How much phosphorus fertilizer should be applied to alfalfa?
The phosphorus fertilizer rate recommendation is based on soil testing. Soil test values of >15, 11-15, 6-10, and <6 ppm bicarbonate extractable P correspond to none, 50-150, 140-250, and 200-300 pounds P2O5 per acre, respectively, applied at planting for a 3-year crop. For annual applications or multiple applications per year, the total annual application should be a third of the above fertilizer application rates. Annual or multiple applications per year may be necessary to maintain the soil test level in a desirable range for soils with a high phosphorus fixing capacity.