Evaluating the Effects of Biostimulants on Soil Microorganisms in Turfgrass.

Resource use efficiency is a primary focus of research in the turf industry in order to reduce costs for turf management programs and promote sustainable turf systems. Wetting agents, plant growth regulators (PGRs), and microbial inoculants are products implemented in turf care programs to promote playability and turfgrass resiliency. The effects of these products on native microbial communities in turf are not well known. The microbiology of soil contributes important ecosystem functions that include organic matter decomposition, chemical degradation, and nutrient cycling which support healthy turf growth. Minimal research examining the microbiology of turf soils has been conducted, although interest among researchers and professionals in the turf industry is growing. A one-year study is currently underway at a golf course in Johns Creek, GA to evaluate the short-term effects of select wetting agents, PGRs, and the microbial inoculant Trichoderma atroviride on microbial abundance and function. Trials testing two wetting agents, T. atroviride, and a non-treated control (NTC) were initiated in March 2017 in a 4 × 5 randomized complete block (RCB) design in 1.6-m × 2.3-m experimental plots. Two PGRs and a NTC were applied in separate 1.5-m × 3.0-m experimental plots in May 2017 in a 3 × 5 RCB design. Soil samples were collected 4 h, 14 d, and periodically throughout the growing season after treatment applications. Microbial function was evaluated by measuring enzyme activities and soil respiration. Standard culture methods were used to preliminarily evaluate microbial abundance, and quantitative polymerase chain reaction (qPCR) analyses are currently underway to quantify total bacteria and fungi, ammonia-oxidizers, nitrogen-fixing bacteria, and arbuscular mycorrhizal fungi. The results will provide data to help turf managers make better informed decisions about best management practices.