Evaluation of zinc seed treatments for rice

Zinc seed treatments for rice (Oryza sativa L.) were previously evaluated as an alternative to soil-applied Zn. Recommendations concerning the effectiveness of Zn seed treatments were never clearly stated. Our objectives were to evaluate the utility of Zn seed treatments for supplying Zn to rice grown on soils prone to Zn deficiency, In 1998, a study with three cultivars compared Zn-treated seeds [2.8 g Zn (kg seed)(-1)] with a control and 11 kg Zn ha(-1) as ZnSO4 applied to the soil. Because tissue Zn concentration did not differ among cultivars, a single cultivar, Drew, was used in studies at two locations in 1999. The control and the soil-applied Zn were compared with seeds that were treated with three rates of ZnSO4 and ZnEDTA (ethylenediaminetetraacetic acid). Analysis showed net seed concentrations of 1.0, 2.2, and 3.7 g Zn (kg seed)(-1) as ZnSO4 and 1.4, 2.8, and 5.7 g Zn (kg seed)(-1) as ZnEDTA. In 1998, neither visual Zn deficiency symptoms nor significant yield differences were observed among treatments. Soil applied Zn and Zn seed treatments increased tissue Zn concentration by 11.9 and 4.7 mg Zn kg(-1), respectively, above that of the control (19.7 mg Zn kg(-1)). In 1999, Zn deficiency occurred at both locations. Measurements of dry matter, tissue Zn concentration, and grain yield showed that Zn-treated seed performed equal to or better than soil-applied Zn. These data suggest that seed Zn concentrations between 2.2 to 5.7 g Zn (kg seed)(-1) are an economical alternative to soil-applied Zn.