THE DATA REQUIREMENTS for an assessment of the profitability of alternative farm management systems are the technical rates of substitution of one enterprise for another, and their price ratios. In a mixed arable system it is necessary to determine relative yields of cash crops, stocking rates and stock performance, and to assess the requirements -of these enterprises for variable and fixed resources. While the basis of analysis would usually .be average yields and current or expected prices, it is often desirable to explore the effect of variation in the critical parameters.
