To apply three years of P and K in a single application as lagoon effluent would require unmanageably high application rates that would exceed allowable rates of N. Preplant applications of manure do not work well when alfalfa is seeded with oats as a nurse crop because the high N level that comes from the manure application promotes lodging of oats. A second strategy of manure application involves annual top-dressing. Manure can be applied to established stands to supply required P and K or as an annual disposal application of manure nitrogen. Annual applications to meet the soil fertility needs of alfalfa are typically based on the most limiting nutrient. P or K. Disposal applications are based on the N or P removal capability of alfalfa hay.
Annual applications are usually surface applied.
Soil fertility recommendations for alfalfa Alfalfa demands an aggressive phosphorus and potassium fertility program to ensure stand persistence. Maintaining soil test P and K in alfalfa hayfields also requires maintenance applications of P, K, and boron because of its high nutrient removal capabilities. On low pH soils, apply lime at least one year before planting alfalfa to allow time for it to react with the soil. Do not apply boron in the seeding year because boron can be toxic to seedling alfalfa. Alfalfa does not require nitrogen fertilizer for establishment or yields because it can fix atmospheric nitrogen through a symbiosis with microorganisms in the soil.