Common chelating agents used in horticultural fertilizers like ethylenediaminetetraacetic acid (EDTA), diethylenetriaminepentaacetic acid (DTPA), and ethylenediaminedi(o-hydroxyphenylacetic) acid (EDDHA) are not readily biodegradable and may persist in the environment, maintaining the capacity to solubilize heavy metals. For this reason, biodegradable chelating agents like ethylenediaminedisuccinic acid (EDDS) are being evaluated for use in horticultural crop production. Therefore, the objectives of the study were to determine the effects of FeEDDS and EDDS on substrate pH and copper (Cu), iron (Fe), manganese (Mn), and zinc (Zn) solubility in peat-based substrate compared with various Fe and chelate-ligand sources. Extractions were performed using the 1:2 by volume substrate analysis method with an incubation period of 24 hours. The control was distilled deionized water extractions. Iron-source (FS) extractants consisted of 1 mg·L−1 Fe solutions derived from FeEDDS, FeEDTA, FeDTPA, FeEDDHA, and FeSO4. Iron-source extractant solution pH ranged from 7.1 (FeEDDS) to 5.4 (FeSO4). The extract pH for all Fe-source treatments was similar at pH 6.7, demonstrating the buffering capacity of the peat-based substrate. Iron recovery rates for FS treatments were determined after subtracting Fe that was freely extracted with distilled-deionized water: FeSO4 (13%), FeEDDHA (68%), FeEDDS (73%), FeEDTA (102%), and FeDTPA (121%). Iron-source treatments were not different for Mn, averaging 0.03 mg·L−1, and Cu (0.04 mg·L−1) and Zn (0.24 mg·L−1) were greatest in the FeEDDS treatment. Chelate-ligand (CL) extractants consisted of 5 mm solutions of EDDS, EDTA, and DTPA. Chelate-ligand extractant solution pH ranged from 9.7 (EDDS) to 2.3 (DTPA), and extract solution pH ranged from 7.2 (EDDS) to 4.7 (DTPA). Extractant solutions of EDDS and DTPA resulted in the lowest and highest levels of Cu (0.06 and 0.14 mg·L−1, respectively) and Fe (4.3 and 13.1 mg·L−1, respectively) in extract solutions. Overall, these results suggest that there are no negative implications for the use of FeEDDS with peat-based substrate in terms of horticultural crop production based on substrate Fe solubility, which was not different from FeEDTA.
Joseph P. Albano
Aminopolycarboxylic acid (APCA) complexones, commonly referred to as ligands or chelating agents, like ethylenediaminetetraacetic acid (EDTA) and diethylenetriaminepentaacetic acid (DTPA), are commonly used in soluble fertilizers to supply copper (Cu), iron (Fe), manganese (Mn), and/or zinc (Zn) to plants. Offsite runoff and contamination of surface waters with these chelating agents is of increasing concern as a result of their reported ability to remobilize heavy metals in sediments and their low susceptibility to biodegradation. The APCA ethylenediaminedisuccinic acid (EDDS) is a structural isomer of EDTA with the [S,S′] stereoisomer of the complexone, a compound naturally produced by actinomycetes, and is biodegradable. Information on the use of [S,S′]-EDDS as a chelating agent in formulating soluble fertilizers for the production of horticultural crops is limited. Therefore, a series of studies were conducted with the objectives of evaluating Fe[S,S′]-EDDS as an Fe-chelate fertilizer agent in the production of marigold and [S,S′]-EDDS (free ligand) and/or Fe[S,S′]-EDDS spectral properties and vulnerability to photodegrdation. Marigold grown in peat-based media were fertilized with complete nutrient solution containing 1 mg·L−1 Fe from FeEDDS, FeEDTA, or FeDTPA. There was no significant difference in foliar Fe or Mn between Fe-chelate treatments, averaging 140 μg·g−1 and 88 μg·g−1, respectively, nor were there significant differences in leaf dry weight (2.30 g) between Fe treatments. Spectra of [S,S′]-EDDS and Fe[S,S′]-EDDS produced from ferrous or ferric sources of Fe absorbed maximally in the 210 to 230 nm and 238 to 240-nm range, respectively. The [S,S′]-EDDS complexone used in the current study, a 30% assay solution, had chromaphoric properties, appearing light yellow in color. When exposed to light, Fe[S,S′]-EDDS quickly degraded at a rate at least twice that of FeEDTA.
P. Chris Wilson and Joseph P. Albano
Nitrate-nitrogen (N) losses in surface drainage and runoff water from ornamental plant production areas can be considerable. In N-limited watersheds, discharge of N from production areas can have negative impacts on nontarget aquatic systems. This study monitored nitrate-N concentrations in production area drainage water originating from a foliage plant production area. Concentrations in drainage water were monitored during the transition from 100% reliance on fertigation using urea and nitrate-based soluble formulations (SF) to a nitrate-based controlled-release formulation (CRF). During the SF use period, nitrate-N concentrations ranged from 0.5 to 322.0 mg·L−1 with a median concentration of 31.2 mg·L−1. Conversely, nitrate-N concentrations during the controlled-release fertilization program ranged from 0 to 147.9 mg·L−1 with a median concentration of 0.9 mg·L−1. This project demonstrates that nitrate-N concentrations in drainage water during the CRF program were reduced by 94% to 97% at the 10th through 95th percentiles relative to the SF fertilization program. Nitrate-N concentrations in drainage water from foliage plant production areas can be reduced by using CRF fertilizer formulations relative to SF formulations/fertigation. Similar results should be expected for other similar containerized crops. Managers located within N-limited watersheds facing N water quality regulations should consider the use of CRF fertilizer formulations as a potential tool (in addition to appropriate application rates and irrigation management) for reducing production impacts on water quality.
Cindy L. McKenzie and Joseph P. Albano
Tomato irregular ripening (TIR) disorder is associated with sweetpotato whitefly (Bemisia tabaci) biotype B feeding and is characterized by incomplete ripening of longitudinal sections of fruit. Our objective was to determine the effect of time of sweetpotato whitefly infestation on plant nutrition and the development of TIR disorder. Healthy tomato plants (Solanum lycopersicum ‘Florida Lanai’) were introduced to sweetpotato whitefly infestations at different developmental stages of plant growth: 1) five to seven true leaves, 2) flower, 3) green fruit, and 4) breaking red fruit and were compared with noninfested control plants of the same age. Plants were fertilized every 7 to 14 days. Plant nutrition was monitored over time between the noninfested control and the longest infestation interval (five to seven true leaves) and between all infestation intervals at harvest. Sweetpotato whitefly (egg, nymph, and adult) and plant parameters (height, canopy diameter, number of leaves, flowers, and fruit per plant) were taken every 7 to 14 days after sweetpotato whitefly infestation. Almost all of the fruit (99%) produced by tomato plants infested with sweetpotato whitefly at stages 1 and 2 (78 and 56 days of sweetpotato whitefly exposure, respectively) developed TIR with fruit exhibiting internal and external symptoms. Plants infested at stage 3 (35 days of sweetpotato whitefly exposure) had 79% to 80% of the fruit develop TIR. Surprisingly, 58% of fruit from plants infested at stage 4 (14 days of sweetpotato whitefly exposure) also developed the disorder, indicating that tomatoes may need to be protected from sweetpotato whitefly until harvest to avoid this disorder. Seed germination was unaffected by TIR. Plants infested with sweetpotato whitefly had mean foliar levels of calcium, copper, iron, phosphorous, potassium, magnesium, manganese, and zinc that were greater than in noninfested control plants at final harvest for both studies, regardless of time of infestation.
Joseph P. Albano and Donald J. Merhaut
The objectives of the study were to determine effects of iron (Fe) source on plant growth, plant nutrition, substrate chemistry, and runoff chemistry. Iron source (FS) treatments consisted of Fe-aminopolycarboxylic acid (APCA) complexones iron ethylenediaminetetraacetic acid (FeEDTA), iron [S, S′]-ethylenediaminedisuccinic acid (FeEDDS), iron diethylenetriaminepentaacetic acid (FeDTPA), and iron ethylenediaminedi(o-hydroxyphenylacetic) acid (FeEDDHA) and non-chelated iron sulfate (FeSO4) added to a base nutrient solution at the rate of 1 mg·L−1 Fe final concentration. Marigold (Tagetes erecta) ‘First Lady' was grown in peat-based media fertilized with FS treatments over a period of 22 d. Iron source treatments were nonsignificant for foliar Fe, manganese (Mn), or zinc (Zn) averaging 162 μg·g−1 Fe, 228 μg·g−1 Mn, and 35 μg·g−1 Zn but were significant for foliar copper (Cu). Main effect of FS on pour-through (PT) leachate pH was statistically different but not practically significant, averaging 6.42. The FeDTPA treatment resulted in higher levels of Cu, Fe, and Zn in PT extracts. Leachate-runoff (LR) was collected and analyzed over the course of the study. Results of LR were similar to PT with levels of Cu, Fe, and Zn for the FeDTPA treatment resulting in higher concentrations of these metals. In both PT and LR, the highest concentration of Mn was associated with the FeEDTA treatment. Spectrophotometer analyses of PT and LR leachates determined the presence of all Fe chelates tested in those solutions.
Joseph P. Albano and William B. Miller
Excised roots of `First Lady' marigold (Tagetes erecta L.) grown in an aerated 0 Fe nutrient solution had Fe(III)-DTPA reductase activity 14-fold greater, and an enhanced ability to acidify the rhizosphere than plants grown in a solution containing 0.018 mm (1 ppm) Fe-DTPA. Reductase activity and rhizosphere acidification of plants grown in 0.018 and 0.09 mm Fe-DTPA were similar. Manganese concentration in leaves of plants grown in the 0 Fe treatment was 2-fold greater than in leaves of plants grown in the 0.018 mm Fe-DTPA treatment. These results indicated that `First Lady' marigold is an Fe-efficient plant that possesses both an inducible or adaptive reductase system and the ability to acidify the rhizosphere, and that these Fe-efficiency reactions do not occur when Fe is sufficient. Chemical name used: ferric diethylenetriaminepentaacetic acid, monosodium salt (Fe-DTPA).
Mary C. Halbrooks and Joseph P. Albano
A specific physiological disorder of the recently matured leaves of Tagetes erecta has been demonstrated to be associated with high levels of iron and manganese in affected tissues. In previous work by the authors, the disorder was inducible and increased in severity with increasing levels of iron DTPA supplied to plants grown in peat-based media, but was much less severe when iron DTPA treatments were applied to plants grown hydroponically. At low concentrations of iron DTPA in solution, the occurrence of the disorder was more closely correlated with increased levels of manganese in leaf tissue than iron, Objectives of this study were to determine the effects of iron chelate (DTPA) on occurrence of the disorder and the availability of iron and manganese in the media in the absence of added manganese. Iron DTPA (1, 5, 15, and 20 ppm) was supplied to two cultivars of Tagetes erecta, `Voyager' and `First Lady', grown in a commercial peat-based media product under controlled environmental conditions. Concentrations of iron and manganese in leachate samples taken weekly, and in symptom and non-symptom tissue at harvest, and the progression of the symptoms in leaf tissue over time. will be discussed.
Joseph P. Albano and William B. Miller
Our objective was to determine the effects on plant growth and physiology that a photodegraded Fe-chelate containing lab-prepared nutrient solution would have when used in plant culture. Plants grown hydroponically in the irradiated Fe-DTPA containing nutrient solution had ferric reductase activity 2.2 times greater, foliar Fe level 0.77 times less, and foliar Mn level 1.9 times greater than in plants grown in an identical but non-irradiated solution, indicating that plants growing in the irradiated solution were responding to Fe deficiency stress with physiological reactions associated with Fe efficiency. The youngest leaves of plants that were grown in the irradiated solution had symptoms of Mn toxicity. Restoration of the irradiated solution by removing the precipitated Fe by centrifugation and adding fresh Fe-chelate resulted in plants that were, in general, not different from those grown in the non-irradiated solution (control).
Joseph P. Albano and William B. Miller
The susceptibility of seven African marigold (Tagetes erecta L.) cultivars to iron toxicity was assessed. Plants were grown in a greenhouse in a soilless medium and Fe-DTPA was incorporated into the nutrient solution at either 0.018 mmol·L-1 (low) or 0.36 mmol·L-1 (high). Symptoms of Fe toxicity (bronze speckle disorder in marigold characterized by chlorotic and necrotic speckling and downward leaf cupping and curling) developed only in the high-Fe treatment. The concentration of Fe in leaves in the high-Fe treatment was 5.6 and 1.7 times as great as in the low-Fe treatment for `Orange Jubilee' and `Discovery Orange', respectively. Based upon the percentage of plants affected and leaf symptom severity, relative cultivar susceptibility to Fe toxicity was Orange Jubilee > First Lady > Orange Lady > Yellow Galore > Gold Lady > Marvel Gold > Discovery Orange. Chemical names used: ferric diethylenetriaminepentaacetic acid, disodium salt dihydrate (Fe-DTPA).
Joseph P. Albano and William B. Miller
Irradiation of, ferric ethylenediaminetetraacetic acid (FeEDTA, iron chelate)-containing commercial fertilizer solutions by fluorescent plus incandescent lamps resulted in the loss of both FeEDTA and soluble iron (Fe), and the formation of a yellow-tan precipitate that was mostly composed of Fe. The ratio of soluble Fe:manganese (Mn) was altered due to FeEDTA photodegradation from 2:1 in the nonirradiated solutions to 1:4 in the irradiated solutions, respectively. Storing fertilizer solutions in containers that were impervious to light prevented FeEDTA photodegradation.