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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

2009 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

This congressionally mandated Specific Cooperative Project works in concert with four other projects for improvements in the efficient production of bedding plants. This aspect of the project focuses on pH management and water quality in container production. Current research on pH management is focused on two areas: lime and fertilizers. Laboratory protocols (the LimeR series) are being developed for media companies to measure the reactivity of different lime sources, which affects how quickly lime reacts to achieve a target pH; unreacted residual lime in growing media, which affects buffering to pH change; and how much lime is required for a particular batch of substrate. Models that predict lime reaction and protocols to estimate the lime requirements of different batches of growing media in order to achieve a target pH are being developed. 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 are underway that estimate the pH effect of fertilizers in container production. A draft model of fertilizer acidity and basicity is being developed based on the charge balance principle where cations (such as ammonium) are acid and anions (such as nitrate) are basic. Leaching and recharge of nutrients are the topic of water quality research. During propagation of cuttings, a large amount of water is typically applied, leading to a high volume of water and nutrients leached; up to 49,249 gallons leached per acre over a 4-week crop cycle in commercial greenhouses has been measured. This research aims to understand how to best manage leaching and applied fertilizer concentration during plug and cutting production. It was found that after 1.5 container capacities (about one soil volume) of water is applied, nutrients in the soil are mostly replaced by the applied fertilizer solution. That means it is very easy to leach out pre-plant fertilizer under mist. Tissue nutrient levels tend to drop during the rooting of cuttings, and that petunias can take up nutrients through the leaves even before roots form. Management approaches include ensuring adequate fertilizer is applied during the stock plant phase to have moderate to high initial tissue nutrient levels in cuttings, applying a low fertilizer concentration in the mist, and recharging nutrients after plants are removed from mist. Experiments are running that investigate leaching pre-plant fertilizer from commercial and research media in plug trays, and also recharging nutrients. A further step is to investigate the effect of water quality and fertilizer solution on pH drift under mist propagation conditions. Progress of this cooperative project was monitored through monthly electronic (email) communication, shared participation in industry-related educational courses, and twice annual face-to-face communication at national meetings.


Last Modified: 9/1/2014
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