Compatibility of a petroleum spray oil and foliar zinc fertilisers

Abstract

The performance of 7 commercial zinc (Zn) foliar nutrients sprays, based on sulfate (Top ZM), hydrated sulfate (Pivot Zinsol; Pivot Mangasol-zinc), oxide (Phosyn Zintrac), and ligninsulfonate (Spray-gro Zn PC; Spray-gro Zn/Mn PC; SJB), were assessed with and without addition of a horticultural petroleum spray oil (PSO), Ampol D-C-Tron NR. Foliar Zn deposition and absorption was quantified by Inductively Coupled Plasma-Atomic Emission Spectrometry (ICP-AES) after solvent washing and acid extraction. Effects on photosystem II were measured by chlorophyll fluorescence. Although none of the Zn sprays were soluble in PSO, all but Zn oxide could be suspended adequately before spraying. A partial emulsion break occurred with Zn sulfate and hydrated sulfates. All treatments increased the Zn content of leaves by an amount likely to alleviate Zn deficiency. Addition of PSO decreased deposition and absorption of Zn when used with the inorganic formulations or with Spray-gro Zn PC. Zinc deposition and absorption were increased by PSO in Spray-gro Zn/Mn PC, and were unaffected by PSO in SJB. Plant chlorophyll fluorescence and phosphorus content did not differ among treatments. The ligninsulfonates Spray-gro Zn/Mn PC and SJB were most compatible with Ampol D-C-Tron NR, and had relatively low potential for Zn pollution of the environment.