Peat-based Medium Research Articles

Comparison of the Physical Characteristics of Growing Media Containing Composted Oak Sawdust and Sphagnum Peat

The physical characteristics of a container growing medium containing 2 oak sawdust composted with poultry manure: 1 vermiculite: 1 perlite were compared with those of a similar medium containing sphagnum peat rather than compost. Both media were amended with inorganic nutrients based on laboratory analysis to make them nutritionally comparable and with AquaGro wetting agent at 800 g·m–3. Moisture release characteristics of the media were evaluated using tension cups in which desorption at 5, 10, 20, 40, 80, 100, and 160 cm of water was measured. While bulk density of the peat mix (0.129 g·cm–3) was, significantly lower than that of the compost mix (0.157 g·cm–3), total porosity of the peat mix (84%) was significantly greater than that of the compost mix (79%). Air-filled and water-filled porosities of the peat and compost mixes were 18.2% 16.2% and 75.2% 70.5% of container volume, respectively. While the peat mix held more water at tensions between 5 and 20 cm, there was no significant difference between the volumetric water contents of the two media between 20 and 160 cm. Fresh and dry weights of corn plants grown for 3 weeks in compost- and peat-based media were not significantly different.

The Effect of Lime, Irrigation-water Source, and Water-soluble Fertilizer on Root-zone pH, Electrical Conductivity, and Macronutrient Management of Container Root Media with Impatiens

Hybrid impatiens (Impatiens Wallerana Hook. F.) were planted in a peat-based medium containing two dolomitic liming materials (1.8 kg Ca(OH)2·Mg(OH)2/m3 or 8.4 kg CaCO3·MgCO3/m3) and subirrigated for 17 weeks using four irrigation-water sources (IWSs) with varied bicarbonate alkalinity, Ca2+, Mg2+, and SO4-S content and three water-soluble fertilizers (WSFs) that contained (in mg) 200N-20P-200K/liter but a variable NH4: NO3 ratio, Ca2+, Mg2+, and SO4-S content. The factorial arrangement of the IWS and WSF resulted in a range of Ca2+, Mg2+, and SO4-S concentrations varying by a factor of 10. After 8 weeks, medium pH ranged from 4.5 to 8.5. The maximum critical medium pH for PO4-P uptake was 7.4 to 7.7, which probably was due to a change in most of the water-soluble P to the less-available HPO42- form. Lime type did not affect the long-term increase in medium pH, Ca2+, and Mg2+ concentrations with nutrient solutions containing low NH4+-N and high Ca2+ and Mg2+. The carbonate lime buffered the medium pH and Ca2+ and Mg2+ concentrations with nutrient solutions containing high NH4+-N and low Ca2+ and Mg2+ compared to that measured with the hydrated lime. With both lime types, there was a linear increase in tissue Ca and Mg as the applied concentrations of the various nutrient solutions increased from 18 to 210 mg Ca2+/liter and 7 to 90 mg Mg2+/liter. The relationship was similar for both lime types up to week 8, after which tissue Ca and Mg decreased more rapidly with the hydrated lime and low solution Ca2+ and Mg2+ compared to that of the same carbonate lime treatments. The minimum critical SO4-S concentration in the applied nutrient solution for plant uptake was 30 to 40 mg S/liter. Below this concentration, tissue S decreased rapidly; above, there was little effect on tissue S.

Root-zone Medium Influences Growth of Poinsettias Treated with Paclobutrazol-impregnated Spikes and Drenches

An experiment was conducted to determine the influence of eight commercial root-zone media (four peat based and four pine bark based) on the effects of paclobutrazol applied to Euphorbia pulcherrima Willd. `Eckespoint Celebrate 2' as an impregnated spike or a drench. Paclobutrazol treatments had the least influence on stem elongation of poinsettias grown in the peat-based medium containing Bacctite, a compressed peat product designed to increase aeration and cation exchange capacity, or composted pine bark ground to a particle size that could pass through an opening 1 cm or smaller. Spikes were more effective at reducing shoot elongation than drenches. Spike treatments also resulted in lower bract dry-matter accumulation than drenches. Paclobutrazol applied as a spike to poinsettias at pinch could combine pinching and chemical growth regulator application into one simultaneous operation. Chemical name used: (±)-(R*,R*)-beta-[(4-chlorophenyl)methyl]-alpha-(1, 1,-dimethyl)-1H-1,2,4,-triazole-1-ethanol (paclobutrazol).

Pest and Disease Control for Vesicular–Arbuscular Mycorrhiza (VAM) Pot-grown Plants

Increased use of VAM for pot-grown cultures has sustained certain inquiries as to the compatibility of pesticides and biocontrol agents with this novel practice. Asparagus, Boston fern, geranium, and poinsettia were cultivated in a peat-based medium (SB-Mix) with various fungicides, insecticides, and insect predators. Each plant consisted of an individual trial. All treatments were randomly set up in a complete block experimental design consisting of a noninoculated control and pre-inoculated with Glomus intraradices, in combination with the different pesticides used for a given plant species. Commonly used pesticides in greenhouses were chosen, and the concentration applied was as recommended by the manufacturer. A control, consisting of water, was included with the pesticides tested. The effect of a given pesticide varied from one plant species to another concerning root colonization by the VAM and plant growth. The poinsettia growth results were significantly superior with the water-treated plants than with those that received insecticidal soap, dienochlor, and dicofol on a regular basis. Colonization rates, however, were low with all treatments, but significantly lower with oxine benzoate. Growth parameters and colonization rates of geranium, Boston fern, and asparagus showed no significant differences between water and pesticide treatments, even those treated with benomyl, which has been reported in the past to reduce colonization rates. These results show that a good pesticide and insect predator integration control program will not alter the VAM colonization rates.

Effect of Lime, Irrigation Water Quality, and Water-soluble Fertilizer on pH and Macronutrient Management of Peat-based Root Media

Impatiens were planted into peat-based media containing two dolomitic liming materials [Ca(OH)2·Mg(OH)2 at 1.8 kg·m–3 or CaCO3·MgCO3 at 8.4 kg·m–3] and subirrigated for 17 weeks using four irrigation water qualities (IWQ) with varied alkalinity, Ca2+, Mg2+, and SO4-S content and three water-soluble fertilizers (WSF) with varied NH4:NO3 ratio, Ca2+, Mg2+, and SO4-S content. After 8 weeks, medium pH ranged from 4.5 to 8.5. Lime type did not affect the long-term increase in medium pH, Ca2+, and Mg2+ concentrations with IWQ/WSF solutions containing low NH4-N and high Ca2+ and Mg2+ concentrations. The carbonate lime did buffer the medium pH, Ca2+, and Mg2+ concentrations with IWQ/WSF solutions containing high NH4-N and low Ca2+ and Mg2+ concentrations. With both lime types, there was a linear increase in tissue Ca and Mg as the applied concentrations increased from 0.5 to 4.0 mol·m–3 Ca2+ and 0.3 to 3.0 mol·m–3 Mg2+ with the various IWQ/WSF. The relationship was similar for both lime types up to week 8, after which tissue Ca and Mg decreased with the hydrated lime and low solution Ca2+ and Mg2+. Relationships were also developed between the applied SO4-S concentration and tissue S and medium pH and tissue P.

Effect of Lime, Irrigation Water Quality, and Water-soluble Fertilizer on pH and Macronutrient Management of Peat-based Root Media

Impatiens were planted into peat-based media containing two dolomitic liming materials [Ca(OH)2·Mg(OH)2 at 1.8 kg·m–3 or CaCO3·MgCO3 at 8.4 kg·m–3] and subirrigated for 17 weeks using four irrigation water qualities (IWQ) with varied alkalinity, Ca2+, Mg2+, and SO4-S content and three water-soluble fertilizers (WSF) with varied NH4:NO3 ratio, Ca2+, Mg2+, and SO4-S content. After 8 weeks, medium pH ranged from 4.5 to 8.5. Lime type did not affect the long-term increase in medium pH, Ca2+, and Mg2+ concentrations with IWQ/WSF solutions containing low NH4-N and high Ca2+ and Mg2+ concentrations. The carbonate lime did buffer the medium pH, Ca2+, and Mg2+ concentrations with IWQ/WSF solutions containing high NH4-N and low Ca2+ and Mg2+ concentrations. With both lime types, there was a linear increase in tissue Ca and Mg as the applied concentrations increased from 0.5 to 4.0 mol·m–3 Ca2+ and 0.3 to 3.0 mol·m–3 Mg2+ with the various IWQ/WSF. The relationship was similar for both lime types up to week 8, after which tissue Ca and Mg decreased with the hydrated lime and low solution Ca2+ and Mg2+. Relationships were also developed between the applied SO4-S concentration and tissue S and medium pH and tissue P.

Effect of Vesicular–Arbuscular Mycorrhizal Fungi on Rooting of Sciadopitys verticillata Sieb & Zucc. Cuttings

A vesicular–arbuscular mycorrhizal fungus in a peat-based medium significantly increased survival, callus development, and rooting percentage of Sciadopitys verticillata cuttings over noninoculated cuttings. The presence of a nurse host plant for the mycorrhizal fungi to colonize in the absence of S. verticillata roots decreased survival and rooting percentage, but not callus development, relative to the fungus without the nurse host. Among plants that did produce roots, however, there were no significant differences among treatments for root number, weight, or length per cutting.

Growth of Two Subtropical Ornamentals Using Coir (Coconut Mesocarp Pith) as a Peat Substitute

Growth of Pentas lanecolata (Forssk.) Deflers `Starburst Pink' and Ixora coccinea L. `Maui' was compared in container media using sphagnum peat, sedge peat, or coir dust as their peat components. Growth index and top and root dry weights of both crops were significantly better in coir-based medium than sedge peat-based medium. Pentas grew equally well in coir- and sphagnum peat-based medium. Growth index and top dry weight of Ixora were significantly lower in the coir-based than the sphagnum peat-based medium, although root dry weights were equal. This difference was not apparent and may have been caused by N drawdown in the coir-based mix. The sedge peat-based medium had the highest air porosity and the lowest water-holding capacity of the three media at the initiation of the trials, but at the termination of the study, it showed a reversal of these characteristics. The coir-based medium showed the least change in these attributes over time. Coir dust seems to be an acceptable substitute for sphagnum or sedge peat in soilless container media, although nutritional regimes may need to be adjusted on a crop-by-crop basis.

Irrigation Requirements, Root-medium pH, and Nutrient Concentrations of Easter Lilies Grown in Five Peat-based Media with and without an Evaporation Barrier

Subirrigated Easter lilies were grown in five commercially formulated root media using one water-soluble fertilizer applied independently to each medium based on water-holding capacity and water loss. The number of irrigations ranged from 12 to 20 and the amount of applied water ranged from 5.3 to 6.8 liters for the uncovered media treatments. When the root-medium surface was covered with an evaporation barrier, the average amount of applied water was reduced by 35% compared to the uncovered media. The largest effect on root media pH was between uncovered and covered media due to the reduced amount of water applied. Similar macronutrient concentrations were measured in the five media during the experiment with few exceptions. The greatest differences in nutrient concentrations were found within the pots. The top 2.5 cm (top layer) contained nutrient concentrations up to 10 times higher than those measured in the remaining root medium (root zone) of the same pot. Covering the root-medium surface with an evaporation barrier reduced the stratification of fertilizer salts. Root-zone soluble salt concentrations of plants in the covered pots were similar to those of uncovered plants even though 36% less fertilizer was applied to the covered plants.

257 LEAF PETIOLE NITRATE AND POTASSIUM LEVELS IN POTTED PLANTS GROWN AT THREE NITROGEN AND POTASSIUM LEVELS

Twelve species of flowering potted plants were grown in a peat-based medium with water soluble fertilizer concentrations of 50, 100, or 200 mg·liter-1 N and K2O. Leaf blade or leaf petiole samples were collected six to eight weeks after planting. Sap was expressed using a hydraulic press and levels of nitrate nitrogen and potassium were determined using Cardy flat sensor ion meters. Petiole nitrate level ranged from 520 to 6300 mg·liter-1 and potassium levels ranged from 870 to 3600 mg·liter-1. The petiole nitrate concentration and change in petiole nitrate levels with changes in media nitrate levels was crop dependent. Leaf blade nitrate and potassium concentrations were lower than leaf petiole concentrations. The relationship of petiole nitrate to final plant fresh and dry mass and appearance at flowering will be presented.

PINE BARK-AND PEAT-BASED MEDIA INFLUENCE THE EFFECTS OF PACLOBUTRAZOL AND UNICONAZOLE DRENCH ON `GUTBIER V-14 GLORY' POINSETTIAS.

The objective of this study was to determine the influences of 8 commercial media, 4 peat-based and 4 pine bark-based, on the effects of paclobutrazol and uniconazole applied as a media drench to `Gutbier V-14 Glory' poinsettias. The peat-based media were Baccto Grower's Mix, Baccto High Porosity Professional, Baccto High Porosity Professional with Bacctite, and Baccto Rockwool Mix. The pine bark-based media were Metro 360, 366, 700, and 702. Paclobutrazol and uniconazole were each applied to plants grown in each media at 5 rates (0, 0.125, 0.250, 0.375, and 0.500 mg·15 cm pot-1). Paclobutrazol and uniconazole effectively reduced plant height in all media. Plants grown in the Metro products, however, tended to be larger than those grown in the Baccto products. Plants grown in the peatbased media were more sensitive to growth regulator drenches. Plants grown in Metro 360 and 366 were the least sensitive to plant growth regulator drenches compared to the Baccto media.

672 (PS 5) PINE BARK-AND PEAT-BASED MEDIA INFLUENCE THE EFFECTS OF PACLOBUTRAZOL SPIKES ON `CELEBRATE 2' POINSETTIAS

The objective of this study was to determine the influences of 8 commercial media, 4 peat-based and 4 pine bark-based, on the effects of paclobutrazol applied to the media of each plant at pinch in a spike formulation or as a drench (two weeks after pinch) to `Celebrate 2' poinsettias. The peat-based media were Baccto Grower's Mix, Baccto High Porosity Professional, Baccto High Porosity Professional with Bacctite, and Baccto Rockwool Mix. The pine bark-based media were Metro 360, 366, 700, and 702. Paclobutrazol was applied to the media at 10 treatment combinations (0, 2, 4, 6 and 8-0.05% spikes, 1 and 2-0.2% spikes, 1 0.08% spike, and 0.25 and 0.50 mg drenches in each 15 cm pot). Spike and drench formulations of paclobutrazol reduced plant size. Plants grown in the peat-based media were more sensitive to paclobutrazol than those grown in bark-based media. Stem length of those plants treated with paclobutrazol spikes was less than those treated with an equal amount of paclobutrazol as a drench in all media except the Rockwool Mix and Metro 702.

679 (PS 5) Evaluation of Hand Held, Flat Electrode pH, Electrical Conductivity, Potassium, and Nitrate Meters

Cardy flat electrode pH, electrical conductivity, potassium and nitrate meters were evaluated for their application to greenhouse solution and media testing. The pH, EC, K, and NO3-N levels in 7 recirculated nutrient solution reservoirs were monitored weekly for 8 weeks using Cardy meters and standard methods. Regression analysis of the results of the Cardy meters against those of standard methods resulted in slopes of 0.64, 0.94, 1.05 and 1.03 for pH, EC, NO3-N and K respectively. Saturated media extract (SME) samples of a peat-based medium were diluted to provide concentrations of 10 to 200 mg·liter-1 NO3-N. The regression equation describing the relationship between the colorimetric and Cardy determinations was: ppm NO3-N = 0.86 * Cardy ppm NO3-N + 11.1 (R2=0.98). In a separate experiment, KNO3 and Ca(NO3)2 were added to a commercial peat-based medium to provide 27 to 490 mg·liter-1 NO3-N using the SME method. The regression equation describing the relationship between the colorimetric and Cardy determinations was: ppm NO3-N = 1.05 * Cardy ppm NO3-N -2.05 (R2=0.98). Chloride in the range of 0 to 1400 mg·liter-1 resulted in a 0.02 mg·liter-1 increase in NO3-N with every 1 mg·liter-1 increase in chloride.

Peat-based Potting Media is an Extraneous Source of Iron When Using an Iron Chelate.

The use of an iron chelate, Fe-DTPA, has been associated with an Fe toxicity disorder affecting the leaves of cutting geranium, Pelargonium × hortorum. In previous research Fe concentrations in medium leachates were higher than applied Fe-DTPA. The blank chelate DTPA has been shown to be an effective extractor of micronutrients from soilless media. Plants were grown in a controlled environment chamber at 22C and 16HR photoperiod, in a peat-based medium. In experiment 1 treatments of 0, 0.2 and 2 mM DTPA were applied to the growth medium and in experiment 2 treatments of 0, 0.02 and 0.2 mM DTPA and Fe-DTPA were used. Tissue and leachates were analyzed for Fe concentrations. Leachates of experiment 1 revealed that 2 mM DTPA extracted up to 1.79 mM Fe for the first week and then decreased to 0.3 mM while 0.2 mM DTPA extracted Fe in concentrations that generally increased during the experiment to 0.3 mM. In experiment 2 leachate concentrations of Fe from the 0.02 mM DTPA and Fe-DTPA treatments were similar and increased from 0.02 mM to 0.035 mM. The 0.2 mM Fe-DTPA increased from 0.14 mM to 0.26 mM while the 0.2 mM DTPA decreased from 0.17 mM to 0.054 mM. The 0 treatment of both experiments had 0.0027 mM Fe in the leachates. The tissue analysis of experiment 1 was inconclusive. Experiment 2 revealed no differences in weight and no difference in the total amount of Fe accumulated by the plants. This indicates that the practice of using Fe-DTPA, which increases the amount of potentially available Fe, may be a causal factor in geraniums accumulating toxic levels of Fe.

PINE BARK AND PEAT-BASED MEDIA INFLUENCE THE EFFECTS OF UNICONAZOLE DRENCH ON `GUTBIER V-14 GLORY' POINSETTIAS.

The objective of this study was to determine the influences of 8 commercial media, 4 peat-based and 4 pine bark-based, on the effects of uniconazole applied as a media drench to `Gutbier V-14 Glory' poinsettias. The peat-based media were Baccto Grower's Mix, Baccto High Porosity Professional, Baccto High Porosity Professional with Bacctite, and Baccto Rockwool Mix. The pine bark-based media were Metro 300, 360, 500, and 700. Uniconazole was applied to plants grown in each media at 5 rates (0, 2, 4, 6, and 8 mg · 15 cm por1). Uniconazole effectively reduced plant height and width, bract dry weight, and bract number in all media. Plants grown in the Metro products, however, tended to be larger than those grown in the Baccto products. Bract size and number, plant weight, width and height were greatest in Metro 360. The rockwool mix produced the smallest plants. Plants grown in the peat-based media were more sensitive to uniconazole drenches. Plants grown in Metro 360 were the least sensitive to uniconazole drenches.

Propagation of Peach Cuttings Using Foam Cubes

Synthetic polyurethane foam cubes were evaluated as an alternative to conventional peat-based media for rooting of expanded nodal, semihardwood, and hardwood cuttings of peach [Prunus persica (L.) Batsch]. Semihardwood cuttings taken in August had higher rooting percentages in foam cubes than in either of two peat-based media. There were no differences in the number of root initials or lengths of roots among the three media. Semihardwood cuttings of 18 cultivars of peach and nectarine had a mean rooting percentage of 58% in the peat-perlite-vermiculite medium compared to 77% for those in foam cubes. There was no difference between rooting percentage or root grade for hardwood cuttings collected in October from either foam cubes or the peat-based medium. Although rooting percentages were lower for expanded nodal cuttings than for semihardwood or hardwood cuttings, there were no differences between the two peat-based media and the foam cubes.

Relationship of Matric Water Potential and Air-filled Porosity of Container Media to Development of Phytophthora Root Rot of Rhododendron

Matric water potential and air-filled porosity were determined at four sampling dates during the growing season for trickle-irrigated pine bark and peat-based media that differed in composition and particle size distribution. At low and high inoculum densities (nine and 30 infested oat grains per container) of Phytophthora cinnamomi, severity of Phytophthora root rot of Rhododendron sp. was significantly less in pine bark media than in peat/sand/soil. Differences in root rot severity between the pine bark media and the peat/sand/soil medium were best explained by differences in air-filled porosity and matric water potential among media (...)

Plant Response to Container Planting Method and Media

Abstract Shoot dry weight and relative root density of Ilex crenata Thunb. ‘Compacta’ and Rhododendron obtusum (Lindl.) Planch. ‘Hino Crimson’ were greater when liners were transplanted into holes with a core removed (excavated) compared to holes formed by compression (dibbled). Growth index, relative root density, and shoot dry weight increased as the percent pine bark in the growth media increased from 50% to 80 or 90% pine bark with holly and from 50% to 90% pine bark with azalea. Bulk density decreased and air porosity and irrigation frequency increased as the percent pine bark in pine bark:sandy loam container media increased from 50% to 100%. In a second experiment, root density and shoot dry weight of Ilex crenata Thunb. ‘Helleri’, but not Rhododendron × ‘Trouper’, were greater in pine bark and pine bark-sandy loam media when the planting hole was excavated rather than dibbled. Plant growth of the 2 species in peat-based media was not influenced by planting method.

A Comparison of Seeding Mixes for Bedding Plant Production1

Abstract Ten species of bedding plants were seeded into either a sphagnum peatmoss or pine bark-based germination medium. Marigolds and peppers had higher germination percentages and petunia, scarlet sage, verbena, marigold, impatiens, coleus, tomato, and pepper were heavier at time of transplanting when germinated in the sphagnum peat-based medium. Plant weight was markedly decreased at the time of sale by early checks in seedling growth resulting from seed germination in the bark-based medium.