Assessing Lignin’s Role in Soil Nitrogen Dynamics and Predicting Its Content in Maize

After maize grain harvest, there remains an abundant biomass of carbon-rich stalk, leaf, and cob tissue, also known as stover, that helps sustain soil carbon and fertility as it decomposes. Stover also has considerable potential value for biofuel production and livestock feed. The value of stover is limited by its degradability, which is largely determined by lignin, a complex polyphenolic polymer that is a major component in maize stover. The impacts of lignin content (total amount of lignin) and composition (relative makeup of lignin’s constituent monomers) in maize stover on soil health, specifically nitrogen cycling, are less well understood. This research comprises two projects surrounding lignin concentration in maize stover: (1) a soil incubation experiment to assess how lignin content in maize stover impacts the nitrification process and (2) genomic prediction models for lignin content and composition in maize stover. Soil samples containing maize stover from three different genotypes of contrasting lignin content were incubated over a four week period. Weekly measurements to assess microbial activity and soil nitrogen dynamics included potential nitrification rate, inorganic nitrogen levels, and soil respiration measurement. Results support that lignin content has a statistically significant impact on soil respiration, but does not have a measurable impact on soil nitrogen cycling during the first month of decomposition. For genomic prediction, pyrolysis-molecular beam mass spectrometry was used to determine lignin content and composition in 347 maize hybrids from the Genomes to Fields population in New York. Five-fold cross-validation was then used to evaluate the performance of two models, BayesB and GBLUP. Both models were able to predict levels of lignin content with moderate accuracy, though were not able to accurately predict lignin composition. Thus, genomic prediction can be used to improve the efficiency of breeding for lignin content in maize to advance both environmental and economic sustainability.

This summer research experience has been incredible to live the life of a scientific researcher and meet brilliant students from around the country. The hands-on research project, problem solving, weekly seminars, and interactions with people in the field has been an invaluable opportunity for me to reaffirm my interests in a research career and in the crop and soil sciences field. Being relatively new to the research world, I am immensely grateful for the mentorship I received and the welcoming environment in my lab to grow both academically and personally. Through this experience, I have gained skills that will equip me to be a better scientist and that I can apply to future projects. I am excited to carry on what I have learned into my research at my home institution and beyond.