Rice Response to Granular Zinc Sources Varying in Water‐Soluble Zinc

Abstract

Water‐soluble Zn (WsZn) levels in granular Zn fertilizers are reported to be a reliable estimate of fertilizer Zn availability to crops. Our objectives were to evaluate the immediate and residual effects of four commercial Zn fertilizers with WsZn ranging from 14 to 98% on the growth, Zn nutrition, and yield of field‐grown flood‐irrigated rice (Oryza sativa L.). Mehlich‐3 extractable Zn response to Zn fertilization was also evaluated. Zinc fertilizers were applied at rates ranging from 2.3 to 18.0 kg Zn ha−1 at two locations in 2000. The immediate and residual effects of Zn fertilizer treatments on rice growth were measured in 2000 and 2001, respectively. Dry matter, tissue Zn concentration, and grain yield were increased from application of 13.5 kg Zn ha−1 for both sites during both years, but the magnitude of response varied between locations. During the first year, at both locations, whole‐seedling Zn concentrations increased linearly as Zn rate increased and was affected by Zn source. Tissue Zn concentration generally declined as the fertilizer WsZn level declined. Zinc rate had the greatest influence on grain yields with near maximum yield produced when >9 kg Zn ha−1 was applied. During the second year, tissue Zn concentration and yield increased linearly or nonlinearly, depending on location, as Zn rate increased and were not affected by Zn source. During the first year, Zn source and rate influenced early season growth and Zn concentrations, but grain yield, Mehlich‐3 soil Zn, and the residual benefits of Zn fertilization were affected only by application rate.