The main source of feed of Sahelian livestock is the annual herbaceous layer of Sahelian rangeland. The annual grass has a quick growth during the rainy season. The growth stop when the grass is flowering because of the photoperiod. The study of phenology is a key factor for the understanding of herbaceous growth. The objective of our study was to evaluate the impact of management on phenology. On ungrazed rangeland in northern Senegal, we tested 22 different irrigation, cutting, and fertilization treatments repeated four times. Treatments included water regime (rainfall with and without irrigation), cutting (height and period of cutting), and fertilization (cattle manure). Each water regime was composed of treatments coupled or not with cutting or fertilization. We monitored the phenology of each treatment every ten days. The phenology was noted in three categories: vegetative stage, reproductive stage, senescence stage. At the beginning of the rainy season, before cutting, irrigation has effect on vegetative stage. During the season, this effect disappeared. Only the effect of cutting is expressed until the end of the season on the three phenological stage. This study confirms previous results that showed that phenology is mostly influenced by cutting in the Sahel region.