The symptoms of magnesium (Mg) deficiency resemble those of potassium (K) and iron (Fe) deficiencies in a number of respects. However, there is a major difference in the location of the initial symptoms in the case of K. Unlike K deficiency, the new leaves of Mg-deficient wheat plants are pale in contrast to the old leaves. This, however, is similar to Fe deficiency. The new leaves soon become chlorotic and remain unopened, resulting in a twisted appearance that gives the plant an unthrifty look reminiscent of drought stress.

If Mg deficiency is severe enough, the entire length of the leaf will remain folded or rolled. After some time, several leaves including the new shoot may be folded or rolled. Over time, the chlorosis of the new leaves referred to earlier becomes mottled and finally necrotic, although the leaves remain erect. Even the oldest leaves develop a mottled chlorosis and in some cases a reddish coloration along the leaf margins.

In the field, Mg deficiency of wheat is not common; however, it can occur where Mg has become unavailable or on sandy acid soils in high rainfall areas. Symptoms of Mg deficiency in the field appear as patchy yellowing and stunting of the crop. Examination below ground would reveal a poorly developed root system.