Reducing the Impact of Drought with Biostimulants – Can It Be Done?
M. Berger, T. Morris, E. Nangle
OSU CFAES Wooster Campus, Wooster OH 44691
Abstract
The golf course industry is known for its high water consumption, using nearly 2.08 billion gallons daily in the continental United States. Creeping bentgrass (Agrostis stolonifera L.), a popular cool-season grass on golf courses, has a high evapotranspiration rate, necessitating sustainable water management practices. Biostimulants, which are compounds or microorganisms that enhance plant nutrition and stress tolerance, could offer a solution by reducing water usage while maintaining turf quality. Although biostimulants have demonstrated success in other sectors, they remain understudied in turfgrass systems.
This study investigates the potential of a biological or biostimulant treatment to enhance creeping bentgrass’s response to water deficit stress. The research objectives are to: (1) assess whether biological treatments improve responses to water-deficit environments, (2) evaluate the efficacy of biological treatment-based biocontrol products or similar in reducing physiological stress in turfgrass, and (3) determine the persistence of applied biological treatments in different turfgrass soil types.
By understanding turfgrass responses to water stress and exploring the role of biological treatment biostimulants, this research aims to contribute to more sustainable water management practices in golf course maintenance.
Introduction
Turfgrasses are highly valued for their environmental benefits and their role in sports fields and golf courses—industries that have become both well-managed and lucrative. However, the significant water consumption in the golf course industry raises environmental concerns. Creeping bentgrass Agrostis stolonifera, widely used in cool-season courses, demands high maintenance, including substantial water usage, due to its high evapotranspiration rate. The species produces high quality playing surfaces and can tolerate extremely low mowing heights however and these desirable traits have not been found in other turfgrass species that might have lower water use requirements. Further to this the turfgrass species Annual bluegrass Poa annua has an even greater need for irrigation due to the notoriously short root structure combined with disease susceptibility and so turfgrass managers tend to try manage towards the creeping bentgrass species where possible.
To address these concerns, exploring innovative solutions like biostimulants is essential. Biological treatments, defined as beneficial compounds or microorganisms, could help reduce water usage while maintaining turf quality. Although they have shown promise in other applications, they remain understudied in turfgrass systems.
Rationale
Biostimulants present a potential alternative for improving plant health and mitigating environmental stressors. However, their application in the turfgrass industry is complex and not yet fully understood. Determining the critical water potential of creeping bentgrass seedlings and improving methods for screening germplasm for water deficit stress are crucial steps in managing the water requirements of golf courses. Further to this field trials should also be used for comparison purposes against what might be considered industry standards or similar products that might be of use.
Research Methods
This study evaluates the effectiveness of biological treatment products in mitigating water deficit stress on ‘Pure Distinction’ creeping bentgrass at research sites in Wooster, Ohio and a mixed stand of creeping bentgrass Agrostis stolonifera / annual bluegrass Poa annua. The trials were initiated at the Ohio State University Turfgrass Research Facility in Columbus, OH, and at the Ohio State ATI in Wooster, OH. The study uses a randomized complete block design with varying rates of the biological treatment and a urea treatment applied over two summers (Figure 1). Plots were 3ft x 5ft in size and replicated four times. Treatments were applied four times prior to initiation of drought, 6/11, 6/25, 7/9, 7/23 with a fight application made post drought during recovery on August 5th 2024. Drought stress was initiated on July 15th 2024 and completed on July 29th 2024 with no water being applied and the overhead canopy blocking any rainfall from occurring during this time.
Data were collected for various indicators of turf health, including color, quality, normalized difference vegetation index (NDVI), and volumetric water content. Plots were replicated four times, as shown in Figure 1.
Figure 1: Plot plan for Columbus Biological trials
|
Treatment |
5 Cytogro – .4 Floz/M = 1.1mL/1L |
|
1 Grigg Bros Carboplex 6-4-4 – 6 Floz/M = 16mL/1L |
6 Urea .1N/M = 9g/1L |
|
2 Foliar Pak Foundation Forty 4-0-8 – 3 Floz/M = 7.9mL/1L |
7 Harrells Bio Max Root Enhancer Iron(5%) plus Fulvic Acid – 6 Floz/M = 16mL/1L |
|
3 Plant food Co Green T Impulse 6-0-0 – 9 Floz/M = 23.9mL/1L |
8 Urea .05N/M = 4.5g/1L |
|
4 Progressive Turf Greater Green 5-0-7 – 12.8 Floz/M = 34.1mL/1L |
9 Untreated |
During the trial, color ratings were taken on a 1-9 scale, with 6 indicating acceptable quality. NDVI data and images were collected weekly using an NDVI camera, focusing on stress levels (% of turf stressed) and turf quality, particularly voids and loss of density (1-9 scale, with 6 = acceptable). During the dry-down period, soil moisture readings (% volumetric water content) will be taken using Spectrum Technologies’ TDR 300. Post drought recovery was initiated through reapplication of water which begun on July
Soil samples will also be collected at various stages of application and drought stress to assess the impact of water deficit and recovery periods. The focus will be on determining the persistence of applied biological treatments within different turfgrass soil types and communities.
All data were analyzed using SAS 9.4 with means separation carried out at p=0.05.
Results:
The 2024 trial has shown once again a somewhat different set of results compared to the 2022 and 2023 data.
Color rankings were found to be significantly higher for the Griggs Bros and Harrells products compared to the Cytogro, UTC and higher rate of Urea (Figure 2)
Figure 2. Average color rankings for treatments used in biostimulant trial exposing turfgrasses to drought in Columbus OH, Summer 2024
NDVI rankings followed a somewhat similar pattern with Griggs products providing significantly higher ratings than the Untreated check, Progressive Turf Greater Green and Cytogro.
Figure 3. Average NDVI ratings for treatments used in biostimulant trial exposing turfgrasses to drought in Columbus OH, Summer 2024 
Quality ratings did not agree with the initial data however as Foliar Pak was found to provide higher quality ratings (1-9 scale) throughout the trial compared to 6 of the other treatments. Only the two rates of Urea were found to be within statistical significance to the Foliar Pak treatment (Figure 4).
Figure 4. Average quality ratings for treatments used in biostimulant trial exposing turfgrasses to drought in Columbus OH, Summer 2024
Percent stress showed a broad range of variability and while the untreated check, Progressive Turf Greater Green and Cytogro trended higher, the amount of variability limited significance being attached to any of the data. Interestingly the Griggs product did have the lowest rating but again this was not significant. (Figure 5)
Figure 5. Average percent stress on plots for treatments used in biostimulant trial exposing turfgrasses to drought in Columbus OH, Summer 2024
Volumetric Water content showed some variability but no single treatment was found to be significantly wetter than another (Figure 6) and a majority of plots by the end of the two week trial were found to be around 10-12% VWC which is extremely low on native soil based greens.
Figure 6. VWC averages two week after water was cutoff for treatments used in biostimulant trial exposing turfgrasses to drought in Columbus OH, Summer 2024