Early symptoms are similar to those of nitrogen deficiency. Leaves of the entire plant change gradually from green to light green, then to light yellow with a faint tinge of green remaining. Veining is not a prom- inent feature of nitrogen or sulfur deficiency. With time, however, symptoms for sulfur and nitrogen gradually differ from each other. The new, center leaves of sulfur-deficient plants become a light green to almost yellow, rather than the deep green of nitrogen deficiency. During this time, the leaves remain erect; the petioles and blades are brittle and break readily when compressed by the hand. In extreme cases of sulfur deficiency, brown blotches of an irregular pattern, without regard to veination or location, form on the leaf blades. The brown blotches may also appear on the petioles, but, as a rule, these do not become necrotic.

Sulfur-deficient petioles are usually high in nitrate. Thus, the use of the diphenylamine reagent can rule out the possibility of yellowing due to nitrogen deficiency. When the reagent turns blue to a deep blue- black on the cut petiole surface of a yellow leaf, it is quite likely sulfur deficiency. Blade tissue should be used for sulfate analysis to confirm this diagnosis.