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  • Author or Editor: Michael R. Evans x
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Cucumis sativus (cucumber), Pelargonium × hortorum (geranium), Tagetes patula (marigold), and Cucurbita pepo (squash) seed were sown into plug cells (5 ml volume) filled with a germination substrate containing peat, vermiculite, and perlite. After the seed were sown, the substrate was saturated with solution containing 0 (deionized water) 2500, or 5000 mg/L humic acid (HA). Additional treatments included seed which were sown into the substrate and saturated with nutrient solutions corresponding to the nutrient concentration of each humic acid solution. Seed were placed in a growth chamber and maintained at 22°C and under a 12-h photoperiod with a PPF of 275 μmol·m–2·s–1. After 10 d for cucumber and squash and 14 d for marigold and geranium, plants were harvested and root and shoot fresh mass recorded. Shoot fresh mass was not significantly affected by treatment for any of the species tested. Except for squash, root fresh mass was significantly increased by humic acid treatments. For cucumber, root fresh mass ranged from 0.24 g in deionized water to 0.34 g in 2500 and 5000 mg/L HA. Geranium root fresh mass ranged from 0.03 g in deionized water and 5000 mg/L HA to 0.05 g in 2500 mg/L HA. Marigold root fresh mass ranged from 0.02 g in deionized water to 0.03 g in 2500 and 5000 mg/L HA. Root fresh mass for nutrient controls were similar to those for deionized water.

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Vegetative 6-cm Euphorbia pulcherrima `Freedom' cuttings were placed in black 200-ml bottles containing humic acid solutions, nutrient solutions, or deionized water. Humic acid solutions were prepared using Enersol SC (American Colloid, Arlington Heights, Ill.). Concentrations of 500, 750, and 1000 mg/L humic acid were compared to solutions containing mineral element concentrations equivalent to those contained in humic acid solutions. After 4 weeks, 88%, 75%, and 88% of cuttings had rooted in the 500, 750, and 1000 mg/L humic acid solutions, respectively. Cuttings placed in nutrient controls or deionized water failed to form roots after 4 weeks. Average root fresh mass was 175, 80, and 72 mg for cuttings placed in 500, 750, and 1000 mg/L humic acid solution, respectively. Average number of roots formed per cutting ranged from 21 in the 500-mg/L solution to 6 in the 1000-mg/L solution. Average lengths ranged from 26 mm in the 500-mg/L to 12 in the 1000-mg/L solution. As humic acid concentration increased, average root fresh mass, average number of roots, and the length of the longest root significantly decreased.

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Pepper (Capsicum annuum) and impatiens (Impatiens walleriana) plants were grown in substrates composed of 20% perlite and 20%, 40%, 60% or 80% of a coarse, medium or fine grind of fresh rice hulls with the remainder being Sphagnum peat. Impatiens grown in substrates containing 40% of a coarse, medium or fine and 80% of a fine grind of rice hulls had similar shoot dry weights as those grown in a substrate containing 80% peat. Only impatiens grown in a root substrate containing 40% of the coarse grind of fresh rice hulls had lower root dry weight than those grown in substrates containing 80% peat. Peppers grown in a substrate containing 60% and 80% of a coarse, 60% of a medium or 60% and 80% of a fine grind of fresh rice hulls had similar shoot dry weights as those grown in a substrate containing 80% peat. There were no significant differences in pepper root dry weights among the substrates. Impatiens and pepper plants grown in a substrate containing 80% of the fine grind of fresh rice hulls were similar to those grown in 80% peat, and therefore, the fine grind of fresh rice hulls served as a suitable substitute for Sphagnum peat.

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Biological substrate amendments including SG-11, Subtilex, SoilGuard, ActinoIron, Companion, RootShield and BioYield were evaluated for their efficacy to control common soil-borne fungal and fungal-like pathogens when incorporated into the substrate at transplanting. The biological agents were incorporated into an 80% Sphagnum peat and 20% perlite substrate at the label recommended rates and four-to-six-leaf plugs of the test species were transplanted into the substrates. Substrates were either inoculated or uninoculated with a test pathogen. Pathogen-host combinations included Pythium ultimum on geranium (Pelargonium ×hortorum), Phytophthora nicotianae and Pythium aphanidermatum on vinca (Catharanthus roseus), and Theilaviopsis basicoli on pansy (Viola ×wittrockiana). The incidence of disease development, plant mortality and root fresh weights did not differ among the biological agents and the inoculated controls. Therefore, under the conditions of this study, the biological agents did not provide significant disease suppression. Pansy and vinca plants grown in uninoculated substrates amended with Subtilex had significantly higher shoot dry weights than those grown in unamended substrates. Pansy, vinca and tomato plants grown in uninoculated substrates amended with SG-11 had significantly higher shoot dry weights than those grown in unamended substrates.

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Seedlings of Catharanthus roseus (L.) G. Don `Pacifica Red' were transplanted into substrates composed of either 80% sphagnum peat or coir with the remaining volume being perlite, sand, or vermiculite. The six substrates were inoculated with Pythium irregulare Buisman at 0 or 50,000 oospores per 10-cm container. The containers were irrigated daily to maintain moisture levels near container capacity. No visually apparent symptoms of infection or significant differences in shoot and root fresh and dry weights were observed among the uninoculated substrates and the inoculated coir substrates. Inoculated peat substrates had an 80% infection rate and significantly reduced shoot and root fresh and dry weights as compared to uninoculated substrates. Seedlings of C. roseus were transplanted into pasteurized and unpasteurized substrates composed of 80% (v/v) coir or sphagnum peat with the remaining 20% being perlite. Substrates were inoculated with 0, 5000, or 20,000 oospores of P. irregulare per 10-cm container. No visually apparent symptoms of infection or significant differences in shoot and root fresh and dry weights were observed among the uninoculated substrates and the inoculated pasteurized coir. The inoculated pasteurized peat substrate, inoculated unpasteurized peat substrate, and the inoculated unpasteurized coir substrate grown plants had an 88% infection and a significant reduction in the shoot and root fresh and dry weights.

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Fresh parboiled rice hulls ground in a hammer mill and screened through a 1.18-mm screen and collected on a 0.18-mm screen (RH3) and particles with a specific diameter of 0.5 to 1.0 mm had total pore space (TPS), air-filled pore space (AFP), and water-holding capacity (WHC) similar to that of Canadian sphagnum peat (peat). However, RH3 had more available water, a higher bulk density (BD), and a higher particle density (PD) than peat. When blended with 20% to 40% perlite or 1 cm aged pine bark, RH3-based substrates had lower TPS, similar AFP, and lower WHC than equivalent peat-based substrates. The RH3-containing substrates had higher BD and average PD than equivalent peat-based substrates. When blended with parboiled rice hulls (PBH), RH3-based substrates had lower TPS than equivalent peat-based substrates. When blended with 20% to 40% PBH, RH3-based substrates had lower AFP than equivalent peat-based substrates. RH3-based substrates containing up to 20% PBH had lower WHC than equivalent peat-based substrates. RH3-based substrates containing 40% PBH had a higher WHC than equivalent peat-based substrates. When blended with PBH, all RH3-based substrates had higher BD and average PD than equivalent peat-based substrates. The addition of 40% RH3 to a peat-based substrate containing 20% perlite decreased substrate TPS, whereas the addition of 10% to 40% decreased AFP. The addition of 10% to 30% RH3 increased WHC. The addition of 30% RH3 to a peat-based substrate containing 20% 1 cm aged pine bark decreased substrate TPS and the addition of 20% to 40% RH3 decreased AFP. The addition of 10% RH3 increased WHC, but the addition of 20% or more RH3 did not affect WHC. The addition of 30% RH3 increased the BD, but the addition of RH3 had no effect on average PD. The addition of 20% or more and 30% or more RH3 to a peat-based substrate containing 20% PBH decreased substrate TPS and AFP, respectively. The addition 20% RH3 decreased WHC. The addition of 10% to 40% RH3 increased BD. Overall, RH3 was the ground rice hull product that had physical properties most similar to peat. Peat-based substrates in which up to 40% of the peat was replaced with RH3 had physical properties that, although different from peat controls, were within commonly recommended ranges for substrates used to grow greenhouse crops.

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Nonplanted Caladium × hortukmum Birdsey `Candidum' tubers were exposed to 26 (control), 38,43, or 48C for 1,2, or 3 days. Then tubers were planted and forced in a glasshouse for 4 weeks at 18 to 33C (air). Leaf emergence from tubers exposed to 48C for 1 or 2 days required 3-12 days longer than leaf emergence from control tubers. No leaves emerged from tubers treated at 48C for 3 days. Exposing tubers to 38C for 3 days or 43C for 1 day did not affect subsequent plant growth. Exposing tubers to 43C for 2 or 3 days or 48C for 1 or 2 days resulted in plants with reduced shoot fresh weights and fewer leaves ≥ 15 cm. In a second experiment, planted tubers were forced for 10 days at 26C so that roots had developed to the edge of the pot and shoots had emerged to the soil surface. These planted (sprouting) tubers were exposed to 43C for 0,4,8,12,16,20, or 24 hours/day for 1,3, or 5 days and then forced for 7 weeks in a glasshouse. With 3- or 5-day treatments, days to leaf emergence increased as the hours of exposure to 43C increased. Only 33% of planted tubers exposed to 43C for 24 hours/day for 5 days sprouted. Tubers exposed to 43C for≤ 12 hours/day for 3 days produced plants of similar or greater height, numbers of leaves □≥15 cm wide, and shoot fresh weights, but additional hours of daily exposure decreased these plant characteristics. At 5 days, plant height, number of ≥ 15-cm-wide leaves, and shoot fresh weight decreased linearly with increased hours of exposure of tubers to high temperature.

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Before being forced as potted plants, tubers of two Caladium ×hortulanum Birdsey cultivars were subjected to different methods of de-eyeing (terminal bud removal), either before or after 6 weeks of curing and storage. The cultivar Frieda Hemple (`FH'), a type with numerous buds that does not require de-eyeing, was less affected by deeyeing than `Fannie Munson' ('FM'), which has a single dominant bud and requires deeyeing. De-eyeing had little effect on `FH' development. For `FM', regardless of the time of de-eyeing, all treatments reduced height, increased the number of leaves, increased total leaf area, and reduced mean leaf area when compared to intact tubers. However, as the size of the tuber piece removed during de-eyeing increased, the variability within each treatment increased. Based on the results of this research, the best method of de-eyeing would be to destroy or remove the dominant terminal bud while removing as little of the surrounding tissue as possible. The time of de-eyeing can depend on producer preference, since the time of de-eyeing did not affect development significantly.

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A comparison was made of Philippine coconut coir dust and Canadian spaghnum peat as components of three growing media for greenhouse production of Dieffenbachia maculata `Camille'. The soilless media were prepared using coir or peat in various amounts (by volume) combined with pine bark, vermiculite, and/or perlite (Media A–50% coir/peat: 25% vermiculite: 25% perlite; Media B–40% coir/peat: 30% vermiculite: 30% bark; Media C–50% coir/peat: 50% bark). Chemical and physical properties of the soils were determined at the beginning and the end of the five-month production cycle. Plant root and top growth and grades were determined at the end of the experiment. Initially, saturated media extracts from coir-containing media had elevated K, Cl, and soluble salts levels compared to peat-containing media; however, by the end of the experiment those levels were lower in coir- than in peat-based media. Water-filled pore space and water-holding capacities were generally higher and air-filled pore space lower in coir- than in peat-based media, probably due to differences in particle size distributions. There were no interaction effects on plant growth between growing media and coir versus peat. Plant root and top growth in Media A > Media B > Media C and plant top growth was greater in coir- than in peat-based media. Differences in growth could be due, in part, to differences in media water-holding capacities.

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Chemical properties of unprocessed coconut husks varied significantly between 11 sources tested. The pH was significantly different between sources and ranged from 5.9 to 6.9. The electrical conductivities were significantly different between sources and ranged from 1.2 to 2.8 mS·cm–1. The levels of Na, K, P, and Cl were significantly different between sources and ranged from 23 to 88, 126 to 236, 8 to 33, and 304 to 704 ppm, respectively. The B, Cu, Fe, Ni, S, Zn, Mn, and Mo levels were all significantly different between sources and ranged from nondetectable levels to 12.7 ppm. The NH4-N, NO3-N, Ca, and Mg levels were not significantly different between sources and ranged from 0.2 to 1.8, 0.2 to 0.9, 2.9 to 7.3, and nondetectable to 4.6 ppm, respectively. Coir dust produced by screening of waste grade coir through 13-, 6-, or 3-mm screens had significantly different bulk densities, air-filled pore space, water filled pore space and water-holding capacities compared to nonscreened waste grade coir. However, total pore space and total solids were not significantly affected by screening. Screen size did not significantly affect physical properties. Compression pressures used for formation of coir dust blocks significantly affected physical properties. Additionally, coir dust age significantly affected chemical properties.

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