a1 Field Drainage Experimental Unit, Ministry of Agriculture, Fisheries and Food, Anstey Hall, Trumpington, Cambridge
Crop yield results from three long-term drainage experiments are analysed and show that increases of up to 1 t/ha of winter wheat can be attributed to the effect of drainage. Mole drainage is clearly the preferred treatment on heavy clay soils. There is also a suggestion that drainage permits more efficient utilization of nitrogen.
(Received January 11 1978)