The balance is positive if the sum of the two sources is greater than the amount removed in harvested crops, and negative if the sum is less. Nitrate pollution of water becomes more likely as the nitrogen balance becomes increasingly positive. The model activities are production, purchasing, marketing, and financial management. Crop production encompasses corn, soybeans, wheat, alfalfa, and sweet clover, each of which is produced by different methods and in different rotations. Purchasing and marketing activities include buying inputs and selling farm outputs, with all grain being sold at harvest.
Financial management includes credit, debt, and investment or loan management.
These financial activities run on an annual basis for the entire five-year planning period. The resource constraints are land, labor, and capital. Land is considered homogeneous. The number of acres remains constant because no land is purchased or sold. The constraint on labor is the amount of labor available in each month of the year.