Fertility Management for Forages

Soon the cold days will give way to spring thaw, and right around that corner we’ll be preparing to apply fertilizer to our forages. While hay supplies have been adequate so far this season, that is never a guarantee moving forward. Keeping forage fields productive is key to ensuring an adequate supply when conditions turn less favorable.

A common misconception is that hay fields don’t remove much fertility, or that they only require nitrogen. While nitrogen is critical—especially in grass-dominated stands—a hay field producing 2–3 bales per acre actually removes more phosphorus and potassium than a 60-bushel soybean crop. With that in mind, it’s important to replace nutrients based on balanced removal rates. Doing so helps maintain yields as stands age and improves forage persistence during periods of dryness or stress.

Pastures are slightly different. Roughly 80% of the phosphorus and potassium removed by grazing animals is recycled back to the field through manure. The challenge lies in distribution. Spring harrowing can help spread nutrients more evenly, but it doesn’t account for the remaining 20% that leaves the field with the animals, nor does it correct deficiencies in fields that started low in fertility.

If a pasture has never been soil sampled, that is the best place to start. Soil testing establishes a baseline for pH and fertility levels, allowing producers to make informed decisions. Resampling every four to five years helps ensure fertility stays on track and supports long-term pasture productivity.