Location: Application Technology Research2017 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:
Silicon (Si) can be supplied to crops to mitigate the effects of abiotic and biotic stress. We are continuing to evaluate Si fertilization for plants grown in protected horticulture systems. Research indicates that providing supplemental Si to geranium (Pelargonium ×hortorum) stock plants enhances rooting of the cuttings, but only when subjected to simulated shipping conditions prior to propagation. Additionally, we are modeling Si uptake in plants in response to various Si sources and amendments in order to begin developing Si application recommendations for growers. Sub-ambient CO2 concentrations are a common occurrence in greenhouses during winter and spring production, and can potentially limit crop growth. It has received little attention, as more focus is placed on the benefits of supplemental CO2 in controlled environments. Growing sunflowers (Helianthus annuus) in an environment where CO2 naturally fluctuated during the day, as in a greenhouse, resulted in sub-ambient CO2 concentrations (~370 ppm, or 30 ppm below ambient) and plants had reduced flower diameter, plant height, rooting, and dry mass. Single-factor photosynthesis curves have been developed in previous years for protected horticulture crops in response to light, temperature, and CO2 and incorporated into PhotoSim. This program allows growers to more effectively manage heating, cooling, lighting, shading, and CO2 supplementation decisions in greenhouses or controlled environments. On-going research is being conducted to develop multi-parameter photosynthetic models (e.g., light intensity x CO2 concentration) to account for potential interactions between factors. This will allow us to determine optimization points on a systems level. Seeds of many weeds, most notably bittercress (Cardamine flexuosa) and creeping woodsorrel (Oxalis corniculata), stick to plastic containers and trays and are reintroduced into the production system reused. We determined the specific temperatures and exposure times necessary to kill weed seeds on plastic containers and propagation trays using either hot-water or steam. Temperatures of 90 C provided nearly complete control of both species. Future experiments will evaluate temperatures in the range of 80 to 90 C to more accurately determine killing temperatures. Leaching of nutrients, especially nitrate and phosphate, from nursery and greenhouse substrates can impair surface and ground waters. Research has been conducted to determine the impact of lime application and container substrate pH on nitrate and phosphate leaching. Results have varied by the source of bark, and thus it has been concluded that modification of substrate to have low pH will not be a reliable cultural practice to reduce nitrate and phosphate leaching. Parallel research is determining if metal oxides can be amended to the substrate to bind anions such as nitrates and phosphates and reduce their leaching. That research is ongoing.
1. Elevated CO2 and heat stress decrease root nutrient uptake. Elevated CO2 often enhances plant growth, whereas heat stress often reduces plant growth. The combination of elevated CO2 and heat stress is expected to be more common in the future, and understanding the impact on plant growth and nutrient relations can provide insights for crop improvement. Researchers at the University of Toledo, Toledo, Ohio, in collaboration with ARS researchers, have developed biomarkers for nutrient-uptake proteins in roots. Elevated CO2 or chronic heat stress individually had minimal impact on plant growth and nutrient status, but the combination of elevated CO2 and heat stress severely reduced plant growth, nutrient uptake, and nutrient assimilation, in part by decreasing the concentration of nutrient-uptake proteins in roots. This may lead to decreased yield and food quality of plants grown under these conditions, but there is potential utility to use these biomarkers as a tool for selection of new genotypes more tolerant of these conditions.
2. Determining nutrient release from bagged potting substrates. A critical obstacle for producing bagged substrates is the over-release of nutrients from amended fertilizers while they sit in storage. This necessitates manufacturers to produce bagged substrates at or near the time of spring sales, which causes major logistical problems. USDA-ARS in Wooster, Ohio, determined the impact of initial moisture content, temperature, and storage duration on the release of nutrients from organic and conventional fertilizers in bagged potting substrates. Based on these results, substrate producers can better predict how nutrients will be released in bagged substrates as a function of storage conditions and time.
3. Small fruit production in containers with soilless substrates. There are many geographical and environmental conditions that prevent the traditional production of crops in soil. Soils of vacated urban areas may contain industrial pollutants, and soils of some regions in the U.S. have unsuitable mineralogical properties for crop production. USDA-ARS in Wooster, Ohio, is collaborating with Ohio State University scientists to develop cultural practices for growing small fruit crops (blueberries, raspberries, and blackberries) in large containers filled with a soilless pine bark substrate. Fertilizer and irrigation requirements have been refined to optimize growth of these crops. Based on these results, rural and urban farmers can produce harvestable fruit crops in areas where regional soil properties had once prevented their adoption.Altland, J.E., Boldt, J.K., Krause, C.R. 2016. Rice hull mulch affects germination of bittercress and creeping woodsorrel in container plant culture. American Journal of Plant Sciences. 7:2359-2375.
Altland, J.E., Locke, J.C. 2017. High rates of gasified rice hull biochar affect geranium and tomato growth in a soilless substrate. Journal of Plant Nutrition. http://dx.doi.org/10.1080/01904167.2016.1249800.
Jayawardena, D.M., Heckathorn, S.A., Bista, D.R., Mishra, S., Boldt, J.K., Krause, C.R. 2017. Elevated CO2 plus chronic warming reduces nitrogen uptake and levels or activities of nitrogen -uptake and -assimilatory proteins in tomato roots. Physiologia Plantarum. 159:354-365.