This work considered the effect of the nitrogen content in non-woody fiber crops on the extent of decay and selectivity of lignin degradation by the white-rot fungus Bjerkandera sp. strain BOS55. Solid-state fermentation studies were conducted with three different lignocellulosic materials including, hemp (Cannabis sativa), miscanthus (Miscanthus sinensis) and wheat straw (Triticum aestivum) as well as with the hardwood birch (Betula sp.). Fungal decay studies were also performed with hemp stemwood containing different amounts of nitrogen, including N-reduced and N-amended treatments. The results show that the extent of fungal decay was positively correlated with the N-content in the various feedstocks. Protease pretreatment combined with hot-water extraction proved effective to reduce N-levels in hemp stemwood and led to a considerable increase of the lignin degradation selectivity.