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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

2010 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 pH of growing media affects plant health and nutrition, particularly because micronutrient solubility and availability for plant uptake is highly pH- dependent. Our research focused on effects of lime and fertilizer on achieving and maintaining a target pH during ornamental plant production in containers. A range of laboratory protocols (LimeR series) for media companies have been developed to measure the reactivity and pH-buffering of lime. We are continuing to model lime reaction, currently with analyzing data from experiments where media moisture level and temperature were varied. These protocols help estimate the amount and type of lime required by different batches of growing media in order to avoid out-of-range pH issues. The potential acidity or basicity of a fertilizer written on the fertilizer bag is based on a model developed in the 1920’s for soil application of solid fertilizer. Many of the assumptions of this model do not apply to greenhouse culture. Experiments have been run in hydroponic and peat-based media systems with geraniums, impatiens, and petunia to compare reported pH influence of water soluble fertilizers with measured pH response. A draft model of fertilizer acidity and basicity is being developed based on the charge balance principle where cations (such as ammonium) are acidic and anions (such as nitrate) are basic. We are now analyzing data and developing coefficients for different nutrient ions to develop the new estimate of acidity or basicity. Growers recognize the importance of water conservation, and the capture and reuse of runoff. However, the potential spread of waterborne pathogens has also highlighted the need to treat and manage water quality, especially in recycled water. During 2009 we undertook a survey of organic and biological load in irrigation water in 24 greenhouse and nursery locations around the U.S. Mean bacteria count and chemical oxygen demand (a measure of requirement for sanitizing agent) in subirrigation nutrient tanks, collection ponds, and ebb-and-flood benches and floors were above EPA and extension-recommended levels for irrigation water. Efficacy of treatment systems varied widely between locations, even within the same class of active ingredients. Organic load remained high following filtration and in some cases we even observed an increase in bacterial load following chemical treatment. Our results highlight a need to monitor water quality, and evaluate design and operation of treatment systems. In consultation with growers and industry experts in the area of water treatment, we have identified a number of key knowledge gaps that are important for growers to have success in water treatment. Future research will develop an onsite monitoring method for waterborne pathogens, evaluate two key reasons why treatment systems may be failing (compatibility with fertilizer solutions, and excess organic matter through inadequate filtration), and analyze the economic costs and benefits of treatment technology options. Progress was monitored through quarterly phone calls, 3 face-to-face meetings, and regular email communication.


Last Modified: 4/17/2014
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