Can Nitrogen Fertilization and Intercropping Modify the Quality and Nutrient Yield of Barley–Field Bean Forage?

Abstract

Barley (Hordeum vulgare L.) and field bean (Vicia faba L. var minor) are often used for forage production in the Mediterranean environment. Their bromatological and productive characteristics are known when cultivated as sole crops, but if grown simultaneously in intercropping, the changes in their morphological and physiological characteristics could affect the quality and the nutrient yield of the resulting forages. In a two-year field research in Central Italy, we determined the bromatological traits and nutrient yields of barley and field bean, grown as sole crops or intercrops in a 1:1 additive design harvested at the heading and early dough stage with five nitrogen (N) rates (i.e., from 0 to 200 kg ha−1). Both intercropping and N fertilization increased the concentration of crude protein and fiber but decreased the general quality of the forage. However, the effects on nutrient yields were more marked; those of crude protein and total digestible nutrients increased by 46 and 29% with intercropping and by 49 and 46% with 150 kg N ha−1. Thus, we concluded that N fertilization should not exceed 50 kg ha−1 to maximize the relative feed value, while 150 kg ha−1 are suitable to boost nutrient yields.