Location: Application Technology Research2015 Annual Report
1a. Objectives (from AD-416):
The overall objective of this project is to conduct research that is relevant to the containerized nursery and greenhouse production (protected horticulture) industry, which will produce outcomes that enhance efficiency, improve economic return, and reduce environmental impact. The following objectives, which have been identified during the past project cycle; have been carefully selected by the Greenhouse Production Research Group to meet priority researchable needs of the industry. Staff and resources have been assembled to address these researchable objectives, and initial research has yielded a base of knowledge, appropriate research skills, and procedures to address this project. Over the five-year planned duration of this project, it is anticipated that there will be significant enhancement of floricultural and nursery productivity with optimization of water, nutrient, fertilizer, and crop protection inputs while minimizing agrochemical, labor, and environmental impacts. Objective 1: Determine the role of silicon in management of abiotic stresses in protected horticulture production systems. Sub-objective 1.1: Elucidate the mode of action of supplemental silicon on the alleviation of abiotic stress symptoms. Sub-objective 1.2: Identify a strategy for supplying supplemental silicon in protected horticulture systems. Objective 2: Determine the influence of environmental parameters on growth and development of protected horticulture crops and incorporate the information into user friendly decision support software such as Virtual Grower. Sub-objective 2.1: Quantify photosynthetic responses of protected horticulture crops to environmental parameters. Sub-objective 2.2: Evaluate energy-efficient lighting and heating strategies for bedding plant production. Sub-objective 2.3: Expand the decision support model Virtual Grower to include additional production parameters and crops. Objective 3: Develop management strategies for containerized crop production systems that improve crop growth, reduce costs, and reduce loss of nutrients and agrichemicals to the environment. Sub-objective 3.1: Quantify the chemical and physical properties of novel materials that provide producers with substrates that are economical, sustainable, and effective. Sub-objective 3.2: Determine the utility of biochar for supplying phosphate and potassium in peat and bark-based substrates. Sub-objective 3.3: Through improved understanding of weed biology, develop methods for weed control in crops and sites where herbicides are not labeled.
1b. Approach (from AD-416):
A multi-disciplinary team will address the goal of enhancing containerized crop production in the context of protected horticulture by utilizing a three-fold approach to address production efficiency, economic return, and environmental impact. Plant nutrition, including the role of silicon as mediated through soilless media composition, will be studied to determine how plant stress is impacted by nutrient supply in both floricultural and nursery crops. Environmental parameters, such as light, temperature, and carbon dioxide, will be evaluated for their influence on growth and development and results will be incorporated into our decision support software model, Virtual Grower. Management strategies will include chemical and physical quantification of substrate components, as well as determination of the utility of novel components as sources of macronutrients in nutrient deficient soilless media, and the improved understanding of weed biology to improve control approaches for crops and sites which lack current herbicide alternatives.
3. Progress Report:
Greenhouse plant trials were conducted to determine the potential usefulness of biochar and steel slag as amendments to soilless container growing media. Rice hull biochar additions of up to 30% (v/v) slightly increased substrate water holding capacity, decreased unavailable water, and increased substrate bulk density. Substrate cation exchange capacity was unaffected but pH was elevated by up to 1 point. The most important observation was the increase in availability of nutrients, especially phosphorus and to a lesser extent potassium. These levels were sufficient to provide good growth response for up to 6 weeks of growth but only if a micronutrient package was provided. Steel slag, a byproduct of the steel manufacturing industry, was evaluated in greenhouse and nursery substrates at varying rates to determine its potential for adjusting pH and providing micronutrients. Steel slag has a high concentration of calcium oxide, as well as other nutrients and micronutrients, such as iron, silicon, and manganese. Steel slag demonstrated a greater pH neutralizing potential than dolomitic limestone and provided higher concentrations of plant-available silicon. Despite having high concentrations of other micronutrients such as iron and manganese, steel slag alone did not provide sufficient micronutrients for acceptable plant growth. Photosynthesis curves, developed for protected horticulture crops in response to light, temperature, and CO2 were modeled and incorporated into a new decision-support software program called PhotoSim. This program will allow growers to more effectively manage heating, cooling, lighting, shading, and CO2 supplementation decisions in greenhouses or controlled environments. Currently, the program includes 13 crops, and more crops will be added. Virtual Grower is a decision-support software tool that allows users to design a virtual greenhouse, predict energy usage, compare relative efficiencies of different structures, and predict crop growth. An updated version, Virtual Grower 3.1, has been released. Program enhancements include the addition of more site locations, additional plant species, and system performance enhancements. Development continues on the creation of Virtual Grower4. Experiments were conducted to determine the role of silicon (Si) in plants during cold stress. A stress-induced Si-accumulation (SISA) response was noted in most species evaluated, quantified as an increase in foliar Si concentration following exposure to chilling temperatures. Additional research is planned to determine the physiological benefits of Si during cold stress and how it plays a role in stress tolerance. The role of Si in mitigating nutrient deficiencies in ornamental crops is being evaluated. Sunflower and petunia fertilized with a complete nutrient solution were grown with low to moderate rates of phosphorus. When supplemental Si was provided in conjunction with very low phosphorus rates, sunflowers flowered a few days earlier and petunias had enhanced flower number. Continued studies will look at the effects of supplemental Si in the presence of deficiency levels of other plant-essential elements. Studies evaluating energy efficient production strategies for spring greenhouse production indicate that plants can be grown in a warm/high light environment and transferred to a cool/low light environment for up to two days per week without appreciable delay in flowering or reduction in plant growth. The potential savings in energy costs, calculated over the length of production, was estimated to be 8 to 23%. Experiments were conducted to determine the impact of light quantity and light quality on foliar nutrient concentration. In microgreens and bedding plant seedlings grown with sole-source lighting, the accumulation of plant macro- and micronutrients varied with light quantity and quality. Additional studies will focus on the impact of light quality on nutrient uptake when provided as supplemental lighting in greenhouses. Pine bark is often amended with varying levels of peat moss in order to increase water holding capacity of the substrate. Our research demonstrated that increasing the peat moss amendment rate from 0 to 40% changed the bulk physical properties of the substrate, most notably by increasing the water holding capacity and easily available water. Despite changes in bulk physical properties, the volumetric water content at the substrate surface was the same in substrates with 0% to 40% peat moss. As a result, herbicide longevity and weed germination were similar in pine bark substrates amended over this range.
1. Steel slag can be effectively used as a component in soilless container media to adjust pH, provide beneficial silicon, and some nutritional elements. Soilless growing media, typically used in containerized production, generally has a low initial pH and it contains minimal nutrition for plant growth. Steel slag a by-product of the steel manufacturing industry has been used to elevate field soil pH and is associated with elevated plant nutrition. ARS researchers at Toledo and Wooster, OH demonstrated that media pH can be adjusted utilizing steel slag as a substitute for dolomitic lime in soilless growing systems. In addition, some nutritional benefits can be realized, including elevation of silicon, but these inputs were insufficient to eliminate the use of additional fertilization, especially for micro elements. However, with careful management, the use of steel slag could enable greenhouse and nursery growers to reduce fertilizer inputs resulting in less nutrient contamination of the environment.
2. Development of PhotoSim as a decision-support tool for plant production in protected horticulture systems. Plant photosynthetic rate is impacted by light intensity, CO2 concentration, and temperature. Lighting, shading, heating, cooling, and CO2 enrichment decisions are often made without an understanding of how they impact photosynthetic rate and plant growth. ARS scientists in Toledo, OH developed single-leaf photosynthetic response curves for popular bedding and potted crop species in response to light, temperature, and CO2. The data were modeled and packaged into a decision-support software tool called PhotoSim that provides growers the ability to estimate the impact that changing one of these parameters will have on plant growth, thereby allowing them to better manage the greenhouse or protected horticulture environment, improve plant growth, and reduce production costs.
3. Amendment of nursery pine bark substrates with peat moss improves bulk physical properties without affecting herbicide performance or weed growth in containers. Weeds are very problematic in greenhouse and nursery containers. Cultural practices that improve growth of the ornamental crop often exacerbate weed growth. ARS researchers at Wooster, OH, documented the impact of amending pine bark substrates with peat moss on both the ornamental crop and weed growth. The peat moss improved the water holding characteristics of the bulk substrate. However, the volumetric water content on the substrate surface was not affected and thus herbicide longevity and weed emergence were also unaffected. This provides U.S. nursery growers with greater knowledge on how to use an important media component (peat moss) to improve their container substrate without adversely affecting weed control.
4. Indaziflam and flumioxazin provide preemergence horseweed (Conyza Canadensis) control in field nursery production. Glyphosate is considered to be a useful for weed control in field nursery crops. However, there is an increasing presence of glyphosate-tolerant horseweed populations in the U.S. that cannot be effectively controlled with glyphosate. ARS researchers in Wooster, OH explored the use of preemergence herbicides for preventing establishment of horseweed in field nursery cropsResearchers found that indaziflam and flumioxazin are effective at suppressing horseweed and other weed species when applied in either fall or spring. This information will help nursery growers implement more effective preventative weed management programs and avoid manual removal of horseweed, thus drastically reducing the cost of weed management in nursery crops.
Hoskins, T., Owens, J., Fields, J., Altland, J.E., Easton, Z., Niemiera, A. 2014. Solute transport through a pine-bark based substrate under saturated and unsaturated conditions. Journal of the American Society for Horticultural Science. 139:634-641.
Altland, J.E., Locke, J.C., Zellner, W.L., Boldt, J.K. 2015. Steel slag raises pH of greenhouse substrates. HortScience. 50(4):603-608.
Altland, J.E., Zellner, W.L., Locke, J.C. 2015. Substrate pH and butterfly bush response to dolomitic lime or steel slag amendment. Journal of Environmental Horticulture. 33(2):89-95.
Mishra, S., Heckathorn, S., Krause, C.R. 2015. The levels of boron-uptake proteins in roots are correlated with tolerance to boron stress in barley. Crop Science. 55:1741-1748.