And questions are often raised about what is the best way to apply fertilizer to existing stands. Some of this issues was addressed last year in our agronomy notes detailing studies along the Powder River. More information for Canadian researchers supports our previous guidelines. Phosphorus can be broadcast on perennial forages with very good results on phosphorus deficient soils in wet regions of the state or just prior to anticipated rainy periods or irrigation. Alfalfa, for example, has a root system with many roots close to the soil surface and thus can effectively utilize broadcast applications of phosphorus.
Grasses can also use broadcast phosphorus.
Applying the phosphorus in the fall is usually more effective on the first cut of forages the following year than adding phosphorus in the spring - but farmers and ranchers should not disregard late winter and early spring applications. Single-large applications of phosphorus, prior to forage establishment, can provide phosphorus for at least the first few years of forage production but is less effective than annual applications. Alfalfa stands are more likely to respond to K fertilization than are cereal crops because large quantities of K are removed by alfalfa before it is harvested. O. Good responses of alfalfa to K fertilizer have been observed on many soils that have tested relatively high in K. Coarse-textured soils are chronically K deficient and forages grown on these soils usually require K fertilization. Older stands of alfalfa are more susceptible to K deficiency than younger stands.