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Mark V. Yelanich and John A. Biernbaum

The evaporation of water is a major source of water loss from potted plants which can be eliminated by placing a barrier at the exposed surface of media in the pot. To better understand the effect of reducing surface evaporation on growth and media nutrient concentration, 15 cm subirrigated poinsettias were produced with and without a pot cover. Both treatments received the same quantity of fertilizer, 75 mg·week-1 N for a total of 13 fertilizations. Uncovered pots received 12 more irrigations than pots with covers (20 vs. 32). Sixteen weeks after planting, covered plants had significantly less leaf area (2175 vs 2628 cm2), bract area (1655 vs 2137 cm2), height (24.1 vs 27.6 cm), fresh mass (116 vs 144 g) and dry mass (17 vs 20 g) than uncovered plants. Concentrations of N, P, K, Ca and Mg and EC (4.23 vs 2.65 mS·cm-1) were higher in the root-zone of covered plants than in uncovered plant. Covering the media surface did reduce the EC and the concentrations of N, P, K, Ca and Mg in the top layer (eg 13.47 mS·cm-1 vs 15.74 mS·cm-1) but stratification of salts to the top layer still occurred. Fertilizer salts in the top layer were shown to be less available to the plant than those in the root zone.

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John A. Biernbaum and Natasha Bos Versluys

Important components of water management for transplant production include water quality, the frequency and volume of water application, and the method of application. Water quality factors of concern are alkalinity, soluble salts including sodium absorption ratio (SAR), and ions at potentially toxic concentrations including boron and fluoride. The available water in individual transplant cells is influence by container size and geometry, medium particle size, medium moisture release characteristics, and wetting agents but is primarily determined by irrigation frequency and the amount of water applied at each irrigation. Irrigation scheduling can be done using several methods but is influenced by the crop stage, the water volume applied, and the frequency of drying desired. Transplants can be watered by hose and breaker, stationary sprinklers, traveling boom sprinklers, fog nozzles, or subirrigation. The outcome of experiments testing effects of transplant size, transplant age and fertilizer rates are all influenced by water management.

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William R. Argo and John A. Biernbaum

Impatiens were planted into peat-based media containing two dolomitic liming materials [Ca(OH)2·Mg(OH)2 at 1.8 kg·m–3 or CaCO3·MgCO3 at 8.4 kg·m–3] and subirrigated for 17 weeks using four irrigation water qualities (IWQ) with varied alkalinity, Ca2+, Mg2+, and SO4-S content and three water-soluble fertilizers (WSF) with varied NH4:NO3 ratio, Ca2+, Mg2+, and SO4-S content. After 8 weeks, medium pH ranged from 4.5 to 8.5. Lime type did not affect the long-term increase in medium pH, Ca2+, and Mg2+ concentrations with IWQ/WSF solutions containing low NH4-N and high Ca2+ and Mg2+ concentrations. The carbonate lime did buffer the medium pH, Ca2+, and Mg2+ concentrations with IWQ/WSF solutions containing high NH4-N and low Ca2+ and Mg2+ concentrations. With both lime types, there was a linear increase in tissue Ca and Mg as the applied concentrations increased from 0.5 to 4.0 mol·m–3 Ca2+ and 0.3 to 3.0 mol·m–3 Mg2+ with the various IWQ/WSF. The relationship was similar for both lime types up to week 8, after which tissue Ca and Mg decreased with the hydrated lime and low solution Ca2+ and Mg2+. Relationships were also developed between the applied SO4-S concentration and tissue S and medium pH and tissue P.

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John A. Biernbaum, William Argo, and Janet Pumford

Unlike vegetable and fruit crops, where petiole analysis has been used for many years, root media analysis is the primary method of checking fertility status of container-grown flowering greenhouse crops. With the emphasis on lower constant water-soluble fertilizer rates to prevent nutrient runoff, petiole analysis may be a better indicator of N and K status. During Fall 1993, samples were collected from 10 flowering pot plant species subirrigated with either 50, 100, or 200 mg·liter–1 N and K concentrations. During Spring 1995, samples were collected from major bedding plant species and Easter lilies. Sap was extracted using a hydraulic press and nitrate and potassium were measured with the Cardy flat electrode ion meters. Sampling methods and protocols will be presented with results of sampling technique experiments. Floriculture plant nutrition researchers were contacted to identify other research in progress, potential applications, and possible concerns with using this technique. Further research needed will be identified.

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Mark V. Yelanich and John A. Biernbaum

The influence of fertilizer concentration and leaching volume on the quantity of applied N and water that were leached from a container-grown poinsettia crop (Euphorbia pulcherrima Willd.) was investigated. The NO3-N quantity leached after 71 days increased with higher NO3-N application rates (7, 14, or 28 mol NO3-N/m3) and higher leaching volumes; it ranged from 0.03 g NO3-N [7 mol·m-3, 0.00 container capacity leached (CCL)] to 7.65 g NO3-N (28 mol·m-3, 1.0 CCL). The NO3-N concentration for saturated media extracts increased with lower leaching volumes and higher fertilizer concentrations. For example, when 7 mol NO3-N/m3 was applied, NO3-N in the medium was 27.1 mol NO3-N/m3 when 0 CCL was used, but it was 8.6 mol NO3-N/m3 when 1.0 CCL was used. Shoot height and dry mass were not affected by the treatments. Leaching treatments also did not influenced leaf area, but leaf area was larger at 7 compared to 14 or 28 mol NO3-N/m3.

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John A. Biernbaum and William R. Argo

Impatiens were planted in media containing either hydrated or carbonate dolomitic lime and subirrigated for 17 weeks using four irrigation water qualities (IWQ) and three water-soluble fertilizers (WSF). Micronutrients (Fe, Mn, Zn, Cu, B, and Mo) were incorporated into all root media at planting with fritted trace elements (FTE 555) at 0.07 kg·m–3 and were added to all WSF treatments with a commercially available chelated material (Compound 111) at a constant 50 mg·liter–1. Root-medium pH obtained from the various IWQ/WSF solutions at 4, 8, 12, and 17 weeks after planting were used to determine relationships with shoot tissue micronutrient concentrations. Tissue Fe concentrations decreased linearly as root-media pH increased from 5.0 to 8.5. Below pH 5.0, the tissue Fe concentration increased at a rate indicating greater nutrient availability in the root medium. However, between pH 4.0 and 7.5, tissue Fe was within acceptable levels. A linear relationship also was found with tissue Zn and B, but without the rate increase below a pH of 5.0. Tissue Mn decreased to a minimum as the rootmedium pH increased from 4.0 to 6.0 and increased again as the root medium pH increased from 6.0 to 8.5. Tissue Mo concentrations increased as root medium pH increased. Tissue Cu concentrations were unaffected by medium pH.

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William R. Argo and John A. Biernbaum

Four experiments were conducted with six liming materials of different particle sizes and six commercially available blended preplant nutrient charge (PNC) materials in the laboratory and in container culture with subirrigation for durations up to twenty-eight days. Liming material, particle size, and incorporation rate affected both the initial and final stable pH of one type of peat without an incorporated PNC. Saturated media extract (SME) Ca2+ and Mg2+ concentrations were below the acceptable recommended concentrations for both pulverized and superfine dolomitic lime at incorporation rates up to 7.2 kg·m-3. For the blended PNC materials, initial N, P, K+, Ca2+, and Mg2+ concentrations for five of the six PNC materials were at or above the optimal concentrations recommended for an SME, but did not remain persistent in the root zone. A large percentage of all nutrients tested moved from the root zone into the top 3 cm (top layer) of the pot within two days after planting. Nutrient concentrations in the top layer continued to increase even when nutrient concentrations in the root zone fell below acceptable levels for an SME. The importance of this fertilizer salt stratification within the pot lies in the reduced availability of nutrients to the plant.

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William R. Argo and John A. Biernbaum

Impatiens were grown in media containing either hydrated or carbonate dolomitic lime and subirrigated for 17 weeks with four irrigation water qualities (IWQ) and three water-soluble fertilizers (WSF). The WSF concentration was 14N–0.6P–5K mol·m–3 but contained either 50%, 25 %, or 3 % NH4-N. After 8 weeks, rootmedium pH ranged from 4.5 to 8.0. In general, the higher the percent NH4-N content of the WSF, the lower the root-medium pH, although there were significant interactions between IWQ and lime type with WSF on root-medium pH. With the same WSF, the concentration of NH4-N measured in the root media depended on root-medium pH. For example, with WSF containing 50% NH4-N, root-medium pH with the various IWQ ranged from 4.5 to 6.0, and media NH4-N ranged from 5.0 to 0.1 mol N/m3. Tissue N concentrations were higher with the higher NH4: NO4 ratio WSF at all four sampling dates. The effect of IWQ on tissue N resulted from the root-medium pH effects produced by the various IWQ/WSF combinations. Shoot fresh and dry weights were unaffected by the NH4: NO3 ratios in the WSF.

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Mark V. Yelanich and John A. Biernbaum

`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.