Physiological Responses of Creeping Bentgrass (Agrostis stolonifera L.) to a Tryptophan‐Containing Organic Byproduct

Abstract

Amino acid‐based products have been used as alternative fertilizer nitrogen (N) sources to improve turfgrass performance, especially where there is a strong reliance on synthetic N sources. However, the physiological mechanisms underlying improvements in turfgrass performance are not well documented. The objective of this research was to determine whether applications of a tryptophan‐containing organic byproduct (TRP‐B) or tryptophan (TRP) + urea improve creeping bentgrass (Agrostis stolonifera L.) performance compared with standalone applications of urea, a commonly used synthetic N source. At two separate universities, mature ‘A‐4’ creeping bentgrass plugs were transplanted into containers and allowed to re‐establish in growth chambers before being treated. Treatments included TRP‐B, urea, and TRP + urea applied every 14 d at three different N rates: 2.5, 12.25, and 24.5 kg N ha−1. At the trial's end, TRP‐B and TRP + urea increased leaf indole‐3‐acetic acid (IAA) by 227 and 255%, respectively, relative to urea at the high N rate, as measured at day 42 of the study. Applications of TRP‐B and TRP + urea also increased root biomass by 22 and 20%, respectively, when compared with urea only at the high N rate. The TRP‐B and TRP + urea treatments did not impact leaf total amino acids or photochemical efficiency when compared with urea only. Overall, results indicate that application of TRP‐B or TRP + urea at 24.5 kg N ha−1 every 2 wk may improve leaf and root IAA content, root biomass, and subsequent creeping bentgrass quality relative to applications of urea only.

Utilizing Branched-chain Amino Acids for Increasing Shoot Density and Establishment Rate in Creeping Bentgrass

“…When foliarly applied, some of these organic materials can enter the plant through leaf tissue, where they become a possible N source for plant growth (Joy and Antcliff, 1966;M€ akel€ a et al, 1996). Compared with mineral nutrition, AA-containing products have been reported to improve root growth, increase the rate of establishment, aid recovery, and enable grasses to better withstand environmental stresses (Aamlid et al, 2017;Jones and Christians, 2011;Mertz, 2015;Mertz et al, 2017;Zhang et al, 2013). Furthermore, the industry standard urea N must be converted to ammonium (NH 4 + ) before entering plant leaves and being assimilated into AA inside the plant (Hull et al, 2014); therefore, supplying AA directly may be a more efficient method of providing plants with N.…”

The horticultural potential of wastewater-grown algae fertilizers

“…Additionally, seaweed extracts, composts, and co-products of waste and food-processing industries have been tested experimentally. Successful bio-based fertilizers lead to increased soil organic matter, greater nutrient retention, and higher color quality and quantity of turf biomass (Fetter et al, 2013;Mertz et al, 2017;Zhang and Ervin, 2004). However, there is evidence that heightened ammonium concentrations and phytotoxicity following the application of bio-based fertilizers can inhibit establishment of turf, so the growth stage of plants must be considered when using these materials .…”