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Title: FEEDTA PHOTODEGRADATION IN COMMERCIALLY PRODUCED SOLUBLE FERTILIZERS AFFECT IRON UPTAKE IN TOMATO

Author
item Albano, Joseph
item MILLER, WILLIAM - CORNELL UNIVERSITY

Submitted to: HortTechnology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 1/2/2003
Publication Date: 4/1/2003
Citation: Albano,J.P.,Miller,W.B. 2003. FEEDTA Photodegration in commercially produced soluble fertilizers affect iron uptake in tomato. HortTechnology, 13:289-292.

Interpretive Summary: Iron-chelates are common components of soluble fertilizers used in nursery and greenhouse industries to supply iron in a soluble form for plant uptake. Iron-chelates are chromophores (i.e., a compound that absorbs spectral energy) that absorb strongly in the ultra violet (UV) and blue regions of the spectrum. Absorption of UV and blue radiation (from sunlight or lamps) causes the iron-chelate complex to photooxidize (i.e., destruction of the iron-chelate complex), rendering iron insoluble. The effects of using an irradiated iron-chelate [FeEDTA (ferric ethylenediaminetertraacetic acid)] containing fertilizer solution on plant growth and nutrition under commercial conditions were studied. Application of the irradiated fertilizer solutions to greenhouse grown tomato plants (Lycopersicon esculentum Mill, variety 'Florida 91') under commercial growing conditions in peat-based media resulted in lower levels of iron (6 percent) and zinc (9 percent), and higher levels of manganese (8 percent) and copper (25 percent) in leaf tissue. Leaf macronutrient levels (phosphorous, potassium, calcium, and magnesium), leaf number, and plant height was not affected by the irradiated fertilizer solution. These results demonstrate to growers the importance of properly storing liquid, iron-chelate containing fertilizer stock solutions to prevent destruction of iron-chelates (i.e., prevent exposure of fertilizer stock solutions to light) and the associated alteration in fertilizer formulation (i.e., insoluble Fe while maintaining solubility of other micronutrients). Using a fertilizer solution where all iron-chelates have been photodegraded can alter micronutrient levels of tomato under commercial production.

Technical Abstract: Irradiating an FeEDTA (ferric ethylenediaminetetraacetic acid)- containing commercially available soluble fertilizer with ultra violet (UV) and blue radiation from high intensity discharge (HID) lamps caused the photooxidation of the FeEDTA complex, resulting in the loss of 98 percent of soluble iron. The loss of soluble iron coincided with the development of a precipitate that was mostly composed of iron. Application of the irradiated fertilizer solutions to greenhouse grown tomato plants (Lycopersicon esculentum Mill, variety 'Florida 91') under commercial growing conditions in peat-based media resulted in lower levels of iron (6 percent) and zinc (9 percent), and higher levels of manganese (8 percent) and copper (25 percent) in leaf tissue compared to control plants that received a non-irradiated fertilizer solution. These data for micronutrients suggest that plants responded to lower levels of soluble iron in the irradiated fertilizer solution with iron efficiency-strategy-I reaction that is characterized by enhanced root- associated ferric-chelate reductase activity. Leaf macronutrient levels (phosphorous, potassium, calcium, and magnesium), leaf number, and plant height was not affected by application of the irradiated fertilizer solution.