Factors Affecting Efficacy of Biological Nutritional Products for Plant Health.

Increasing pressure to reduce synthetic inputs in recreational turf areas has increased the interest and use of biological products among turf managers. Biological products are used for nutritional purposes and to deliver or stimulate beneficial microbes for disease suppression by enhancing the soil and phyllobiology. Since using biological products has resulted in variable field responses, any factors that might decrease product efficacy like exposure to ultraviolet light, lack of moisture in the turf canopy, or possibly the composition of the water used as the spray carrier, are of strong interest. The objective of this study was to determine if water containing chlorine (e.g. similar to many potential municipal water sources) affected the biology of various biological products. Several commercially available liquid products (e.g broad-based bionutritionals and vermicompost extracts) were mixed with ultra-pure, sterile water and ultra-pure, sterile chlorinated water to determine (1) the bacterial populations as total bacterial colony forming units (CFUs), and (2) whether the presence of chlorine at 2 parts per million (ppm) affected populations. Products were plated on plate count agar (PCA) and incubated at room temperature. The number of CFUs varied substantially between products, with some products containing as few as 4.1 x 10² CFUs per mL and some as much as 34.2 x 10⁶ CFU per mL. The highest populations were associated with the bionutritionals and lowest with vermicompost extracts. Water with chlorine at 2ppm reduced product CFUs and the reduction varied by product, with some products being reduced to as few as 2 x 10² CFU per mL. Further studies need to be conducted, including plating on more selective media to isolate specific bacteria.