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United States Department of Agriculture

Agricultural Research Service

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

Location: Application Technology Research Unit

2012 Annual Report


1a.Objectives (from AD-416):
The objective of this research 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 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:

With an increase in global water scarcity, efficient water use has become a critical factor. Particularly, agricultural production needs to improve water use efficiency as there is increasing pressure on water use for agriculture, which may become worse due to climate change, degradation of available water sources, and increased water demand from urban areas. These factors, along with water restrictions on agriculture, make it a pressing challenge to use available water efficiently for quality production. Efficient water use will not only reduce production cost, but also increase profitability by reducing fertilizer runoff. It has been documented that plant growth regulators (PGR) improve water use efficiency; however, very little information is available about ornamental plants. Moreover, this study was conducted to optimize the PGR rate for selected ornamental species. Two potted bedding plants, ‘Pacino Gold’ sunflower and ‘Magellan Pink’ zinnia, and four plug crops, ‘Moonsong Deep Orange’ marigold and ‘Magellan Pink’ zinnia, grown from seed, and ‘Fiesta Burgundy’ impatiens, and ‘Suncatcher Coral Prism’ petunia, grown from vegetative cuttings, were used in this study. For all species, plants were grown in either 36 cell (for potted plants), or 128 cell (for plug studies) trays using 1P Fafard substrate. Potted plants were transplanted to either 5-in. (sunflower), or 4.5-in. pots (zinnia) at 2-true leaf stage. Two weeks after transplanting, plants were sub-irrigated to field capacity (FC), drained for 48 h and drenched with 4 oz. of paclobutrazol at 0, 1.0, 2.0 and 4.0 mg L-1 for sunflower, and 2 oz. of 0, 0.5, 1.0 and 2.0 mg L-1 for zinnia. For plugs, when plants reached the 2-leaf stage, trays were sub-irrigated to FC, drained for 30 min., and sprayed with ancymidol at 0, 40, 80 and 160 mg L-1. After PGR application, further irrigations were made when the fresh weight was less than 40% of available water, which was the difference in weight of the container, substrate and plant between field capacity and permanent wilting point. Plants were weighed twice a day for plug studies and daily for potted plants; those requiring irrigation were sub irrigated for 5 min. in a calculated water amount followed by draining them on top of saucer for 30 min. and water uptake was recorded by measuring remaining water in the saucer. Data were collected on daily water use, total water use, termination fresh weight, termination dry weight, leaf relative water contents, and water use efficiency. Plant height and plant diameter were also measured at termination for potted plants. As PGR concentration increased, plant growth (fresh weight, dry weight, plant height and diameter) and total water use was less for all tested species. For potted sunflower, the optimal concentration of paclobutrazol for reduced water use was 1.0-2.0 mg of active ingredient, which had 24% less water use at 1.0 mg and 31.5% less water at 2 mg concentration. For potted zinnia, optimal concentration would be 0.5 – 1.0 mg L-1 as it decreased water use by 33 and 45% at 0.5 and 1 mg L-1 compared to control. For plugs, the optimal concentration of ancymidol would be foliar application of 80-160 mg L-1 as these concentrations reduced water use by 6-15% for impatiens, 1-7% for marigold, 17-25% for petunia, and 10-18% for zinnia. Application of plant growth regulators not only control excessive plant growth, but also reduced water use. Producers should consider the water use reduction from using PGRs in addition to the traditional benefit of growth control as a best management practice. 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: 8/22/2014
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