Potassium deficiency in pastures

Abstract

Summary Legumes and grasses were analysed from two series of trials (a) pure species trials (b) mixed pastures from which legumes and grasses were dissected out for separate analysis. In the pasture trials on Horotiu sandy loam under cow grazing, yield responses to potassium fertilisers commenced in September, reached a maximum in summer (November to January), declined in autumn and were at a minimum in winter. The appearance of deficiency symptoms in white and red clovers corresponded to this pattern of growth responses which followed the seasonal growth cycle. Symptoms were not detected in winter. On deficient soils, uptake responses to potassium fertilisers were appreciable over the whole range from severe deficiency to adequacy, but were small or not detectable on soils with high available potassium. Large differences in analytical levels were found in different tissues of plants well supplied with potassium. Differences were much smaller in potassium-deficient plants. Seasonal decline in the potassiu...