Sulphur deficiency (S)
In contrast to nitrogen deficiency, sulphur deficiency in vegetables will first show as a yellowing of the young shoot tips. The apex will turn yellow, with young and middle leaves following suit. The abaxial leaf surface with show a reddish colouration. Leaves will become rough and brittle; growth in general is delayed. Due to a similarity of symptoms sulphur deficiency is frequently mistaken for nitrogen deficiency.
A pronounced lack of sulphur rarely occurs in vegetable cultivation. One exception is brassica cultivation, as brassicas (eg. cabbage, cauliflower, broccoli etc.) require sulphur for the production of isothiocyanate (mustard oil) glycosides. Onions and leeks also have an increased demand for sulphur, as they need it to create allicin, an important odour and taste component.