Viticulture
Ensuring adequate potassium supply can improve the yield, disease resistance and juice quality of grapes and has also been implicated in improved winter hardiness.
In most of the eastern states, potassium fertiliser is broadcast or banded in autumn so that winter rains can move it into the root zone. In Western Australia, fertiliser is more often applied in spring. Top-up applications, foliar sprays or fertigation may be necessary as fruit fills and ripens.
The potassium status of vines and the fertiliser requirement for maximum economic production is best indicated by analysis of petiole tissue concentrations and a monitoring program should be implemented. It is also important to note that rootstocks have varying abilities to access soil potassium reserves.
In temperate areas, grape vines may suffer a potassium nutritional disorder called "spring fever". Cold, moist soil conditions in early spring reduce the availability of potassium to plants during rapid growth periods. These symptoms often disappear as the season progresses and soil becomes warmer. However extra potassium should be applied if potassium deficiency symptoms persist after flowering.
Overapplication of potassium can have a negative impact on the quality of red wine produced through an increase in pH and a reduction in colour and flavour.