Economics of irrigating grassland in the United Kingdom

A mathematical model which simulates the response of grass to irrigation over a range of rainfall and soil conditions is described. Using the model the probable costs and benefits from investing in irrigation facilities for intensive beef and dairy production have been determined. Irrigation only appears to show a reasonable return on investment where the mean summer rainfall is less than 350 mm or the water‐retaining capacity of the soil is low. Furthermore, investment in irrigation is only likely to be logical where the rate of fertilizer N applied is greater than 300 kg N ha‐1. It also appears that a strategy of partial irrigation is unlikely to yield the maximum financial gain. Overall the indications are that for the foreseeable future only a small percentage of the total grassland area in the UK can be irrigated profitably.