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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

2011 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 that some propagators use 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 2011, 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 2011, we have begun to identify the actual water requirements of cuttings in propagation. This phase of the project has begun with experiments that quantify the effect of media water content in propagation on adventitious root formation and leaf wilting. Experiments are currently underway where cuttings are 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. The current experiments use poinsettia and osteospermum as model plants. The results of the mist irrigation water use survey of commercial propagators were presented at two meetings of leading commercial growers (Floriculture Research Alliance Meeting, Oct. 2010; Ohio Floriculture Association Short Course, July 2011). Growers have taken this information back to their businesses to re-evaluate their water use practices, especially the growers that tended to have higher water use practices. We anticipate going back to some of these facilities in coming years to compare their current practices to the baseline data collected in 2010 in order to quantify the practical impact of this project. The capillary mat system built to provide constant media water content is a major improvement in the development of our facilities to address the questions that we seek to answer about the actual water requirements of cuttings in propagation. Having this system now fully constructed will allow us to collect some very useful data in the coming year. As propagation cycles take ~21 days, we are able to run experiments relatively quick now that this system is operational. This research relates to ARS parent project sub-objective 2a: evaluate the use of non-destructive sensor technology to measure and predict the impact of biotic and abiotic stresses in ornamental crops. The project was monitored through periodic reports and conference meetings.


Last Modified: 9/2/2014
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