A. Luxury uptake of potassium occurs in rapidly growing Spring grass which has the ability to take up a lot more potassium than it needs for normal plant functioning. High levels of potassium in the plant interfere with the uptake of magnesium and low magnesium in the animal’s diet is one of the factors causing grass tetany. The risk of luxury uptake can be reduced by avoiding large applications of potassium to grazing fields in Spring. Applications of grazing fertilizers containing low levels of potassium e.g. 27-2.5-5 will not cause problems. Precautions against grass tetany should be taken regardless of what fertilizer programme is followed.