Controlled release fertilizers

Controlled-release fertilizers (CRFs) use a coating around the fertilizer granule to regulate how nutrients are released into the rootzone over time.

Rather than making the full nutrient content immediately available after application, the coating controls nutrient release over an extended period. This can provide a more consistent nutrient supply and reduce the number of fertilizer applications required during the release period.

The release characteristics depend on the coating technology, product formulation and environmental conditions, particularly temperature.

Why use controlled-release fertilizers?

For professional turf management, controlled nutrient release can provide several practical advantages:

• Extended nutrient supply — nutrients are released progressively over several weeks or months, depending on the product.
• Fewer applications — a longer nutrient release period can reduce the frequency of fertilizer applications compared with short-term conventional nutrition.
• Reduced risk of nutrient losses — controlling the rate at which soluble nutrients become available can help reduce the potential for losses through leaching.
• More consistent turf response — gradual nutrient availability can help avoid the pronounced growth peaks associated with large applications of readily available nitrogen.

CRFs are particularly useful where the objective is to maintain a steady nutritional supply over an extended period while reducing the need for repeated applications.

How controlled release works

The nutrient granule is surrounded by a coating that regulates the movement of water into the granule and nutrients back into the soil solution.

Once moisture penetrates the coating, the nutrients inside begin to dissolve. They are then released gradually through the coating rather than becoming available immediately.

Different coating technologies provide different release characteristics, so product selection should take account of the required longevity, growing conditions and nutritional objective.