Conclusions from the GCSAA-USGA wetting agent study: September, 2005

Cultural, Water,

With the August, 2005 publication of updated and corrected data from the GCSAA-USGA wetting agent evaluation, we wanted to provide you with our conclusions from this important study.

• The products that most consistently reduced hydrophobicity (soil water repellency) were Aqueduct, Brilliance, Cascade Plus, HydroWet, Primer Select and TriCure. The ranking of these products is shown in more detail in Table 1.

• Products that consistently did the best job of reducing hydrophobicity also unfortunately had potential (though limited potential) to cause some reduction in turf quality (Table 2). However, this decrease in quality was seen in a maximum of two out of nine locations. And in most cases, it is likely that the benefits of reduced water repellency will outweigh the potential for turf damage.

• Products that consistently peformed poorly in reducing hydrophobicity included Naiad, Respond 2 and Surfside 37. As luck would have it, these products were among the group that had the least potential for reducing turf quality as well. Ah well.

Table 1. Ability of wetting agents to reduce soil hydrophobicity. The values shown represent the number of experiments in which each product was in the top performance group based upon analysis of variance.

Table 2. Potential for reduction in turf quality. In most cases, wetting agents caused either no reduction in quality or even improved turf quality. However, in a few cases, turf quality was reduced. The values shown represent the number of trials in which each product caused significantly reduced turf quality (based on analysis of variance) when compared to the non-treated control.

This trial has provided some very useful information that superintendents can put to use immediately. We encourage you to read the Golf Course Management article for details on the study design and execution.

For a more detailed explanation of how we conducted our analysis, see the article below on "PACE analysis of the GCSAA-USGA wetting agent evaluation"

PACE analysis of the GCSAA-USGA wetting agent evaluation: September, 2005

Trial locations: In both 2003 and 2004, the GCSAA and USGA worked with researchers in 9 states to implement wetting agent field studies. In six of those locations (Florida, New Mexico, California, Georgia, Michigan and Washington), soil hydrophobicity was high enough to allow researchers to detect significant differences between the different products that were tested. However, in three locations (Texas, New York, Missouri), hydrophobic soils failed to develop (this is why it's so important to set up multiple trials! There is always a risk that the problem you are hoping to evaluate won't show up), and there were few (if any) differences among the treatments. For this reason, we omitted the data from NY, TX and MO in our analysis.

Number of experiments analyzed: You will notice in Table 1 that we analyzed data from a total of 14 experiments, which had their origins as follows: In five states (FL, CA, GA, MI and WA), the average hydrophobicity readings for all soil depths were averaged annually (in 2003 and 2004), for a total of 10 experiments. In NM, there was significant data produced from two different soil depths -- 0.5 cm (0.2 inches) and 1.5 cm (0.6 inches). This data was averaged annually (in 2003 and 2004) for a total of 4 experiments from NM. This brings the grand total to 14 experiments where hydrophobicity was evaluated. For turf safety data, the story is a little bit different, since not all of the researchers took this type of data. For this reason, only 9 experiments were available for analysis, as shown in Table 2 above. These 9 experiments took place in 2003 and 2004 in TX, GA, MI and WA, for a total of 8 experiments. In NY, the results from 2003 and 2004 were averaged together; this data was handled as 1 experiment. This brings the grand total to 9 experiments were turf quality was evaluated.

Site-specific vs. summary data -- which is best? One of the problems we deal with in research studies is that no field trial -- no matter how well designed and no matter how large -- can account for all of the different site-specific conditions in turf type, climate, soil and water quality, and golfer/management expectations that superintendents cope with. For example, we have clients that are literally across the street from one another and while one deals with severe localized dry spot, the other has no problems at all.

How do we deal with this problem? In two ways. First, by looking for the most robust products and practices -- those that work well and consistently in as wide a range of locations and environments as possible. In the wetting agent study, there were 6 products that met this criteria -- Aqueduct, Brilliance, Cascade Plus, HydroWet, Primer Select and TriCure. These were the top performers across all of the trials.

After narrowing down the choices to the top performers, the second step is to encourage superintendents to conduct on-site evaluations to be sure that the field response matches the expected performance. How well does the product perform under the unique conditions at your golf course? Is there unacceptable damage to the turf (see below)? The bottom line: both site-specific data and summary data are important in selecting products and practices.

Turf safety: Another problem that comes up when evaluating research results is the trade off between performance and turf quality. Ideally, there should be no trade-off -- we always look first for those products that solve the problem without causing any damage to turf. Unfortunately, though, superintendents are often faced with the dilemma of using an effective product that has some risk of causing damage, OR using a less effective product that has less risk. There is no one "right" way to solve that dilemma. Each superintendent needs to balance the level of damage caused by dry spot or other factors against the potential risk from the product or practice. In the case of localized dry spot, there was a small but significant risk associated with the top performers -- they caused some reduction in turf quality in 1 (Brilliance, Cascade, HydroWet) or 2 (Aqueduct, Primer Select, Tricure) of the 9 locations where quality was evaluated. If this is of concern, then a look at LescoFlo, which had moderate efficacy but no impact on turf quality, might be an option. It is all a balancing act that each superintendent approaches differently. But having the data at hand can help make the decision much easier. The GCSAA-USGA study should be a great decision-support tool for superintendents who are faced with these dilemmas.