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United States Department of Agriculture

Agricultural Research Service

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

Location: Application Technology Research Unit

2012 Annual Report


1a.Objectives (from AD-416):
The objective of this unified research effort is to improve the efficiency of plant production through a multi-disciplinary team approach that focuses on scheduling, the environment, energy, nutrient, water, and chemical growth regulator resources.


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:

We have continued to refine a new method to estimate the potential of a water soluble fertilizer (WSF) to raise or lower substrate-pH. The current “Pierre’s Method” model was developed using mineral field soil systems, based on assumptions that may not apply in container substrates. The new nitrogen-based method predicts fertilizer acidity or basicity based on the ratio and concentration of nitrogen (N) forms from ammonium, urea, or nitrate. Validation experiments were run with varying water alkalinities, ratios of ammonium to nitrate nitrogen, and N concentrations. The nitrogen-based method was as accurate at predicting fertilizer effect on substrate-pH as Pierre’s Method, but with simpler and more grower-friendly assumptions. We found that ammonium-N was approximately 9 times more acidic than nitrate-N was basic in greenhouse trials. However, when there is low alkalinity water and no residual lime in the substrate, a further complication is that substrate-pH tends to decline as fertilizer concentration increases, even with application of a basic-reaction fertilizer, because of nutrient interactions with substrate cation (positive-charge) exchange. Following further experimental refinements to incorporate a substrate-EC component, we should have a validated predictive model in the coming year. Irrigation water in ornamental greenhouse and nursery operations can be a source or dispersal mechanism for diverse biological problems including algae, biofilm and pathogens. Growers face the challenge of selecting between alternative treatment technologies such as chlorination, copper ionization and ozone for control of waterborne microbial problems. An online survey was carried out to identify the perceived key attributes of water treatment technologies for control of algae, biofilm, and pathogens that growers should consider in technology selection. A panel of three Expert Types (43 ornamental growers, 28 water treatment industry suppliers, and 34 research and extension faculty) was asked to rate their level of agreement, on a scale from 1 (strongly disagree) to 5 (strongly agree), on the importance of 23 listed financial, social, technical, and environmental attributes when selecting between treatment technologies. Response rate was 60%, including 27 growers, 15 suppliers and 21 faculty. There was a significant interaction between Attribute and Expert Type (P <0.05). Attributes with an average rating above 4.5 for all Expert Types included residues that are not toxic to plants, effective control of plant pathogens; effective control of biofilm; ease of monitoring; worker safety; low risk of environmental impacts; and suitable for large operations. Cost was also perceived as an important attribute, with low operating cost per volume having a higher rating (4.17±0.64, mean ± standard deviation) than low installation cost (3.37 ± 1.15), with no statistical difference between Expert Types. Control of target microorganisms varied in perceived importance from plant pathogens (4.63 ± 0.56), algae (4.39 ± 0.781), and biofilm (4.31 ± 0.81). A lower rating for human food safety pathogens (3.61 ± 0.90) was probably influenced by this ornamental grower population and nursery application of the technologies. All 23 attributes had an average rating of at least 2.9 both across and within Expert Types. Results suggest that selection of water treatment technologies for the control of waterborne biological problems encompasses technical, economic, environmental and social attributes. Our next step is to combine these survey results with other research data, to develop an online tool to help growers match their own water treatment goals with available technologies. This project relates to two sub-objectives of the parent project. Sub-objective 1a: Elucidate the optimal tissue concentration of P and B in different light environments for major production species and how their susceptibility to foliar and root pathogens are influenced by nutrient status and light; and sub-objective 2b: Improve the Virtual Grower software model to enable growers to optimize their production systems by making more informed economic decisions about energy use, plant growth, and scheduling to meet premium market windows. Each 12-month milestone adds 6 to 8 new species, and this project will assist in meeting that goal. Additionally, features such as supplemental lighting, water use, nutrient use, can be added and improved, and additional model validation will be accomplished. It is planned that every 12 months, an additional version will be publicly released.


Last Modified: 11/23/2014
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