The effect of kernel number on growth, yield and quality of forage maize

The number of reproductive sinks can affect dry matter production and forage quality. Trials were conducted during two years to study the effect of kernel number per ear upon production and distribution of dry matter and forage quality in maize. Treatments were four kernel reduction levels in the first year (0%, 33%, 66% and 100%) and three in the second year (0%, 50% and 100%). Kernel number reduction was obtained by covering the ear to prevent pollination at different times during silking. In the crop without or with very few kernels total dry matter yield was 23% lower and stem biomass was 55 to 60% higher than in the control. In the first period after silking (from R1 to R3), the plants with the least kernel number had the greatest rate of stem growth. This alternative sink supported unrestricted crop growth and photosynthetic rate only during the initial stages of grain filling. Reduction in biomass yield was directly proportional to the reduction in kernel number per plant. The increase in the number of grains per ear resulted in a significant reduction in neutral detergent fiber (NDF) of the fresh material and in stem dry matter digestibility. The treatments did not significantly affect dry matter percentage, dry matter digestibility, nor total protein percentage of the forage at harvest. The low proportion of grain in the forage in the treatments with low number of grains per ear was at least partially compensated for by an increase in stem dry matter digestibility. The fermentative parameters pH and total N did not differ among treatments. Contrarily, the buffer capacity and the NH3/NT ratio were significantly higher for the treatment with no grains than for the control treatment. The similar pH values among treatments would indicate that the amount of substrate was adequate to achieve an appropriate fermentation. In treatments with no grain, and because of its high buffer capacity, a greater substrate consumption was needed to lower the pH to values similar to those obtained with the control treatment.