Availability of Fertilizer Zinc to Corn in a Calcareous Mineral Soil

Abstract Powdered ZnSO 4 · 7H 2 O was plowed down for corn ( Zea mays L.) in a Zn‐deficient Fieldon silty clay loam at five rates, row banded, or banded at four rates after mixing with NH 4 NO 3 . The effect of dusting corn seed with Na 2 Zn‐EDTA was also compared, using leaf Zn and grain yields for 5 years as criteria. Soil analyses and greenhouse studies with 65 Zn, eight years after Zn fertilization, were conducted to determine possible cause(s) of extreme variations in field availability of indigenous soil Zn for corn, and the residual effect remaining where Zn fertilizer was used eight years previously. Plowing down ZnSO 4 · 7H 2 O at higher rates resulted in higher leaf Zn in all 5 years, whereas initially effective lower treatment rates decreased with time. Banded Zn and/or N had little or no effect on leaf Zn. Grain yields were increased by both plow down and band ZnSO 4 · 7H 2 O treatments until the fifth year. Dusting corn seed with Na 2 Zn‐EDTA had no effect on leaf Zn or on annual grain yield, but increased the 5‐year yield. Soil analyses 8 years after Zn fertilization showed that vegetative Zn‐deficiency symptoms of corn in the field and subsequent low grain yields were significantly related to high extractable P/extractable Zn ratios in the surface 30.5‐cm soil depth. There was no observed effect of temperature, moisture, pH, conductivity, calcium carbonate equivalent, or exchangeable K. More Zn was extracted from the surface soils where Zn had been applied nearly 8 years previously, but “A values” were larger only in soils receiving the heaviest 1962 Zn treatment of 44.8 kg/ha.