Franksred red maple (Acer rubrum `Franksred') trees were sampled from nursery fields in 2003 and 2004 to determine the cause of a common foliar chlorosis. Plots in 21 and 39 different nurseries were identified in 2003 and 2004, respectively. A single plot from each nursery was sampled in June of each year, whereas two to four plots per nursery were sampled in September. Each plot consisted of 20 consecutive trees in a single row. From each plot, a foliar tissue sample was analyzed for the complete range of essential nutrients. Plant height, stem diameter, leaf chlorophyll content, and a subjective plant quality rating were also recorded. From each plot, a soil sample was collected and analyzed for pH, EC, organic matter, and a range of essential nutrients. The foliar chlorosis was determined to be incited by manganese (Mn) deficiency. Tissue Mn was highly correlated with soil pH. Chlorotic plants were smaller with less stem diameter than nonchlorotic plants. Sufficiency ranges for tissue and soil tests were determined and are provided for red maple nursery production.
Magdalena Pancerz and James E. Altland
Stability of substrate pH in container-grown crops is important for proper nutrient management. The objective of this research was to determine the pH buffering capacity of pine bark substrates as a function of particle size and compare those results to sphagnum peat. The weight equivalent of 100 cm3 for fine, medium, and coarse pine bark and sphagnum peat, either as a whole or partitioned into several particle size ranges, was placed in a 250-mL glass jar and filled with 100 mL of an acid or base solution ranging from 0 to 50 meq·L−1 in 10 meq·L−1 increments. After 24 hours, pH was measured. An experiment was also conducted in the greenhouse. The weight equivalent of 500 cm3 of sphagnum peat, fine pine bark, or coarse pine bark was filled into 10-cm plastic pots and irrigated with one of the following: tap water or 10 meq·L−1 of HCl, NaOH, H2SO4, or KHCO3 and with or without a water soluble fertilizer. Substrate pH was determined 4 and 8 weeks after potting using the pour-through method. In all experiments, sphagnum peat had less buffering capacity than pine bark against pH changes from acidic solutions, whereas pine bark had less buffering capacity than sphagnum peat to pH changes from basic solutions. Substrate pH buffering in pine bark increased with decreasing particle size, whereas pH buffering in sphagnum peat was less responsive to particle size. These results will help growers and substrate manufacturers understand how substrate components contribute to pH management during crop production.
James E. Altland and Charles Krause
Loblolly pine (Pinus taeda L.) bark is the primary component of nursery container substrates in the eastern United States. Shortages in pine bark prompted investigation of alternative substrates. The objective of this research was to determine if ground switchgrass (Panicum virgatum L.) could be used for short production-cycle woody crops. Two experiments were conducted using ‘Paprika’ rose (Rosa L. ‘ChewMayTime’) potted in 15-cm tall and wide containers. In Expt. 1, substrates were composed of coarse-milled switchgrass (processed in a hammermill with 1.25- and 2.5-cm screens) amended with 0%, 30%, or 50% peatmoss and fertilized with 100, 250, or 400 mg·L−1 nitrogen (N) from ammonium nitrate. In Expt. 2, substrates were composed of coarse-milled (similar to Expt. 1) or fine-milled switchgrass (processed through a single 0.48-cm screen), amended with 0% or 30% peatmoss, and fertilized with the same N rates as in Expt. 1. Summarizing across both experiments, coarse switchgrass alone had high air space and low container capacity. Fine switchgrass had physical properties more consistent with what is considered normal for nursery container substrates. Switchgrass pH was generally high and poorly buffered against change. Fine switchgrass had higher pH than coarse switchgrass. Tissue analysis of rose grown in switchgrass substrate for 7 to 9 weeks revealed low to moderate levels of calcium and iron, but all other nutrients were within acceptable ranges. Despite varying substrate physical properties and pH levels, all roses at the conclusion of the experiment were of high quality. Switchgrass processed to an appropriate particle size and amended with typical nursery materials should provide a suitable substrate for short production-cycle woody crops.
Neil C. Bell and James Altland
Ninety-three species, cultivars, and hybrid selections of rockrose (Cistus spp., Halimium spp., and ×Halimiocistus spp.) were evaluated for growth, flowering, and cold hardiness in a landscape trial in Aurora, OR, from 2004 to 2009. Plants were irrigated to aid establishment when planted in summer 2004, but thereafter were not watered, fertilized, or pruned throughout the trial. Cold damage was recorded following freezing events in Feb. 2006 and Dec. 2008 in which low temperatures were 20 and 17 °F, respectively. Those plants that consistently suffered the most cold damage were Halimium atriplicifolium, Cistus creticus ssp. creticus ‘Tania Compton’, Cistus ×pauranthus, and Cistus albidus forma albus. Other plants showed cold damage related to poor vigor. The length of the flowering period and foliage quality varied widely among plants in the evaluation. The plants with the longest flowering period were Halimium ×pauanum, Cistus inflatus, Cistus ×pulverulentus ‘Sunset’, and ×Halimiocistus ‘Ingwersenii’, all of which flowered for more than 55 days. Plant form and foliage quality declined drastically for some plants during the evaluation. Those that retained the best foliage quality included Cistus ×obtusifolius, Cistus ×laxus, Cistus salviifolius ‘Gold Star’, Cistus ‘Gordon Cooper’, Halimium lasianthum ‘Sandling’, Halimium ‘Susan’, and ×Halimiocistus sahucii. Based on ratings of foliage and bloom time, as well as hardiness, several Cistus are recommended as drought-tolerant groundcovers, including Cistus ×gardianus and C. ×obtusifolius. Cistus ×laxus, C. inflatus, Cistus ‘Gordon Cooper’, Cistus ‘Ruby Cluster’, and Cistus ‘Snow Fire’ are suggested as tall groundcovers or landscape specimens. Several Halimium are recommended for landscape use, including H. lasianthum ‘Sandling’, Halimium ‘Susan’, H. ×pauanum, and ×Halimiocistus ‘Ingwersenii’.
James E. Altland and Charles Krause
Switchgrass (Panicum virgatum) biomass is being evaluated as a potential alternative to pine bark as the primary potting component in containerized nursery crops. Substrates composed entirely of switchgrass have higher pH than what is considered desirable in container substrates. The objective of this research was to evaluate the influence of elemental S, sphagnum moss, and municipal solid waste compost (MSC) as amendments for reducing substrate pH and buffering it against large changes over time. Three experiments were conducted; the first two experiments were conducted using annual vinca (Catharanthus roseus ‘Pacifica Blush’) to quickly assess how pH was affected by the three amendments, and the final experiment was conducted with blueberry (Vaccinium corymbosum ‘Duke’) to assess the long-term effects of substrate amendments. Summarizing across the three experiments, elemental S was effective in reducing substrate pH; however, rates 1 lb/yard3 or greater reduced pH below the recommended level of 5.5 and lower S rates did not maintain lowered pH over time. Sphagnum moss and MSC together at 20% and 10% (v/v), respectively, were effective at reducing substrate pH and buffering against change. Sphagnum moss and MSC provided the additional benefit of improving physical properties of the switchgrass substrates.
James E. Altland and James C. Locke
A series of column studies were conducted to determine the influence of three different biochar types on nitrate, phosphate, and potassium retention and leaching in a typical greenhouse soilless substrate. A commercial substrate composed of 85 sphagnum peatmoss : 15 perlite (v:v) was amended with 10% by volume of three different biochar types including: gasified rice hull biochar (GRHB), sawdust biochar (SDB), and a bark and wood biochar (BWB). The non-amended control substrate, along with substrates amended with one of three biochar materials, were each packed into three columns. Columns were drenched with nutrient solution and leached to determine the impact of biochar on nutrient retention and leaching. Nitrate release curves were exponential and peaked lower, at later leaching events, and had higher residual nitrate release over time with each biochar amendment. The impact of biochar amendment on phosphate retention and release was more variable within and across the two experiments. In both experiments, the GRHB was a net source of phosphate, providing more phosphate to the system than the fertilizer application and hence obscuring any retention and release effect it might have. Potassium release varied by amendment type within each experiment, but within each amendment type was relatively consistent across the two experiments. All biochar types were a source of potassium, with GRHB providing more than SDB, but both providing far more potassium than the fertilizer event. The BWB amendment resulted in more leached potassium than the control substrate, but relatively little compared with GRHB and SDB amendments.
James E. Altland and James C. Locke
Byproducts of pyrolysis, known collectively as biochar, are becoming more common and readily available as ventures into alternative energy generation are explored. Little is known about how these materials affect greenhouse container substrates. The objective of this research was to determine the effect of one form of biochar on the nutrient retention and release in a typical commercial greenhouse container substrate. Glass columns filled with 85:15 sphagnum peatmoss:perlite (v:v) and amended with 0%, 1%, 5%, or 10% biochar were drenched with nutrient solution and leached to determine the impact of biochar on nutrient retention and leaching. Nitrate release curves were exponential and peaked lower, at later leaching events, and had higher residual nitrate release over time with increasing biochar amendment rate. This suggests that biochar might be effective in moderating extreme fluctuations of nitrate levels in container substrates over time. Peak phosphate concentration decreased with increasing biochar amendment rate, whereas time of peak release, girth of the peak curve, and final residual phosphate release all increased with increasing biochar amendment. Additional phosphate levels in leachates from biochar-amended substrates, in addition to the higher phosphate concentrations present in later leaching events, suggest this form of biochar as a modest source of phosphate for ornamental plant production. Although there was not sufficient potassium (K) from biochar to adequately replace all fertilizer K in plant production, increasing levels of this form of biochar will add a substantial quantity of K to the substrate and should be accounted for in fertility programs.
James S. Owen Jr and James E. Altland
A study was conducted to quantify the effect of substrate texture on water-holding capacity of douglas fir [Pseudotsuga menziesii (Mirb.) Franco] bark (DFB) in containers of varying height. Medium (less than 2.2 cm) and fine (less than 0.9 cm) DFB were packed into 7.6 cm i.d. aluminum cores 3.8, 7.6, and 15.2 cm tall to determine container capacity (CC) and air space (AS) at varying container heights. Increasing container height resulted in a linear decrease in CC and a linear increase in AS. Fine texture DFB bulk density (Db) increased 18% with increasing container height, whereas Db of medium texture DFB was unaffected. Water-holding capacity decreased 20% and 42% in medium and fine textured DFB, respectively, with increasing container height from 3.8 to 15.2 cm. A second study was conducted to investigate water distribution in a 15.2-cm tall container for a given substrate texture. Polyvinyl chloride cores (15.2 cm tall × 7.6 cm i.d.) were packed with the same substrates, drained to CC, frozen, and sawed into 2.5-cm sections to determine water-holding capacity at each height. A finer substrate texture increased the amount of water throughout the container profile, but percent of total water for each strata remained similar. Container height and plant size (i.e., transplant or salable), in relation to substrate texture, should be considerations when producing containerized crops. In addition, bark texture alters water-holding capacity and water distribution within the container, ultimately affecting water management practices.
Jennifer K. Boldt and James E. Altland
Silicon (Si) is a plant-beneficial element that can alleviate the effects of abiotic and biotic stress. Plants are typically classified as Si accumulators based on foliar Si concentrations (≥1% Si on a dry weight basis for accumulators). By this definition, most greenhouse-grown ornamentals are low Si accumulators. However, plants that accumulate low foliar Si concentrations may still accumulate high Si concentrations elsewhere in the plant. Additionally, screening cultivars for variability in Si uptake has not been investigated for low Si accumulator species. Therefore, the objective of this study was to assess cultivar variability in Si accumulation and distribution in petunia (Petunia ×hybrida). Eight cultivars (Supertunia Black Cherry, Supertunia Limoncello, Supertunia Priscilla, Supertunia Raspberry Blast, Supertunia Royal Velvet, Supertunia Sangria Charm, Supertunia Vista Silverberry, and Supertunia White Improved) were grown in a commercial peat-based soilless substrate under typical greenhouse conditions. They were supplemented with either 2 mm potassium silicate (+Si) or potassium sulfate (-Si) at every irrigation. Silicon supplementation increased leaf dry mass (4.5%) but did not affect total dry mass. In plants not receiving Si supplementation, leaf Si ranged from 243 to 1295 mg·kg−1, stem Si ranged from 48 to 380 mg·kg−1, flower Si ranged from 97 to 437 mg·kg−1, and root Si ranged from 103 to 653 mg·kg−1. Silicon supplementation increased Si throughout the plant, but most predominantly in the roots. Leaf Si in the 2 mm Si treatment ranged from 1248 to 3541 mg·kg−1 (173% to 534% increase), stem Si ranged from 195 to 654 mg·kg−1 (72% to 376% increase), flower Si ranged from 253 to 1383 mg·kg−1 (74% to 1082% increase), and root Si ranged from 4018 to 10,457 mg·kg−1 (593% to 9161% increase). The large increase in root Si following supplementation shifted Si distribution within plants. In nonsupplemented plants, it ranged from 51.2% to 76.8% in leaves, 8.2% to 40.2% in stems, 2.8% to 23.8% in flowers, and 1.2% to 13.8% in roots. In Si-supplemented plants, it ranged from 63.5% to 67.7% in leaves, 10.5% to 22.6% in roots, 9.4% to 17.7% in stems, and 1.6% to 9.6% in flowers. This study indicates that petunia, a low foliar Si accumulator, can accumulate appreciable quantities of Si in roots when provided supplemental Si.
Ka Yeon Jeong and James E. Altland
Bagged potting mixes can be stored for weeks or months before being used by consumers. Some bagged potting mixes are amended with controlled release fertilizers (CRFs). The objective of this research was to determine how initial substrate moisture content and storage temperature affect the chemical properties of bagged potting mix with CRF incorporated and stored for up to 180 days. The base substrate composed of 60 sphagnum peat: 30 bark : 10 perlite (by vol.) amended with 5.5 g·L−1 dolomitic limestone and 0.5 g·L−1 granular wetting agent. This base substrate was either not amended with additional fertilizer (control) or amended with 0.59 kg·m−3 N of a CRF (Osmocote 18N–1.3P–5K) that was either ground (CRF-G) or whole prills (CRF-P). Substrates had initial moisture contents (IMCs) of 25%, 45%, or 65% and were stored at temperatures of either 20 or 40 °C. IMC and fertilizer type affected pH, electrical conductivity (EC), and nutrient release. Substrate pH increased with increasing IMC due to greater lime reactivity. About 25% of N from CRF-G treatments was immobilized between 2 and 14 days of storage. Low moisture content of bags, due to low IMC or storage at 40 °C, reduced the rate of N release from CRF-P treatments. Substrate P was rapidly immobilized by microbial communities.