Abstract
Golf course superintendents are often under pressure to maintain high-quality turf. Such demand entails use of inputs, which can include biostimulants that are often marketed as a way of combating plant stress and improving turf quality. However, the extent of their use by superintendents and their level of efficacy are not well understood. This survey study was designed to better describe biostimulant use by the golf industry and to gain insights on the research needs of superintendents to address them effectively. A survey instrument was developed using online software and included a total of 13 questions relating to general familiarity with biostimulants and specific familiarity with five biological products. The instrument was disseminated electronically via the online survey tool to attendees (N = 80) during the annual conference of the Georgia Golf Environmental Summit in 2022. The respondents were from 62 golf courses, geographically representing the entire state of Georgia. The response rate was 62.5%. The majority of the respondents (86%) were familiar with biostimulants. The main reason for using biostimulants was predominantly agronomic, indicating a focus on turf performance and aesthetics. Of the respondents who used biostimulants, the overwhelming majority (93%) use humic acids and plant growth hormone-containing biostimulants. Respondents also indicated that research in microbial products would be the most relevant to the industry. This may be explained by the challenges in using such products (shelf life and microbial survival in soil). In conclusion, the survey indicated that Georgia golf course superintendents have high a level of familiarity with biostimulants. The survey yielded useful results to help formulate future research objectives to better serve the Georgia golf course industry.
Golf course superintendents are often under pres4ure to maintain high-quality turf under climatic, pest, and use-induced stresses (Rossi, 2006). Such demand entails the use of water and chemical inputs such as fertilizer, pesticides, wetting agents, and growth regulators (Christians et al., 2017). Maintaining optimal quality during the recent public health crisis and economic recession was estimated at $56/acre per month (mowing and fertilizing golf putting greens), and annual irrigation cost ranged from $276 to $3672 per acre (Soldat et al., 2020). Golf courses spend an average of $15,000/year on fungicides in Georgia (Kane and Wolfe, 2012). As a result, the golf course industry is one of the most expensive sectors of agriculture. In addition to cost concerns, improper use of chemical inputs could cause environmental problems associated with leaching and runoff losses of nutrients and pesticides (Stier et al., 2013). Superintendents understand the need to be proactive in reducing chemical input to help reduce cost and minimize environmental impacts. In response to their effort to find alternative products such as nonsynthetic fertilizers to achieve these goals, they are often marketed with various types of products. Biostimulants are one collection of such products.
According to du Jardin’s (2015) definition, a biostimulant is “any microorganism or substance applied to plants with the aim of enhancing nutrient efficiency, stress tolerance and/or crop quality traits, regardless of its nutrient content.” Biostimulants are often described as having ingredients such as enzymes, plant growth hormones, chemical activators, chelators, antioxidants, and vitamins that can bring about the benefits mentioned above (du Jardin, 2015). However, there is limited evidence regarding their efficiency in a golf course setting. Existing studies in other systems offer conflicting accounts of their effectiveness. In a meta-analysis of 28 field studies, Edmeades (2002) concludes that the products were not effective on a wide range of crops that included root crops, legumes, pastures, and vegetables. In contrast, Van Dyke (2008) and Zhang and Ervin (2004) reported increased root depth and plant biomass with the use of products containing humic acid and seaweed extracts in field and laboratory studies, respectively. More recent reviews of studies (e.g., Halpern et al., 2015; Yakhin et al., 2017) further highlighted the inconsistency of their impacts on plant growth and yield. This is compounded by the lack of requirement for third-party testing and verification of biostimulants, unlike products such as fertilizers and fungicides (Wang et al., 2017). In their review article, Stingl et al. (2022) contended that “the limited knowledge on microbiomes of golf turf ecosystems” and “the lack of holistic studies addressing the structure and function of golf turf microbiomes, including their responses to intense turf management procedures, is currently the main bottleneck for development and improvement of reliable, well-functioning microbial products.”
Superintendents often reach out to extension experts seeking guidance on the use of biostimulants. There is a need for clarity on the myriad biological products on the market. The ambiguity is often filled with anecdotal evidence and exaggerated claims that are confusing to practitioners. Although there were more than 1000 scientific articles on “plant biostimulants” from 2010 to 2020 (Rouphael and Colla, 2020), and the market for biostimulants was estimated at $3.2 billion in 2021 and expected to exceed $4 billion by 2025 (Madende and Hayes, 2020), there is a lack of studies on the use of biostimulants by the turf industry. To the best of our knowledge, the only survey on the use of biostimulants was conducted by Golfdom (a golf magazine) in 2004 (Andorka, 2004). Forty-nine percent of the 118 respondents indicated that they used biostimulants as part of their maintenance programs, and only 7% used them frequently as a supplement during times of severe turf stress (Andorka, 2004). The only other survey on the use of biostimulants is by Kirksey (2021), who surveyed blueberry (Vaccinium sp.) farmers in Georgia and found that 27% of the farmers reported currently using plant biostimulants in their production.
This survey study was therefore designed to better understand the use of different biostimulants by the Georgia golf course industry and also to gain insights on the research needs of superintendents to address them effectively.
Materials and methods
The survey instrument was developed via online polling software (Poll Everywhere, Inc., San Francisco, CA) and included 13 questions relating to general familiarity with biostimulants, and specific familiarity with five biological products (Table 1). Each question was framed as follows: “Have you used biostimulants that contain …?” The follow-up question contained three to five commonly used commercial products as well as a write-in option. Multiple answers were allowed. Because of the abundance of commercial products, they were grouped into four categories based on their ingredients (Halpern et al., 2015). The categories were products containing the following 1) microbial inoculants, 2) humic substances, 3) plant growth hormones, and 4) amino acids. No demographic questions were included.
Questionnaire instrument used to assess knowledge and familiarity of golf course superintendents during the Georgia Golf Environmental Summit in Feb. 2022. The survey was administered via online polling software.
The survey was brief for two main reasons: to ensure a high response rate within a short 10-min time frame and to supply researchers with the necessary information regarding specific product use on Georgia golf courses. The survey was evaluated by the University of Georgia Office of Human Subjects (STUDY 00005271) and assigned a determination of Not Human Research. The survey was developed in consultation with a golf course superintendent and extension specialists to ensure the clarity of questions.
The instrument was disseminated electronically via an online polling instrument to all attendees (N = 80) of the Georgia Golf Environmental Summit held at the University of Georgia–Griffin Campus (Griffin, GA) in Feb. 2022. The resulting nonrandom convenience sample (a nonprobability sample that is easy to reach, such as a defined set of conference registrants) was composed of people who responded to the survey link (provided via a QR code projected on screen). From the conference attendee list, we surmised that respondents were from 62 golf courses, geographically representing the entire state. Descriptive statistics were used to report survey results.
Results
Of the 62 golf courses represented at the conference, 81% were semiprivate or managed by municipalities, 16% were private, and 3% were operated by public institutions. Fifty of the 80 recipients responded to the survey, for a response rate of 62.5%. The majority (86%) of the respondents were familiar with biostimulants, and 82% of respondents reported using biostimulants on their golf course (Table 2). The reasons for using these products were predominantly agronomic (Fig. 1). Of the biostimulants used by respondents, 71% contained microorganisms, 93% contained humic acids, 88% contained amino acids, 93% contained seaweed extracts (or plant growth–promoting hormones from other sources); only 15% contained biochar (Table 3). Percentage of use was calculated based on 41 respondents who have used biostimulants as indicated in Table 2.
Georgia (USA) golf superintendents’ reasons for using biostimulants (N = 50). The highest percentage chose agronomic reasons, followed by environmental and economic. The survey was conducted in 2022 and responses were collected via online polling software.
Citation: HortTechnology 32, 4; 10.21273/HORTTECH05059-22
Georgia (USA) golf superintendents’ reasons for using biostimulants (N = 50). The highest percentage chose agronomic reasons, followed by environmental and economic. The survey was conducted in 2022 and responses were collected via online polling software.
Citation: HortTechnology 32, 4; 10.21273/HORTTECH05059-22
Georgia (USA) golf superintendents’ reasons for using biostimulants (N = 50). The highest percentage chose agronomic reasons, followed by environmental and economic. The survey was conducted in 2022 and responses were collected via online polling software.
Citation: HortTechnology 32, 4; 10.21273/HORTTECH05059-22
Survey responses of Georgia golf superintendents in regard to their familiarity and use of biostimulants (N = 50). Numbers represent people who answered either in the affirmative (“yes”) or the negative (“no”). The survey was conducted in 2022.
Survey responses of Georgia golf superintendents in regard to their use of different types of biostimulants depending on their composition (N = 50). Numbers represent people who answered either in the affirmative (“yes”) or the negative (“no”). The survey was conducted in 2022.
When queried about specific product use, out of the preset (options) products containing plant growth–promoting microbes, 24% of the respondents chose MycoApply (Valent BioSciences, Libertyville, IL) and Companion (Growth Products, Ltd., White Plains, NY), and 14% of the respondents selected KaPre RemeD8 (LidoChem Inc., Hazlet, NJ) (Table 4). Percentages were calculated based on a total of 29 respondents who used products containing plant growth–promoting microbes (Table 3). Eight other products were indicated in the write-in answers.
Survey responses of Georgia golf superintendents with respect to their use of biostimulants that contain plant growth promoting microbes (N = 50). The survey was conducted in 2022.
When asked about specific product use, out of the preset products containing humic acids, 37% of the respondents chose each TurfRx C-85 (Aquatrols, Paulsboro, NJ) and Maxiplex (Floratine Products Group Inc., Collierville, TN), and 18% selected Humacarb (Advancing Eco Agriculture, Middlefield, OH) (Table 5). Percentages were calculated based on a total of 38 respondents who used products containing humic substances (Table 3). Eleven other products were indicated in the write-in answers.
Survey responses of Georgia golf superintendents with respect to their use of biostimulants that contain humic substances (N = 50). The survey was conducted in 2022.
When asked about specific product use, out of the preset products containing amino acids, 25% of the respondents chose Pennamin (LidoChem Inc.), 33% of the respondents chose Essential (Growth Products, Ltd.), and 47% selected Muscle (Monarch Scientific, Alpharetta, GA) (Table 6). Percentages were calculated based on a total of 36 respondents who used products containing amino acids (Table 3). Four distinct products were indicated in the write-in answers (one product is listed twice).
Survey responses of Georgia golf superintendents in regard to their use of biostimulants that contain amin oacids (N = 50). The survey was conducted in 2022.
When queried about specific product use, out of the preset products containing seaweed extracts or plant growth hormones from other sources, 55% of the respondents chose Agra Rouse (LidoChem Inc.), 16% chose Essential, and 19% of the respondents selected AlgaeGreen (C&B AgriEnterprises Ltd., Donegal, Ireland), and only 5% selected SeaBlend (Ocean Organics, Ann Harbor, MI) (Table 7). Percentages were calculated based on 38 respondents who used products containing seaweed extracts (Table 3). No one chose Acadian (Acadian Seaplants Ltd., Dartmouth, Canada), and no other products were indicated in the write-in answers.
Survey responses of Georgia golf superintendents with respect to their use of biostimulants that contain seaweed extracts or plant growth hormones (N = 50). The survey was conducted in 2022.
Respondents indicated that research in microbial products was the most relevant to the industry, followed by amino acid containing products, and products containing seaweed extract (ranked second and third, respectively; Table 8). Biochar was given the lowest priority.
Georgia golf superintendents answers to the survey question: “What type of university research is most relevant to the industry (rank the five options)?” (N = 50) The survey was conducted in 2022.
Discussion
The high response rate and the fact that respondents were from a variety of golf courses provide confidence that the sample is representative of the population of Georgia superintendents and reflect a range of socioeconomic conditions. The survey results indicated that most golf course superintendents are familiar with biostimulants, and a high proportion incorporate biostimulants in their cultural practices. Superintendents use the products mainly for agronomic reasons, rather than financial or environmental reasons. This level of familiarity and use of biostimulants is not evident in other agricultural sectors. For example, in a study that surveyed blueberry growers in Georgia, Kirksey (2021) reported that growers are often not sure what biostimulants are and are reluctant to use them. Turf on golf courses, especially on the putting greens, is intensely managed because the turf quality directly affects the game and customer satisfaction (Cavas-García et al., 2021). This may explain the main reason for using biostimulants because the turf quality (and the related exacting specifications) is of paramount importance (The Turgrass Group, Inc., 2022). Additionally, the challenge in maintaining turfgrass health is rooted in the intensity of use (e.g., wear, play, traffic, divoting), and it this sets turfgrass apart from other plants. The need for aesthetics, peak plant health, and financial viability of golf courses may explain why superintendents use biostimulants more often than growers and farmers in other agricultural sectors. Growers of ornamental plants (i.e., floriculture and nursery) face similar pressures to produce an aesthetically pleasing plant product; it would be informative to survey those sectors for their use of biostimulants.
The superintendents also indicated that they mainly used humic- and amino acid–containing products. Although not asked “why,” it could be indicative of several factors: 1) these products are promising in improving turf performance compared with others (De Luca et al., 2020; Zhang and Ervin, 2004; Zhang et al., 2003); 2) these products are often easy to store and use for extended periods of time [unlike microbecontaining products that might need special storage conditions or have short shelf lives (Kamnisky et al., 2019)], and/or 3) the products reported as most commonly used could simply be related to better marketing of these products to superintendents. As more biostimulant research has been performed on cool-season turf, could this explain or affect biostimulant use by superintendents managing warm-season turf?
The stated factors warrant future investigation. Some products appear under more than one category; e.g., TurfRx C-85 and Muscle were write-ins in the question asking about plant growth–promoting microbes (Table 4). This may be explained by the fact that many biostimulant products contain more than one type of substance. Muscle contains amino acids as well as growth-promoting microbes. However, it is possible that the respondents were unsure how best to answer the question and listed the products in two places.
On the basis of these results and our conversations with some superintendents, they do not use biochar as much as other biological products, which may be because they are not as familiar with it (M. Hoban, personal communication). Biochar has been shown to be generally effective in boosting yield in a wide variety of agricultural systems (Tenic et al., 2020), but studies in turf are scant. Biochar did not affect tall fescue establishment rates compared with controls in both field and greenhouse studies (Montgomery, 2018). However when water stressed, turf grown in biochar amended soils were able to maintain higher visual quality with reduced supplemental irrigation (Montgomery, 2018). In the current survey, we did not probe the reasons for biochar’s low use; however, with more research and focused outreach (Harris et al., 2020), biochar may become more acceptable.
The respondents indicated a desire to see more academic research on microbe-containing products compared with the other four categories of biological products. This survey did not probe the reasons behind their views. However, their desire to see more research on microbe-containing products might reflect the challenges of working with such products. The success of of this category of products is largely dependent on storage conditions and a good understanding of the soil environment to which they are applied (Stingl et al., 2022). Lack of such understanding leads to poor survival of the microorganisms in soil. This is often compounded by lack of clear protocols on the storage and application conditions on most product labels (Wang et al., 2017). Some studies have questioned the adequacy of the application rates to supply enough microorganisms to cause any noticeable changes (Zuberer, 2012). There is also a lack of information on the survival of the microbial inoculants in soil where they face competition and antagonism from soil microbial communities. With some exceptions (e.g., symbiotic nitrogen fixers) most microbial inoculants are not well studied and lack the necessary information that is needed to use them effectively with most plants under specific conditions (Abbott et al., 2018).
In conclusion, this survey indicates that Georgia golf course superintendents have a high level of familiarity with biostimulants and have used them in turf management. They mainly use these products for agronomic reasons to improve turf quality and to maintain the high aesthetic value of golf courses. The survey yielded results to help us formulate future research objectives. In particular, efforts should be focused on conducting research on microbe and amino acid–containing products and how they affect turf quality and soil health. By doing so, data-driven information will become available to turfgrass managers to help them make informed decisions on the use of such products in a way that will not only achieve their main goal (agronomic; improved turf quality) but also improve the long-term sustainability of the system (soil health).
Units
Literature cited
Abbott, L.K., Macdonald, L.M., Wong, M.T.F., Webb, M.J., Jenkins, S.N. & Farrell, M. 2018 Potential roles of biological amendments for profitable grain production—A review Agric. Ecosyst. Environ. 256 15 34 50 https://doi.org/10.1016/j.agee.2017.12.021
Andorka, F.H. 2004 Bridging the biostimulant gap Golfdom 60 6 72 74
Cavas-García, F., Martínez-Moreno, A., López-Gullón, J.M. & Díaz-Suárez, A. 2021 A golf course quality scale (GCQS): Validity and reliability resting on Spanish golf courses Int. J. Environ. Res. Public Health 18 24 13301 https://doi.org/10.3390/ijerph182413301
Christians, N.E., Patton, A.J. & Law, Q.D. 2017 Fundamentals of turfgrass management 5th ed Wiley Hoboken, NJ
du Jardin, P. 2015 Plant biostimulants: Definition, concept, main categories and regulation Scientia Hort. 196 11 3 14 https://doi.org/10.1016/j.scienta.2015.09.021
De Luca, V., de Barreda, D.G., Lidón, A. & Lull, C. 2020 Effect of nitrogen-fixing microorganisms and amino acid-based biostimulants on perennial ryegrass HortTechnology 30 2 280 291 https://doi.org/10.21273/HORTTECH04236-19
Edmeades, D.C. 2002 The effects of liquid fertilisers derived from natural products on crop, pasture and animal production: A review Aust. J. Agric. Res. 53 8 965 976 https://doi.org/10.1071/AR01176
Halpern, M., Bar-Tal, A., Ofek, M., Minz, D., Muller, T. & Yermiyahu, U. 2015 The use of biostimulants for enhancing nutrient uptake Adv. Agron. 130 141 174 https://doi.org/10.1016/bs.agron.2014.10.001
Harris, B.A., Florkowski, W.J. & Pennisi, S.V. 2020 Horticulture industry adoption of biodegradable containers HortTechnology 30 3 372 384 https://doi.org/10.21273/HORTTECH04563-19
Kane, S.P. & Wolfe, K.L. 2012 Economic contribution of turfgrass production, ornamental horticulture, landscape services and related industry in the Georgia economy, 2010 Univ. Georgia, Ctr. Agribusiness Econ. Dev., Ctr. Rep. CR-12-05. 19 May 2022. http://economic-impact-of-ag.com/GA/2012GA_Economic_Contribution_of_Turfgrass_Production_Ornamental_Horticulture_Landscape_Service_and_Related_Industry_in_the_Georgia_Economy_2010-1b9gazr.pdf
Kaminsky, L.M., Trexler, R.V., Malik, R.J., Hockett, K.L. & Bell, T.H. 2019 The inherent conflicts in developing soil microbial inoculants Trends Biotechnol. 37 2 140 151 https://doi.org/10.1016/j.tibtech.2018.11.011
Kirksey, J. 2021 Understanding grower perceptions of plant biostimulants in Georgia blueberry production MSc Thesis, Univ. Georgia, Athens, GA, 19 May 2022. https://esploro.libs.uga.edu/esploro/outputs/graduate/Understanding-Grower-Perceptions-of-Plant-Biostimulants/9949390461702959
Madende, M. & Hayes, M. 2020 Fish by-product use as abiostimulants: An overview of the current state of the art, including relevant legislation and regulations within the EU and USA Molecules 25 5 1122
Montgomery, J.F. 2018 The impacts of biochar on turfgrass health and drought tolerance PhD Diss., Univ. California, Riverside, CA, 19 May 2022. https://escholarship.org/uc/item/5j82b7xw
Rossi, F. 2006 Effects of microbial and organic products on putting green performance Golf Course Manage. 74 9 101 105
Rouphael, Y. & Colla, G. 2020 Toward a sustainable agriculture through plant biostimulants: From experimental data to practical applications Agronomy (Basel) 10 10 1461 https://doi.org/10.3390/agronomy10101461
Soldat, D.J., Brosnan, J.T., Chandra, A., Gaussoin, R.E., Kowalewski, A., Leinauer, B., Rossi, F., Stier, J.C. & Unruh, J.B. 2020 Estimating economic minimums of mowing, fertilizing, and irrigating turfgrass Agric. Environ. Lett. 5 1 1 6 https://doi.org/10.1002/ael2.20032
Stier, J.C., Steinke, K., Ervin, E., Higginson, F.R. & MacMaugh, P. 2013 Turfgrass benefits and issues 105 145 Stier, J.C., Horgan, B. & Bonos, S. Turfgrass: Biology, use and management. Am. Soc. Agron., Crop Sci. Soc. Am., Soil Sci. Soc. Am. Madison, WI
Stingl, U., Choi, C.J., Dhillon, B. & Schiavon, M. 2022 The lack of knowledge on the microbiome of golf turfgrasses impedes the development of successful microbial products Agronomy (Basel) 12 1 71 https://doi.org/10.3390/agronomy12010071
Tenic, E., Ghogare, R. & Dhingra, A. 2020 Biochar—A panacea for agriculture or just carbon? Horticulturae 6 3 37 https://doi.org/10.3390/horticulturae6030037
The Turfgrass Group. Inc. 2022 Why Zeon zoysiagrass is the best turf for golf course fairways—and your home 27 May 2022. https://theturfgrassgroup.com/zeon-zoysia/why-zeon-zoysiagrass-is-the-best-turf-for-golf-course-fairways-and-your-home/
Van Dyke, A. 2008 Do humic substances influence moisture retention and phosphorous uptake in putting greens? MSc Thesis, Utah State Univ., Logan, UT, 19 May 2022. https://archive.lib.msu.edu/tic/thesdiss/vandyke2008a.pdf
Wang, Z., Laudick, J. & Kleinhenz, M. 2017 Microbe-containing crop biostimulants in grower toolboxes Tilth Prod. Quart. 27 2 9 11
Yakhin, O.I., Lubyanov, A.A., Yakhin, I.A. & Brown, P.H. 2017 Biostimulants in plant science: A global perspective Front. Plant Sci. 7 1 23 https://doi.org/10.3389/fpls.2016.02049
Zhang, X. & Ervin, E.H. 2004 Cytokinins-containing seaweed and humic acid extracts associated with creeping bentgrass leaf cytokinins and drought resistance Crop Sci. 44 5 1737 1745 https://doi.org/10.2135/cropsci2004.1737
Zhang, X., Ervin, E.H. & Schimdt, R.E. 2003 Physiological effects of liquid applications of a seaweed extract and a humic acid on creeping bentgrass J. Amer. Soc. Hort. Sci. 128 4 492 496 https://doi.org/10.21273/JASHS.128.4.0492
Zuberer, D. 2012 Soil microbes: Some practical aspects for turfgrass systems. USGA Green Sec Rec. 50 1 5
