A MODEL FOR INVESTMENT APPRAISAL OF GRASSLAND DRAINAGE SCHEMES ON FARMS IN THE UK

This paper describes a model constructed for investment appraisal of grassland drainage schemes on farms in the U.K. The basis of the model is an empirical relationship which simulates grass production before and after drainage. Grass growth is estimated assuming a theoretical maximum growth rate, which is modified daily for non-optimal conditions of temperature, radiation, nitrogen fertiliser, weight of crop and water balance. The difference in the amount of herbage which can be utilized before and after drainage is valued. Historical weather data for a given site are used to estimate the future annual benefits for the site. An analysis of the future discounted costs and benefits is calculated. © 1990.