Iron uptake by native grasses in a sewage sludge amended semiarid grassland

Publisher Website
Google Scholar
Abstract
Iron chlorosis is commonly associated with calcareous soils due to precipitation of Fe in hydroxide forms. Single applications of sewage sludge have been known to correct Fe deficiency symptoms for up to five years in crop plants grown on such soils. The effect of sludge on the Fe nutrition of native grassland species is less well known. In June 1985, a degraded semiarid grassland site was amended with surface applications of dried, anaerobically digested, sludge at rates of 22.5, 45, and 90 Mg/ha. While DTPA extractable soil Fe increased, tissue concentrations of Fe in the three predominant native grasses tested declined significantly (p ? 0.05) with increasing sludge application. However, plants in amended plots did not become Fe deficient, but rather flourished relative to controls. The greater production of aboveground biomass on amended plots compared to unamended plots suggested the possibility of a dilution effect. Calculations of total tissue Fe, based on biomass measurements and tissue Fe concentrations, only partially supported this hypothesis. Consequently, a more comprehensive tissue analysis of the highly responsive cool‐season grass, bottlebrush squirreltail (Sitanion hystrlx), was undertaken. As suspected, tissue Fe concentration was highly correlated with tissue fiber concentration, and total tissue Fe in amended plots was equal to or greater than that in control plots. Both results confirmed the dilution effect hypothesis. However, Fe uptake did not increase significantly on amended plots compared to controls indicating that treated plants did not require additional amounts of Fe to produce greater biomass.