A model for dairy nutrient management was constructed to evaluate stra
tegies for nutrient recycling using farm-specific information. The mod
el used linear programming to determine optimal cropping systems that
used nutrients from dairy manure applied to cropland. The optimal syst
em minimized total feed costs, including purchased commodities, based
on the ability of crops to take up manure nutrients and supply forages
for cow rations. Nutrient uptake requirements to meet mandated regula
tions were incorporated as constraints to the linear programming model
and were for either N or P. Results from sensitivity analyses showed
that rations balanced for maximum DMI versus solutions with less than
maximum DMI affected the craps used in the optimal cropping system and
increased feed costs. The effect was greater on feed costs at low pro
duction than at high production. The value of additional acreage was l
ower with no minimum requirement on DMI. Winter was the limiting seaso
n for N and P recycling because of less uptake by crops. Feed costs we
re almost always lowered by increasing crop acreage beyond the minimum
required for N recycling.