Simulation of dairy manure management and cropping systems

The dairy forage system model (DAFOSYM) was expanded to include submodels for the prediction of suitable days under a range of soil and crop residue conditions, draft of a wide range of tillage and seeding implements, and scheduling of manure handling, tillage and planting operations. Through simulation, the long-term performance, costs and net return for three tillage and four manure handling systems were compared on 150 and 400-cow representative dairy farms in Michigan. The analysis included all factors of milk production including manure production, storage and application, tillage, planting, crop growth, harvest, feed storage, and feeding. Mulch-tillage was the most economical tillage system, returning $15 to $26/cow-yr over conventional tillage with a 30% reduction in machinery, fuel, and labor costs. The highest net return among manure handling systems was associated with short-term storage and daily hauling, but the economic advantage of this system diminished if credit was not given for the value of all manure nutrients when spread daily. Long-term manure storage concentrated labor for spreading in the spring and fall. This delayed tillage and planting and increased feed costs as much as $24/cow-yr when manure hauling, tillage, and planting occurred in series. When labor and machinery were available for parallel field operations, manure handling method had little effect on the timeliness of tillage and planting.