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- Author or Editor: Robert D. Wright x
Abstract
Rooted cuttings of Ilex crenata Thunb. ‘Helleri’ were grown in sand culture with varied Ca and Mg levels in a factorial experiment. No increase in total dry weight was achieved by increasing Ca or Mg rates above 5–10 ppm. Necrosis of shoot apices occurred at 0 ppm Ca. The tissue level of Ca required for optimal growth (0.23–0.38%) was lower than has been reported for broadleaf evergreens. In a 2nd experiment with pine bark, Ca was supplied at 0 and 120 ppm and Mg at 0 and 60 ppm. No differences in dry weight due to added Ca and Mg were observed. In a 3rd experiment, the influence of dolomitic limestone (0, 2, 4, and 8 kg m−3) and gypsum (1 and 2 kg m−3), added to pine bark, on Ca and Mg availability over time was determined. The addition of dolomitic limestone increased Ca and Mg in the growing medium solution, but unamended bark supplied both elements in quantities sufficient for growth of I. crenata ‘Helleri’ The addition of gypsum caused a large initial increase in Ca in the growing medium solution, but levels dropped precipitously thereafter.
Abstract
Leaves, upper stems and lower stems of Ilex crenata cv. Convexa cuttings were analyzed for N, P, K, Ca, and Mg at 3 day intervals for 27 days during intermittent mist propagation. No mobilization of nutrients from the upper portions of a cutting into the base was noted during the root initiation period.
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°.
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.
Ilex crenata `Helleri' rooted cuttings were container grown for one summer with Osmocote 18N-2.6P-7.6K which was reapplied at different times. Beginning in April and every month thereafter until October, five plants were harvested and separated into roots and shoots for dry weight and nitrogen (N) analysis. Plants that had received a reapplication of Osmocote in June or July were larger in October than those that received no supplemental fertilizer. If reapplication occurred in August or September, no influence on growth was realized. Plants that were not supplemented had lower percent tissue and medium solution N. These data demonstrate that tissue nutrient analysis as well as the medium nutrient levels extracted with the pour-through procedure can be used to determine when reapplication of a slow-release fertilizer is necessary to promote optimal growth.
Abstract
Rooted cuttings of Ilex crenata Thunb. ‘Helleri’, Rhododendron obtusum Planch. ‘Rosebud’, and Juniperus chinensis L. ‘San Jose’ were grown in a 100% pine-bark medium amended with dolomitic limestone at 0 to 8 kg m-3 with resulting pH from 3.4 to 7.2. Except for juniper at 2 kg m-3, growth was not increased by liming, and 8 kg m-3 tended to reduce shoot and root growth. This reduced growth was attributed in part to greater NH4 adsorption by the bark, reducing the amount available for plant uptake, and a higher nitrification rate, leading to an elevated NO3 to NH4 ratio in the medium. Liming pine bark to improve growth of these woody plants may be unnecessary.
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.
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.
The influence of K nutrition (25, 75, 150, 300, 450, and 600 mg K/liter) and moisture stress conditioning (MSC) (exposing plants to four sublethal dry-down cycles) on leaf water relations, evapotranspiration, growth, and nutrient content was determined for salvia (Salvia splendens F. Sellow `Bonfire'). Potassium concentration and MSC had an interactive influence on osmotic potential at full (π100) and zero (π0) turgor. Differences in osmotic potential between MSC and non-MSC plants for π100 and π0 increased with increasing K concentration. Increasing K concentration and MSC resulted in active osmotic adjustment and, consequently, increased cellular turgor potentials. Foliar K content increased with increasing K concentration and MSC. High K concentrations and MSC both reduced plant evapotranspiration on a per-plant and per-unit-leaf-area basis. Greatest shoot dry weight occurred for plants grown with 300 mg K/liter and non-MSC. Total leaf area increased with increasing K concentration, but MSC had little effect.