Correcting iron deficiency in calibrachoa grown in a container medium at high pH
2003
Fisher, P.R. | Wik, R.M. | Smith, B.R. | Pasian, C.C. | Kmetz-Gonzalez, M. | Argo, W.R.
The objective was to evaluate and compare foliar spray and soil drench application methods of iron (Fe) for correcting Fe deficiency in hybrid calibrachoa (Calibrachoa xhybrida) grown in a container medium at pH 6.9 to 7.4. Untreated plants showed severe chlorosis and necrosis, stunting, and lack of flowering. An organosilicone surfactant applied at 1.25 mL.L(-1) (0.160 fl oz/gal) increased uptake of Fe from foliar applications of both ferrous sulfate (FeSO4) and ferric ethylenediamine tetraacetic acid (Fe-EDTA). Foliar sprays at 60 mg.L(-1) (ppm) Fe were more effective when Fe was applied as Fe-EDTA than FeSO4. Increasing Fe concentration of foliar sprays up to 240 mg.L(-1) Fe from Fe-EDTA or 368 mg.L(-1) Fe (the highest concentrations tested) from ferric diethylenetriamine pentaacetic acid (Fe-DTPA) increased chlorophyll content compared with lower spray concentrations, but leaf necrosis at the highest concentrations may have been caused by phytotoxicity. Drenches with ferric ethylenediaminedi(ohydroxyphenylacetic) acid (Fe-EDDHA) at 20 to 80 mg.L(-1) Fe were highly effective at correcting Fe-deficiency symptoms, and had superior effects on plant growth compared with drenches of Fe-DTPA at 80 mg.L(-1) Fe or foliar sprays. Efficacy of Fe-DTPA drenches increased as concentration increased from 20 to 80 mg.L(-1) Fe. An Fe-EDDHA drench at 20 to 80 mg.L(-1) Fe was a cost-effective option for correcting severe Fe deficiency at high medium pH.
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