Seaweed or algae products have become a tool for turfgrass managers as biostimulants. One such product is AlgeaGreen® from the Irish company OGT. According to the label, this biostimulant has been extracted from pure Ascophyllum nodosum at low temperature. Plots of creeping bent (Agrostis stolonifera) ‘Independence’, chewings fescue (Festuca rubra spp. commutata) ‘Musica’, perennial ryegrass (Lolium perenne) ‘Chardin’ and annual meadow grass (Poa annua) were established on a USGA green at NIBIO Landvik in June 2016.
AlgeaGreen® was applied every second week at a rate of 15 L/ha from mid-August to late October 2016 and 2017. Turfgrass quality and diseases (microdochium patch, red thread, take-all, anthracnose and superficial fairy rings) were assessed and leaf chlorophyll index was measured regularly in autumn 2016, spring 2017 and autumn 2017. In autumn 2017 there was a tendency for AlgeaGreen to increase leaf chlorophyll index, exacerbating fairy rings in creeping bent but not in the other species. Otherwise, there was no effect of AlgeaGreen on quality characteristics determined in the field. Freezing tolerance of the turfgrasses (LT50, lethal temperature for 50% of plants) was determined on 28 Nov. 2016 and 24 Nov. 2017. Results from the first freezing test in 2016 showed a significant effect of AlgeaGreen® on freezing tolerance. The mean LT50 value was 1.1 °C lower for grass treated with AlgeaGreen® than for the untreated control (-21.5 °C vs. -20.4 °C, respectively). In 2017, the mean LT50 value for untreated grass and grass treated with AlgeaGreen® was -18.5 °C and -18.8 °C, respectively, but the difference was not significant. The ranking in freezing tolerance among the grass species in 2016 and 2017 was as follows: creeping bent (-27.8 °C and 28.7 °C) > chewings fescue (-20.2 °C and -17.5 °C) > perennial ryegrass (-18.1 °C and -13.8 °C) = annual meadow grass (-17.5 °C and -14.6 °C).
