Effects of copper deficiency and liming on the yield,quality and copper status of tomatoes,lettuce and cucumbers grown in peat

Tomatoes, lettuce and cucumbers, grown in beds of peat, received 3 levels of copper sulphate (0, 0.5 and 5 g/m²) in factorial combination with 2 rates of liming (average pH values 6.5 and 6.9). Omission of copper resulted in copper deficiency and decreased the yield of tomatoes, lettuce and cucumbers by 11% (P < 0.01), 53% (P < 0.001) and 48% (P < 0.001), respectively. In addition, this deficiency increased the proportion of unmarketable lettuce six-fold (P < 0.001) and that of poorly developed cucumbers by 67% (P < 0.05), but had no effect on the proportion of unevenly ripened tomatoes. Heavy liming (pH 6.9) reduced the yield of lettuce (14%; P < 0.01), but had no effect on quality throughout the trial. Although lettuce and cucumber leaves from the intermediate copper treatment contained only 2 μg/g Cu, the yield and quality of the produce were only slightly, and not significantly, inferior to those obtained at an adequate level of copper (> 7 μg/g).