Potassium (K) - soil and crop
Definition
Potassium (K) is an essential plant nutrient, second only to nitrogen in terms of the quantity absorbed by crops. It plays a critical role in moisture regulation and plant metabolism, making it indispensable for healthy growth.
Importance
A deficiency in potassium directly limits crop growth and productivity. Potassium improves:
- Water balance within plant cells
- Enzyme activation for metabolic processes
- Stress tolerance against drought, frost, and disease
Grass and alfalfa are particularly rich in potassium and highly sensitive to its availability. Maize and by-products such as CCM, pressed beet pulp, and brewer grains contain significantly lower potassium levels.
Potassium content in common forages
(Eurofins Agro data, 2009–2013)
| Fresh grass | Grass silage | Maize silage | Lucerne | |
| Average | 34 | 33 | 11 | 29 |
| Target range | 25-35 | 25-35 | 10-14 | 25-35 |
Challenges in potassium availability
Potassium is prone to leaching, especially in lighter soils. Its availability is declining in many regions due to:
- Reduced manure application (tightening fertilisation rules)
- Lower potassium content in manure
Additional fertilisation
Supplementing potassium (usually as K₂O, potash) can:
- Increase crop yield and quality
- Reduce susceptibility to drought, frost, and fungal infections
- Improve shelf life of harvested crops
