Location: Application Technology Research2016 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:
Studies have evaluated the effect of silicon on Xanthomonas gardneri infection in tomato. Inoculation produced more symptoms in silicon-fed plants compared to plants not grown with silicon, which is the opposite of the many beneficial effects observed in many biotic and abiotic stressors. Silicon-fed plants had significantly larger symptomatic leaf area for the two cultivars tested (Early Girl and H1015). Further analyses suggest that stomatal conductance and foliar permeability in silicon-fed plants are not the leading cause for the increase in symptom formation. Studies were carried out that concluded silicon did not have direct effects on Xanthomonas species infectivity rate and symptom formation in tomatoes. Taken together, it suggests silicon is having a direct effect on the plants, exacerbating an immune response against the bacterial pathogen. We continue to evaluate silicon (Si) fertilization in plants, characterizing the beneficial effects following exposure to abiotic stress, its uptake and distribution in plants, and species and cultivar variability in response to Si supplementation. Silicon fertilization mitigated chilling injury in horticultural plants. The severity of chilling injury was reduced in most cold-sensitive species evaluated, and to a greater extent at colder temperatures, but little response was observed in cold-tolerant species. In addition, a stress-induced Si-accumulation (SISA) response, quantified as an increase in foliar Si concentration following exposure to chilling temperatures, was noted in most species evaluated. Our research has shown that species and cultivars exhibit varied patterns of Si accumulation and distribution in roots, stems, leaves, and flowers. Additional photosynthesis curves have been developed for protected horticulture crops in response to light, temperature, and CO2. They have been incorporated into PhotoSim, a decision-support software program, increasing the number of available species to 19. This program allows growers to more effectively manage heating, cooling, lighting, shading, and CO2 supplementation decisions in greenhouses or controlled environments. Carbon dioxide (CO2) concentrations were monitored in greenhouses to determine the frequency and duration of sub-ambient CO2 concentrations during winter and spring production. Follow-up studies are currently being conducted to evaluate the impact of sub-ambient CO2 concentration on inhibiting crop growth and development. Steam or hot water are being used by some nurseries for controlling weed and disease populations on reused plastic containers and propagation trays. There is little knowledge on what temperature is needed for controlling weed seeds. Research has been conducted to determine the killing temperature and exposure time for killing bittercress (Cardamine flexuosa) and creeping woodsorrel (Oxalis corniculata) seed. Our research has shown that temperatures of 70 to 90 C are needed for providing 100% control of these weed species. More research is needed to determine a more precise temperature range for each species, and more precise exposure times. Additional research is planned to validate these laboratory findings in a nursery setting.
1. Rice hulls provide weed control in containers by liming water on the container surface. Weed control is the most labor-intensive and expensive aspect in production of container nursery crops. USDA-ARS in Wooster, Ohio, determined the mechanism by which parboiled rice hulls provide weed control in container crops. Parboiled rice hulls are a clean, light-weight, Organic Materials Review Institute -approved organic mulch product that can be used for controlling weeds in nursery containers. Weed seed and spores (from liverworts and mosses) that land on top of the mulch surface fail to establish due to volumetric water content of the mulch layer. Compared to pine bark and sphagnum peatmoss, rice hulls retain very little water from an irrigation event, and they dry quickly from what little water they do retain. For weed seeds present on the surface of the container at the time of mulch application, rice hulls must form a physical barrier to prevent weed establishment. A mulch layer at least 1.25 cm thick is needed to physically impede weed establishment from beneath the rice hull mulch layer. Use of rice hulls for weed control provides a viable option for weed control in propagation houses where chemical herbicides are not labeled, it reduces costs associated with hand weeding crops (one of the most labor-intensive and expensive management activities in container crop production), and reduces reliance on chemical herbicides.
Zellner, W.L., Friedrich, R.L., Kim, S., Sturtz, D.S., Frantz, J., Altland, J.E., Krause, C.R. 2015. Continuing assessment of the 5 day sodium carbonate-ammonium nitrate extraction assay as an indicator test for silicon fertilizers. Journal of AOAC International. 98(4):890-895.
Gerovac, J.R., Craver, J.K., Lopez, R.G., Boldt, J.K. 2016. Light intensity and quality from sole-source light-emitting diodes impact growth, morphology, and nutrient content of Brassica microgreens. HortScience. 51(5):497-503.
Altland, J.E., Locke, J.C., Zellner, W.L. 2016. Micronutrient availability from steel slag amendment in pine bark substrates. Journal of Environmental Horticulture. 34(3)67-74.