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United States Department of Agriculture

Agricultural Research Service

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

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:

Vapor pressure deficit (VPD) is a measurement used in commercial propagation greenhouses to make dynamic mist control decisions based on the ambient climate rather than a static time clock situation. The greatest error in these systems is the measurement or estimate of leaf temperature which is a measurement required to calculate VPD. During the spring 2012, environmental measurements were made at a commercial propagator in order to quantify the potential error in VPD resulting from the use of artificial leaf sensors compared to actual leaf temperature. These data are still being evaluated. In 2012, the optimal water requirements in the media for unrooted cuttings in propagation were identified. Experiments were carried out where cuttings were provided a range of media water contents through the use of a slanted table outfitted with a capillary mat dipped into a water bath. A constant height is maintained in the water bath with a float valve, thus as the capillary mat height increases above the waterline, the water potential decreases and the water content of the media decreases. This system allows for a constant media water content to be maintained throughout the experiments. These levels ranged from 100% down to approximately 70% of saturation. We used both Poinsettia and Osteospermum as model plants. The Osteospermum rooted best at 94% saturation while the Poinsettia rooted best at 82% saturation. This data along with the information on VPD have been used by growers and propagators to re-evaluate their water use practices. We are currently working on identifying evapotranspiration and transpiration rates of Osteospermum cuttings in propagation. These plants tend to wilt badly during the first 3 days in propagation so we are looking at their water use for days 1, 3, 5 and 7 to see how it changes. The goal of this project is to be able to model how the water is being used by the cuttings in order to predict when wilting would occur in various environments. Using the data from our experiments we should be able to model how the cuttings use the water and predict when mist should be applied. This experiment is still in progress. We are also working on a project with environmental sensors placed in commercial greenhouses that use wireless technology. We are able to access the data from this system in real time to observe the current environment. Light levels, temperature, relative humidity, mist events and VPD are measured by this system. This system is still under development and will continue to improve our understanding of commercial propagation environments. 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: 4/19/2014
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