Potassium leaches rather quickly so needs to be replenished. In areas with heavy rainfall, potassium may be completely leached from the soil. A potassium deficiency shows in the older leaves first. It looks like the leaf was scorched. The leaves may turn purple.
Young shoots become stunted, stalks are weak, stems are shorter, and blooms become distorted.
It is claimed that a deficiency of potassium will increase a plant's susceptibility to diseases, and produce blind shoots. In our area, it is unlikely that you would see a deficiency of potassium. Heavy clay particles can also interfere with the uptake of potassium since they can displace other mineral ions such as calcium. When potassium is attached to the clay micelle, it becomes unavailable to the plant. Excessive potassium causes chlorosis, poor root growth, and wilted new shoots.