Search Results

You are looking at 1 - 7 of 7 items for

  • Author or Editor: Mary Jane Clark x
Clear All Modify Search
Full access

Mary Jane Clark and Youbin Zheng

The objective of this study was to determine the optimal controlled-release fertilizer (CRF) application rates or ranges for the production of five 2-gal nursery crops. Plants were evaluated following fertilization with 19N–2.6P–10.8K plus minors, 8–9 month CRF incorporated at 0.15, 0.45, 0.75, 1.05, 1.35, and 1.65 kg·m−3 nitrogen (N). The five crops tested were bigleaf hydrangea (Hydrangea macrophylla), ‘Green Velvet’ boxwood (Buxus ×), ‘Magic Carpet’ spirea (Spiraea japonica), ‘Palace Purple’ coral bells (Heuchera micrantha), and rose of sharon (Hibiscus syriacus). Most plant growth characteristics (i.e., growth index, plant height, leaf area, and shoot dry weight) were greater in high vs. low CRF treatments at the final harvest. Low CRF rates negatively impacted overall appearance and marketability. The species-specific CRF range recommendations were 1.05 to 1.35 kg·m−3 N for rose of sharon, 0.75 to 1.05 kg·m−3 N for ‘Magic Carpet’ spirea, and 0.75 to 1.35 kg·m−3 N for bigleaf hydrangea and ‘Green Velvet’ boxwood, whereas the recommended CRF rate for ‘Palace Purple’ coral bells was 0.75 kg·m−3 N. Overall, species-specific CRF application rates can be used to manage growth and quality of containerized nursery crops during production in a temperate climate.

Restricted access

Mary Jane Clark and Youbin Zheng

The objectives of the current study were to 1) determine the best topdressed controlled-release fertilizer (CRF) application rates for quality and growth of two nursery crops under temperate climate outdoor nursery production conditions in the Niagara region, Ontario, Canada, and 2) evaluate the nutrient status of the growing substrate following topdressing of two CRF types during the growing season. Fall-transplanted Goldmound spirea (Spiraea ×bumalda ‘Goldmound’) and Wine & Roses® weigela [Weigela florida (Bunge) A. DC. ‘Alexandra’] were grown in 2-gal (7.56 L) containers and topdressed on 7 May 2015 with Osmocote Plus 15N–3.9P–9.9K, 5–6 month CRF or Plantacote 14N–3.9P–12.5K, 6 month Homogeneous NPK with Micros. CRF was applied at rates of 1.5, 3.0, 4.5, 6.0, 7.5, and 9.0 g nitrogen (N)/pot for both species. The best plants at the end of the growing season (i.e., 23 Sept. 2015) were spirea at 3.0–4.5 and 3.0–6.0 g N/pot, and weigela at 3.0–4.5 and 6.0 g N/pot, with Osmocote and Plantacote, respectively. At CRF rates above these rates, the majority of plants showed no increase in growth or quality attributes. All weigela plants, despite CRF application rate, showed K deficiency symptoms during the study. Using marketable-size criteria and plant growth data over time, estimates of production timing are presented for fall-transplanted, spring-topdressed weigela and spirea. These estimates may assist growers in choosing CRF application rates to meet time-sensitive production goals. Early in the growing season, NO3-N and P concentrations in the growing substrate were highest at CRF rates ≥4.5 and ≥6.0 g N/pot, respectively, and P continued to be high in August and September at 9.0 g N/pot. NH3-N and K concentrations at all CRF application rates were greater early in the growing season and decreased over time. At high CRF rates toward the end of the growing season, concentrations of NO3-N, NH3-N, and P once again increased. Considering crop-specific CRF application rates and understanding changes in growing substrate nutrient status during the growing season may help nursery growers prevent negative environmental impacts from over-fertilizing.

Free access

Youbin Zheng and Mary Jane Clark

To determine the optimal growing substrate pH values for Sedum plants, Sedum album, Sedum reflexum ‘Blue Spruce’, Sedum spurium ‘Dragon’s Blood’, Sedum hybridum ‘Immergrunchen’, and Sedum sexangulare were grown in containers using peatmoss and perlite-based substrates at five target pH levels (i.e., 4.5, 5.5, 6.5, 7.5, and 8.5). Optimal pH levels, calculated from dry weight regression models, were 6.32, 6.43, 5.71, 6.25, and 5.91 for S. album, S. reflexum, S. spurium, S. hybridum, and S. sexangulare, respectively, and 5.95 overall. Sedum spurium dry weight varied the most among pH treatments (i.e., 9.5 times greater at pH 6.3 vs. 8.3), whereas S. reflexum varied the least (i.e., 1.3 times greater at pH 6.3 vs. 4.4), indicating species-specific growth responses to growing substrate pH. These findings identified a narrow range of optimal growing substrate pH levels within a wider pH range tolerated by five Sedum spp. Therefore, by adjusting substrate pH to optimal levels, Sedum growth can be maximized.

Free access

Mary Jane Clark and Youbin Zheng

The objectives of this study were to compare fertilizer rates and types to identify an optimum rate to maintain green roof vegetative coverage and encourage plant growth (i.e., plant performance) while minimizing the amount and concentration of nutrients leached from a green roof module system. Sedum-vegetated modules with no added fertilizer (control) were compared with modules fertilized with 5, 7.5, 10, 15, 20, 30, and 60 g·m−2 nitrogen (N) of 16N–2.6P–10K POLYON® Homogenous NPK plus Minors, 5–6 month controlled-release fertilizer (CRF), 5 g·m−2 N of a 2.9N–2.2P–2.3K fly-larvae processed chicken manure fertilizer (5-Sus), or 5 g·m−2 N of 4N–4P–4K Gaia Green All Purpose organic fertilizer (5-OR). The total amount and concentration of aluminum (Al), calcium (Ca), cadmium (Cd), chromium (Cr), copper (Cu), iron (Fe), mercury (Hg), potassium (K), magnesium (Mg), sodium (Na), NH4 +, nickel (Ni), NO3 , phosphorus (P), lead (Pb), sulfur (S), and zinc (Zn) in leachate as well as plant overall appearance, winter injury, vegetative coverage, shoot height, bloom duration, and leaf color of green roof modules were evaluated between July 2011 and Aug. 2012. A CRF fertilizer rate of 15 g·m−2 N maximized vegetative coverage and overall plant appearance while maintaining leachate quality within Ontario and Canadian guidelines for most of the measured elements. The amount of Zn in the CRF appeared to be higher than plant demand and the high amount and concentration of P in leachate was likely the result of release from the growing substrate. The 5-Sus fertilizer resulted in increased coverage the first spring and increased greenness soon after application compared with the same rate of CRF. Overall, 15 g·m−2 N of CRF was the best treatment based on vegetative coverage and plant growth in sedum-vegetated green roof modules.

Free access

Mary Jane Clark and Youbin Zheng

This study compared the effect of fertilizer rates and types on plant performance and leached nutrients for an installed sedum-vegetated green roof mat system. Sedum-vegetated mats in non-fertilized plots (control) were compared with plots fertilized with 16N–2.6P–10K plus Minors 5–6 month controlled-release fertilizer (CRF) at 5, 10, 15, or 20 g·m−2 nitrogen (N) or 5 g·m−2 N of a fly-larvae processed chicken manure (Sus). Plot overall appearance was among the highest for 10 g·m−2 N in Mar., May, June, and July 2012, whereas 15 and 20 g·m−2 N resulted in the highest winter injury ranking in Mar. 2012. Vegetative coverage was highest for 10 and 15 g·m−2 N in Oct. 2011 but did not differ among treatments in 2012. Sedum spp. composition within plots remained closest to the original when fertilized at 10 g·m−2 N. Of all species, S. acre flowered for the longest duration and flowered longer in 10 g·m−2 N than 15 g·m−2 N or Sus. Leaf greenness of S. acre for 5, 10, 15, and 20 g·m−2 N was higher than the control in May 2012. Leached amounts of NH4 +, NO3 , potassium (K), calcium (Ca), magnesium (Mg), sulfur (S), sodium (Na), iron (Fe), and aluminum (Al) did not differ among treatments, and cadmium (Cd), chromium (Cr), copper (Cu), mercury (Hg), nickel (Ni), and lead (Pb) were not detected. All nutrients but NO3 in all plots and zinc (Zn) in the 5 g·m−2 N (CRF and Sus) and control plots were leached at levels above target nutrient loss thresholds. Among fertilizer types, Sus leached more phosphorus (P) without greater plant performance compared with 5 g·m−2 N CRF. A fertilizer rate of 10 g·m−2 N is recommended to benefit plant performance of this green roof system. However, in the first year after installation, to prevent negative environmental impacts resulting from initial substrate fertility, no fertilizer (CRF or Sus) is needed for this green roof system.

Free access

Mary Jane Clark and Youbin Zheng

With the increasing popularity of green roofs, efficient green roof plant production is required to adequately supply the industry. Applying fertilizer at an appropriate rate can provide sufficient plant nutrition for efficient plant growth without excess nutrient leaching into the environment. This study compared rates of controlled-release fertilizer (CRF) applied to green roof modules at the plant production stage to determine an optimum CRF rate for encouraging plant growth and vegetative coverage while minimizing the amount and concentration of leached nutrients. After sedum cuttings were rooted in green roof modules on 29 Aug. 2011, CRF was applied at 5, 10, 15, 20, 25, 30, and 35 g·m−2 nitrogen (N) and modules were compared with an unfertilized control. Plant growth, vegetative coverage, and overall appearance requirements were met after fertilization at 20 g·m−2 N. Modules fertilized at less than 20 g·m−2 N did not reach the target proportion coverage during the study. When fertilized at 20 g·m−2 N, green roof modules reached the target proportion coverage after 240 days of growth. Differences in leachate volumes were observed among treatments 35 days after fertilization and fertilization at 20 g·m−2 N minimized leaching of most nutrients. Therefore, with the green roof module system used in this study, an application of 20 g·m−2 N for green roof module or sedum cutting production is an optimum CRF rate for plant growth and vegetative coverage while minimizing negative environmental impacts.

Free access

Mary Jane Clark and Youbin Zheng

Vegetation success on green roofs in northern climates is challenged by extreme weather conditions, especially in winter, and is influenced by season of installation and substrate fertility. Appropriate fertilization with phosphorus (P) and potassium (K) can reduce winter injury for some plant species. The objectives of this study were to identify both the effect of P and K fertilizer rates on Sedum spp. survival over the first winter and the response of Sedum spp. growth to fertilizer rates when applied at installation. In a fall-installed extensive green roof system, survival, growth, and visual appearance of Sedum mats in non-fertilized plots (control) were compared with plots fertilized with 16–6–13 POLYON® Homogenous NPK plus Minors 3-4 month controlled-release fertilizer at 20.0 g nitrogen (N)/m2 either alone or with additional P to total 28.8, 54.4, or 80.0 g P/m2 or K to total 32.5, 51.6, or 70.6 g K/m2. Sedum mats were installed on 8 Oct. 2010 and plants in all plots survived the winter and the next year. During the 2011 growing season, vegetative coverage was not significantly different among any individual fertilized treatments; however, vegetative coverage data combined for all fertilized treatments was larger than the control. Fertilized treatments also showed larger plant height and biomass after one year, taller S. acre and S. sexangulare inflorescences, increased leaf greenness, and higher visual appearance rankings compared with the control. For individual Sedum species, S. album showed the greatest coverage in P-fertilized treatments, and effects on S. acre and S. sexangulare were treatment-dependent. Application of a controlled-release N–P–K fertilizer, without additional P or K, can be used to encourage vegetative coverage, plant growth, leaf greenness, inflorescence height, and visual appearance in fall-installed extensive Sedum green roof systems.