Effect of slow release iron fertilizers on chlorosis in grape

Abstract

Iron-EDTA (Fe-EDTA), ferrous sulfate (FeSO 4 ), and a combination of both (50:50) were coated with a natural resin material and tested in a concentration of 75 and 100 mg Fe/kg soil, respectively, for three years in pot experiments with the susceptible grape (Vitis vinifera L.) vine rootstock Couderc 3309. In 1990, two locations in the field were fertilized with coated Fe-EDTA. The application of coated Fe-EDTA increased the iron (Fe) content in the youngest leaves about 10% and the chlorophyll content about 71% compared to the three year average values of the untreated plants. The most obvious effect was a better growth, which resulted in a higher dry weight and a greater Fe uptake in the leaves and shoots. Organic acids decreased about 11% and chlorosis symptoms, as in untreated plants, did not appear. By itself, FeSO 4 was only applied in the first year, after which chlorosis symptoms occured. The combination of Fe-EDTA and FeSO 4 resulted in an increase of iron content, dry weight, Fe uptake and chlorophyll content and a slight decrease of organic acids. All data except the Fe content were higher by singly applying coated Fe-EDTA. At one location of

Iron sources for citrus rootstock development grown on pine bark/vermiculite mixed substrate

“…The results obtained in the present experiment are in agreement with those obtained by Natt (1992), who reported the Fe-DTPA source as the least efficient in iron supply, with plants usually showing visual iron deficiency symptoms; and also, the results reported by Álvarez-Fernández et al (1996), who classified the chelates Fe-EDDHA and Fe-EDDHMA as the most efficient iron sources for plant growth, in function of the existence of isomeric orto-orto in composition, larger solubility and maintenance of high amounts of chelated iron in the solution.…”

“…(1998) observed that the total iron concentration was always higher in chlorotic leaves as compared to green leaves and was not related to the chlorosis degree. The application of Fe-EDTA increased young plant leaf iron concentrations in 10% when compared to three-year-old plants treated with and without iron chelates (Natt, 1992). However, opposite results were obtained in this experiment, where plants treated with Fe-EDTA showed severe visual chlorosis symptoms of iron deficiency, despite the high total iron concentration found in them (Table 4).…”

“…As alternatives, other iron chelates, like Fe-DTPA, Fe-EDTA and Fe-HEDTA might be used. However, their efficiency in correcting iron chlorosis is smaller when compared to other chelates (Lucena et al, 1992;Sánchez-Andreu et al, 1991 (Natt, 1992). On the other hand, iron can easily precipitate in nutrient solution due to Fe displacement from the chelate by other elements, and subsequent precipitation of iron hydroxide, turning Fe unavailable to plants, inducing chlorosis and blocking the drip system.…”

“…The Fe-HEDTA is moderately stable under acid and neutral conditions, between pH 4.8 and 6.7. Above pH 7.5 this chelate presents very low stability (Norvell, 1972).…”

FeDFOB and FeEDDHA immobilized on Sepharose gels as an Fe sources to plants

“…These mixtures were an unsatisfactory source of Fe. In another study, FeEDTA, FeSO 4 and a combination of both were coated with a natural resin material and tested as slow release Fe fertilizers for susceptible grapevine rootstock (Natt 1992) with relatively low success. Wallace (1991) attempted to produce a slow release Fe fertilizer by preparing cross-linked swelling gel polymers saturated with Fe chelates, but these polymers released Fe rapidly upon irrigation.…”