Golf Course Management

AUG 2019

Golf Course Management magazine is dedicated to advancing the golf course superintendent profession and helping GCSAA members achieve career success.

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70 GOLF COURSE MANAGEMENT 08.19 ences among chelates were minimal at each measurement time (one hour, and one, seven, 14 and 21 days after application), indicat - ing that EDTA, DTPA or EDDHA would be useful iron sources for turfgrass managers who desire to apply iron to the soil. Conclusion After application, non-chelated iron sources oxidized into insoluble forms in less than one hour, rendering the iron unavail - able. e results of this study do not support the application of iron to soils unless the iron is chelated as EDTA, DTPA or EDDHA. If a cost-effective granular source of one of these three chelates is available, then granular ap - plications of iron may be an effective method of supplying iron. Otherwise, these results indicate that granular iron will be largely in - effective in treating iron-deficiency in turf- grasses. Iron chelates other than EDTA, DTPA and EDDHA may also increase solu - ble iron in soils, but their effectiveness should be confirmed through similar soil incubation studies prior to use. Closing remarks Some iron sources that may be applied to soil are actually intended to be applied as a foliar treatment. ese products may include sulfate, citrate, polysaccharide and glucoheptonate. Foliar applications of iron circumvent the soil oxidation process and are an effective method of supplying iron. In turfgrass response studies conducted between 2014 and 2018, the foliar applica - tion of iron resulted in equivalent turfgrass responses between iron sources regardless of whether the iron was chelated or not. Although confirmatory research is needed, these preliminary results indicate that fo - liar iron sulfate applied with an adjuvant will result in turfgrass greening equivalent to that produced by the more expensive iron chelates. However, if the iron is washed off the leaf and into the soil, non-chelated iron will become insoluble almost immediately. erefore, foliar-applied iron must be al - lowed sufficient time for plant absorption before rainfall or irrigation washes the iron off the leaf and into the soil. Future research may determine the precise time required for maximizing foliar iron uptake. Until then, allowing the application to dry for two to four hours is generally sufficient. Figure 4. Iron solubility following application to soils. Error bars represent standard error. 100 80 60 40 20 0 100 80 60 40 20 0 100 80 60 40 20 0 1 hour 1 day 1 week 2 weeks 3 weeks 1 hour 1 day 1 week 2 weeks 3 weeks 1 hour 1 day 1 week 2 weeks 3 weeks Soluble iron in soil (% of applied) Time after application Soils with pH > 7.9 Soils with pH > 7.0 and < 7.9 Soils with pH < 7.0 Wolftrax Vigiron Glucoheptonate Sulfate Sweet Iron Citrate IDHA EDTA DTPA EDDHA

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