Location: Application Technology Research2018 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. Objective 4: Develop improved techniques for monitoring invasive ambrosia beetles in nurseries based on new knowledge of behavior, movement, and flight activity across different habitats. Objective 5: Characterize the role of tree health on the host-selection and host preference behavior of ambrosia beetles in ornamental nurseries. Objective 6: Develop improved technology for applying or improving the efficacy of chemicals to effectively manage ambrosia beetles and evaluate alternatives to conventional insecticides for managing ambrosia beetles in nurseries.
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:
Lifetime summary: This is a summary of the progress reports for the life time of this 5-year project which will expire 10/28/2018 and will be replaced with a bridging project. Research continued on determining the role of silicon (Si) in management of abiotic stresses in protected horticulture production systems. Silicon mitigated nutrient deficiencies in ornamental crops. The effects of supplemental Si in the presence of deficiency levels of other plant-essential elements was evaluated. The effect of Si on Xanthomonas gardneri infection in tomato was evaluated. Inoculation produced more symptoms in Si-fed plants compared to plants not grown with Si, which is the opposite of the many beneficial effects observed in many biotic and abiotic stressors. Studies were carried out that concluded Si did not have direct effects on Xanthomonas species infectivity rate and symptom formation in tomatoes. Taken together, it suggests Si is having a direct effect on the plants, exacerbating an immune response against the bacterial pathogen. 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. Finally, Si concentration was found to be greater in the leaves than in the roots, stems, or flowers for both an accumulator (sunflower) and non-accumulator (petunia) species. Silicon concentration increased in both the roots and aerial portions of the accumulator species with Si supplementation, but only in the roots of the non-accumulator species. This suggests a difference in Si uptake and regulation between foliar Si accumulator and non-accumulator species. Research continued to determine the influence of environmental parameters on growth and development of protected horticulture crops. Short-term reductions in light and temperature can reduce greenhouse energy costs without reducing plant quality. These periodic short-term reductions in temperature and irradiance could reduce energy costs by 10 – 20% without reducing plant quality. Single-leaf photosynthetic response curves were developed for popular bedding and potted crop species in response to light, temperature, and carbon dioxide (CO2). The data were modeled and packaged into a decision-support software tool called PhotoSim that provides growers the ability to estimate the impact 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. Biomarkers were developed for nutrient-uptake proteins in roots and used to characterize plant response to abiotic stress. During drought, a decrease in % phosphorus (P) was correlated with a decrease in both the concentration and activity of P-uptake proteins, and a decrease in % nitrogen (N) was due, in part, to a decrease in the activity of N-uptake proteins. Elevated CO2 and heat stress decreased root nutrient uptake. Management strategies were developed for containerized crop production systems that improve crop growth, reduce costs, and reduce loss of nutrients and agrichemicals to the environment. The effects of biochar type on macronutrient retention and release in soilless substrate was determined. The role of biochars, produced from differing feed-stocks, in moderating the release of nutrients (nitrates, phosphate, potassium) from soilless growing substrates was documented. Nutrient release from bagged potting substrates was evaluated. The impact of initial moisture content, temperature, and storage duration on the release of nutrients from organic and conventional fertilizers in bagged potting substrates was determined. 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. Steel slag can be effectively used as a component in soilless container media to adjust pH, provide beneficial silicon, and some nutritional elements. Media pH can be adjusted utilizing steel slag as a substitute for dolomitic lime in soilless growing systems. And finally, cultural practices were developed 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. Management strategies for containerized crop production were also developed for weed control issues. Amending nursery pine bark substrates with peat moss improves bulk physical properties without affecting herbicide performance or weed growth in containers. 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. Rice hulls provide weed control in containers by limiting water availability on the container surface. 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. Hot water and steam can be used to sanitize plastic nursery pots and trays for weed seed. Seeds of many weeds, most notably bittercress (Cardamine flexuosa) and creeping woodsorrel (Oxalis corniculata), stick to plastic nursery containers and trays and are reintroduced into the production system when that plastic is reused. The specific temperatures and exposure times necessary to kill weed seeds on plastic containers and propagation trays using either hot-water or steam were determined. Progress report for FY 2018: Silicon (Si) can help mitigate the effects of abiotic and biotic stress. As part of Objective 1, which seeks to determine the role of silicon in management of abiotic stresses in protected horticulture production systems, the utility of supplying supplemental Si to stock plants was evaluated. This enhanced the rooting of cuttings following simulated shipping. Additionally, Si uptake in ornamental plants in response to Si sources, rate, and delivery method continues to be evaluated in order to begin developing Si application recommendations for growers. Optimized environmental conditions in greenhouses and other controlled environments are often crop specific, and important for enhancing yield while minimizing resource use and cost. As part of Objective 2, single-factor photosynthesis curves have been developed for protected horticulture crops in response to light, temperature, and CO2. This research was expanded to include development of multi-parameter photosynthetic response curves to account for potential interactive effects between factors (e.g., light intensity x CO2 concentration). Pine bark pH and how it responds to water and fertilizer additions is unpredictable. This research relates to Sub-objective 3.1, which aims to quantify the chemical and physical properties of commonly used, but increasingly expensive, substrate components and then explore novel materials that ultimately provide producers with substrates that are economical, sustainable, and effective. Research was conducted to create pH buffering curves that could be used to model pine bark response to acidic and basic inputs. It was found that pine bark particle size was a major influence on pH response, so further work was conducted to determine pH buffering as a function of particle size. Further experiments will determine the accuracy of our models in plant production systems. The microbial community is poorly understood in pine bark substrates. Research was conducted to document the influence of common container nursery practices on diversity of the microbial community in pine bark substrates, and to document changes over time. This research furthers Objective 3, which aims to develop management strategies for containerized crop production systems that improve crop growth, reduce costs, and reduce loss of nutrients and agrichemicals to the environment. The first attempt at this research revealed that substrate components can influence the microbial community early in the production cycle (0 to 1 month), but over time microbial communities become more similar across substrate treatments (3 to 4 months). Future research is aimed at improving our precision and resolution for measuring the microbial community, and to establish standard operating procedures to collecting and processing samples from this unique soil environment. Weed control in container nursery production continues to be a major expense and use of labor. Research was conducted to determine how pre-emergence herbicides dissipate over time. This research furthered Objective 3, which aims to develop management strategies for containerized crop production systems that improve crop growth, reduce costs, and reduce loss of nutrients and agrichemicals to the environment. Of the four herbicides evaluated, all dissipated differently in response to irrigation. Future research will evaluate herbicide longevity as a function of shade, irrigation frequency, fertilization, and substrate type.
1. Hot water and steam can be used to sanitize plastic nursery pots and trays for weed seed. Seeds of many weeds, most notably bittercress (Cardamine flexuosa) and creeping woodsorrel (Oxalis corniculata), stick to plastic nursery containers and trays and are reintroduced into the production system when that plastic is reused. An ARS scientist in Wooster, Ohio, 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. The results of this work can be used by greenhouse and nursery producers to control weed seeds on between crops, drastically reducing weed populations in propagation and other phases of production where herbicides are limited.
2. The conventional system for identifying plants as silicon (Si) accumulators is flawed. Plants are classified as Si accumulators or low Si accumulators based on foliar Si concentration, and most greenhouse-grown ornamentals are considered low Si-accumulators. However, little knowledge exists on Si distribution within these species. ARS researchers in Toledo, Ohio determined that Si concentration was greater in the leaves than in the roots, stems, or flowers for both an accumulator (sunflower) and non-accumulator (petunia). Additionally, Si concentration increased in both the roots and aerial portions of the accumulator species, but only in the roots of the non-accumulator species. This suggests a difference in Si uptake and regulation between foliar Si accumulator and non-accumulator species, and the results of this work can be used by researchers to further understand how plants take up, store, and utilize Si.
3. Drought stress affects nutrient uptake proteins in plants. Drought stress impacts plant productivity and nutrient concentration in plants, but its impact on nutrient uptake proteins was not well understood. Researchers at the University of Toledo, Toledo, Ohio, in collaboration with ARS researchers, have developed biomarkers for nutrient-uptake proteins in roots. It was determined the decrease in %P was correlated with a decrease in both the concentration and activity of P-uptake proteins, and the decrease in %N was due, in part, to a decrease in the activity of N-uptake proteins. This occurred in both drought-tolerant and drought-sensitive species. Results of this research will be useful to plant breeding efforts focused on improving the tolerance of crops to drought and minimizing yield losses, including adaptations that help roots maintain bulk root protein levels or increase the expression of nutrient uptake proteins.Altland, J.E., Boldt, J.K. 2017. Effect of rice hull mulch on nutrient concentration of fertilized irrigation water. HortScience. 52(9):1288–1292.
Altland, J.E., Jeong, K.Y. 2017. Initial substrate moisture content and storage temperature affects chemical properties of bagged substrates containing controlled release fertilizer at two different temperatures. HortScience. 52(10):1429-1434. doi:10.21273/HORTSCI12216-17.
Boldt, J.K., Locke, J.C., Altland, J.E. 2018. Silicon accumulation and distribution in petunia and sunflower grown in a rice hull-amended substrate. HortScience. 53:698-703. https://doi.org/10.21273/HORTSCI12325-17.
Altland, J.E., Boldt, J.K. 2018. Influence of substrate physical properties on container weed germination. Journal of Environmental Horticulture. 36(1):1-6.
Bista, D.R., Heckathorn, S.A., Jayawardena, D.M., Mishra, S., Boldt, J.K. 2018. Effect of drought on nutrient uptake and the levels of nutrient-uptake proteins in roots of drought-sensitive and –tolerant grasses. Plants. 7(2):28-44. http://doi:10.3390/plants7020028.
Albano, J.P., Altland, J.E., Merhaut, D., Wilson, S., Wilson, C. 2017. Irrigation water acidification to neutralize alkalinity for nursery crop production: Substrate pH, electrical conductivity, nutrient concentrations, and plant nutrition and growth. HortScience. 52(10):1401-1405. doi: 10.21273/hortsci11439-17.
Altland, J.E., Locke, J.C., Boldt, J.K. 2018. Pyrolysis temperature and heating time affect rice hull biochar properties. Acta Horticulturae. 1191:145-152.