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  • Author or Editor: Alexander X. Niemiera x
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Amending soilless media with micronutrients is a routine nursery practice. The objective of this research was to determine the micronutrient status of pine bark amended with two sulfate micronutrient sources and a control (unmended). Limed pine bark was unamended, amended with Ironite (1 and 2 g/l), or Micromax (1g/l). Bark was irrigated with distilled water in amounts equivalent to 30, 60, 90, and 120 irrigations (.63 cm per irrigation). Following irrigations, Cu, Fe, Mn, and Zn were extracted with a modified saturated media extract method using .001M DPTA as the extractant. Irrigation amount had no effect on Cu and Mn concentrations which were greater in the Micromax treatment than the Ironite or control treatments. A micronutrient source × irrigation interaction existed for Fe and Zn concentrations requiring regression analysis. In general, slope values indicating the decrease in micronutrient values with increasing irrigations were quite low (≤ .001) for each source. Regardless of irrigation amount, Fe and Zn concentrations were similar for amended and unamended bark.

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Shoot and root water potentials were determined for bare-root Norway maple (Acer platanoides L.) and washington hawthorn (Crataegus phaenopyrum Med.) seedlings subjected to shoot and root exposure treatments for six cold storage durations. Shoot and root water potentials for all exposure treatments and both species decreased with increased time in storage, and the greatest degree of water stress occurred during the first six weeks of storage. Maple shoot and root water potentials for the exposed shoot treatment were the same as the whole plant covered treatment. In contrast, hawthorn shoot and root water potentials for the exposed shoot treatment were the same as values for the roots exposed treatment. Based on these data, we conclude that desiccation sensitive species such as washington hawthorn require root and shoot protection to minimize water loss.

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The influence of intermittent and continuous irrigation on the growth, substrate nutrient accumulation and leaching from container-grown marigolds was determined. During a three week period. Tagetes erecta L. `Apollo' in a pine bark substrate received 12 irrigations. Each irrigation allotment was applied intermittently (multiple applications) or continuously (single application). Irrigation occurred when bark reached a targeted water content; irrigation water contained a complete nutrient solution. Leachates were cumulatively collected for each container and analyzed for N; plant dry weight. size, and nutrient composition were determined. Compared to continuously irrigated plants, intermittently irrigated plants had 43% greater root dry weight, 0.7% greater N concentration, and 43% more N leached from the substrate. Shoot mass. size. K, and P concentrations, substrate (pour-through extraction) and leachate N concentration were unaffected by irrigation method. Results demonstrated that. compared to conventional irrigation practices, intermittent irrigation was an effective method to reduce fertilizer effluent and increase N absorption for container-grown plants.

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Two-year-old Washington hawthorn (Crataegus phaenopyrum Med.) and Norway maple (Acer platanoides L.) seedlings were subjected to varying cold storage durations and four storage treatments: whole plant covered in polyethylene bags, shoots exposed, roots exposed, and whole plant exposed. After storage, half the seedlings were immediately plant and half received a 12-hour desiccation treatment before transplanting. Root growth potential (RGP), time to budbreak, and marketability were measured. With the root covered treatments, Norway maple RGP increased while Washington hawthorn RGP decreased with increased cold storage duration. RGP for both species remained low throughout storage for treatments exposing roots. The 12-hour desiccation treatment reduced RGP for both species with hawthorn being more affected than maple. Days to budbreak for both species decreased with increased storage time for whole plant covered treatments but increased for both species when stored with exposed roots. Maple marketability for root covered treatments was high for most storage durations. Hawthorn marketability was generally low except for the whole plant covered treatment during the first 6 weeks of storage. For the respective storage durations, hawthorn RGP, time to budbreak and marketability values for the shoots exposed treatment were similar to the root exposed treatments. In contrast, values for the shoots exposed treatment were similar to the whole plant covered treatment for maple. There was a high positive correlation between RGP and marketability for both species.

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A study was conducted to determinethe feasibility of using crop water stress index (CWSI) to schedule irrigation of eight species of freeway landscape plants, Acacia redolens B.R. Maslin, Acacia salicina Lindl., Caesalpinia pulcherrima Sw., Cassia nemophila A. Cunn. ex Vogel, Cercidium floridum Benth., Eucalyptus microtheca F.J. Muell., Nerium oleander L., and Prosopis chilensis Mol. Nerium oleander and C. pulcherrima were suited to the use of the CWSI, tolerated repeated exposures to CWSI values of 0.6, and remained aesthetically acceptable. Irrigation of N. oleander via the CWSI resulted in a 19% reduction in water use, compared to the conventional method. CWSI data of other species were too variable, and, thus, irrigation could not be scheduled by CWSI values. Variability was attributed, in part, to lack of a dense canopy, which is necessary to fill the view of the infrared thermometer.

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Experiments were conducted to determine if applying a container-grown plant's daily water allotment in multiple applications (intermittently) increased application efficiency relative to the allotment applied in a single application (continuous). Water was applied (simulated overhead sprinkler system) to marigold plants in a pine bark substrate. Time interval between intermittent applications and water movement in the substrate were investigated. Application efficiency was greater when the water allotment was applied intermittently compared to a single application. Efficiency was also greater when the interval between applications was increased from one to two h. Sectioning substrate into top, middle, and bottom thirds showed that the bottom layer of the intermittent treatment contained more water than the bottom layer for the continuous treatment. There were no differences in water content in the top and middle layers between the two treatments.

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Abstract

Pine bark-filled containers were subjected to 10°, 20°, 30°, or 40°C for 24 days and fertilized periodically with 210 ml of a solution containing 100 ppm NH4-N. Every 6 days, medium solutions were tested for NH4-N and NO3-N concentrations and a NO3-N accumulation rate (NAR) was determined. Medium solution NH4-N concentrations were lower at 20° and 30° than at 10° and 40°, while those at 40° were considerably greater than at other temperatures and increased over time. In general, medium solution NO3-N concentrations at 10°, 20°, and 30° were comparable and higher than at 40°. Over time, the general order of NAR was 20° = 30° > 10° > 40°.

Open Access

Abstract

Nitrification in a pine bark medium in response to a range of applied NH4-N levels (25, 100, and 200 ppm) was studied. Medium solution NH4-N concentrations at the 25 ppm N treatment decreased from 30 ppm at day 1 to 0 ppm at day 40. Ammoniacal-N concentration values decreased from 64 to 6 ppm and from 105 to 20 ppm for the 100- and 200-ppm N treatments, respectively, by day 60. Rapid increases in medium solution NO3-N concentrations coincided with these NH4-N decreases, resulting in low medium solution NH4-N:NO3-N ratios. During the periods of NO3-N increase, medium solution pH decreased 0.3, 0.7, and 1.3 units for the 25-, 100-, and 200-ppm N treatments, respectively. Similarly treated bark without plants was used to determine a NO3-N accumulation rate (NAR). NAR data indicated that the NH4-N supply of the 100- and 200-ppm N treatments exceeded the oxidative capacity of nitrifiers during a 96-hr period.

Open Access

Abstract

Three genera of woody plants were container-grown in a pine bark medium. Pine bark was amended or unamended with nitrapyrin (NI) and fertilized with an NH4-N fertilizer. Medium solution NH4-N concentrations of bark without NI decreased rapidly for the first 3 to 5 weeks with a concomitant increase in NO3-N concentrations. Medium solution pH at 0 NI decreased 0.8 unit during periods of rapid NO3-N accumulation. The low medium solution pH of the 0 NI treatment resulted in solution Ca, Mg, and Mn concentrations that were several times greater than at 82 μg of NI. Correspondingly, tissue concentrations of these ions were generally greater at the 0 NI treatment than at the 82 μg NI treatment. In general, there were no differences in shoot dry weight in response to NI treatment. Results indicate that nitrification is important in the nutrition of container-grown plants.

Open Access

Abstract

A 100% pine bark medium was amended with dolomitic lime at 0, 3, or 6 kg·m−3 and periodically fertilized with 210 ml of a nutrient solution containing 100 ppm N as (NH4)2S04. At the 3- and 6-kg lime treatments, medium solution NH4-N concentrations decreased rapidly while N03-N concentrations increased. At 0 kg lime, the NH4-N decrease was slower than at the 3- and 6-kg lime treatments and N03-N was not found. Similarly treated bark without plants was used to determine a N03-N accumulation rate (NAR). NAR was greatest at 6 kg of lime, except at the last 2 sampling dates, when NAR did not differ between 3 and 6 kg of lime. This lack of difference was attributed to a limiting NH4-N supply at 6 kg of lime. In a 2nd experiment, NAR of bark treated with 6 kg of lime per m3 and fertilized with 300 ppm NH4-N was 3 times greater than with bark treated with 100 ppm NH4-N, thus supporting the contention that, over time, the NH4-N supply of the 100-ppm treatment limited nitrification. These results indicate that the stimulative influence of lime on nitrification is subject to medium pH and NH4-N status that changes over time.

Open Access