The forms of potassium in the soil

The intricate relationship of the elements generate forms of potassium in the soil beyond potassium oxide (K₂O) which is advertised on the fertiliser bags.

Potassium can be differentiated according to plant availability into four forms:

• Potassium not available

This potassium is bound to the crystalline structure of feldspar minerals. So they are not soluble until the mineral is completely weathered. Therefore, a very long-term supply of potassium is always being made in the soil. But unfortunately this potassium is not available as a soil fertiliser.

• Fixed potassium or slowly available potassium

When rock weathering occurs, it turns into clays. Both clays and organic matter have the capacity to retain different elements electrostatically between their layers. A balance is formed between the available and unavailable forms, forming a kind of potassium store in the soil. This balance means that potassium applied as fertiliser can be slowly converted into available potassium.

The force that attracts them to the clay is not very great; it is reduced by rainfall. Leaching can be avoided by applying liming to maintain a neutral pH in acid soils. And it is possible that during the plant growth period, the soil may run out of exchangeable potassium, but it is almost impossible to run out of slowly exchangeable potassium.

Fixed potassium is responsible for maintaining available potassium levels in the medium term.

• Exchangeable potassium or potassium readily available

Part of the balance described above is water-soluble, and plants readily absorb the elements dissolved in water. As soon as the potassium concentration in the soil water drops, potassium is gradually released from the slowly assimilable potassium.

This solution is very washable and it is important to ensure that only the most essential part is in solution to facilitate plant growth.

This element is really abundant on the earth's surface, it is present in the crystalline structure of most feldspars. This mineral is ubiquitous in the rocks of the earth's crust. But this does not indicate that it is in a state available for cultivation.

Do you need to spreader for your dosage?

We are talking that of the 100% of potassium in soil more than 90% is not available to the plant: only 8% is slowly available and 2% is what is available to the plant. plant.

There are instruments such as these pen-sensors capable of measuring the potassium in the soil solution in order to apply the necessary fertilisers and not waste product in the fraction of the soil that is washed away.