Biostimulant Use in the Turf Industry

Editor’s Note: This is a short summary of an essay submitted by Quincy Law to the GCSAA Student Essay Contest that received second place. The topic was selected based on an undergraduate research project completed by the author in 2010.

As environmental stewards, golf course superintendents need to produce the highest quality turf while retaining a healthy environment for both people and wildlife. Turf areas need to be maintained with environmental sensitivity while controlling pests and combating harsh environmental conditions. Despite increasingly stringent environmental regulations, water quality issues, and negative public perceptions of pesticides and fertilizers, golfers still expect their local course to appear and play as those on television: uniformly green and perfectly manicured.

Outside of chemical control and fertility, a superintendent has various options to maintain a high turf quality throughout the growing season. Mowing practices, species selection, water management, and cultivation can all improve plant vigor. Unfortunately, many of these options have already been implemented by the superintendent, cannot be changed, or are simply not feasible. There is, however, an alternative that has slowly been gaining popularity and is supported by research.

Biostimulants are materials that, in small quantities, stimulate plant growth. Although they can be synthetic chemicals, naturally occurring organic materials are excellent sources. Since the category includes a diversity of substances, biostimulants are defined by what they do more than by what they are. They stimulate growth, but they do much more too; stress tolerance is perhaps the most important benefit. Biostimulants can assist turfgrass in surviving dry, hot, high salinity, and even disease.

Products may contain one or more of a broad range of ingredients, including nutrients, organic acids, hormones, amino acids, vitamins, microbial inoculants, plant extracts, and others. They have limited nutritional value and promote plant growth by providing amino acids, chelating nutrients, and altering the hormonal status of a plant, which can exert large influences in plant growth and health.

Seaweed is the most widely used biostimulant in both agriculture and turfgrass management. Humic substances are another common component of biostimulant products. Both seaweed and humic acid have been shown to effectively stimulate plant growth and increase stress tolerance. In addition, these materials also complement each other when used in combination.

Seaweed and humic acid may affect the plant in several ways because they contain various hormones, vitamins, amino acids, plant nutrients, and other components. The stimulating influences, especially for turfgrasses growing under environmental stress, have mainly been attributed to hormonal activity. Humic acid and seaweed extract both exhibit cytokinin and auxin activity, which are two classes of plant hormones. When the plant is exposed to certain environmental and cultural stresses, levels of some hormones, such as cytokinins, may drop. Under these conditions, applications of cytokinins or other plant hormones could help ameliorate the stress.

Biostimulant applications may only be beneficial where root growth, moisture stress, salinity, or other issues are present. Turfgrass typically grows well without biostimulants when the environment is favorable; plants growing under minimal stress may perform similarly regardless of biostimulants. In these situations, the positive effects of biostimulants may not be easy to identify. When the plants become stressed, however, biostimulant-treated turfgrasses perform better because they have developed a better defense system. For the maximum effectiveness, biostimulants should be applied prior to the onset of stress. Treatments may be most effective when applied early in the season when the plant is actively growing.

Golfers, greens committees, and the general public hold golf course superintendents to a double standard. Golf courses are expected to be maintained at a high quality, such as those played on the PGA Tour. However, that high level of maintenance exposes turfgrass to a significant amount of stress. In addition, the fertilizers, pesticides, water, and other controls used to combat these stresses often carry a negative stigma.

In order to keep turf plants healthy in the presence of stress with limited use of fertilizer and chemicals, biostimulants may be a viable option for superintendents. Not only can biostimulants reduce the usage of chemicals harmful to the environment, most are natural and are composed of chemicals not available in synthetic products. Turf managers may be able to “go green” while still maintaining healthy turf, and they may prove to be an environmentally friendly component to turfgrass management.

Quincy Law
ISU Turfgrass Research Assistant