Use of deep tillage and liming to reduce zinc toxicity in peanuts grown on flue dust contaminated land

Abstract

Flue dust is a by-product of the steel industry which contains about 10% Zn. In the 1980's, flue dust was applied to at least 4000 ha of farmland in Georgia, which resulted in severe Zn toxicity in peanuts. We evaluated the potential of deep tillage (subsoiling, deep disking, deep turning) in combination with limestone application for reduction of Zn toxicity in three soils which had been contaminated with flue dust. Tillage redistributed Zn vertically within soils. Deep disking reduced Mehlich-1 extractable soil Zn level in the 0–20 cm depth and increased soil Zn level in the 30–60 cm depth, and deep turning decreased soil Zn level from 0–20 cm deep and increased soil Zn level from 20–40 cm deep. Deep tillage also resulted in chemical redistribution of Zn among fractions; deep disking and turning both reduced the Zn percentage in the organically-bound fraction and increased the percentage in the Fe oxide fraction. Although Zn was successfully redistributed physically and chemically through deep tillage, this redistribution did not reduce plant Zn concentrations or increase yield. Limestone application increased soil pH, reduced plant Zn concentration, and increased yield when moisture was adequate, but these effects were not impacted by tillage treatment. Therefore, deep tillage was not successful in remediation of flue dust contaminated land, and limestone application was the most promising technique tested.