Potassium deficiency (plants)
Potassium deficiency, also known as potash deficiency, is a plant disorder caused by the depletion of potassium ions (K+) in the soil. Potassium deficiency causes brown scorching and curling of leaf tips, as well as chlorosis (yellowing) between leaf veins.
Source: Wikipedia — Potassium deficiency (plants) (CC BY-SA 4.0)