Growth, Quality, and Foliar Iron Concentration of Kentucky Bluegrass Treated with Chelated Iron Sources

Abstract

Supplemental Fe fertilization to improve turfgrass quality has become an increasingly common practice on many turfgrass areas. Field studies were conducted to evaluate the nutrient uptake, growth, and quality of Kentucky bluegrass (Pea pratensis L.) treated with chelated Fe sources. Iron sources were evaluated over 2 years at 1.5,3.0, and 6.0 kg Fe/ha applied in May, July, and September of each year. Turf treated with an iron orthophosphate citrate source (Fe-PC) exhibited more foliar growth than nontreated turf on seven of 11 sampling dates during the study. Iron citrate sources [Fe-C(EI) and Fe-C(T)] and Fe-DTPA applications resulted in similar growth rates, never stimulating growth more than the Fe-PC source and rarely increasing growth compared with nontreated turf. Increasing the Fe rate within source did not typically increase growth. Iron-treated turf exhibited quality superior to nontreated turf throughout the study with all sources performing comparably. Increasing Fe rate did not result in a corresponding increase in quality, due to greater phytotoxicity at higher rates. Although several sources produced notable phytotoxicity at 6.0 kg Fe/ha, repeated application did not decrease turfgrass density. Iron tissue content increased linearly with rate on four of five sampling dates during the study however, no source resulted in tissue Fe content significantly higher than other sources. Application of sources containing supplemental P and/or K did not increase tissue P or K content. Chemical names used: iron citrate (Fe-C); iron diethvlenetriamine pentaacetate (Fe-DTPA); iron orthophosphate citrate (Fe-PC).