Yield and quality components in maize grown for silage

SUMMARY Results from three trials are presented. The main variables were date of harvest, plant density and variety. Measurements were made of whole-crop yields and yields from plant fractions (leaf, stem, cob). Quality components—digestibility, acid-pepsin solubility, water-soluble carbohydrates, nitrogen and ash—were estimated for whole crop and fractions. There were successive samplings for quality components. Whole-crop yield from fractions and yield of quality components increased with density. Whole-crop yield differed significantly with harvesting date as did all fractions except cob, although the proportion of cob increased with time. The earlier harvesting date gave greater yields of quality components. There was no effect of density on the dry-matter content but later harvesting resulted in higher dry matter. The only quality component affected by density was nitrogen content but there were large effects of harvesting date on digestibility and the acid-pepsin components. Regressions were computed for quality components on dry-matter proportion of cob and the dry-matter content of the whole crop. Regressions were significant for the acid-pepsin soluble components and the water-soluble carbohydrate component on the proportion of cob. Regressions of digestibility and pepsin-soluble components (total and organic) on dry-matter content were significant. The implications of these findings to the breeding of maize varieties are discussed.