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United States Department of Agriculture

Agricultural Research Service


Location: Application Technology Research

2013 Annual Report

1a. Objectives (from AD-416):
Objective 1: Evaluate plant nutritional requirements to optimize production and enhance quality. 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. Sub-objective 1b: Determine the uptake, accumulation, and potential benefit of silicon in ornamental crops and explore the potential for its use as a buffer to Cu toxicity and an alternative approach to pathogen control. Objective 2: Develop new and/or improved methods to detect, quantify, and manage biotic and abiotic stresses in ornamental crops grown in soilless and/or hydroponic greenhouse culture. Sub-objective 2a: Evaluate the use of existing non-destructive sensor technology and develop new molecular probes to measure and predict the impact of biotic and abiotic stresses on ornamental crops. 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, pest management, and other production inputs. Objective 3: Evaluate existing and alternative growth medium amendments to determine the potential to deliver Si and buffer pH without negatively impacting beneficial microorganisms or crop growth.

1b. Approach (from AD-416):
Impatiens, geranium, vinca, and zinnia will be grown in media amended with different concentrations of phosphorus and boron under different light environments to determine optimum supply and tissue concentrations of these nutrients. Plants containing different amounts of these nutrients will then be inoculated with Pythium, Phytophthora, Botrytis, and powdery mildew to determine host susceptibility. These same plant species will also be grown with supplemental silicon in the fertilizer solution or incorporated into the substrate as rice hulls or Si-containing slags, and inoculated with the same pathogens or expose them to elevated Cu concentrations in the rootzone to determine if Si plays a role in a plant’s ability to withstand pathogen attack and Cu toxicity. Plants grown in different amounts of light and exposed to the aforementioned pathogens will be monitored with various sensors (e.g. digital cameras, infrared temperature probes, fluorometers, chlorophyll meters) and molecular tools to detect initial onset of stress symptoms. Finally, the production methods developed within these tests can be incorporated into the existing computer decision support software Virtual Grower to help growers make decisions in crop management.

3. Progress Report:
Experiments were conducted to determine the optimum rate for amending greenhouse substrates with gasified rice hull biochar (GRHB). It was determined that substrates amended with 10% (by volume) of GRHB were optimal. At this rate, the GRHB supplied sufficient phosphorus (P) and potassium (K) such that these two elements could be eliminated from the fertilizer regime. At these rates, there were negligible effects on substrate pH or EC levels. Despite detection of moderate levels of all micronutrients in the GRHB, it was determined that micronutrients must be included in the fertilizer program in conjunction with the GRHB in order to produce optimal plant growth. Building on the success with GRHB, we conducted a series of experiments to determine if other forms of rice hulls (parboiled or torrefied) would provide similar quantities of P and K for production of greenhouse crops. Using a leaching column procedure and plant studies, we determined that GRHB releases far greater P and K than either parboiled or torrefied rice hulls.

4. Accomplishments
1. Use of biochar as a component in greenhouse substrates. Fertilizers are becoming increasingly expensive due to the energy required to manufacture them or the cost for mining them. Phosphorus (P) and potassium (K) are two of the primary nutrients used in fertilizers. Gasified rice hull biochar (GRHB) is a commercially abundant byproduct from the processing of rice. Our research has shown that GRHB contains a high concentration of P and K, and has potential as an alternative source for use in commercial potting substrates for greenhouse and nursery crops. Leaching column and plant growth studies determined that the optimal rate for amendment with GRHB into typical greenhouse potting substrate is 10% by volume. At this rate, sufficient P and K are provided for a variety of crop species without any additional P and K being provided in the fertilizer program. These rates do not adversely affect substrate pH or electrical conductivity. Although the GRHB utilized in these trials is available in large commercial quantities for non-horticultural purposes, there is not a labeled use for the product in horticultural applications. Despite this, our data provides the industry with baseline information on rates of application should this product, or a similar product, become available to the horticultural industry to potentially enhance sustainability.

Review Publications
Krug, B.A., Whipker, B.E., McCall, I., Frantz, J. 2013. Elevated relative humidity increases the incidence of boron deficiency in bedding plants. HortScience. 48:311-313.

Locke, J.C., Altland, J.E. 2012. Use of ground wheat straw in container nursery substrates to overwinter daylily divisions. Journal of Environmental Horticulture. 30(4):207-210.

Andiru, G., Pasian, C., Frantz, J., Jones, M. 2013. Greenhouse production of Impatiens wallerana using a controlled-release fertiliser produces quality finished plants with enhanced garden performance. Journal of Horticultural Science and Biotechnology. 88(2):216-222.

Runkle, E.S., Blanchard, M.G., Frantz, J. 2012. Using flowering and heat-loss models for improving greenhouse energy-use efficiency in annual bedding plant production. Acta Horticulturae. (ISHS)957:99-106.

Adams, C., Frantz, J., Bugbee, B. 2013. Macro- and micro-nutrient release characteristics of three polymer-coated fertilizers: Theory and measurements. Journal of Plant Nutrition and Soil Science. 176(1):76-88.

Andiru, G., Pasian, C., Frantz, J., Jourdan, P. 2013. Longevity of controlled release fertilizer influences the growth of bedding Impatiens. HortTechnology. 23(2):157-164.

Barnes, J., Whipker, B., McCall, I., Frantz, J. 2012. Nutrient disorders of 'Evolution' mealy-cup sage. HortTechnology. 22(4):502-508.

Last Modified: 06/27/2017
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