Evaluation of the Potential Phytotoxicity of Gro-Bark Feedstocks

February 1, 2021

Phytotoxins are defined as substances that are poisonous or detrimental to the growth of plants. These substances may result from human activity, as with herbicides, or they may be produced by plants, microorganisms, or by naturally occurring chemical reactions. As Gro-Bark utilizes a number of natural recovered resources for growing media feedstocks, we recently undertook a trial to examine for the potential presence of phytotoxic compounds in our bark and compost to assure our customers that all our materials are phytotoxin free.

Due to the overabundance of potential phytotoxic compounds and the varying rates of sensitivity of different plant species and cultivars, it is practically impossible to conduct a laboratory analysis for the presence of individual substances which may cause phytotoxicity. Therefore, in order to assess whether there are harmful substances in Gro-Bark materials, growth and germination tests were performed.

Overall, the results of this growth and germination tests demonstrate that Gro-Bark’s Blend A, Compost, CPM and Aged Bark are free of any phytotoxic compounds at levels which can cause issues to plant germination, growth rate and root elongation. For the detailed trial report, please click here.

The Use of Biostimulants in Gro-Bark Media

Biostimulants are microorganisms or substances which are applied to plants, seeds, or soils with the aim to enhance stress tolerance, nutrition efficiency and/or overall crop quality and growth. Biostimulants differ from nutrient amendments, plant growth regulators, and fertilizers as they do not provide nutrients or implement any direct action on to the plant. For example, a biostimulant will aid a plant by easing the acquisition of nutrients from the surrounding soil rather than providing nutrients directly like a fertilizer. In recent years, the popularity of biostimulants has been increasing, however there is little applied research which supports the benefit of their use in nursery or greenhouse container production.  

Accordingly, Gro-Bark recently undertook two trials which were designed to investigate the benefit of adding commercial biostimulants to Gro-Bark growing media. These trials examine five popular and commercially available biostimulants approved for use in Canada and tested their efficacy in improving plants in a stress-inducing environment (i.e. drought stress).

The results of the trial concluded that none of the biostimulants examined showed any benefit when added to the growing media.