1. Two series of simple nitrogen manuring trials, one on level of sulphate of ammonia applied to the seedbed at twenty-two centres and the other on the time of top dressing with ‘Nitro-Chalk’ at nineteen centres, were conducted on commercial farms in south-east Scotland during 1954 to 1957.2. The optimum level of sulphate of ammonia varied with season and farm type. The optimum dressing was at least 0·9 cwt. N/acre in the dry season of 1955, and in the other years was estimated to be 0·9 cwt. N/acre on arable farms and about 0·-25–0·4 cwt. on ley rotation farms when the barley did not follow sheeped turnips. In the latter event no fertilizer was best.3. The nitrogen content of the grain increased little until after the 1 cwt. sulphate of ammonia level, although the optimum yield was not obtained in many experiments without some rise in the grain nitrogen content.
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