Studies on the nutrition of pasture plants in the south-west of Western Australia. 2. Visual symptoms of mineral deficiencies on the Dwalganup strain of Trifolium subterraneum L

Abstract

The visual symptoms of several mineral deficiencies on the Dwalganup strain of subterranean clover are outlined. Phosphorus, nitrogen, and molybdenum deficiencies particularly reduce the rate of leaf production and leaf size. They may be distinguished by leaf colour-dark green in phosphorus deficiency and greenish yellow to pale yellow in nitrogen and molybdenum deficiency. Sulphur deficiency reduces the rate of leaf production after the onset of symptoms. Leaf size was not greatly affected by the degree of sulphur deficiency studied. The older leaves were uniformly lemon yellow in colour. Both potassium and zinc deficiency result in very pronounced reduction in leaf size. Potassium deficiency, in addition, shows marginal necrosis of older leaves, while with zinc deficiency leaf shape is profoundly affected. Copper deficiency particularly reduces seed production. The leaves are lighter green in colour than normal. With calcium (and manganese) deficiency, no prominent symptoms were recorded on the soils used. The advantages and limitations of diagnosis by visual symptoms are discussed.