Location: Application Technology Research2009 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
Studies investigating the role of light on phosphorus uptake and plant requirements began on vinca and zinnia, which will help define optimum nutrient requirements for a variety of bedding plant species in more realistic production environments. The crops celosia, sedum, mini rose, garden chrysanthemum, florist chrysanthemum, African violet, poinsettia, pepper, tomato, okra, onion, Swiss chard, and spinach were grown in silicon-containing and silicon-free fertilizer solutions, harvested, and quantified for silicon uptake; okra and garden chrysanthemum had significantly higher accumulation than most crops. Studies were completed on reflectance signals in New Guinea impatiens and geranium that had been fertilized with different amounts of phosphorus. These studies help define non-destructive measures of nutrient status and nutrient stress that are specific to a given element. Over the range of wavelengths from 350-1000 nm, there was no consistent signal that correlated to phosphorus status. Virtual Grower 2.5 was released in July, 2009. It has 19 species to simulate growth and development, supplemental lighting, improved calculations for the impact that shade/energy curtains can have on energy conservation strategies, opportunities to add new and theoretical greenhouse coverings or fuels to test for energy performance, and real-time weather “calls” in which the next two days of weather at a grower’s US site can be simulated within the model. Studies were completed investigating the feasibility of using a cellulose-based polymer derived from eucalyptus trees and a polyethylene-based polymer (PET) as a growth substrate. The PET material had excellent physical characteristics that allow it to substitute for up to 50% of traditional media types; however, long-term sustainability issues eliminate it from consideration as a substrate. The cellulose-based polymer, while it could be sustainably produced, did not have physical characteristics in production environments that would allow it to substitute for peat-based media. The cellulose served as a food source for many types of saprophytic fungi causing the substrate to lose mass during crop production. Six new Specific Cooperative Agreements were assigned through this project in conjunction with the Floriculture and Nursery Research Initiative: The Young Plant Alliance (five related projects that investigate annual floriculture crop production and quality from unrooted plants through post-harvest performance) and the Ornamental Plant Germplasm Center (OPGC). Collaborative research activity with the Young Plant Alliance has centered on incorporating some crop-specific information into the Virtual Grower software. While not a new project, the OPGC had a change in focus in 2006. Research activity over the past year consisted of increasing the interaction the Center had with floriculture researchers so that the Center’s plant collection could be better characterized. For example, an agreement was developed to begin screening the Begonia collection for tolerance in growth and development to less-than-optimum temperatures and tolerance to the root pathogen Pythium ultimum.
1. Virtual Grower 2.5 Was Released. Growers of greenhouse crops face many complex, interrelated systems on a daily basis wherein one decision influences others in sometimes counterintuitive ways. Virtual Grower software allows users to build greenhouses with many different types of materials, select from different fuel types, simulate heating needs and costs, and see the impact of those decisions on the growth and development of some commonly grown greenhouse crops. This version of the program has added supplemental lighting, several more species, the ability to add more fuels and materials for testing, improved calculations for energy curtains, and real-time weather “calls” in which the next two days of weather at a grower’s US site can be simulated within the model. This software has assisted both large and small growers in identifying energy (and money) saving strategies in their operations, improved efficient scheduling of crops, and helped growers obtain energy efficiency improvement grants through various funding sources.
2. Factors Controlling Sudden pH Decline Determined. When crops such as geranium and marigold are grown in containers in a greenhouse setting, growers have noticed that in a matter of a few weeks, the pH of the root zone declines two to three units. This condition, called sudden pH decline or SPD, leads to loss of crop quality or total crop failure. While it is linked with some specific crop types, the basic cause of SPD was not known. In a cooperative project, it was found that low phosphorus, high light, and high temperature by themselves and in concert with one another can lead to SPD. In each case, the nutrient, light, and temperature stress shifts the ratio of uptake of nitrate and ammonium forms of nitrogen to more preferentially ammonium uptake. This results in more acidification of the root zone. Knowing this information, growers can better avoid the environmental conditions that lead to the condition, can more appropriately supply these crop types with phosphorus, nitrate, and ammonium, and take comprehensive corrective action (management of environment and fertility) when faced with the condition. Breeders could also apply these environments during crop breeding and selection to select for varieties that are more resistant to SPD.
Frantz, J., Locke, J.C., Datnoff, L., Omer, M.A., Widrig, A.K., Sturtz, D.S., Horst, L., Krause, C.R. 2008. Detection and Quantification of Silicon in Floricultural Crops Utilizing Three Distinct Analytical Methods. Communications in Soil Science and Plant Analysis. 39:2734-2751.