Sunday, August 31, 2008

Turf - Biostimulants

The following is summary of some research from Virginia on the use of biostimulants in turf as well as basic information on biostimulants.

Biostimulants, plant biochemical regulators, and plant growth regulators are terms used to describe materials other than fertilizer, that when applied to plants in small quantities effect biochemicals that influence the physiological processes within plants. Examples are materials that contain high percentages of hormones. Hormones are designated organic compounds such as auxins, cytokinins, gibberellins, abscisic acid, and ethylene that influence plant function. Auxins, gibberellins and cytokinins stimulate growth while abscisic acid and ethylene are inhibitors of growth. The use of these stimulating hormones as foliar-applied materials to manipulate plant conditioning is currently pursued in cultural aspects of turfgrass management.

The biostimulant studies at Virginia Tech initially were attempts to enhance cool season turfgrass sod production. Results from research concluded in 1979 in our department showed applications of a synthetic cytokinin at 24 gm per acre, significantly increased soybean seed yield generated interest in evaluating cytokinin treatments in our on-going turfgrass sod enhancement project.

After several attempts to utilize commercial seaweed products as the source of cytokinins, positive results were realized when seaweed extracts were obtained from seaweed processes at low temperatures. Results from these seaweed extracts gave more consistent results that the synthetic cytokinins. It was concluded that in addition to cytokinins, seaweed supplied other compounds such as auxins and amino acids to provide more positive responses. More consistent results were eventually obtained when humic acid was applied with seaweed extracts, indicating that the auxin activity of the humic acid enhanced the hormone activity supplied by seaweed.

In the mid-1980’s, Dr. Petrovic of Cornell University, indicated that enhanced rooting of Kentucky bluegrass was observed when a triazole fungicide was applied. Our subsequent research confirmed this observation. Since then we have documented that in addition to treatments with seaweed, humic acid, and triazole fungicide, applications of amino acid or trinexapae ethyl have biostimulant effects. Most recently we have detected biostimulant effect when silicate was applied to creeping bentgrass.

Various graduate student projects over the past ten years showed that application of seaweed, and humic acid to cool season turfgrass, conditioned the grass to enhance toleration of salinity, drought, nematode invasion, disease infestation, herbicide toxicity, and shade. One doctoral student obtained data showing that bermudagrass was affected less by chilling temperatures when treated with cytokinin and iron.

The measurements of turfgrass growth provided strong evidence that, indeed, plant growth regulators did condition turfgrass to better tolerate stressful environments.

The antioxidant content of turfgrasses can be stimulated with applications of biostimulants. The application of humic acid (HA) plus seaweed extract (SE) to creeping bentgrass will significantly enhance the antioxidant, superoxide dismutase (SOD), activity. The enhance vigor of bentgrass associated with antioxidant content can be demonstrated. Infection of Dollarspot disease is
decreased with the increase of antioxidant content of the bentgrass leaves.

Results of our studies strongly suggest that the benefits derived from applications of biostimulant materials to turfgrass results from the stimulation of antioxidant produced in the grass. Biostimulants enhance gene expression under different environmental stresses. As more is learned about he biostimulant influence on turf, the better cultural tools the turfgrass manager has at his disposal.

Extracted in part from "BIOSTIMULANT PRODUCTS: WHAT RESEARCH HAS SHOWN: HOW THEY WORK", by R. E. Schmidt, Professor, Dep. of Crop and Soil Environmental Sciences, Virginia Tech, Blacksburg, Virginia.

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