| Abstract: | Abstract Zinc availability was studied using five soils from Hawaii which had histories of massive phosphorus applications. Heavy phosphate fertilization usually increased extractable Zn, irrespective of the extractant used. The extra extractable Zn associated with the added P probably came from Zn as an accessory element in the fertilizer. Treble superphosphate commonly used in Hawaii contains about 1400 ppm Zn. The Zn content of phosphate fertilizers must be considered before making statements about the effect of fertilizer P on Zn solubility and availability in soils. Two solutions (0.1N HCl and 0.005M DTPA) were compared as Zn extractants for Hawaii soils. DTPA extracted less Zn than 0.1N HCl. Zinc extracted by repeated HCl treatment was more closely related to the labile Zn pool (E‐values and L‐values) than was DTPA‐extractable Zn. The results suggest that 0.1N HCl extractable Zn, Zn E‐value and Zn L‐value measured the quantity of a single fraction of soil Zn. Repeated extraction of soil with 0.1N HCl seems to be a suitable procedure for evaluating the Zn status of acid, highly weathered soils of Hawaii. |
