleopatra mandarin) showed no difference in stem diameter or total dry mass (TDM) when supplied N at concentrations between 25 and 200 mg ·l-1 N in the nutrient solution over a 12 month growing period. Free leaf arginine increased when N was supplied at 400 mg·l-1 N. The form of N affected the growth of rough lemon. High NH4-N:NO3-N (75:25) ratios decreased TDM when Sulfur (S) was absent from the nutrient solution, but not if S was present. Free arginine increased in leaves at high NH4-N (No S) ratios, but not at high NH4-N (S supplied) ratios. Free leaf arginine was correlated with free leaf ammonia. These results have important implications for reducing the concentration of N in nutrient solutions used in citrus nurseries and may indicate that higher NH4-N ratios can be used when adequate S is also supplied.

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John D. Lea-Cox and James P. Syvertsen

The objectives of this greenhouse study were to determine the rate of nitrogen (N) uptake over a 30 day period, use efficiency and N partitioning within two citrus rootstock species. Sixteen-week old seedlings of Cleopatra mandarin (C. reticulata Blanco) and Swingle citrumelo (C. paradisi × P. trifoliata) were assigned to treatments (harvest day × rootstock species) in a completely randomized design, grown in a Candler fine sand for 6 weeks and fertilized weekly with a N:P:K (5:1:5) plus minor elements solution at 200 mg N · liter-1. A single application of 15NH4 15NO3 (20% 15N) was substituted for a normal weekly fertigation. Six replicate plants of each rootstock species were harvested at ½, 1½, 3½, 7½, 10½ and 30 days after I5N application. Uptake of 15N was more rapid in SC over the first 7½ days (17% of applied) than in CM (11%), but uptake over 30 days was similar (52-53%) for both species. A higher proportion of 15N was found in the photosynthetic tissues of CM (74%) than in SC (48%), whereas a lower proportion was found in the fibrous roots of CM (9%) than SC (22%).

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John D. Lea-Cox and Laurie F. Ruberg

BioBLAST is a NASA-funded multimedia curriculum supplement, targeted to enrich high school biology classes. It is modeled after the CELSS scenario and currently is being developed by the Classroom of the Future at Wheeling Jesuit College. Through innovative applications of educational technologies and interactions with active researchers in life sciences based at the various NASA centers and by incorporating alternative assessment measures, the BioBLAST project seeks to improve student learning and assist biology teachers. The studentsed life-support system, which uses biological processes to supply astronauts with recycled food, water, and oxygen. The students will be encouraged to formulate hypotheses, devise hands-on experiments to investigate key processes, and use computer simulations to investigate what systems are required to achieve stability of these life-support systems in a simulated lunar base. To succeed in their mission, students will learn basic principles in plant physiology, microbiology, human physiology, nutrition, and the interdependence of systems, and the impact of physical constraints such as temperature, light, and water availability on biological system functioning. BioBLAST will be supported by extensive interactive CD-ROM-based materials and World Wide Web and other internet resources, together with intelligent tutor, frequently asked question lists, and mentor networks that will include the ability to contact NASA and other scientists on-line. An early version of this software will be prototyped to selected schools throughout the United States in Fall 1996.

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John D. Lea-Cox and James P. Syvertsen

We studied whether foliar-applied N uptake from a single application of low-biuret N-urea or K NO to citrus leaves was affected by N source, leaf age, or whole-shoot N content. In a glasshouse experiment using potted 18-month-old Citrus paradisi (L.) `Redblush' grapefruit trees grown in full sun, 2- and 6-month-old leaves on single shoots were dipped into a 11.2 g N/liter (1.776% atom excess N-urea) solution with 0.1% (v/v) Triton X-77. Two entire trees were harvested 1.5,6,24, and 48 hours after N application. Uptake of N per unit leaf area was 1.6- to 6-fold greater for 2-month-old leaves than for older leaves. The largest proportion of N remained in the treated leaf, although there was some acropetal movement to shoot tips. In a second experiment, 11.2 g N/liter (3.78% atom excess) urea-15N and 3.4 g N/titer (4.92% atom excess) KNO solutions of comparable osmotic potential were applied to 8-week-old leaves on 5-year-old `Redblush' grapefruit field-grown trees of differing N status. Twenty-four percent of the applied N-urea was taken up after 1 hour and 54% after 48 hours. On average, only 3% and 8% of the K NO was taken up after 1 and 48 hours, respectively. Urea increased leaf N concentration by 2.2 mg N/g or 7.5% of total leaf N after 48 hours compared to a 0.5 mg N/g increase (1.8% of total leaf N) for KNO. Foliar uptake of N from urea, however, decreased (P < 0.05) with increasing total shoot N content after 48 hours (r = 0.57).