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Jianjun Chen, Richard C. Beeson Jr., Thomas H. Yeager, Robert H. Stamps, and Liz A. Felter

Irrigation runoff water from a containerized landscape plant production bed was blended with rainwater from green house roofs in a constructed collection basin. Water from both the collection basin and an on-site potable well were characterized and used to grow foliage and bedding plants with overhead and ebb-and-flow irrigation systems. Over a 2-year period, a total of 18 foliage and 8 bedding plant cultivars were produced with plant growth and quality quantified. Alkalinity, electrical conductivity, hardness, and concentrations of nutrients of water from both sources were well within desired levels for greenhouse crop production. Turbidity and pH were relatively high from algal growth in the collection basin. However, substrate pH, irrigated by either water source, remained between 6 and 7 throughout the production periods. All plants at the time of finishing were of marketable sizes and salable quality independent of water source. No disease incidences or growth disorders related to water sources were observed. Results suggest that captured irrigation runoff blended with rainwater can be an alternative water source for green house crop production.

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Serge Yelle, Richard C. Beeson Jr., Marc J. Trudel, and André Gosselin

Lycopersicon esculentum Mill. cv. Vedettos and Lycopersicon chmielewskii Rick, LA 1028, were exposed to two CO2 concentrations (330 or 900 μmol·m-3) for 10 weeks. The elevated CO2 concentration increased the relative growth rate (RGR) of L. esculentum and L. chmielewskii by 18% and 30%, respectively, after 2 weeks of treatment. This increase was not maintained as the plant matured. Net assimilation rate (NAR) and specific leaf weight (SLW) were always higher in C02-enriched plants, suggesting that assimilates were preferentially accumulated in the leaves as reserves rather than contributing to leaf expansion. Carbon dioxide enrichment increased early and total yields of L. esculentum by 80% and 22%, respectively. Carbon exchange rates (CER) increased during the first few weeks, but thereafter decreased as tomato plants acclimated to high atmospheric CO2. The relatively constant concentration of internal C0 with time suggests that reduced stomatal conductance under high CO2 does not explain lower photosynthetic rates of tomato plants grown under high atmospheric CO2 concentrations. Leaves 5 and 9 responded equally to high CO2 enrichment throughout plant growth. Consequently, acclimation of CO2-enriched plants was not entirely due to the age of the tissue. After 10 weeks of treatment, leaf 5, which had been exposed to high CO2 for only 10 days, showed the greatest acclimation of the experiment. We conclude that the duration of exposure of the whole plant to elevated CO2 concentration, rather than the age of the tissue, governs the acclimation to high CO2 concentrations.

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Erin Alvarez, S.M. Scheiber, Richard C. Beeson Jr, and David R. Sandrock

Nonnative Miscanthus sinensis Anderss ‘Adagio’ and native Eragrostis spectabilis (Pursh) Steud. were evaluated for drought tolerance in a rain-excluded landscape setting in sandy soil in response to irrigation application volumes of 0 L, 0.25 L, 0.5 L, or 0.75 L. As irrigation rates increased, plant mass, canopy size, and shoot-to-root ratios increased for both species, being greatest at the 0.75-L rate. Shoot dry weight, root dry weight, total biomass, and shoot-to-root ratios were greater for E. spectabilis than M. sinensis. Cumulative water stress integral was also greater for E. spectabilis. Greater growth in conjunction with higher cumulative water stress indicates the native E. spectabilis is anisohydric and more drought-tolerant than the isohydric nonnative M. sinensis.

Open access

Amy Fulcher, Anthony V. LeBude, James S. Owen Jr., Sarah A. White, and Richard C. Beeson

Nursery and greenhouse producers, research and extension faculty, and representatives from allied fields collaborated to formulate a renewed vision to address water issues affecting growers over the next 10 years. The authors maintained the original container irrigation perspective published in “Strategic vision of container nursery irrigation in the next ten years,” yet broadened the perspective to include additional challenges that face nursery crop producers today and in the future. Water availability, quality, and related issues continue to garner widespread attention. Irrigation practices remain largely unchanged due to existing irrigation system infrastructure and minimal changes in state and federal regulations. Recent concerns over urbanization and population growth, increased climate variability, and advancements in state and federal regulations, including new groundwater withdrawal limitations, have provided an inducement for growers to adopt efficient and innovative practices. Information in support of the overarching issues and projected outcomes are discussed within.

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Sloane M. Scheiber, Maria Paz, Edward F. Gilman, Kimberly A. Moore, Sudeep Vyapari, and Richard C. Beeson Jr.

Landscape water consumption has become a prime target for water conservation and regulation. Imposing water restrictions during landscape establishment is detrimental to plants that have not developed sufficient root systems to compensate for transpirational water losses. Generally, municipalities regulate irrigation frequency but not application rate. Application frequency affects establishment rates of shade trees, but the effects on shrub establishment are not well documented. This study evaluated three irrigation frequencies during establishment of Ilex cornuta `Burfordii Nana' and Viburnum odoratissimumin a landscape. To simulate maximum stress, both species were transplanted into field plots in an open-sided, clear polyethylene covered shelter. Each species was irrigated either every 2, 4, or 7 days, and received 9 L of water per plant per event. Predawn, midday, and dusk water potentials were recorded at 28-day intervals and cumulative stress intervals calculated. Water potentials were taken the day prior to irrigation (maximum stress day) and the day of irrigation (minimum stress). Growth indices were also recorded. As days after transplant (DAT) increased, significant declines in cumulative water stress of Ilexwere found among treatments on the day of maximum stress. The 7-day treatment declined at a faster rate than the other treatments tested. No differences were found for Viburnum. No significant differences were found on the day of irrigation as DAT increased. Differences in canopy size were not significant among treatments for either species.

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Nisa Leksungnoen, Roger K. Kjelgren, Richard C. Beeson Jr., Paul G. Johnson, Grant E. Cardon, and Austin Hawks

We investigated if salt tolerance can be inferred from observable cues based on a woody species’ native habitat and leaf traits. Such inferences could improve species selection for urban landscapes constrained by soils irrigated with reclaimed water. We studied the C3 tree species Acer grandidentatum Nutt. (canyon maple; xeric-non-saline habitat) that was hypothesized to have some degree of salt tolerance based on its semiarid but non-saline native habitat. We compared it with A. macrophyllum Pursh. (bigleaf maple) from mesic/riparian-non-saline habitats with much larger leaves and Eucalyptus camaldulensis Dehnh. (eucalyptus/red gum) from mesic-saline habitats with schlerophyllous evergreen leaves. Five levels of increasing salt concentrations (non-saline control to 12 dS·m−1) were applied over 5 weeks to container-grown seedling trees in two separate studies, one in summer and the other in fall. We monitored leaf damage, gas exchange, and hydric behavior as measures of tree performance for 3 weeks after target salinity levels were reached. Eucalyptus was the most salt-tolerant among the species. At all elevated salinity levels, eucalyptus excluded salt from its root zone, unlike either maple species. Eucalyptus maintained intact, undamaged leaves with no effect on photosynthesis but with minor reductions in stomatal conductance (g S). Conversely, bigleaf maple suffered increasing leaf damage, nearly defoliated at the highest levels, with decreasing gas exchange as salt concentration increased. Canyon maple leaves were not damaged and gas exchange was minimally affected at 3 dS·m−1 but showed increasing damage at higher salt concentration. Salt-tolerant eucalyptus and riparian bigleaf maple framed canyon maple’s moderate salt tolerance up to 3 dS·m−1 that appears related to seasonal soil drying in its semiarid native habitat. These results highlight the potential to infer a degree of salt tolerance from either native habitat or known drought tolerance in selecting plant species for urban landscapes limited by soil salinity or brackish irrigation water. Observable cues such as xeri-morphic leaf traits may also provide visual evidence of salt tolerance.

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John D. Lea-Cox, Cindy Zhao, David S. Ross, Theodore E. Bilderback, J. Roger Harris, Susan D. Day, Chuanxue Hong, Thomas H. Yeager, Richard C. Beeson Jr, William L. Bauerle, Andrew G. Ristvey, Mary Lorscheider, Sarah Dickinson, and John M. Ruter

Increasing environmental concerns and legislation in many states and in other countries require that we take a more comprehensive sustainable “best management” approach to production techniques in nursery and greenhouse operations. This is particularly important because these production facilities are typically intense users of resources that are applied to relatively small land areas. We have developed an online knowledge center to facilitate the implementation of more sustainable practices within the nursery and greenhouse industry. A web-based knowledge center provides the most cost-effective mechanism for information delivery, as our potential audiences are extremely diverse and widespread. We currently have a registered user database of over 450 educators, growers, and industry professionals, and undergraduate and graduate students. A gateway website provides an overview of the issues and the goals of the project. The associated knowledge center currently has 25 in-depth learning modules, designed in a Moodle learning management framework. These learning modules are designed to actively engage learners in topics on substrate, irrigation, surface water, and nutrient and crop health management, which are integral to formulating farm-specific strategies for more sustainable water and nutrient management practices. Additional modules provide assessment and implementation tools for irrigation audits, irrigation methods and technologies, and water and nutrient management planning. The instructional design of the learning modules was paramount because there can be multiple strategies to improve site-specific production practices, which often require an integration of knowledge from engineering, plant science, and plant pathology disciplines. The assessment and review of current practices, and the decision to change a practice, are often not linear, nor simple. All modules were designed with this process in mind, and include numerous resources [pictures, diagrams, case studies, and assessment tools (e.g., spreadsheets and example calculations)] to enable the learner to fully understand all of the options available and to think critically about his/her decisions. Sixteen of the modules were used to teach an intensive 400-level “Principles of Water and Nutrient Management” course at the University of Maryland during Spring 2008 and 2009. The water and nutrient management planning module also supports the nursery and greenhouse Farmer Training Certification program in Maryland. The Maryland Department of Agriculture provides continuing education credits for all consultants and growers who register and complete any module in the knowledge center. Although these learning resources were developed by faculty in the eastern region of the United States, much of the information is applicable to more widespread audiences.