Physiology of forage maize (Zea mays L.) in relation to its production and quality

This thesis describes and discusses the quantitative effects of changes in temperature, light intensity and photoperiod on the development, dry-matter production, dry-matter distribution, digestibility and dry-matter content of forage maize. Cultivation techniques and hybrid choice are also discussed. The productivity of maize in North-West Europe mainly depends on the rate of development during early seedling growth. Yet, development, productivity, maturation and digestibility are also strongly affected by climatic conditions during later stages of growth. Moreover, significant aftereffects of adverse conditions are often found. Some steps in the plant's development are especially sensitive, e.g. tassel initiation, silking and grain set.<p/>Digestibility was found to be less variable than yield and dry-matter content. Climatic factors affected digestibility mainly through their effects on the proportion of (less digestible) structural material in the organic matter. Only prolonged high temperatures can induce large depressions in final cellwall digestibility. Since the production of cell-wall components does not develop over time in the same way as the production of cell solubles, digestibility is not always affected in the same direction as yield. Differences between hybrids were predominantly caused by differences in cell-wall digestibility. Therefore selection for improved digestibility should be possible without affecting earliness or yield. The suitability of the Dutch climate for growing forage maize is evaluated. Furthermore, the ideal weather and the ideal genotype for North-West Europe are described.