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content in them ( Perkins and Bassuk, 1995 ). An interesting fact would be to examine the effect of rooting hormone and rooting media overrooting and subsequent overwintering. Higher concentration of auxins could lead to ethylene biosynthesis, increased

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Small volumes (2% to 20%) of a variety of calcined clay-type products are being used as components of soilless root media because of their potential to increase nutrient retention, air space, water retention, and bulk density of mixes used for

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Our research emphasis has been on utilization of industrial by-products as components of plant root substrates. Coal bottom ash (CBA) collects at the base of furnaces of coal-fired power plants, in contrast to fly ash, which is removed from stack fumes by electrostatic precipitators. A majority of CBA is disposed in landfills. Its low cost and availability in large quantities (in 1994, >14 million tons were produced in the United States, of which only ≈5 million tons were marketed) recommend it for trial as a component of root media, which currently contain far more expensive ingredients. CBA tends to increase pH and EC and decrease water and air capacities of root media. When used as a root medium in a closed loop nutriculture system, it caused an increase in Ca, K, and Na in the nutrient solution. Crops grown in CBA root media include pot and cut chrysanthemums, roses, rhododendrons, poinsettias, Easter lilies, peperomia, zonal and ivy geraniums, impatiens, New Guinea impatiens, and hydrangeas. In general, growth parameters such as plant dry weight and flower number tended to decline at media CBA levels of 75% or more. At CBA levels of 50% or less, these parameters tended to equal or surpass those of plants in control (0% CBA) media.

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Acidification of the irrigation water with phosphoric acid is a common practice to avoid nutrient deficiencies/toxicities from alkaline root media. It has been suggested high phosphorus levels could cause phosphorus toxicity.

Euphorbia pulcherrima Willd. cultivars Supjibi and Celebrate 2 cuttings were potted on June 6, 1991 in a root medium of peat, perlite and soil (40:40:20 by volume) amended with N, K, Ca and micro-nutrients, plus six phosphorus (0-40-0) rates of .89, 1.78, 3.55, 7.11, 10.67, and 14.22 kg/meter3. Foliar samples were analyzed for NH4, P, and K every two weeks after the start of short days. Root media samples were also collected and analyzed pH, SS and NO3, P, K and NH4. Bract diameter, bract edge burn, days to anthesis, and plant height were recorded at anthesis.

Media P levels increased as the phosphorus rate increased, but a significant treatment*harvest interaction for media P was observed. There was decreased bract size and increased incidences of bract edge burn as phosphorus rate increased. Root media P levels did not affect the levels of other nutrient elements in the foliar samples. No visual symptoms of phosphorus toxicity was observed except for bract edge burn at anthesis.

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`V-14 Glory' poinsettias (Euphorbia pulcherrima Willd. ex Klotzsch) were grown in five root media using top watering with 20% leaching for 112 days. Root media with a high water-holding capacity required fewer irrigations and fertilizer applications than those with a lower water-holding capacity. However, similar amounts of water were applied and leached with both types of root media over the entire experiment. The reduction in the number of fertilizations was compensated for by an increase in the amount (volume) of fertilizer applied at any one irrigation. The greatest differences in root-media nutrient concentrations were found between the top 2.5 cm (top layer) and the remaining root medium within the same pot (root zone). After 58 days, when fertilization with water-soluble fertilizer (28.6N–0P–8.5K mol·m–3) was stopped, nutrient concentrations in the top layer were 3 to 6 times greater than those in the root zone for all five root media tested. For the final 42 days of the experiment after fertilization was stopped, nutrient concentrations in the root zone remained at acceptable levels in all root media. The nutrients contained in the top layer may have provided a source of nutrients for the root zone once fertilization was stopped.

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When using the closed, insulated pallet system (CIPS), it is desired to apply the fertilizers once at the beginning of planting and last through harvest. When doing so, the electrical conductivity (EC) of the root environment needs to be at a reasonable level. Therefore, the objective of this experiment was to determine the effect of fertilizer conserver placement and increasing rate on the EC of the growth media. When delivering nutrients in such a manner, the fertilizer ions have limited surface area in contact with the root growth media that limits ion diffusion rate. Five fertilization rates, 15, 45, 60, 75, and 105 g per 1.5-L media pouch, were tested in a completely randomized arrangement. In each pouch, two fertilizer conservers were placed in the center of the lower half of media, each containing a different source of fertilizer. Tomato cv. `Pik Red' was used to test the growth response to treatment. At day 100, the ECs of the middle 5 cm stratum of the growth media for the 15–75 g treatments were not significantly different from each other. Their ECs ranged from 2.52 to 4.51 dS/m. However, middle layer in the 105g treatment was 12.97 dS/m, while EC for the layer immediately below it was 1.18 dS/m. Because there were no differences in shoot and fruit weights among all fertilization treatments, compensation nutrient uptake and water uptake specialization may have occurred in the high salinity and lower salinity, respectively. The data illustrate that delivery of nutrients in small conservers is a feasible approach for the CIPS. Only small amounts of fertilizer are required for a 100-day tomato crop grown in CIPS.

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obtain the greatest continuous SMR while producing quality microshoots that will root and acclimatize successfully to ex vitro conditions. ‘Abacus’ and ‘Wife’ responded differently to the culture media tested, which was not surprising, because variability

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The effects of two rooting media [5 pine bark : 1 soil (v/v) and 5 Tufflite (a volcanic pumice) : 1 soil (v/v)] and (+ or -) phosphorus fertilizer [Ca(H2PO4)2H2O @ 6.58 g P per pot] on root architecture of Colorado mesquite (Prosopis alba Grieb. 'Colorado') were studied. Rooted cuttings were transplanted into 10-liter containers, topdressed with 45 g of 20N-0P-16.5K (IBDU slow release formulation) and 3 g Micromax micronutrient fertilizer, grown outdoors on black polyproplyene fabric, and irrigated daily to container capacity for three months. With or without P, specific root length was less for mesquite roots in Tufflite than for those in pine bark. Without P fertilizer, extended path length and root altitude were higher for roots grown in Tufflite than for those in pine bark. Adding P fertilizer decreased specific root length regardless of media type. In the pine bark medium, root altitude and extended path length were highest for trees fertilized with P; however, P fertilizer did not affect root altitude and lowered the extended path length when trees were grown in the Tufflite medium. These results indicate that roots were thicker and more branched in the Tufflite medium compared to pine bark and that P fertilizer caused a more herringbone branching pattern for mesquite roots when grown in pine bark, but resulted in a slightly more dichomatous branching pattern for roots when grown in Tufflite.

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Abstract

Toyon [Heteromeles arbutifolia (Ait.) M.J. Roemer] cuttings were grown in container media having air-filled porosity (Ea) values ranging from 1% to 20%. Plants were inoculated with Phytophthora cinnamomi Rands zoospores, and all media were maintained at or near container capacity for 3 weeks, after which plants were evaluated for root rot symptoms. Inoculated plants grown in media with <10% Ea developed severe root rot, while those grown in media having Ea values of 10-20% appeared relatively healthy. Roots of noninoculated plants growing in low-Ea media were not adversely affected during the experimental period.

Open Access

Abstract

Cuttings of three ornamental species [Ilex × ‘Nellie R. Stevens’, (I. aquifolium × I. cornuta) Van Lennep, × Cupressocyparis leylandii Jacks & Dall. ‘Haggerston Grey’, and Lagerstroemia indica L.] were inserted in 11 media to determine the effects of physical properties of propagation media on rooting response. The physical properties of seven propagation media were altered by manipulating particle size distribution of a 1 aged pine bark : 1 composted hardwood bark (v/v) medium. Four other propagation media were used for comparison. Container capacity air space ranged from 12% to 40%, and water held after drainage in the root zone ranged from 35% to 55%. Variation in rooting response of cuttings occurred, but differences could not be attributed to the physical properties of the various media. In addition, no relationship between rooting response and engineered combinations of hardwood bark and pine bark were detected.

Open Access