Nitrogen Influences on Yield Determination in Maize1

Abstract

The components of reproductive yield in maize (Zea mays L.) are influenced by the crop's status for C and N substrates at critical stages of development. The specific role of N was clarified by comparing plant performance under conditions that lead to differences in N and photosynthate supply per plant. This was achieved in a field experiment on a Mollic Haploxeralf with differences in initial N supply (0 and 167 kg N ha 1 added) and plant density (28 700 and 86 100 plants ha 1). Variations in grain yield came from changes in grain number per ear and grain weight. Number seemed to be controlled initially at pollination by emergence of apical silks. Weight variations arose mainly from variations in the duration of the effective grain‐filling period. The C/N uptake ratio to the ear during the initial phases of grain growth was nearly constant over treatments. Nitrogen supply seems to have affected initial spikelet weight through preanthesis events and that influenced the length of the exponential phase of grain growth. Carbon flow to the ear during the exponential phase, while highly correlated with leaf area per plant, seemed to depend more on the size of the grain sink.