This paper provides a general review of the effect of nitrogenous fertilizers on the yields of wheat, barley and oats. The results of 270 experiments carried out during the last decade in England and Wales have been examined.

With the exceptions noted below wheat and barley crops have produced a grain response of 3·0–3·5 cwt./acre to a standard dressing of 0·25 cwt. N/acre; this agrees well with earlier results obtained by Crowther & Yates. The widely grown winter wheat varieties, Hybrid 46, Cappelle Desprez, Bersée, Nord Desprez and Atle each produced an average response of more than 4·0 cwt./acre to the standard dressing. Of the spring barleys, Kenia, Proctor and Herta are also of greater than average responsiveness. The average response of spring oats to the standard dressing was only 1·2 cwt./acre.

The number of experiments is insufficient to allow precise conclusions to be drawn on the effect of autumn dressings, but the evidence suggests that in the drier eastern counties autumn nitrogen may give as good a response as the equivalent spring application. Small dressings of nitrogen provide equal responses whether applied early or late in spring; larger applications need to be applied early in spring (March or April) to obtain the highest yields. There is no evidence that divided dressings are more efficient than a single dressing applied in early spring.

For highly responsive varieties of winter wheat and spring barley mentioned above a dressing of 0·6–0·7 cwt. N/acre is recommended, producing a net return of approximately £10 per acre. For other varieties of winter wheat, and for spring wheat and spring barley, the recommended dressing of 0·5 cwt. N/acre produces a net return of about £5 per acre.