Geoscience Reference
In-Depth Information
When should potassium be applied?
This depends on the type of enterprise. Potassium fertilisers leach readily, and may
also be taken up by plants in excess quantities. If high application rates are needed,
it is suggested that more than one application over the plant's growing season
should be applied to minimise potassium losses. This is especially true of perennial
pastures and lucerne.
Potassium on crops is usually applied just prior to or at planting, and in
horticultural situations it is usually applied as a NPK mix with each successive
crop. Potash fertilisers can scorch crops if top dressed on damp leaves; however,
plants usually recover quickly.
Note 1 . Muriate of potash (potassium chloride) contains chlorine that may
adversely affect soils and plants; however, some chloride in the soil solution is
essential.
Note 2 . Soils vary in their potassium content and its availability, depending on
the rock type they were formed from and the coarseness of the soil particles. Fine
soils hold potassium better than coarse soils and potassium can be leached readily
from sands and soil organic matter.
What happens if adequate potassium is not applied?
Total potassium levels in soil are usually more than adequate, but most is not
readily available to plants unless soil microbiology is active. If potassium supplies
become the limiting factor, plants grow slower, become spindly and need more
water for respiration. Seeds and fruit may become shrivelled.
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