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Michael R. Evans and Andrew A. Waber

Euphorbia pulcherrima `Freedom' (poinsettia) and Pelargonium ×hortorum `Pink Elite' (geranium) were grown in 75:25:0, 50:50:0, 27:75:0, 75:0:25 50:0:50, 25:0:75 (v/v sphagnum peat: 0.25-grade rubber: 0.10-grade rubber) substrates or in a 50 sphagnum peat: 30 perlite: 20 loam (v/v) standard greenhouse substrate. Geranium root and shoot fresh weights, height, and number of axillary shoots were reduced when grown in rubber-containing substrates compared to plants grown in the standard control. As the proportion of either grade of rubber increased, root and shoot fresh weights, height, and number of axillary shoots decreased. Flowering in geranium was delayed and the number of inflorescences reduced as the proportion of the 0.10-grade rubber increased. Plants grown in the 0.25-grade rubber failed to flower by the termination of the experiment. Poinsettia plants grown in rubber-containing substrates had reduced shoot fresh weight, height, number of bracts, and bract area compared to plants grown in the standard control. As the proportion of either grade of rubber increased, height, shoot fresh weight, number of bracts, and bract area decreased. Number of axillary branches was reduced in substrates containing 50% and 75% of the 0.10-grade rubber. Days to anthesis was unaffected by substrate.

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Jack A. Hartwigsen and Michael R. Evans

Seed of Pelargonium ×hortorum L.H. Bailey `Freckles' (geranium) and Tagetes patula L. `Bonanza' (marigold) were soaked for 12, 24, or 48 h in solutions containing 0 (deionized water), 5000, 10,000, or 15,000 mg·L-1 humic acid (HA) or nutrient controls (NC) containing similar levels of nutrients prior to planting. Soaking in deionized water (DI) and NC treatments had no significant effect on root fresh weight. However, several of the HA treatments increased root fresh weight of marigold seedlings, and all increased geranium root fresh weight. Percentage of germination and shoot fresh weight were not significantly affected by treatment. Seed of Cucumis sativus L. `Salad Bush' (cucumber), Cucurbita pepo L. `Golden Summer Crookneck' (squash), `Freckles' geranium and `Bonanza' marigold were sown into 15-cell plug trays (5 mL volume), and the substrate was drenched with DI, 2500 or 5000 mg·L-1 HA, or 2500 or 5000 mg·L-1 NC. DI and NC treatments did not affect root fresh weight. However, cucumber, squash, and marigold seedlings germinated in substrate drenched with 2500 and 5000 mg·L-1 HA and geranium seedlings germinated in substrate drenched with 2500 mg·L-1 HA had significantly higher root fresh weight than did seedlings from all other treatments. Percentage of germination and shoot fresh weight were not significantly affected by treatment. `Salad Bush' cucumber and `Golden Summer Crookneck' squash seedlings germinated on germination towels soaked with 2500 or 5000 mg·L-1 HA, had significantly higher root fresh weight than did seedlings germinated on towels soaked with DI or NC solutions. Treatment with HA did not affect shoot fresh weight or the number of lateral roots. However, HA treatment increased the total length of lateral roots. The increase in lateral root growth occurred primarily in lateral roots developing from the lower hypocotyl.

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Robert H. Stamps and Michael R. Evans

A comparison was made of Canadian sphagnum peat (SP) and Philippine coconut (Cocos nucifera L.) coir dust (CD) as growing media components for Dieffenbachia maculata [(Lodd.) G. Don] `Camille' greenhouse production. Three soilless foliage plant growing mixes [Cornell, Hybrid, Univ. of Florida #2 (UF-2)] were prepared using either SP or CD and pine bark (PB), vermiculite (V), and/or perlite (P) in the following ratios (percent by volume): Cornell = 50 CD or SP:25 V:25 P, Hybrid = 40 CD or SP:30 V:30 PB, UF-2 = 50 CD or SP:50 PB. Initial CI concentrations and electrical conductivities were higher for CD-containing media (CDM) than SP-containing media (SPM). At termination, Ca, Mg, and NO3-N concentrations were higher for SPM than CDM. Bulk densities were lower for CDM than SPM for one medium, but not for the others. Water-filled pore space (W-FPS) and water-holding capacity (W-HC) were larger and air-filled pore space (A-FPS) generally was smaller for CDM than SPM. Cornell had the highest W-FPS and W-HC, lowest A-FPS and percentage of large particles, and produced the highest grade and heaviest plants. Plant top grades, fresh mass and overall mass, but not root grades and mass, were higher for CDM than SPM. Plant mass was positively correlated with initial medium W-HC but not with A-FPS. Lower K in mix UF-2 compared to the mixes containing vermiculite may have been partly responsible for the lesser growth in that mix.

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Michael R. Evans and Richard L. Harkess

Geranium (Pelargonium ×hortorum L.H. Bailey) `Freckles' and poinsettia (Euphorbia pulcherrima Willd. ex Klotzch) `Freedom' were grown in six peat and shredded-rubber substrates formulated to contain 75:25:0, 50:50:0, 25:75:0, 75:0:25, 50:0:50, 25:0:75 sphagnum peat: fine-grade rubber: coarse-grade rubber (by volume). Additionally, plants were grown in a 50 peat: 30 perlite: 20 loam (by volume) control substrate. Shredded rubber-containing substrates had higher bulk densities, lower total pore space, and higher total solids than the control substrate. Fine rubber-containing substrates had lower air-filled pore space (AFP) and lower water-holding capacities (WHC) than the control substrate. Substrates containing 25% coarse rubber had lower AFP and WHC than the control, but substrates containing 50% and 75% coarse shredded rubber had higher AFP and lower WHC than the control. Shredded rubber-containing substrates had significantly higher levels of Zn than the control substrate. Plants grown in rubber-containing substrates had tissue Zn levels significantly higher than the control and at levels reported to be phytotoxic in other species. Geraniums grown in rubber-containing substrates had lower root and shoot fresh mass, were shorter, and had fewer axillary branches than those grown in the control substrate. Poinsettia plants grown in rubber-containing substrates were shorter, had lower shoot fresh mass, fewer bracts, and lower bract area as compared to plants grown in the control substrate.

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Stephanie A. Beeks and Michael R. Evans

The objective for this research was to evaluate the growth of a long-term crop in biodegradable containers compared with traditional plastic containers using a subirrigation system. Plastic, bioplastic, solid ricehull, slotted ricehull, paper, peat, dairy manure, wood fiber, rice straw, and coconut fiber containers were used to evaluate plant growth of ‘Rainier Purple’ cyclamen (Cyclamen persicum) in ebb-and-flood subirrigation benches. The days to flower ranged from 70 to 79 and there were no significant differences between the plastic containers and the biocontainers. The dry shoot weights ranged from 23.9 to 37.4 g. Plants grown in plastic containers had dry shoot weights of 27.6 g. The dry shoot weight of plants grown in containers composed of wood fiber was 23.9 g and was lower than plants grown in plastic containers. The plants grown in the bioplastic, solid ricehull, slotted ricehull, paper, peat, dairy manure, rice straw, and coconut fiber containers had significantly higher dry shoot weights than plants grown in plastic containers. Dry root weights ranged from 3.0 to 4.0 g. The plants grown in the plastic containers had dry root weights of 3.0 g. Plants grown in paper and wood fiber containers had higher dry root weights than those grown in plastic containers. The only container that negatively affected plant growth was the wood fiber container. Plants preformed the best in solid ricehull, slotted ricehull, and coconut fiber containers based on dry shoot and dry root weights, but all containers were successfully used to produce marketable cyclamen plants.

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Johann S. Buck and Michael R. Evans

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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Michael R. Evans, Brian E. Jackson, Michael Popp, and Sammy Sadaka

The use of biochar as a soil amendment has fostered much attention in recent years due to its potential of improving the chemical, physical, and biological properties of agricultural soils and/or soilless substrates. The objective of this study was to evaluate the chemical properties of feedstocks, common in the southeast United States, and their resulting biochar products (after being torrefied) and determine if the chemical properties were within suitable ranges for growers to use the biochar products as root substrate components. Poultry litter biochar produced at 400 °C for 2 hours had a higher total phosphorus (P), potassium (K), calcium (Ca), magnesium (Mg), sulfur (S), chloride (Cl), copper (Cu), iron (Fe), manganese (Mn), molybdenum (Mo), sodium (Na), and zinc (Zn) concentration than biochar made using the same process with mixed hard wood species, miscanthus (Miscanthus capensis), cotton (Gossypium hirsutum) gin trash, switchgrass (Panicum virgatum), rice (Oryza sativa) hull, and pine (Pinus sp.) shavings feedstocks. The pH of the biochar products ranged from 4.6 for pine shaving biochar to 9.3 for miscanthus biochar. The electrical conductivity (EC) ranged from 0.1 dS·m−1 for mixed hardwood biochar to 30.3 dS·m−1 for poultry litter biochar. The cation exchange capacity (CEC) of the biochar products ranged from a low of 0.09 meq/g for mixed hardwood biochar to a high of 19.0 meq/g for poultry litter biochar. The water-extractable nitrate, P, K, Ca, Mg, sulfate, boron, Cl, Cu, Fe, Mo, Na, and Zn were higher in poultry litter biochar than in all of the other types of biochar. The high EC and mineral element concentration of the poultry litter biochar would prevent its use in root substrates except in very small amounts. In addition, the high degree of variability in chemical properties among all of the biochar products would require users to know the specific properties of any biochar product they used in a soil or soilless substrate. Modifications to traditional limestone additions and fertility programs may also need to be tested and monitored to compensate for the biochar pH and mineral nutrient availability. Users should be aware that biochar products made from different feedstocks can have very different chemical properties even if the same process was used to manufacture them.

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Brian E. Whipker, Shravan K. Dasoju, and Michael R. Evans

Drench applications of paclobutrazol or uniconazole were applied at doses of 0, 0.0025, 0.005, 0.01, 0.02, or 0.04 mg a.i./pot (28,350 mg = 1.0 oz) to vegetatively propagated `Aurora', `Medallion Dark Red', and `Pink Satisfaction' geranium (Pelargonium ×hortorum L.H. Bailey). Geranium total plant height, leaf canopy height, and plant diameter responded similarly to drench applications of either paclobutrazol or uniconazole. There was a significant quadratic relationship between plant growth regulator (PGR) dose and total plant height and leaf canopy height for `Aurora' and `Medallion Dark Red', with total plant height and leaf canopy height being shorter as paclobutrazol or uniconazole doses increased up to 0.02 mg. However, doses of ≥0.02 mg had little additional effect on total plant height and leaf canopy height. Most of the total height control achieved by the use of PGRs was primarily due to a reduction of leaf canopy height, rather than inflorescence height. Doses of 0.005 to 0.01 mg of either PGR produced marketable sized potted plants of `Medallion Dark Red' and `Pink Satisfaction'. `Aurora', which was the most vigorous cultivar, required doses of 0.01 or 0.02 mg of either paclobutrazol or uniconazole to produce marketable sized potted plants.

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Michael R. Evans, Johann S. Buck, and Paolo Sambo

The primary objective of this research was to compare the pH, electrical conductivity (EC), and primary macronutrient status of three ground parboiled fresh rice hull (PBH) products to sphagnum peat when used as a root substrate over 56 days in a greenhouse environment. The three grades of ground rice hull products were produced by grinding PBH and passing the ground product through different screens. One grade (P3) was passed through a 2.00-mm screen and captured on a 1.00-mm screen. The second grade (P4) was passed through a 1.00-mm screen and captured on 0.50-mm screen. A third ground rice hull product (RH3) was a commercially available, ground PBH material that was ground in a hammer mill until it passed through a screen with 1.18-mm-diameter openings and was collected on a screen with 0.18-mm openings. The pH of sphagnum peat ranged from 3.4 to 3.7 across time. The pH of RH3 and P3 increased from 4.7 to 7.1 on day 5 and 14, respectively, before decreasing to 6.3 and 6.7, respectively, on day 56. The pH of P4 increased from 4.8 to 6.9 on day 6 before decreasing to 6.6 on day 56. The P4 had an EC of 1.2 dS·m−1, which was higher than that of peat, RH3, and P3, which had similar EC of 0.7 to 0.8 dS·m−1 regardless of time. The ammonium (NH4 +) concentration was unaffected by time. Peat had an NH4 + concentration of 6.4 mg·L−1, which was lower than that of the ground rice hull products. The P3 had an NH4 + concentration of 14.6 mg·L−1, which was higher than that of RH3 and P4. The RH3 and P4 had similar NH4 + concentrations of 11.8 and 10.8 mg·L−1, respectively. The nitrate (NO3 ) concentration was unaffected by time. The RH3 had a NO3 concentration of 8.2 mg·L−1, which was significantly higher than that of peat, P3, and P4, which had similar NO3 concentrations of 0.5 mg·L−1. The phosphorus (P) concentration in peat ranged from 1.3 to 2.5 mg·L−1 across the sampling times, and peat had a lower P concentration than all rice hull products, which ranged from 57.4 to 104.4 mg·L−1. The potassium (K) concentration in peat ranged from 2 to 5 mg·L−1 across the sampling times and was always lower than that of the rice hull products, which had a K concentration ranging from 195 to 394 mg·L−1. Because pH, P, and K concentrations were above recommended concentrations, ground rice hull products would not be suitable as a stand-alone substrate but might be amended with materials such as elemental sulfur or iron sulfate to adjust the pH or blended with other components to reduce the P and K concentrations to within recommended concentrations.

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Michael R. Evans, Neil O. Anderson, and Harold F. Wilkins

Various durations of rooting at 15C and storage at 5.X and exogenous GA, (1000 ppm) application were used on dormant unrooted peony (Paeonia lactiflora Pall.) tubers of `Sarah Bernhardt', `Festiva Supreme' `Krinkled White', and `Scarlet O'Hara'. Four weeks of cooling were sufficient to break dormancy. Days to emergence, first bud color, and anthesis were reduced as the length of cold storage increased from 4 to 20 weeks. Height and number of shoots emerging per pot increased with increased cooling. All flower buds aborted when tubers were cooled for 20 weeks. When noncooled tubers were given a 1000-ppm GA, soil drench, shoots emerged within 7.5 days; untreated tubers failed to emerge after 5 months. When tubers were treated with GA,, all flower buds aborted.