Evaluation of Creeping Bentgrass (Agrostis stolonifera L.) Responses Following Fertilization with Branched-Chain Amino Acids in a Field Setting.

Branched-chain amino acids (BCAA) leucine (L), isoleucine (IL), and valine (V) are synthesized in plants and are essential to growth in most organisms. Research has demonstrated that when foliarly applied, these compounds can be absorbed by the plant, however, plant catabolism of BCAA is not completely understood. Since the BCAA compounds contain nitrogen in their chemical structure, they could be potentially used as an organic nitrogen source in plants. The objective of this study was to investigate creeping bentgrass (Agrostis stolonifera L.) responses to foliarly applied BCAA in the field. Research was conducted at the Iowa State University Horticulture Research Station on ‘Penncross’ creeping bentgrass mown at 0.3175 cm and established on a United States Golf Association sand-based rootzone. Treatments included an untreated and positive control, a commercially available amino acid product known to increase shoot density, and BCAA applied in a 4:1:1, 8:1:1, and 12:1:1 ratio. All treatments were applied at an equal nitrogen rate of 3.4 kg N ha-1. For the BCAA ratios, leucine was the dominant material. Additionally, each ratio of BCAA was also tested in combination with 50% of the applied nitrogen coming from the addition of urea. Substituting half of the applied nitrogen in the form of urea for the BCAA treatments appears to help those materials more efficiently enter the plant without impacting the plant growth regulating like responses. The 4:1:1 ratio of only BCAA was found to be the most effective treatment to maintain or increase shoot density in the trial. When applied in a 4:1:1 ratio, BCAA had 24.3% and 6.25% greater shoot densities than the positive control and commercially available amino acid product, respectively. This research demonstrates the benefits that can occur when including an organic nitrogen source into a fertilizer program.