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Marysville, OH, United States

Dickson R.W.,University of Florida | Fisher P.R.,University of Florida | Argo W.R.,Blackmore Company | Jacques D.J.,Sun Gro Horticulture | And 3 more authors.
Scientia Horticulturae | Year: 2016

Floriculture crops affect substrate-pH and resulting solubility of micronutrients in the root zone during commercial production. Two hydroponic experiments and tissue data from a container study were analyzed to determine whether (1) cation or anion uptake was related to solution acidity and basicity in the root zone for three floriculture crops [geranium (Pelargonium×hortorum, Bailey. L.H.), petunia (Petunia×hybrid, Vilm.-Andr.), and impatiens (Impatiens wallerana, Hook. F.)] and whether (2) the proportion of NH4 +-N versus NO3 --N uptake differed between these three floriculture species. In the container study, where >96% of nitrogen (N) was provided primarily as NO3 --N, substrate-pH did not change over time when geranium or impatiens were grown, whereas substrate-pH increased with petunia. Geranium had a higher cation/anion uptake ratio than petunia based on analysis of tissue nutrient levels, and impatiens was intermediate. In the hydroponic experiments, the three species were grown in nutrient solutions that varied in ammonium:nitrate (NH4 +:NO3 -) ratio from 0:100 to 50:50. In the first hydroponic experiment, there was an approximately 1:1 relationship between net anion minus cation uptake and net solution acidity or basicity, (milliequivalent (mEq) solution acidity or basicity=0.972±0.195*(net mEq of anions-cations taken up)+0.140±0.478; adjusted-R2=0.739) over all species, which indicated a strong correlation between solution-pH change and net cation or anion uptake. Geranium had the highest cation/anion uptake ratio (1.06) and produced greater acidity than petunia, which had the lowest cation/anion uptake ratio (0.94). Cation/anion uptake ratio increased as applied NH4 +:NO3 - ratio increased. In the second hydroponic experiment, uptake of NH4 +-N versus NO3 --N exceeded the ratio that was supplied in the 10:90 and 20:80 NH4 +:NO3 - solutions for all species, but not in the 50:50 solution. Although some results were inconsistent between experimental runs, petunia overall had a lower NH4 +:NO3 - uptake ratio than the other two species. A NH4 +:NO3 - ratio of 10% NH4 +-N for geranium and impatiens and 20% NH4 +-N for petunia would be expected to result in a neutral pH response in a hydroponic solution with zero alkalinity. Evaluating cation/anion uptake ratio across a range of NH4 +:NO3 - ratios could be used to predict the relative acidity or basicity of other plant species to assist in pH management. © 2015.


Johnson C.N.,University of Florida | Fisher P.R.,University of Florida | Vetanovetz R.P.,Blackmore Company | Argo W.R.,Sun Gro Horticulture
Acta Horticulturae | Year: 2011

Fertilizer is a major factor affecting substrate-pH during crop production. Industry provides an estimate, reported in calcium carbonate equivalents (CCE) per unit weight of fertilizer, of the potential acid or base effect of blended fertilizers. This acid-base estimation can be an important tool for pH management if predicted accurately and using the appropriate assumptions. The current acid-base estimate is based on an agronomic method (Pierre's Method, PM) developed in the 1920s using a mineral field soil system. Certain assumptions of this protocol may not be appropriate for the soilless substrates and water-soluble fertilizers in containerized plant production. The objective was to evaluate the predicted CCE using PM against experimental data, and to identify components of an alternative approach to quantify the potential fertilizer effect on pH of soilless container substrates. Various experimental protocols, which included nutrient uptake charge balance (electroneutrality) and residual alkalinity measurements, were developed and compared with the acidity values expected using PM. These experimental measurements found that PM overestimated the amount of fertilizer acidity applied. Components of an alternative approach are suggested for acid-base estimation which assumes charge balance upon uptake of fertilizer salts, in which anionic salt uptake is assumed basic and cation uptake is acidic with associated plant root exudation of OH- or H+ respectively. This new protocol would consider the relative proportions at which nutrients are taken up and required by plants in predicting the net potential acid or base effect of fertilizers on substrate-pH, in addition to purely chemical processes. Acidification from ammonium-nitrogen uptake, and soil processes such as nitrification, which PM assumptions exclude, should be considered to represent the potential pH effect of fertilizers in containerized production.


Johnson C.N.,University of Florida | Fisher P.R.,University of Florida | Huang J.,University of Florida | Yeager T.H.,University of Florida | And 4 more authors.
Scientia Horticulturae | Year: 2013

The potential of a water soluble fertilizer (WSF) to raise or lower substrate-pH is estimated in calcium carbonate equivalents (CCE) of acidity or basicity per unit mass of fertilizer. The CCE is currently estimated using Pierre's Method, PM, which is based on assumptions as to the effects of nitrogen and other ions in field soils that may not apply in container substrates. In a greenhouse experiment, the substrate-pH change was measured with 18 WSFs that varied in the concentration of NH4-N, NO3-N, urea-N and other nutrients. 'Ringo Deep Red' Pelargonium×hortorum (Bailey. L.H.), 'Super Elfin Bright Orange' Impatiens wallerana (Hook. F.), and 'Ultra Red' Petunia×hybrida seedling plugs were grown in 70%:30% (v:v) peat:perlite substrate amended with dolomitic hydrated limestone. Plants in 900mL, 6-celled containers were top-irrigated with a total of 3.07L over 4 weeks at 100mgL-1 N without leaching. Plant species varied in their pH effect, in the order from acidic to basic of Pelargonium, Impatiens, and Petunia. Fertilizer CCE was positively correlated with substrate-pH, with r2 between 0.54 and 0.80 depending on the species. Multivariate regression also quantified NH4-N, NO3-N, and urea-N concentration effects on substrate-pH and CCE of applied fertilizer. Estimated mequiv. of acid (negative values) or base (positive values) per mmol of each nitrogen form applied were NH4-N -0.6678, -0.6143, -0.8123; NO3-N 0.0713, 0.2746, -0.1296; and urea-N -0.2038, -0.1445, -0.2711 for Impatiens, Petunia, and Pelargonium, respectively. Ammonium-N therefore had a strong acid effect, nitrate-N was a weak base or acid, and urea-N was a weak acid. Calculation of CCE based on PM or nitrogen alone provided a similar R2 with observed pH, despite a wide range in concentrations of macronutrients other than N in the fertilizer blends. Pierre's Method and nitrogen estimates of CCE for fertilizer blends were similar to each other (R2=0.97). However, PM estimates were biased compared with experimental results, over-predicting acidity of high-ammonium fertilizers, and over-predicting basicity of high-nitrate fertilizers. Results indicate that nitrogen form and concentration may provide a simple estimation of the acidity or basicity of blended fertilizers, although research under other growing conditions would be required. Accurate estimation of CCE is important to help growers formulate appropriate fertilizers to balance other factors such as water alkalinity and plant species. © 2013 Elsevier B.V.


Johnson C.N.,University of Florida | Fisher P.R.,University of Florida | Huang J.,University of Florida | Vetanovetz R.P.,Sun Gro Horticulture | Argo W.R.,Blackmore Company
HortScience | Year: 2010

In current horticultural practice, potential acidity or basicity of fertilizers is estimated using Pierre's method (PM) expressed in calcium carbonate equivalents (CCE) per unit weight of fertilizer. PM was developed usingmineral field soil systems and may be inaccurate for quantifying fertilizer acidity in containerized plant production given the widespread use of soilless substrates and fertigation. The PM-predicted acidity of an ammonium-based fertilizer was compared against experimental data obtained when 'Ringo' geraniums [Pelargonium Xhortorum (Bailey. L.H.)] and 'Super Elfin' impatiens [Impatiens wallerana (Hook. F.)] were grown in 70% peat:30% perlite (v:v) limed with either hydrated limestone only (HL) or a combination of carbonate and hydrated limestone (CHL). Plants in 10-cm-diameter (0.35 L) containerswere top-irrigated with a total of 2.0 L over 6 weeks using a 15.2N-1.9P-12.6K fertilizer [100%of nitrogen (N) as NH4-N] applied with each irrigation at 100 mg N/L without leaching. According to PM, 61.8 meq of fertilizer acidity was applied per liter of substrate. During the experiment, the pH of the substrate decreased from 7.05 to 4.41 for the HL substrate and from 7.14 to 5.13 for the CHL substrate. A corresponding drop in substrate-pH was observed when 37.1 (HL) or 43.3 (CHL) meq of CCE from 0.5 N HCl was applied per liter of substrate in a laboratory titration of the same substrates without plants. Gasometric analysis of residual carbonate at Day 0 and at the end of the experiment quantified change in CHL substrate alkalinity with time, resulting in an estimated 30.7 meq of neutralized alkalinity. Using an electroneutrality approach that assumed anion uptake (NO3 -, P2O5 -) was basic, and cations (NH-, K+) were potentially acidic, nutrient analysis of the substrate at the beginning and end of the experiment estimated that an average 48.5 meq of acidity was contributed by the fertilizer. Experimentally measured acidity values were 13.1 to 31.1 meq·L-1 of substrate lower for HL and CHL than those expected from PM, suggesting PM overestimated the amount of fertilizer acidity applied to the substrate. These results support the need for an alternative method to predict fertilizer acidity for plant production in soilless substrates.


Dunn B.L.,Oklahoma State University | Cavins T.,Sun Gro Horticulture | Goad C.,Oklahoma State University
Journal of Plant Nutrition | Year: 2016

Some poinsettia (Euphorbia pulcherrima Willd. ex Klotzsch) cultivars are susceptible to bract calcium (Ca) deficiency in developing bracts. In this study, we evaluated the efficacy of foliar uptake of Ca from milk-based products plus calcium chloride (CaCl2) as a potential Ca source. Weekly foliar applications of 237 mL L−1 whole milk, 80 mL L−1 powdered milk, 30 mL L−1 condensed milk, 0.94 g L−1 CaCl2, or distilled water (used as a control) were applied to runoff of ‘Prestige Red’ for four weeks. The four largest bracts with petioles on three different inflorescences and three leaves with petioles below the transitional leaf per inflorescence were collected per pot. None of the treatments affected bract or leaf Ca concentration. Powdered milk treatments resulted in a higher concentration of zinc (Zn) in bracts and aluminum (Al) in bracts and leaves. White residue remained on the bracts and leaves after treatment with powdered milk, which would reduce marketability. © 2016 Taylor & Francis Group, LLC.

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