Research has led to a new fertilizer recommendation for potassium on grassland. To determine the potassium need of grassland the parameter K-HCl was used until now. This will be replaced by the soil parameters CEC and K-CaCl2. The new recommendation is based on two years of field experiments. The research was carried out by the Nutrient Management Institute (NMI) and Wageningen UR Livestock Research and financed by the Dutch Dairy Board.
In 2011 and 2012 field experiments were set up on 24 dairy farms and three experimental farms on sand, clay and peat soil. Conclusions:
- Adequate potassium fertilization is important to reach an optimal grassland yield
- When potassium is applied before the first cut at low soil fertility for potassium, the yields of all cuts are positively affected.
- The highest grassland yield is reached when all cuts receive sufficient potassium
- Of the analysed soil parameters, K-CaCl2 and CEC are the most accurate basis for the potassium fertilizer recommendation. When CEC cannot be analysed, the recommendation can also be based on K-CaCl2, organic matter and lutum (<2μm). The recommendation based on CEC, however, is preferred.
- Yield level and soil fertility are determining the recommendation for the first cut, potassium withdrawal for the next cuts.
- The new fertilizer recommendation for the first cut is lower than before
The new fertilizer recommendation for potassium is established by the Committee for Fertilization on Grassland and Foddercrops (CBGV) and will appear in the Fertilizer Recommendations on www.bemestingsadvies.nl within a few weeks.
The former potassium fertilizer recommendation for grassland was based on field experiments in the 1950’s and 1960’s and was virtually not changed after 1976. Since then agriculture has changed and new methods for soil analysis have been developed. Also agriculture needs to control expenses and has to produce fodder efficiently.
Pre-research proved that there was perspective to develop a new recommendation based on intensity (directly available) and capacity (available in the longer term) and new methods for soil analysis.