Abstract
The effect of 3 levels of nitrogen fertilization (90, 180 and 240 kgN/ha/year) on the sugar composition of the perennial ryegrass meadow and the fermentation quality of the silages made from it was investigated. The meadow was cut 3 times per year and the silage was made from each cut at each level of N application. The sugar composition of a perennial ryegrass sward (cut 9 times per year, every time when sward height reached 20 cm to simulate grazing) was also investigated. In general, the meadow contained more fructan than the simulated grazing sward. Water soluble carbohydrates (WSC) content of the meadow decreased as the rate of N application increased, mainly because of a decrease in fructan content. All the treatments, except one, gave silage of good fermentation quality. However, the meadow from the 2nd cutting at 240 kgN/ha gave poor quality silage because the WSC content was not sufficient for silage fermentation. Fermentation quality of silage was closely associated with WSC and fructan contents of materials. It is concluded that high rates of fertilizer N application (i.e., 240 kgN/ha/year) to ryegrass meadow reduced the WSC content, and especially fructan affected the silage fermentation quality of the meadow.
