Organic Biostimulants are getting more attention today from turfgrass managers as tools to enhance stress tolerance in turf. Numerous University studies as well as use in the field have validated their importance and efficacy. Articles such as “Biostimulating turfgrasses” in the November 1999 Grounds Maintenance magazine have created a lot of interest in the industry.

Biostimulants are compounds that produce non-nutritional plant growth responses and reduce stress by enhancing stress tolerance. This is in contrast to fertilizers , which produce a nutritional response.

Many important benefits of biostimulants are based on their ability to influence hormonal activity. Hormones in plants (Phytohomones) are chemical messengers regulating normal plant development as well as responses to the enviroment. Root and shoot growth, as well as other growth responses are regulated by phytohormones. Compounds in biostimulants can alter the hormonal status of a plant and exert large influences over its growth and health. Sea kelp, humic acids and B Vitamins are common components of biostimulants that are important sources of compounds that influence plant growth and hormonal activity. Antioxidants are another group of plant chemicals that are important in regulating the plants response to environmental and chemical stress (drought, heat, UV light and herbi-cides). When plants come under stress, “free radicals” or reactive oxygen molecules (e.g., hydrogen peroxide) damage the plants cells. Antioxidants suppress free radical toxicity. Plants with the high levels of antioxidants produce better root and shoot growth, maintain higher leaf-moisture content and lower disease incidence in both normal and stressful environments. Applying a biostimulant enhances antioxidant activity, which increases the plants defensive system. Vitamins C and E and amino acids such as Glycine are antioxidants contained in biostimulants.

Plants typically grow well with out biostimulants when the environment is favorable. Under these conditions, the effects of biostimulants may not be easy to identify. However, when the plant becomes stressed, plants “conditioned” with biostimulants perform better because they have developed a better defense system due to higher levels of antioxidants in the plants system.

Research has found that biostimulants take time to exhibit their influence. Typically growth stimulation is best after 4-6 weeks of treatment. Therefore a good biostimulant program starts in the spring before the summer heats sets in so that the plant is fully conditioned to with stand summer stress.

Mycorrhizal fungi are a group of beneficial soil organisms that improve the health and vigor of turfgrass. Research studies have shown how these specialized fungi can improve fertilizer utilization, rooting depth, speed of turf establishment and recovery, and increases disease and drought resistance of turf. Use of these beneficial mycorrhizal fungi allows turfgrass managers to improve the condition of turfgrass and soil.

What are Mycorrhizae? Most grass species in their undisturbed natural environments form a beneficial association with mycorrhizal fungi. The resulting structure is called a mycorrhiza, or literally “fungus-root”. Mycorrhizal fungi are present in soil as spores, as hyphae (filaments or threadlike structures) or as colonized roots. Hyphae of mycorrhizae, which penetrate into and between the root cells of the plant, provide increased surface area for exchange of food to the fungus, and nutrients and moisture for the plant.

Once established on the root system, mycorrhizae radiate out to form a dense network of filaments. This network obtains 15 macro and minor nutrients (especially nitrogen, phosphorous and iron) plus water, and transports these materials back to the plant. This elaborate network of hyphae beneath the soil surface greatly increases the potential root system to absorb nutrients and water. The network also binds soil particles together, improves soil porosity, and the movement of air and water with the soil.

Where Mycorrhizae Are or Aren’t Soils in a natural setting are full of beneficial soil organisms including mycorrhizal fungi. However, many common practices (construction, tillage, removal of topsoil, site preparation, heavy use of pesticides and chemical fertilizers, compaction, and leaving soils bare) can reduce or eliminate these beneficial soil fungi.

Putting greens constructed according to U.S.G.A. standards and sand based sports fields lack mycorrhizal fungi at the time of seeding or sprigging, and can be slow to increase in the soil mix. Examination of root samples from 17 golf courses by the Soil Food Web Laboratory at Oregon State University indicated that the majority of greens tested had low-levels of mycorrhizal colonization. Only 38% of the greens tested had mycorrhizal colonization above 30% and 22% of the samples had no mycorrhizal colonization at all!  

Recent Research Recent findings (see Mycorrhizae & Turfgrass by Dr. Mike Amaranthus for a complete list of references) from various university studies have shown improved fertilizer utilization and increased turfgrass establishment and root growth. Also increases in resistance to nematodes, disease and drought stress in turfgrass has convinced turf grass managers to include Roots^Ò endoROOTS^Ô granular mycorrhizal inoculations in their construction and maintenance practices. Mycorrhizae can benefit many plants, and results are often very apparent in situation

where environmental stress is high.

Drought Stress Research studies in the Journal of Turfgrass Science (Gemma et al. 1997) reported that bentgrass inoculated with mycorrhizal fungi tolerated drought conditions significantly longer that non-mycorrhizal turf. Mycorrhizal inoculated turf also recovered more quickly from wilting and maintained significantly higher chlorophyll concentrations. Using Roots^Ò endoROOTS^Ô granular to inoculate valuable turf areas is a sensible and cost effective way to deal with the recent droughts in North America.

Faster Grow-in Research indicates that mycorrhizal inoculation at the time of seeding can increase the rate of establishment of bentgrass and other turfgrasses. In recent trials with the University of California-Riverside, seeded bentgrass inoculated with Roots^Ò endoROOTS^Ô granular covered over test plots almost a month earlier than controls, and had up to 82% more root weight. Colonization by mycorrhiza has been seen in as little as eight days from the time of inoculation.

Resistance to Disease and Nematodes Root pathogenic fungi and parasitic nematodes can be acute problems for turfgrass manager. Mycorrhizae have been shown to improve turfgrass resistance to the negative effects of these organisms. Modes of action include enhanced nutrition, less availability for resources for pathogens, physical change of the root and plant tissue, reduction of environmental stress and increased concentration of other beneficial organisms around roots.

When Do I Use Mycorrhizae? Mycorrhizal species vary in their ability to be active in high and low soil temperatures. For the mycorrhizal species mix in Roots^Ò endoROOTS^Ô granular, mycorrhizal fungi become active at temperatures above 34^°F (1^°C).  Maximum mycorrhizal activity is between 40-60^°F(4-16^°C). Roots^Ò endoROOTS^Ô granular should be incorporated ideally both spring and fall during aerification for several years until healthy populations of mycorrhizae are established. Spring is an effective time for root and mycorrhizal colonization. The mycorrhizal filaments increase the utilization of fertilizer and water and help with disease suppression during the active playing period.  Compaction, stress, and chemical use over the summer months can adversely affect soil biological activity and the fall application will invigorate the soil and mycorrhizal activity.

Fall application of fungicides for snow mold control and in-season application of systemic fungicides may occur one month following mycorrhizal application with out long-term adverse effects to the established mycorrhizae. Established mycorrhizal structures within the root are protected and not negatively affected by fungicides.  As the fungicide clears, the mycorrhizal filaments rapidly re-colonize the surrounding soil resource.  Generally contact fungicides do not have a negative affect on mycorrhizal colonies in turfgrass.

Making a Commitment Mycorrhizae can help lower costs over the long run. Healthy living soil and turf will retain nutrients, build soil structure, reduce stress and suppress disease; thus reducing the level of certain expensive maintenance practices. Choosing to incorporate mycorrhizal fungi into construction and aerification programs will not only benefit the environment, but also improve turf cover, recovery, rooting, fertilizer utilization, and disease and drought resistance.

Roots^Ò endoROOTS^Ô granular, The Product to Use: Use Roots^Ò endoROOTS^Ô granular for aerification (brush into holes) at 7 lbs product per 1000 sq. ft., or 10 lbs product for seeding and sodding (incorporate into the planting bed). A 50-pound bag of Roots^Ò endoROOTS^Ô granular delivers 200,000 spores and propagules with eight different species of endomycorrhizae. The inoculant is carried on the granular form of Roots^Ò dry granular biostimulant and a 3-3-4 organic carrier. Roots^Ò endoROOTS^Ô granular has been scientifically formulated and tested, and reflects Roots Inc. continued  commitment to product quality.

This article was condensed from the brochure, Mycorrhizae & Turfgrass by Dr. Mike Amaranthus. For further information, see the full version of this article available from your Roots^Ò distributor or contact Roots^Ò at 800-342-6173. Ed Long, Roots Inc. edited this article.