Legumes (Fabaceae) are plants with the distinct ability to fix atmospheric nitrogen, the atmospheric nitrogen fixation by legumes is known as biological nitrogen fixation. Biological nitrogen fixation is the process whereby atmospheric nitrogen is reduced to ammonia in the presence of the enzyme nitrogenase. Nitrogen fixation in legumes starts with the formation of nodules. Inside the nodules, nitrogen fixation done by the bacteria (Rhizobia), and the ammonia (NH3) produced is absorbed by plant. The symbiotic relationship between a bacterium and a plant makes legumes special plants, which offer benefits when included in farming systems. These benefits are ecosystem, economic and environmental benefits. Inclusion of forage legumes in the form of intercropping in low-input grassland mixtures improves forage quantity, quality and soil fertility trough addition of nitrogen (N) from N2-fixation. Intercropping is a multiple cropping practice, which involves growing two or more crops in proximity. Legumes also improve the nutritive value of the low quality native pastures grown with them and are important component of farming system since they have high nutritive value and able to rehabilitate nutrient depleted soil. There are various factors affecting legume growth and development and these factors need to be taken into account when planning to grow legumes. These factors include pedoclimatic factors especially those associated with the soil acid complex. These factors are known as physical, chemical, biological and environmental factors. The improvement of forage quantity and quality through forage legume inclusion is crucial for improved animal performance, which is a goal of all livestock farmers. The inclusion of forage legumes in low-input grassland mixtures is vital to improve biomass production, forage quality and ultimately soil fertility. The improvement of forage quantity and quality is crucial for improved animal performance, which is a goal of every livestock farmer. Forage legumes have the potential to improve the diets of ruminants because they increase the crude protein (CP) concentration of the herbage mixture relative to that of grass monocultures.
Key words: Legumes, biological nitrogen fixation, forage quality, forage quantity.