Soil surfactants applied to turfgrass can be polymers that retain water in the rootzone, penetrants that improve water percolation or dual-purpose products combining both functions. The ability of surfactants to prevent dry spots is well documented, but less information exists about surfactants in situations with excessive rainfall or irrigation. Thus, the objective of this project was to study turfgrass responses to monthly applications of Syngenta’s dual-purpose surfactant Qualibra under restricted or excessive water supply on a USGA-spec. putting green at NIBIO Landvik, Norway. Restricted water supply involved irrigation to field capacity (FC) once a week (FC1) in 2014, a warm, dry summer, and deficit irrigation to 60% of FC (DEF1) in 2015, a cool, wet summer. Excess irrigation was carried out twice a week (EX2) with 50% more water than needed to replenish FC in both years.
On average for irrigation treatments, Qualibra decreased the volumetric soil water content (SWC) of the 7.5 cm topsoil from 19.3 to 16.6 % (P<0.01) in 2014 and from 19.1 to 17.1 % (P<0.05) in 2015. This shows that Qualibra primarily acted as a penetrant under these irrigation treatments. In 2015 there was a tendency (P<0.10) for an interaction, as the reduction in SWC was stronger with EX2 than with DEF1 irrigation, and this was accompanied by reductions (P<0.05) in thatch thickness and loss on ignition on plots receiving EX2 irrigation. The surfactant significantly reduced soil water repellency, as shown by the water droplet penetration test, regardless of irrigation treatment, and improved turf quality significantly on plots with DEF1 irrigation.
In conclusion, the dual-purpose surfactant Qualibra has varying benefits depending on the amount of natural rainfall/irrigation.
To determine the effect of the soil surfactant Qualibra on soil water content, turf quality and thatch accumulation on a creeping bentgrass (Agrostis stolonifera) green varying in water availability.