Zinc deficiency symptoms are commonly encountered in irrigated soybean crops grown on grey self-mulching clay soils in Northern N.S.W . These experiments aimed to (1) quantify the yield loss due to zinc deficiency at different sites and (2) examine the differences in genotypic sensitivity to zinc deficiency among commercially grown soybean cultivars. Materials and Methods : Experiments were conducted at (1) Narrabri Agricultural Research Station, (2) Breeza Substation and (3) Trangie Agricultural Research Station.