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  • Author or Editor: John A. Biernbaum x
  • Journal of the American Society for Horticultural Science x
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Hybrid impatiens (Impatiens Wallerana Hook. F.) were planted in a peat-based medium containing two dolomitic liming materials (1.8 kg Ca(OH)2·Mg(OH)2/m3 or 8.4 kg CaCO3·MgCO3/m3) and subirrigated for 17 weeks using four irrigation-water sources (IWSs) with varied bicarbonate alkalinity, Ca2+, Mg2+, and SO4-S content and three water-soluble fertilizers (WSFs) that contained (in mg) 200N-20P-200K/liter but a variable NH4: NO3 ratio, Ca2+, Mg2+, and SO4-S content. The factorial arrangement of the IWS and WSF resulted in a range of Ca2+, Mg2+, and SO4-S concentrations varying by a factor of 10. After 8 weeks, medium pH ranged from 4.5 to 8.5. The maximum critical medium pH for PO4-P uptake was 7.4 to 7.7, which probably was due to a change in most of the water-soluble P to the less-available HPO4 2- form. Lime type did not affect the long-term increase in medium pH, Ca2+, and Mg2+ concentrations with nutrient solutions containing low NH4 +-N and high Ca2+ and Mg2+. The carbonate lime buffered the medium pH and Ca2+ and Mg2+ concentrations with nutrient solutions containing high NH4 +-N and low Ca2+ and Mg2+ compared to that measured with the hydrated lime. With both lime types, there was a linear increase in tissue Ca and Mg as the applied concentrations of the various nutrient solutions increased from 18 to 210 mg Ca2+/liter and 7 to 90 mg Mg2+/liter. The relationship was similar for both lime types up to week 8, after which tissue Ca and Mg decreased more rapidly with the hydrated lime and low solution Ca2+ and Mg2+ compared to that of the same carbonate lime treatments. The minimum critical SO4-S concentration in the applied nutrient solution for plant uptake was 30 to 40 mg S/liter. Below this concentration, tissue S decreased rapidly; above, there was little effect on tissue S.

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Using incubation and container culture with subirrigation for up to 28 days, three experiments were conducted with six liming materials of different particle sizes and six blended preplant nutrient charge (PNC) fertilizers. Liming material, particle size, and incorporation rate had an effect on the initial pH (3.5 to 6.1) and the final stable pH (4.8 to 7.8) with one type of Canadian sphagnum peat that did not contain an incorporated PNC. Saturated media extract (SME) Ca and Mg concentrations were <25 and 15 mg·liter-1, respectively, for both pulverized and superfine dolomitic lime at incorporation rates up to 7.2 kg·m-3. For the blended PNC fertilizers in media containing lime, initial electrical conductivity (EC) and SME nutrient concentrations ranged from (EC) 1.0 to 2.9 dS·m-1, (mg·liter-1) 60 to 300 N, 4 to 105 PO4-P, 85 to 250 K, 120 to 400 Ca, and 60 to 220 Mg. However, within two days, the rapid stratification of fertilizer salts within the pot caused macronutrient concentrations to increase in the top 3 cm of root medium (top layer) by an average of 180% and decrease in the remaining root medium in the pot (root zone) by an average of 57% compared to that measured in the medium at planting. Nutrient concentrations in the top layer continued to increase even when those in the root zone fell below acceptable levels recommended for an SME. The importance of fertilizer salt stratification within a pot lies in the reduced availability of nutrients to the plant and illustrates the limited persistence of the PNC fertilizers. Testing nutrients in container media several days after planting rather than in freshly mixed media may be more representative of the starting point for a nutritional management program.

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Rooted cuttings of `Gutbier V-l 4 Glory poinsettia (Euphorbia pulcherrima Willd. ex Klotzsch) were grown in 15-cm pots using two irrigation methods, two water-soluble fertilization schedules, and two preplant root-media fertilization rates. No difference in shoot growth occurred with either top watering with 33% leaching or subirrigation. The top 2.5 cm (top layer) contained nutrient concentrations up to 10 times higher than those measured in the remaining root medium (root zone) of the same pot with both irrigation methods. Constant applications of28 mol N/m3 water-soluble fertilizer (WSF) limited shoot and root growth as measured at 3 and 8 weeks compared to a weekly increase in the concentration of WSF from 0 to 28 mol N/m3 in 7 mol N/m3 increments over a S-week period. The additional incorporation of 0.27 kg·m-3 mineral N to Metro Mix 510 before planting had no effect on fresh- or dry-weight accumulation. When the root-medium surface was covered by an evaporation barrier, 46% less water and 41% less N fertilizer were applied to plants of similar size, and higher root-zone nutrient levels were maintained over the 8 weeks of the experiment. The evaporation barrier had the greatest effect on increasing root-zone nutrient concentrations and reducing the growth of subirrigated plants.

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Hybrid impatiens (Impatiens Wallerana Hook. F.) were planted in six root media containing either 70% (by volume) rockwool, coir, or four types of sphagnum peat and 30% perlite. The six media varied in cation exchange capacities (CEC) (from 5 to 76 meq·L-1) and the amount of a dolomitic hydrated lime [Ca(OH)2 and Mg(OH)2 at 0 to 4.5 kg·m-3) required to obtain an initial pH of ≈6.0. Two additional treatments were produced by using a dolomitic carbonate lime (CaCO3 and MgCO3) at 8.4 kg·m-3 instead of the hydrated lime in two of the sphagnum peat media. Plants were subirrigated for 17 weeks using three nutrient solutions (NS) that contained at 200N-20P-200K mg·L-1 but had a variable NH4 : NO3 ratio and Ca2+ and Mg2+ content. The NS were designed to produce either acidic, neutral, or basic reactions in the medium. In media containing the hydrated lime, the NS was the primary factor controlling medium pH. However, within each NS treatment, the media did have some effect on buffering the pH over time. There was a linear increase in shoot-tissue Ca and Mg as the applied concentration of Ca2+ increased from 18 to 156 mg·L-1 and that of Mg2+ increased from 5 to 56 mg·L-1. Linear regression analysis of shoot-tissue Ca and Mg based on their concentration in the NS indicated a similar overall decrease in the Ca and Mg supply in all six root media over time. For plants grown in media containing the carbonate lime, shoot dry mass was similar to that of plants grown in the same media with hydrated lime. The presence of the carbonate lime in the media increased the pH buffering capacity against decreasing pH with the acidic and neutral NS but not against increasing pH with the basic NS. In the media containing the carbonate lime and given the acidic NS, root-medium and shoot-tissue Ca and Mg increased by weeks 12 and 17 compared to that of the same medium containing the hydrated lime. There were minimal differences in root-media and shoot-tissue Ca and Mg concentration between lime treatments when given the neutral or basic NS.

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`V-14 Glory' poinsettias (Euphorbia pulcherrima Willd. ex Klotzsch) were fertilized at every irrigation with solutions containing 7, 14, or 28 mol N/m3 at four leaching fractions (LFs) of 0, 0.1 to 0.2, 0.3 to 0.4, or 0.5 to 0.6 or with subirrigation. The N applied ranged from 44 to 464 mmol/pot applied over 12 to 25 irrigations. Medium NO3-N and K concentrations and electrical conductivity were highest at the highest fertilizer concentration and lowest LF throughout cropping. Phosphorous concentration in the medium declined until week 12, when phosphoric acid was added for pH adjustment. Subsequently, medium P concentration was highest in treatments with the highest LF. Final shoot height, plant dry mass, and leaf area decreased as fertilizer concentration increased. Highest fresh mass, bract area, and shoot: root ratio were obtained with 14 or 28 mol N/m3 and a 0.55 LF or with 7 mol N/m3 and a 0.15 LF. Leaf N concentration was lower with subirrigation than with surface application. Leaf P and Mg were lower at higher LFs or with subirrigation, but leaf K was not influenced by the treatments.

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Subirrigated Easter lilies were grown in five commercially formulated root media using one water-soluble fertilizer applied independently to each medium based on water-holding capacity and water loss. The number of irrigations ranged from 12 to 20 and the amount of applied water ranged from 5.3 to 6.8 liters for the uncovered media treatments. When the root-medium surface was covered with an evaporation barrier, the average amount of applied water was reduced by 35% compared to the uncovered media. The largest effect on root media pH was between uncovered and covered media due to the reduced amount of water applied. Similar macronutrient concentrations were measured in the five media during the experiment with few exceptions. The greatest differences in nutrient concentrations were found within the pots. The top 2.5 cm (top layer) contained nutrient concentrations up to 10 times higher than those measured in the remaining root medium (root zone) of the same pot. Covering the root-medium surface with an evaporation barrier reduced the stratification of fertilizer salts. Root-zone soluble salt concentrations of plants in the covered pots were similar to those of uncovered plants even though 36% less fertilizer was applied to the covered plants.

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Abstract

Root-zone heating increased the tissue concentration and total uptake of N, P, K, Ca, Mg, S, Cl, Fe, MnZn, and Cu; decreased the tissue concentration but not total uptake of Na and Zn, and had no effect on the tissue concentration of B. The element with the greatest increase in concentration in the shoot was water-soluble NO3-N. The ratio of cations to anions did not change significantly with changes in root-zone temperature. The concentration and balance of cations did not change significantly with changes in percentage of NH4-N at ambient root-zone temperatures.

Open Access

Abstract

Inconsistent yield increases in the United States have prevented recommending triacontanol (TRIA) for commercial application. Based on tests over several years, TRIA is recommended for use on many vegetable and agronomic crops in most provinces in the People's Republic of China. Their formulations were shown either to be less effective or no better than the colloidal dispersion developed by the Procter and Gamble Co. TRIA dispersions passed through 2 standard field sprayers and 3 of 5 experimental small-plot sprayers lost at least 37 % of their activity as measured by the increase in maize (Zea mays L.) seedling growth. Hexane extracts of water passed through sprayers and polyvinyl chloride (PVC) tubing contained more than 5 μg/liter of di-(2-ethyl)hexyl phthalate. This phthalate ester, as well as other phthalates, decreased activity of both the colloidal dispersion and emulsion formulations of TRIA at phthalate concentrations of 5 μg/liter or more. Phthalate esters are common in the environment, including water of developed countries, and are important constituents of the PVC tubing used on most American field and small-plot sprayers. Sprayers equipped with other types of hoses did not inactivate TRIA as measured by the growth of maize seedlings.

Open Access

Abstract

The yield response of crops to triacontanol (TRIA) applied as a colloidal dispersion was tested with 13 crop species in 45 field experiments over a 3-year period. Foliar application of TRIA resulted in treatment effects with 11 of the 13 crops and in 30 of the 45 experiments. The average yield increase was 14% with the optimum TRIA concentration in tests where yield was significantly increased, and was 5% over all 45 experiments. In seven experiments, significant yield decreases averaging 10% were measured with TRIA concentrations that increased crop yield of the same species in other tests. The most effective TRIA concentrations generally were 0.1 to 1.0 μg·liter−1. No particular stage of crop development for treatment was optimal for all crops. Based on the results of these studies, TRIA cannot be recommended for commercial application to crops in Michigan or similar environments. Chemical names used: 1-triacontanol (triacontanol).

Open Access

Abstract

Triacontanol (TRIA), a 30-carbon primary alcohol, was shown to be a more effective plant growth stimulator when formulated as a colloidal dispersion than as a suspension in chloroform and Tween 20 or acetone naphthaleneacetic acid (NAA), and CaCl2. TRIA applied at rates of 0.1 and 1.0 μg/liter consistently increased the dry weight of maize (Zea mays L.) shoots and rice (Oryza sativa L.) seedlings in short-term greenhouse and growth chamber experiments. This application rate is 1000-fold lower than optimum levels applied with other formulations. A 99.45% pure sample of TRIA stimulated maize growth 2 times more than a sample containing 96.40% TRIA at a concentration of 0.5 μg/liter. Neither dispersion pH nor water hardness altered activity of TRIA formulated as a colloidal dispersion. It may be practical to apply TRIA with a controlled-droplet applicator in volumes of water as low as 8–11 liters/ha. The most important environmental factors evaluated for their effect on crop response to TRIA were time of day and temperature prior to spraying. In growth chamber studies, foliar application of TRIA 3 to 7 hours into the photoperiod resulted in twice the growth increase as applications made 11 hours into the photoperiod. In the greenhouse, with supplemental high intensity lamps, sprays were about twice as effective applied 11 hours (5 pm) as 3 hours (9 am) into the photoperiod. There was a positive correlation between the temperature of the growth chamber environment one hour before spraying and the response to TRIA; however, temperature of the environment for one hour after spray application had no effect on TRIA activity.

Open Access