Potassium deficiency can be overlooked, with plants that have a 50 per cent deficiency showing no symptoms [typically yellowing of the leaves], according to Yara agronomist Natalie Woods.
Speaking at the CropTec Crop Nutrition seminar, Ms Woods said: “It is the hidden hunger. Crops can be lacking but you cannot tell – a tissue test would be the only way.”
Potassium is important for transport of sugar through the plant, enzyme activation, cell walls, storage of carbohydrates and regulation of water balance, she said. “Particularly in drought it helps to increase drought tolerance. It is vital for early root growth.”
The key timing for application is in spring at a rate of 35kg/ha, independent of indices, due to high crop demand for potassium at this time, said Ms Woods. “If your soil index is below 1 you will require and autumn application to ensure sufficient levels in the soil for establishment but then still 35kg/ha in spring so don’t apply all the K in that first application.”