The effects of plant biostimulants on cool-season turfgrass seedlings

Humic substances and complex organic materials are shown to have a positive effect on turfgrass performance.


Ryegrass treated with Baccarat
Figure 1. Ryegrass treated with Baccarat had greater fresh and dry mass than the control. Photos by Alejandra Acuña

A plant biostimulant is a natural substance or microorganism applied to plants or soil to enhance growth and stress tolerance. These complexes, including different types of elements, have different types of effects; therefore, the specific modes of action through which they perform are mostly unknown.

Considering that the worldwide market of plant biostimulants was valued at $3.68 billion in 2022 and that the amount, commercial availability and use of these products is increasing globally, it is necessary to generate more technical information regarding their effect on the most important turfgrass species used around the world.

For this study, we were interested in determining if plant biostimulants could be used to increase seedling leaf and root production during establishment. Previous field studies with biostimulants in frequently cut turfgrass (data not published) in Ohio did not show differences between products. Therefore, a controlled environment study was conducted to eliminate the variability often encountered in field studies. The objective of this study was to determine the effect of six commercial plant biostimulants on root and leaf growth in germinating seedlings of three cool-season turf species grown in a controlled environment.

Figure 2
Figure 2. Turfgrass dry mass (g) by three species: Lolium perenne “‘Premier,” Agrostis palustris “Pencross” and Schenodorus arundinaceus “Escalade” using six biostimulant products. Weights followed by the same letter are not significantly different according to Tukey’s honestly significantly different test (α = .05).

Materials and methods

To test this objective, two experiments were conducted in the Howlett Hall Greenhouses on the campus of Ohio State University, Columbus. For each experiment, three turfgrass species — perennial ryegrass (Lolium perenne L. Premier), creeping bentgrass (Agrostis palustris Pencross) and tall fescue (Schenodorus arundinaceous Schreb. Escalade) — were seeded into plastic foam float trays that measured 6.3 inches by 11.6 inches (16.0 centimeters by 29.5 centimeters) (CPG float trays). The seeding rates used were 0.118 ounces per square yard (4.0 grams per square meter) for creeping bentgrass and 1.12 ounces per square yard (37.97 grams per square meter) for perennial ryegrass and tall fescue. In total, 21 plastic foam float trays (three replications for each of six treatments and the untreated control) were used. The three turf species were seeded into one randomly assigned row of four holes each, and then the float trays were placed on top of rectangular 1.5-gallon (5.7-liter) containers filled with a 50% concentration of Hoagland’s solution. The containers were placed on a bench in the greenhouse for the duration of the trial. Fifteen days after seeding, six liquid plant biostimulants were applied into the containers with the tobacco float trays at the concentration indicated by the manufacturer, to be absorbed by the roots.

The products tested were NutexEDA (Sipcam Agro USA Inc.), which has 5% chelated zinc and can be classified as a metabolic enhancer and beneficial chemical element; Baccarat (Sipcam Agro USA Inc.), a concentrated humic substance and a complex organic material; Potente (Sipcam Agro USA Inc.), an amino acid biostimulant; Stilo (Sipcam Agro USA Inc.), a mix of fulvic acid and vitamins; and Apex 10 (Nature’s Wonder), which is a liquid peat extract, a complex organic material. All products have low or no nitrogen content, are applied to the root zone and claim to induce plant stress resistance. Twenty-five days after treatment application, plants were harvested and carefully washed, and fresh leaf and root weight were recorded. Fresh material was oven-dried at a constant 140 F (60 C) until reaching a constant weight, then the leaf and root dry weight were also recorded. The experiment was conducted twice, and data from each round were combined and analyzed with R software (version 3.3.3, R Core Team).

Root growth is significantly less on the ryegrass control.

CCIV fertilizer granules


Turf treated with Baccarat had greater fresh and dry mass (Figures 1 and 2, respectively) than the control. Baccarat is an extended-release humic soil conditioner. A similar effect was observed by Zhang et al. (4), who worked with tall fescue applying humic products. Liu et al. (1), working with humic acids applied to creeping bentgrass grown hydroponically, as in this study, found that applying humic acids significantly enhanced photosynthetic rates and root mass regrowth. Figure 1 shows the differences in the biostimulants’ effects on fresh weight by turfgrass species, considering that perennial ryegrass has a quick germination and can reach up to .18 ounces (5.10 grams) total weight compared with tall fescue (.088 ounce/2.49 grams) and creeping bentgrass (.035 ounce/0.99 gram). Following Baccarat, Stilo and Apex 10 showed an effect on dry and fresh weight (Figures 2 and 1, respectively) in creeping bentgrass. These two products are commercially described as fulvic acid. A field study on creeping bentgrass reported by Van Dyke et al. (3) indicated that fulvic acid products did not show an effect on turfgrass performance, measured as phosphorus uptake and chlorophyll content. Potente, an amino acid root stimulant, did not show significant differences in fresh and dry weight compared with the control in all turfgrass species. This fact can be partially explained by the study performed by McCoy et al. (2), where it was found that amino acid-based biostimulant products, when applied as a foliar treatment, showed an effect on turfgrass, whereas in this experiment, all the products were applied to the root system with the Hoagland solution. 

In this study, we investigated the effect of six commercial products classified as biostimulants on turfgrass fresh weight and dry weight in a controlled environment. The study showed that there was a positive effect on plant performance by humic substances and complex organic materials; however, the dose may be an important factor to consider because of the low doses used in this study (1 or 2 parts per million compared with former studies, such as Liu et al. In addition, species differences in the responses of turfgrass were detected in this study. Future field research should investigate the effects of higher application rates, application timing, and turfgrass species on turfgrass establishment with the humic acid and fulvic acid compounds.

The Research Says

  • There was a positive effect on plant performance by humic substances and complex organic materials.
  • The dose may be an important factor to consider because of the low doses used in this study (1 or 2 ppm) compared with former studies.
  • Following Baccarat, the biostimulants Stilo and Apex 10 showed an effect on dry and fresh weight in creeping bentgrass.


The authors thank Sipcam Agro USA Inc.

Literature cited

  1. Liu, C.H., R.J. Cooper and D.C. Bowman. 1998. Humic acid application affects photosynthesis root development and nutrient content of creeping bentgrass. Hortscience 33(6):1023–1025 (
  2. McCoy, R.M., G.W. Meyer, D. Rhodes, G.C. Murray, T.G. Sors and J.R. Widhalm. 2020. Exploratory study on the foliar incorporation and stability of isotopically labeled amino acids applied to turfgrass. Agronomy 10(3):358 (
  3. Van Dyke, A., P.G. Johnson and P.R. Grossl. 2008. Humic substances effect on moisture retention and phosphorus uptake in Intermountain West putting greens. Applied Turfgrass Science 5(1):1–9 (
  4. Zhang, X., E.H. Ervin and R.E. Schmidt. 2003. Seaweed extract, humic acid and propiconazole improve tall fescue sod heat tolerance and posttransplant quality. Hortscience 38(3):440–443 (

Alejandra Acuña ( is an independent golf consultant and adjunct professor at Pontificia Universidad Católica de Chile in Santiago; David Gardner and Karl Danneberger are professors of turfgrass science at Ohio State University in Columbus; and Luis Villalobos is a postdoctoral researcher in the Department of Plant Physiology at the Centro de Estudios Avanzadados en Fruticultura, Rengo, O’Higgins, Chile.