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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

2013 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 fertilization 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 is the final report for this project. The ultimate goal of the project is to reduce energy and chemical inputs in ornamental crop production. Researchers made significant progress in each of these areas and results from the work are being implemented commercially already and a number of papers are being written or submitted for publication in the scientific press.

Researchers continued to identify the effects of temperature, light, and carbon dioxide on photosynthesis of several ornamental crops. This year researchers focused on the effects of short-term 3 hour high-temperature stress on photosynthesis of heat tolerant and intolerant cultivars of three commercially significant ornamental crops. An experiment carried out to better understand the basis of heat tolerance in flowering and the impact of allowing greenhouse temperatures to rise in the afternoons in greenhouses on flowering. The experiments were conducted in growth chambers. Photosynthetic data were collected using a portable photosynthesis meter that has the capacity to alter irradiance, carbon dioxide. Plant temperature was altered using the growth chamber itself.

In a separate study researchers examined the role of leaf coloration, specifically anthocyanins, in protecting plants from adverse temperature effects on photosynthesis. Coleus and Panicum were used as model plants. In both cases, researchers studied the photosynthetic behavior of 2 cultivars of each – one with high and one with low levels of anthocyanin.

Researchers are also identifying combinations of plant growth regulators that result in synergistic or novel effects, and identifying alternative application strategies to maximize their efficacy. The goal is to reduce total plant growth regulator applied while maintaining the desirable effects of these compounds and reducing labor costs associated with their application. In addition, the novel effects of combinations we are finding offer new uses entirely for their application.

In other work, researchers are studying the basis for variation in disease resistance among geranium and fuchsia cultivars/varieties to Botrytis (major greenhouse disease). Susceptible and resistant cultivars/varieties were identified with industry representatives and were treated with growth regulators that impacted endogenous phytohormone levels to determine whether geranium susceptibility to Botrytis was impacted. Susceptibility was assessed using an assay we developed where a known quantity of Botrytis spores were applied to geranium leaves and disease proliferation in an environment conducive to disease infestation (growth chamber) was quantified after 3 days.

Scientists grew 40 ornamental/herb species under eight lighting treatments that varied in day length and irradiance to identify what conditions induced flowering. The experiment was replicated three times. Such information allows growers to schedule finishing of crops when they want them to and reduces potential inputs in overall crop production by reducing losses due to late finishing, or losses due to unsalable material because plants flowered at a size that is too small for sale.

Aside from this work, scientists continue to do work in identifying different ways to apply growth retardants to increase efficacy and reduce cost, and whether light quality can be altered to reduce growth retardant use and increase disease resistance to decrease pesticide use.

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.


Last Modified: 10/1/2014
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