Commercial Biosynthesis Amino Acids Byproducts Are a Suitable Replacement for Synthetic N Fertilizers in Corn Production.

Commercial biosynthesis of the amino acids tryptophan (TRP) and lysine (LYS) results in byproducts that are disposed of in landfills. Since these byproducts contain significant concentrations of nitrogen (N), they may have value as fertilizer N replacement in corn (Zea mays L.) production. We conducted a two-year field study where soil applied pure TRP, its biosynthesis byproduct and LYS byproduct were evaluated as replacements for synthetic N fertilizers in corn production. The experimental treatments were eight isonitrogenous N formulations applied at 196 kg N ha^-1 in a randomized complete block with four replicates. The N treatments were ammonium nitrate (AN) and ammonium sulfate (AS) as controls; different levels of pure TRP replacing NH₄-N from AN, and combinations of both TRP and LYS byproduct at different levels. In-season plant measurements (leaf area index (LAI), normalized difference vegetation index (NDVI), grain quality (grain protein and oil concentration) and total N accumulation were not affected by N treatments. Additionally, TRP and LYS biosynthesis byproducts did not influence corn grain yield, though some of the byproducts treatments had significantly greater harvest index (HI) relative to control treatments. Our results also highlight the enhancement in grain N partitioning when biosynthesis byproducts are used relative to control treatments, suggesting that N from amino acids may be influencing the physiology of N partitioning. Biosynthesis byproducts from TRP and LYS production can replace AN and AS fertilizers on an equivalent N basis to produce high corn grain yields.