Biomass yield and nitrogen content of annual energy/forage crops preceded by cover crops.

•All energy/forage crops had greater biomass yield, and total N content when preceded by a legume cover crop.•Forage sorghum had the highest average biomass yield among the five energy/forage crops, with 17.8Mgha−1.•Forage pea was the most suitable cover crop to provide additional N for the subsequent crops.•Forage sorghum and sweet sorghum can be considered as the most productive energy/forage crops.