A comparison of slow release potassium fertilisers for pasture

Abstract

Luxury uptake of potassium (K) from potassium chloride (KCl) by pasture plants is a major disadvantage in its use as a fertiliser for pastures. Luxury uptake shortens the fertiliser's effective life and causes excessively high concentrations of potassium relative to calcium, magnesium, and sodium. This can result in health problems for grazing stock. A further disadvantage is that KCl is readily leached from the soil if there is heavy rain. Coating KCl has been tried as a way of slowing the release of K and its uptake by ryegrass, and of reducing loss by leaching. Coating KCl with sulphur reduced its rate of dissolution greatly and avoided luxury uptake by the grass. On an extremely K deficient soil there was some loss of growth relative to uncoated KCl for 2 months, but over the next 4 months, the sulphur-coated KCl gave higher yields. Wax-coated KCl gave practically the same results as uncoated KCI. A leaching test was used to measure rate of solution of KCl and its results related well to the reduction of luxury uptake.

Glacially abraded rock flour from Greenland: Potential for macronutrient supply to plants

“…3). It is possible that K was taken up in excess by the control plants (Saunders et al, 1988;Clover and Mallarino, 2013). McNaught (1958) showed how luxury uptake of K can lead to tissue concentrations more than twice that actually required to sustain optimal growth in ryegrass.…”