Wheat as a dual crop for biorefining: Straw quality parameters and their interactions with nitrogen supply in modern elite cultivars. Issue 2 (21st October 2018) - Jørgensen, Henning
Abstract: Agricultural residues, such as straw, offer an opportunity to produce biofuels and chemicals in biorefineries without compromising food production. The ideal "dual‐purpose cultivar" would have high yield of grain and straw. In addition, the straw should be easy to process in a biorefinery: It should have good degradability, high concentration of carbohydrates, and low concentration of ash. Nitrogen (N) is an essential nutrient important for plant growth, crop yield and grain quality. However, N production and application comes with a high cost and high environmental footprint. The N application should consequently be based on an economical optimum. Limited knowledge exists on how N application affects the potential of straw for biorefining, for example, straw yield and quality. This study, conducted over three cropping seasons, investigated the effect of N supply on the biorefining potential and included 14 wheat cultivars and one triticale cultivar. The N supply directly affected the yield of straw and grain. In addition, the protein concentration in grain and straw increased, but the composition of the straw with respect to carbohydrates and lignin was largely unaffected by N supply. The only significant change was a lower silicon concentration at increasing N application rate, which could be beneficial for lignin valorization in biorefineries. Likely due to the negligible changes in cell wall composition, the effect of N application rate on straw degradability was not significant. N application should therefore primarily be optimized with respect to grain quality and overall yield of grain and straw. Differences between cultivars were also minor with respect to their performance in a biorefinery process. From a breeding and agronomic perspective, focus should therefore be put on maximizing the biomass output from the field, that is, selecting the cultivar with highest grain and straw yield and optimizing the application of fertilizer to get optimum N use efficiency. Abstract : Significant differences in straw yield (up to 30%) were revealed among 14 wheat cultivars, but in particular a triticale cultivar had superior straw yield (50%–70% higher). The composition of wheat straw and its degradability for sugar production were largely unaffected by nitrogen supply and did not differ among the cultivars. Nitrogen application should primarily be optimized with respect to increasing the overall yield of biomass. Selection/breeding for increased biomass yield rather than composition is the most promising route in order to supply biomass for the growing biorefinery industry.