Biostimulants in the Turf World

As all turf managers know, weather conditions change across the season and this affects overall turf growth and health. Each growing season, the grass plant grows and develops in a constant interaction with the local environmental conditions. How “easy” or “hard” the season goes is a direct result of how well the turf could deal with, and respond to, these environmental and weather conditions.

Grass plants do not alter their “normal” growth curve during small changes in environmental conditions. However, when these changes inevitably become large enough that they require the plant to alter their “normal” growth and metabolism, this is when the turf begins to suffer from abiotic stress.

The application of biostimulants can enhance overall turf quality and performance by improving their tolerance to abiotic stress. Over the past 10 to 20 years, the use of biostimulants has been recognized as an effective tool, which assists in making the turf more sustainable and even more environmentally friendly.

What is a biostimulant?

A “biostimulant” is defined as a product that stimulates plant nutrition and growth processes independently of the product’s nutritional content. Biostimulation has the sole aim of improving one or more of the following characteristics of the plant or root zone:

  • Nutrient use efficiency
  • Tolerance to abiotic stress
  • Quality traits
  • Availability of confined nutrients in the soil

The use of biostimulants has been demonstrated to effectively reduce the impact of abiotic stress on turf when applied appropriately, which helps to achieve the turf’s full potential. An important point about biostimulants is that they have no specific effect on pathogens or pests and to control these biotic challenges plant protection products are still needed.

How do biostimulants work?

Biostimulants have the capability to trigger the natural response functions of the turf plant to combat abiotic stress. In essence, with or without biostimulants, the plant will alter its metabolism to respond to abiotic stress. However, the use of biostimulants on turfgrass allows for a quicker and more efficient response in terms of effectiveness and timing.

There are a variety of biostimulants and they differ in their origin and/or their mode of action within the plant. In general, biostimulants in turf can be allocated to one of five groups:

  • Humic / fulvic acids
  • Seaplant extract
  • Beneficial fungi
  • Beneficial Bacteria
  • Protein hydrolysates (Amino acids)

Knowledge about the mode of action of each biostimulant will enable turf managers to make the best decision about what biostimulant to apply, when to do it and what dose to use. They will also know what beneficial effect that is expected from that particular biostimulant application, which ultimately dictates which biostimulant(s) should be used to deliver the best turf conditions possible.

What application timing is best when using biostimulants?

Preventive biostimulant applications require that they be applied before the stress occurs. The majority of biostimulants fall into this category. Think of them like a flu shot; in terms that the inoculation must be administered before the someone gets the flu. The same concept applies with biostimulants.
These biostimulants prepare or prime the response of the grass plant to enable it to better resist abiotic stress before the actual stress occurs. These biostimulants generate a surge of signals that "put the turf on alert" of an impending environmental change. 

When an environmental stress occurs, for example increased heat and humidity, the “alert” previously generated by the preventive biostimulant application allows the grass plant to respond quickly and effectively to the abiotic stress event. This action allows the turf to maintain or minimize disruption to productive growth and metabolism.

Seaplant Extract as preventative biostimulants

One of the most popular and effective type of biostimulants used in turf management that utilizes this preventive alert effect is Ascophyllum nodosum seaplant extract. Preventive biostimulation can help during mild stresses or the early stages of more severe abiotic stress events in turf. These preventive biostimulants should be viewed as the turf manager’s first line defense in minimizing and delay the disruption to normal growth.

Recovery biostimulant applications can be used during or after the stress has occurred. During more severe or prolonged abiotic stress situations, such as a long heat wave or cold spell, the grass plant’s demand for resources will alter away from normal growth and quality production to focus on more essential basic growth and survival functions. This consequently reduces overall health, performance and playability potential.

In these situations, the application of corrective, post-stress or recovery biostimulants will benefit the turf. Recovery biostimulants help the grass plant to return to normal growth as quickly and efficiently as possible, thus recovering some, but not all of the potentially lost health and quality. In these recovery situations, Amino acids are a particularly effective choice.

Amino Acids as recovery biostimulants

Nature consists of the basic elements, such as oxygen, hydrogen and carbon, that combine to make all matter that is present in the world. A similar principle operates in living organisms, like plants, which are composed of the “elements of life”, the twenty or so foundation or elemental Amino acids.

These Amino acids are essential for growth and quality. Additionally, they are also key to help turf recover quickly from abiotic stress and resume their normal growth trajectory. Application of recovery biostimulants, such as Amino acids, is synchronized with the natural growth and recovery cycle of turf.

As knowledge about biostimulants and their preventive and recovery modes of action has improved, it has become clear that, like pest and pathogen management strategies, a combined abiotic stress management program that integrates both a preventive and recovery strategy deliver the optimum result in terms of performance and quality.

It is easy to see that certain biostimulants have very specific roles in helping the turf prevent and recover from environmental and weather stresses. A different source of stress in turf is the stress that occurs each time the grass plant passes through a growth phase, for example when it focused on root growth rather than shoot growth. Like preventive and recovery biostimulants, there are specific biostimulants for growth stage stress.

Humic and fulvic acids for root growth 

Humic and Fulvic Acids help in the recovery of the degraded structure of soils, in the retention and availability of nutrients in soil and facilitate improved soil moisture retention. Humic and Fulvic acids have also been shown to have a direct biostimulation effect in turf, by triggering increased root growth that facilitates improved overall health and carbohydrate reserves. This biostimulation effect is particularly beneficial when the plant is already naturally focused on root growth, such as spring and fall for cool-season turf and in the summer for warm-season turf.

Biostimulants can also be incorporated into fertilizer formulations that contain multiple nutrients, such as the incorporation of Humic and Fulvic acids with nitrogen, phosphorus and micronutrients needed for turf development. The inclusion of Humic and Fulvic acids promote a more balanced root and shoot development paradigm where the grass plant better metabolizes the needed nutrients to consistently provide better overall turf quality.

What is next for biostimulants?

Over the past few decades, the use of biostimulants has grown from almost zero to become a multi-billion-dollar industry. Knowledge about the use and function of biostimulants has also increased at an exponential rate. 

First came the knowledge about which products had biostimulant effects, then came increasing knowledge about the mode of action and how biostimulants work on turfgrass, specifically. This has enabled increasingly precise recommendations regarding timing and dosage of biostimulant applications and has led to more consistent results and greater reliability for turf managers.

The use of biostimulants in agronomic programs continues to expand throughout the industry as this new knowledge is applied. At the same time, a new generation of biostimulants are currently under development, harnessing the knowledge gained during the past decade and including new sources of raw materials.

As a result, the use of biostimulants will continue to expand, while gaining an increasing importance in assisting turfgrass to be more sustainable, while at the same time, helping the individual turf manager deliver consistent and predictable turf conditions.