Isaac Mertz, Horticulture, Iowa State University, Ames, IA and Nick E. Christians, Iowa State University, Ames, IA
The Branched-chain amino acids (BCAA) leucine, isoleucine, and valine are synthesized in plants and are essential to growth in most organisms. Research has shown 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 be used an organic nitrogen source in plants. The objective of this study was to investigate creeping bentgrass (Agrostis stolonifera L.) responses to foliarly applied BCAA. Treatments included two ratios of BCAA, urea, and an untreated control. Creeping bentgrass plugs taken from a sand-based putting green were transplanted to pots containing a sandy growing medium. Samples were allowed to reestablish in the greenhouse for seven days before being treated. All treatments were applied on a 14-day interval, at an equal nitrogen rate of 3.4 kg N ha-1. Additionally, all samples received an application of 3.4 kg N ha-1 in the form of urea halfway through the 14-d interval following each treatment application. At trial end (42-days), plants that received applications of leucine, isoleucine, and valine in a 4:1:1 ratio exhibited a 37% and 27% increase in rooting and shoot density respectively, compared to those receiving urea only. When applied in a 2:1:1 ratio, those increases were less pronounced (18% and 13.5% increase in rooting and shoot density respectively, compared to urea only). These results suggest that the BCAA could be a suitable organic nitrogen source for use on creeping bentgrass.