Fungi, especially those causing winter diseases, are a major problem on golf course putting greens in Scandinavia. Although diseases can be prevented by cultivar selection and optimal maintenance, it is difficult to manage creeping bentgrass (Agrostis stolonifera) and annual bluegrass (Poa annua) greens totally without fungicides. Earlier research funded by STERF showed that two of the most commonly used fungicides, iprodione (Rovral/Chipco Green) and azoxystrobin (Amistar) are liable to leach when used on sand-based putting greens. One possible reason for this is the development of hydrophobic layers or spots causing water to percolate in finger-like patterns instead of uniformly through the root zone. ‘
The objective of this project is to study the effect of one organic amendment and one surfactant on hydrophobicity and fungicide leaching from a USGA putting green. An experiment is conducted with creeping bentgrass ‘Penn A-4’in the field lysimeter facility at Landvik, Norway. The experimental plan includes two rootzones (straight sand vs. sand amended with garden compost); two surfactant treatments (no surfactant vs. monthly application of Primer 604); and two fungicides (iprodione vs. azoxystrobin + propiconazole) in a factorial combination. Turfgrass quality and disease occurrence, infiltration of water vs. ethanol, water droplet penetration time, and spatial variability in soil water content has been determined and related to fungicide detections in leaching water. The preliminary results from the first experimental year have confirmed our hypothesis that fungicide leaching can be minimized by inclusion of organic matter in the root zone and/or by regular use of surfactants. The surfactant improved turf quality on straight sand root zones during the warm and dry summer of 2005, reduced water droplet penetration time at 1 and 2 cm depth in the soil, and reduced the spatial variability in the soil water content at 4-10 cm depth. This indicates that hydrophobicity extended far deeper in the profile than just the thatch layer. The reduction in leaching due to surfactant use was more pronounced for azoxystrobin and propiconazole than for iprodione. At the same time, azoxystrobin and propiconazole were more efficient that iprodione in controlling turfgrass diseases in autumn.
