The development of plant components and their effects on the composition of fresh and ensiled forage maize: 1. The accumulation of dry matter, chemical composition and nutritive value of fresh maize

Abstract

SummaryResults from two trials, in which the effects of genotype, plant density and harvest date on the accumulation of dry matter and the chemical composition and nutritive value of plant components, are presented. Inra 200, LG11, Maris Saffron, Caldera 535, Anjou 210 and White Horse Tooth were established at 5·0, 9·8 and 13·5 plants/m2in factorially designed experiments.In vitrodigestible organic matter in the dry matter, water-soluble carbohydrates, starch, total nitrogen, acid-detergent fibre, cellulose, lignin, phosphorus, magnesium, potassium, calcium, sodium, zinc, manganese and copper were analysed for the whole crop and plant components.With the exception of White Horse Tooth, stem yields declined after reaching a peak 2–3 weeks after mid-silk. This was attributed to movement of water-soluble carbohydrates from the stem to the ear, with greater movement being associated with a larger ear component. As a result thein vitrodigestible organic matter in the dry matter value of the stem component was greater for crops containing a small proportion of ear. The higher stem digestibility value compensated for the small ear component, with the result that the varying proportions of plant components did not markedly affect whole-crop digestibility prior to ensiling.The greater deposition of starch in crops with a large ear component caused a significantly more rapid rise in whole-crop D.M. content than in crops with a small ear component.Acid-detergent fibre and lignin values for the whole crop were much lower than those recorded in the U.S.A. Genotype and plant density had no effect on mineral content but phosphorus and potassium concentrations declined dramatically after frost.