EFFECTS OF Mn AND Fe SUPPLY ON THE GROWTH OF BARLEY IN NUTRIENT SOLUTION

Abstract

The influence of three Fe levels (0.1, 0.5, 2.5 ppm) and four Mn levels (0.005, 0.05, 0.5, 1.0 ppm) in all combinations in nutrient solutions were studied in the greenhouse with barley plants. At the anthesis stage, the dry matter yield increased with increasing Fe supply when the Mn level was below optimum (0.005 ppm) or approximately optimum (0.05 ppm). At maturity, the yields of kernels and straw increased with increasing Fe supply regardless of the Mn level. Mn deficiency symptoms were evident at the lowest Mn level and were not influenced by the Fe supply. Dry matter yields at the two highest Mn levels were lower than those at the 0.05-ppm Mn level at both the anthesis and mature stages. Mn toxicity symptoms were evident only at the highest Mn level. The critical Mn concentration in the four uppermost leaf blades associated with reduced dry matter yield was approximately 15 ppm regardless of the Fe supply. The critical Mn concentration in leaves plus stem was slightly lower than that for leaf blades only. Similar results were obtained with two barley cultivars. It was concluded that increasing the Fe supply does not reduce Mn availability or concentration in barley plants when the Mn supply ranges from below to approximately optimum but may do so when the Mn supply is above optimum.