Abstract
Forage quality is strongly aaected by the phenological development of grassland species. is can be described by means of growing degree days (GDD), which are usually computed using air temperature at 2 m above ground. e eeects of soil water availability on forage quality are less clear. In a three-year study at two experimental sites on permanent meadows (South Tyrol, NE Italy), forage quality was estimated by means of sequential samplings for 7 weeks starting with stem elongation. Meteorological data, including air temperature at 2 m above ground, as well as soil temperature and soil moisture at 5 cm depth, were recorded daily at each experimental site. GDD between one week before stem elongation and harvest, based on air and soil temperatures, as well as several indices for soil water availability, were computed. All variables were tested for inclusion in stepwise-forward built statistical predictive models to estimate forage quality. ere were very little diierences in accuracy by using air or soil temperatures to compute GDD. e indices describing soil water availability aaected only crude protein and Net Energy for Lactation and resulted in a minor improvement of the prediction accuracy. In comparison to the progress of the phenological development, the eeect of water availability is of minor relevance.