Biostimulants for turf. 12

The public has become more aware of the impact of synthetic fertilisers and chemicals on the environment. The result is many turf managers have begun to use biostimulants for turf management in Australia. At very low rates these have many benefits and give a positive growth response. A good example of this response is the use of the turf pigment Vertmax Duo which contains salicylic acid. This not only filters UV light and gives a rapid colour response but also increases growth and lateral root branching.

Yet, their use should be tempered with the knowledge that if you decide to go down this path you need to know what you are using. Simply, using “a biostimulant” and expecting results is no guarantee of success and is most likely going to be a waste of time and money. For example, many turf fungicides kill the very organisms you are trying to encourage. This is also the case with organic control of weeds such as nutgrass.

Biostimulants for turf are substances or microorganisms that you use on turfgrass to enhance plant growth and health. They improve the overall quality of the turf by increasing its resistance to stress and disease, and by promoting root development. Biostimulants work by stimulating the plant’s natural physiological processes, and they can be used in combination with fertilizers and other products to improve the overall health and appearance of turfgrass.

Examples of biostimulants for turf:

• Seaweed extracts: These extracts contain a variety of natural compounds that can promote plant growth and health, such as hormones, minerals, and amino acids.
• Microorganisms: Certain bacteria and fungi can be applied to turfgrass to improve root development, nutrient uptake, and disease resistance.
• Humic acids: These acids are derived from decomposed organic matter and can improve soil structure and water-holding capacity, as well as increase the availability of nutrients.
• Plant extracts: Some plant extracts like aloe vera, can be used to improve plant growth and health.

Biostimulants for turf are not regulated by the APVMA. As a result, it is important to research the product and check the label for the active ingredient, the amount, and the specific use before application. Also, consult with a professional before applying any biostimulant, as different turf types may require different biostimulant treatments.

There is a constant stream of new products coming onto the market which make massive claims with little supporting data. This blog is an attempt to cut through the marketing and get to the facts. 

Humic substances as biostimulants.

• Improve the growth of roots and shoots;
• Cause an increase in the CEC of a soil;
• Improve the structure of the soil;
• Increase the activity of soil microbes;
• Enhance nutrient uptake and plant hormone activity;
• Improve seed germination.

Plant hormones as biostimulants.

Stresses such as heat, cold, and drought cause several hormone responses that turf plants use to survive. 5 major plant hormones play a role in turf grass.

• Indoleacetic acids (IAA). These are also known as auxins and promote root and shoot growth;
• Gibberellic acids. These promote shoot growth and the germination and growth of seeds;
• Cytokinins which regulate turf growth and development;
• Abscisic acids that cause a turf response to environmental factors and
• Ethylene which causes a growth response.

Of these the most important are cytokinins, gibberellic acid, and abscisic acid. Hormones can either be synergistic or antagonistic. An antagonistic effect is when hormones affect the same part of the plant but work against each other. In contrast, a synergistic effect is when the effect of two or more hormones is greater than the effect of the individual hormone. By knowing what specific hormones do, it is possible to tweak them to get the desired turf response.

• Vertmax Duo contains salicylic acid which increases turf stress tolerance, speeds up seed germination, and increases root growth and branching;
• Using strobilurin fungicides and products like Lexicon Intrinsic. This reduces turf respiration meaning more energy goes toward turf growth;
• The use of trinexapac ethyl (Amigo 120ME) in shade. This increases the production of cytokinin and inhibits gibberellic acid.

Seaweed as a biostimulant for turf.

At low levels, seaweed extracts can cause many beneficial plant responses. Its two main uses in the turf industry are to encourage root growth and to increase stress tolerance. Seaweed products contain organic and mineral compounds. These include:

• Growth substances like auxins, cytokinins, GA’s, and brassinosteroids;
• Very low amounts of nutrients;
• Alginates and
• Amino acids.

• Cell division;
• Shoot initiation;
• The growth of lateral buds;
• Leaf expansion;
• Increases in the opening of stomata and
• The production of chlorophyll.

Seaweed on cool season turf.

Studies with cool-season turfgrass show:

• 67% to 175% more roots compared to untreated plots;
• 38% more top and 52% more root growth in the spring;
• Increases in photosynthesis;
• More leaves and shoots having a higher shoot and root mass;
• Higher drought and salinity tolerance and
• If you use seaweed plus iron in the autumn, it helps warm-season turf keep its colour and encourages early spring green-up.

Work in 2013 shows that foliar seaweed extracts result in 15% less root decline over a 42-day heat stress trial. A 30-day interval between applications is fine at first, but as heat and turf metabolism increase, the interval between treatments should be shortened to 14 days. This shorter interval during hot summer weather is because cytokinins etc tend to break down faster in the plant as the temperature increases.

Phylgreen®

Phylgreen® is a natural extract of Ascophyllum nodosum and it maintains all its “goodies” as a result of its extraction process. By pre-stress conditioning the turf, it conditions turf against abiotic stress. This is called a “Primactive Effect” and increases the ability of turf to cope with stresses such as heat or drought.

Delfan® V Plus has also been used as a spray tank additive to reduce the surface tension of turf chemical sprays and increase chemical to target contact.

Kreotec® as a biostimulant for turf

Kreotec® is an inoculant, that contains a blend of bacteria. After application to the leaf surface these enter through the leaf stomata and live inside the plant. Kreotec® increases nitrogen use efficiency and cuts back on the need to apply fertilizer by adding up to 30 Kg of Nitrogen/Ha.

• Work on lettuce shows an increase in growth. It reduces fertilizer needs by up to 60% of the normal rate with no yield decreases.
• In ryegrass there are yield increases.

In the turf industry, several products claim to increase microbes in the soil. This is a great theory but in practice, there is little data to support these claims. 

The reasons for this are very simple:

• At the label use rates it is unlikely that the introduction of non-native organisms will result in their becoming dominant;
• Little thought is given to the non-target effects of turf chemicals and 
• There is an antagonism between endophytes and VAM. If you use products containing VAM on high-endophyte ryegrass they aren’t going to work.

Trichoderma spp.

Trichoderma is a genus of fungi that are commonly found in soil, plant debris, and on the surface of plants. They are known for their ability to form relationships with plants and are often used to protect crops from plant pathogens. Trichoderma species can colonize plant roots and produce enzymes that help to break down organic matter in the soil, making nutrients more available to the plant. They also produce chemicals that can inhibit the growth of plant pathogens. 

Biostimulant uses in turf using VAM.

You can class Mycorrhiza as arbuscular or vesicular-arbuscular mycorrhizas (VAM) and they form relationships with most grass species. When you seed a sand-constructed sports ground or golf green, fungal populations are slow to increase. In this situation, with no dominant microbial population, there are clear benefits to using these fungi:

• They increase turf resistance to nematodes and root diseases;
• They increase chlorophyll levels;
• Seed germination increases;
• They increase drought recovery and finally
• They can increase turf salt tolerance.

But, in reality, what is the impact of fungicides on these?

General Rules on the use of fungicides with fungi inoculants:

• Foliar non­-systemic fungicides have very little impact on mycorrhizal fungi because they live on the roots. Even though some fungicides may reach the soil, it is such a low rate it is not likely to affect these fungi;
• Soil applications of non-­systemic fungicides can have a negative impact on mycorrhizal fungi. This is especially the case if you apply before root colonization occurs. A soil application washes the fungicide into the root zone and so avoid using these too close to when inoculation occurs. A good rule is to avoid using soil drench fungicides 2 weeks before inoculation (longer if systemic) and 4 weeks after inoculation.

After colonization.

Once spores have colonized roots, mycorrhizal fungi tend to be less sensitive to soil-applied non systemic fungicides because:

• Although fungicide levels will be high in the soil they are lower inside the roots;
• High soil fungicide levels can kill off fungae in the soil, but not fungae inside the roots;
• When soil fungicide levels fall, root fungal tissue will recover and grow a new network out into the soil;
• As a general rule we don’t recommend the use of systemic fungicides in conjunction with these.

The effects of fungicides on bio stimulants.

Is there a role for biostimulants in turf?

The short answer is yes but only when using products that have good non biased trial data. Avoid using products because they have a nice brochure or the company that markets them tells you they work. Also if you can’t verify any claims avoid using it and if it hasn’t got an expiry date keep well away.

• Always ask for a certificate of analysis;
• Check on the expiry date and if it doesn’t have one ask why not?
• Watch what fungicides you use. If you don’t these are going to kill the very thing you are trying to encourage.

As a final note we often carry out product tests on behalf of clients. Recent tests on a VAM containing liquid from two laboratories were:

“ Results indicate that 2 types of yeasts dominate the product and there is no presence of VAM. Contact the manufacturer of the product, and carry out further testing to verify results”.

The role of bio stimulants in turf.

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