Mixing grasses with legumes for forage production has been a common cropping system, especially in the Mediterranean countries. However, the nutritive value of the end product is greatly dependent on adopting the suitable cultural practices to achieve maximum benefit from the forage mixture, especially the nitrogen (N) fertilizer level and the mixing rate. Thus, the current study was carried out on the winter season of 2012 and 2013 in the experimental station of the Faculty of Agriculture, Alexandria University, Egypt. The main aim was to investigate the variations in 1st cut dry matter (DM) content and nutritive value of Egyptian clover (EC) and annual ryegrass (RG) grown in pure stands and with three mixing rates, under three N fertilization levels (72, 107, and 143 kg N ha-1). Nutritive value was judged upon investigating the crude protein (CP), carbohydrate content, and fiber fractions [neutral detergent fiber (NDF), acid detergent fiber (ADF) and acid detergent lignin (ADL)]. Results revealed significant variations among the five forage treatments for all the tested parameters (P < 0.001). In addition, significant variations among the three N-levels (P < 0.05) and significant two-way interaction among forage treatment and N-level (P < 0.01) were declared only in case of 1st cut CP content. In general, pure RG was superior in DM (155.08 g kg-1), carbohydrate (273.00 g kg-1), NDF (505.74 g kg-1), and ADF (279.60 g kg-1) contents. While, pure EC produced the highest-significant CP (155.52 g kg-1) and ADL (23.86 g kg-1) contents. Increasing the applied N-fertilizer level significantly increased the CP content of the sole EC (156.63 g kg-1) and the mixture of 70% EC + 30% RG (132.70 g kg-1). Grass-legume mixtures produced fodder of more balanced nutritive value when compared to the pure stands.
Key words: Forage mixture, Egyptian clover, annual ryegrass, nitrogen fertilization, fodder quality.