Yield variation of wheat and barley in Britain in relation to crop growth and soil conditions—A review

Yields of cereals in Britain vary between sites and between years, and average farm yields are less than half of the calculated potential maximum yield. Yield variation is discussed in relation to soil conditions and root growth. An analysis of yield and its components of winter wheat for several sites over several years shows that yield is strongly correlated with number of grains per ear, and number of ears per unit area. These components of yield are influenced by environmental conditions during the reproductive phase of development, particularly light interception, nitrogen absorption and plant water stress. Crop growth analysis shows that total dry matter production is strongly correlated with light absorption, which depends on seasonal variation in leaf area index. Leaf expansion in the field is mainly dependent on temperature, plant water stress, and nitrogen absorption. The environmental factors that are believed to have a strong influence on number of grains per ear, number of ears per unit area, and leaf expansion are discussed. Subjects in which further research is needed are identified. These include: effects of restrictions to root growth on absorption of nutrients and water; effects of soil temperature on leaf expansion and nutrient absorption; the nitrogen requirements of the cereal crop, including the effects of temporary deficiencies of N on the final grain yield.