STEP 6 Choose Your Supplemental Fertilizers
When manure is applied to just meet the crop phosphorous requirements, there will be a shortfall in the nitrogen available to the crop. It is therefore necessary to add supplemental inorganic nitrogen to make up this shortfall (PEI 1999). Enriching the manure with anhydrous ammonia, and applying it at a lower rate, will help to meet crop-nutrient requirements, while lessening the buildup of phosphorus and salts in the soil, and reducing the number of trips across the field (Sutton 1994).
Alternatively, applying manure at the nitrogen rate of about 25 tonnes/ha (11 tons/ac)(dry weight) every four to five years will usually supply enough P, K and S for the time period. Crop nitrogen demands can be met with inorganic sources, such as anhydrous ammonia applied in four out of five years (Gillund et al 1999).