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United States Department of Agriculture

Agricultural Research Service

Research Project: Improved Production Methods: North South Initiative (University of Florida)

Location: Application Technology Research Unit

2011 Annual Report


1a.Objectives (from AD-416)
The object of this project will focus on research to optimize nutrition and irrigation rates during different stages in floriculture crop development taking into account stock plant, propagation, and finishing environments.


1b.Approach (from AD-416)
Develop protocols to flower plants at a specified plant size for the retail environment, and extending the marketing season by producing early- or late-flowering plants for different locations in the U.S. A single product or tank mix growth retardant applications for new crops that reduce elongation most without delaying flowering and whether innovative practices such as rewetting of foliage increases efficiency of growth regulators. Identify the crops and stages of development in which lighting is most effective. In addition, photoperiodic lighting is increasingly being used to induce earlier flowering during the winter and spring. Determine how photoperiodic lighting can be maximized by investigating how light quantity, quality, and duration (including cyclic lighting) impact flowering of a range of popular garden plants. Potential energy savings will be quantified by optimizing light and temperature to produce crops in the most efficient and cost-effective manner for different locations in the U.S. Develop tools and techniques that allow growers to more precisely control and manipulate flowering of greenhouse crops. Techniques will be developed for producing 'programmed' liners that have the branching, height potential, and flower bud development necessary so that the liner can be simply transplanted and quickly finished. "Bud meters" will be developed for important floriculture crops so that growers can manage greenhouse environments in order to properly time flowering on finished crops or to possibly reduce greenhouse temperatures to save fuel costs while still hitting the targeted market dates. Determine optimal fertilziation rates and tissue nutrient levels to maximize growth of flowering plants and characterize the symptoms of nutritional disorders. Measure nutrient uptake through leaves, stems, and roots at different stages of rooting under greenhouse and controlled hydroponic conditions to match fertilizer supply with demand. Quantify the interaction of applied water and fertilizer rates on leaching of different forms of nutrients from propagation media. Identify the fertigation strategies that reduce nutrient leaching while maintaining crop health.


3.Progress Report

The potential of a water soluble fertilizer (WSF) to alter substrate-pH is estimated in carbonate equivalents (CCE) of acidity or basicity per unit weight of fertilizer. In three greenhouse experiments, the substrate-pH change was measured with up to 20 WSFs that varied in the concentration of NH4-N, NO3-N, urea-N and other nutrients. Data were used to model the effect of nitrogen form and concentration on pH change resulting from acidity or basicity of blended fertilizers, and this simple model explained an equal amount of the variation in substrate-pH as the more complex PM model. Accurate estimation of CCE is important to help growers formulate appropriate fertilizers to balance other factors such as water alkalinity and plant species. Recycling of irrigation water increases water use efficiency, but can also increase the risk of disease transmission to crops. We are running a wide range of experiments focused on the chemistry of disinfestant chemicals applied to control pathogens. For example, one objective was to quantify the persistence of sodium hypochlorite, activated peroxide, and quaternary ammonium chloride (QAC) in water to which peat-based substrates were added. Results emphasize that disinfestant efficacy decreases with increasing organic load, particularly for chlorine solutions, resulting in a need for both filtration and real time monitoring of sanitizing chemical concentration. The objective of this project was to summarize literature on chlorine efficacy to control plant pathogens. The compilation of data included mortality efficacy data of 11 genera of plant pathogens (22 species). The efficacy of chlorine varied with pathogens species and within species it varied with life stage. Given the high dose required to control certain pathogens, chlorination should be viewed as only one component of an overall sanitation and integrated pest management approach. This data can be used by growers as a reference guide for whether chlorine is likely to be an effective control for the target pathogen of interest. Three refereed journal publications, four refereed proceedings, and three trade publications were published along with fourteen conference presentations and workshops on plant nutrition and water quality research. Four book chapters were submitted on this topic. A website (watereducationalliance.org) was used to publicize research results, with 2,654 unique visitors over 12 months. A total of 32 grower and allied companies were directly involved in onsite research and as contributors to workshop activities. This research relates to the ARS parent project, Sub-objective 2a: evaluate the use of non-destructive sensor technology to measure and predict the impact of biotic and abiotic stresses in ornamental crops. Progress was monitored through email communication, one face-to-face meeting, and joint presentations.


Last Modified: 12/26/2014
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