Evaluation of lignin and lignin‐nitrogen fractionation following alternative detergent fiber pre‐treatment methods

Abstract

Decomposition of plant material, compost, or mulch may be monitored or predicted by measuring certain key parameters in live or senescent material. Lignin is one of the key parameters to measure as it provides an indication of soil quality. This study evaluates the most promising detergent clean‐up procedures for pre‐treating plant material to provide a more rapid method for lignin determination. Performance was tested with a variety of plant material, typical of vegetation analyzed in decomposition, nutrient cycling and natural ecosystem studies. Lignin‐nitrogen (N) and fiber‐N residues were also determined to assess the efficiency of the clean‐up processes. Good agreement was obtained for lignin on a range of plant material between the time‐consuming classical Klasson method and either modified neutral detergent fiber (NDF) excluding sodium sulphite and Dekalin, or the acidified detergent fiber (ADF) pre‐treatments. We recommend either of the detergent pre‐treatment procedure as they provide rapid and effective preliminary steps for precise lignin determination. Residual lignin‐N following NDF and ADF detergent pre‐treatment methods were on average respectively 31% and 24% of the plant nitrogen.