(44d) Enhancing Fertility of Marginal Soils Using Lignin-Rich Hydrolysis Residues

During lignocellulosic biofuel production, cell wall sugars are converted into fuel. However, residual biomass remains following enzymatic hydrolysis that is enriched in lignin and high in organic carbon and nitrogen. This residue could be used as a cost effective and environmentally friendly soil enhancement. Soils with higher organic carbon content have shown increased water holding capacity and pH. It is also possible for the residual nitrogen to function as a fertilizer, reducing the need for other nutrient amendments. The goal of this experiment was to determine the effect of corn stover lignin residue amendments on the characteristics of maize grown in marginal soil. Onaway-Ossineke fine sandy loam was collected from the MSU Forest Biomass Innovation Center (FBIC) in Escanaba, MI. Lignin residue was generated from enzymatic hydrolysis of ammonia fiber expansion (AFEX) pretreated corn stover. Residue was mixed with soil in amounts that increased the percentage of organic carbon by 0%, 2%, 10%, or 25% and packed in triplicate soil columns. Water was added weekly to the columns to match weekly average precipitation in Houghton, MI. The filtrate was evaluated for pH, volume, and ammonium and nitrate contents. The initial and final CN content of the soil columns was evaluated to determine stability of added carbon and nitrogen. To investigate the effect of amendment addition on maize growth, soils were amended with residue in the same amounts, and added to 3.8 L pots in six replicates for each treatment. Fertilizers were mixed into the soil at amounts equal to 125 lb P₂O₅ and 200 lb K₂O/acre. Urea was also added to half the replicates to maintain a constant nitrogen loading of 230 lb N/acre. Prior to planting, corn seeds were sorted to ensure consistent mass, sterilized, and planted at 1” depth in pots in triplicate. Once 2” in height, the plants were thinned to a single plant per pot and evaluated over time for growth, ear production, and nitrogen deficiency. Initial work showed that the addition of lignin residue had no major effect on pH, which ranged from 8.3 – 8.9 for all levels of amendment, and no significant effect on water holding capacity. Final CN content of the soils was analyzed and showed a decrease in carbon and nitrogen for all soil columns over time, regardless of the level of amendment. Maize greenhouse experiments are currently underway to evaluate the potential for residue nitrogen to improve plant growth.