Plant Growth Analysis: Growth and Yield Component Responses to Population Density in Forage Maize

Forage maize (Zea mays L.) was grown in monocultures at population densities ranging from 4·9 to 11·1 plants m−2. Data for plant growth analysis were obtained from six harvests carried out from 21 to 115 d after planting. Conventional plant growth analysis indicated that improvements in forage productivity per unit land area by high population density resulted directly from increased plant presence. Reduction in dry weight per shoot at high population density was associated with reduced unit leaf rate. Leaf area ratio was little affected, which may imply that competition for soil nutrients or oxygen was the chief cause of plant interference. Yield component analysis demonstrated the increasing importance of population density treatments as a source of variation as growth progressed. Direct relationships between variation in yield per plant and variation in two yield components, stem diameter and the inverse of leaf area ratio, were demonstrated. Both conventional plant growth analysis and yield component analysis indicated complex physiological and morphological adjustments to species population density.