Older leaves of my potato have brown scorched edges and bronzing, is this potassium deficiency?

Brown scorched margins and a bronze or dark dull colour on the older lower leaves of potato, with the crop ageing fast, most likely indicates potassium deficiency. Potato is a heavy potassium feeder, and because potassium is mobile the shortage shows on old leaves first as edge scorch and bronzing, along with weaker plants and smaller, lower quality tubers. Please confirm with your Soil Health Card or a soil test before correcting, because the leaf edge scorch can also come from drought stress, salt injury, or early blight, so rule those out, especially water stress. If low potassium is confirmed, muriate of potash or sulphate of potash is used, with sulphate of potash often preferred for quality potatoes. The dose depends on your soil test value and the high potassium demand of potato, so follow your Soil Health Card and local KVK recommendation rather than a fixed figure, and do not over-apply, because excess potassium can interfere with magnesium and calcium and affect tuber quality.