Effect of Soil Contamination on the Mineral Composition of Forage Fertilized with Nitrogen

Abstract

Mineral analysis of forage from a nitrogen (N) fertilizer, field study produced unexpectedly high iron (Fe) concentrations which were correlated with the N fertilizer level (r2=.92) and the percentage N in the forage (r2=.94). The high Fe values were presumed to be associated with dust on the leaves. The objective of this study was to determine the level of soil contamination on the forage sample and the contribution of mineral in the contaminant to that measured in the sample. Soil contamination of plant tissue samples was calculated from the dilution of soil titanium (Ti) assuming that the uncontaminated tissue contained 0 g Ti/g. Tissue harvested from the 0, 28, 56, or 84 kg N/ha treatments contained 23, 49, 48, and 60 mg soil/g, respectively. Significant N fertilizer effects would have been accepted for each element tested if soil contamination had been ignored. Correcting for contamination resulted in significant N-fertilizer effects on the concentrations of sodium, potassium, manganese, iron, and zinc but not magnesium or calcium in the forage. Some of these effects may be explained by the acidifying effect of the N fertilizer source.