Dry matter and water-soluble carbohydrate contents of Italian ryegrass at cutting as affected by environmental factors.

BACKGROUND. Italian ryegrass (Lolium multiflorum Lam.) is a high yielding crop, that is widely grown in Italy as a winter crop preceding maize for silage in the same year, and is well suited for soil conservation and prevention of groundwater pollution. This research studied the effect of weather conditions, plant maturity, ploidy, and rate of application of fertilizer N on the variation in dry-matter (DM) content, water-soluble carbohydrates (WSC), buffering capacity (BC), crude protein (CP) and nitrate content of Italian ryegrass grown in winter and spring as a double crop with maize METHODS. The research was conducted between 1991 and 1996 in the Po Valley, Italy. A data set of 160 observations was available for regression analyses. A multiple regression analysis was used to correlate the DM content, WSC, BC, CP, and nitrate content to the weather and crop variables. RESULTS. The DM content was inversely related to the nitrogen application. It was high in the very early stages of crop maturity, decreased quickly to reach a minimum around the middle period of stem elongation and then increased with increasing maturity, varying from 101 to 326 g kg-1 fresh matter. The diploid cultivars resulted to have a DM content of 22 g kg-1 FM higher than the tetraploid over the whole growth cycle. The WSC content showed a great variability, ranging from 94 to 474 g kg-1 DM. The factors that negatively affected the WSC content were higher night temperatures in the three days before harvesting, the rate of application of N fertilizer applied in spring, and the advancing stage of development. The BC was observed to have a high variability with no significant relationship to the measured climatic and plant variables. CONCLUSIONS. For ensiling purposes, it is necessary to select diploid cultivars and to take particular care of application of fertilizer as a N top dressing especially when a large amount of organic N is applied to the preceding maize crop in order to avoid herbage with too low DM and WSC contents at cutting.