This element may be reduced or not applied for a year if the soil levels are medium to high, according to a soil test. Phosphorus is expensive and lasts longer in the soil because it does not leach with rainfall. If in times of high fertilizer prices the soil test indicates that phosphorus is at the upper end of the medium range or at the high level, it can be eliminated for one-two years without significant yield reductions. If the soil test shows that soil phosphorus is low or very low, it should be applied to prevent a thinning of stands and crop failure. The potassium requirement of forage plants is almost equal to their nitrogen needs.
Potassium gives grass plants drought, disease and cold tolerance.
Poultry litter and dairy waste are viable alternatives for commercial fertilizer. Animal manure contains slow-release nitrogen along with phosphorus, potassium and other plant nutrients. Animal manure does not provide nutrients in the correct ratio for plants, so extra nitrogen and potassium will need to be applied for optimum forage growth. The increased organic matter will help improve soil structure and water and nutrient-holding capacity. The nutrient and water content of litter is quite variable.