Characteristics and Nitrogen Value of Stratified Bedded Pack Dairy Manure

"Compost" dairy barns are relatively new, and this manure, which we refer to as stratified bedded pack (SBP) dairy manure, has neither been characterized in detail nor defined in terms of its N supply. We measured physical characteristics, nutrient concentration, N mineralization, and N supply to corn (Zea mays L.) of SBP dairy manure from eight Minnesota farms. Concentrations of N, P, and K were generally higher than standard "book values" for solid dairy manure, were lower for P and K than typical solid dairy composts, and were highly variable within and among buildings. Average bulk density of SBP dairy manure was 58.2 lb/ft³. All SBP dairy manures produced nitrate during a 4-month-long incubation in soil, but the four with highest C:N ratios (19 to 21) immobilized N for 30 to 60 days. Infield fertilizer N equivalents to corn ranged from 1.4 to 12.1 lb/ton for quickly incorporated manure, but only -0.3 to 5.3 lb/ton when incorporation was delayed until spring. Guidelines for solid dairy manure were not reliable for predicting N availability from SBP dairy manure. Until validated prediction equations are available, we recommend farmers apply moderate rates of SBP dairy manure, incorporate it immediately to improve N supply, apply a basal rate of fertilizer N near planting time, and sidedress fertilizer N based on recommended soil or plant analysis for their region.