Nitrogen requirement of cereals: 2. Multi-level nitrogen tests with spring barley in south-western England

Summary Seventeen experiments with spring barley testing seven amounts of nitrogen were made on commercial farms in Somerset, Devon and Cornwall between 1965 and 1968. Crop measurements and determinable site factors were only partially successful in accounting for differences between sites and between years in optimal N and efficiency of N use below optimum. The actual optima were found to differ considerably from predicted N requirements based on past cropping and summer rainfall.