The dirt on soil and bionutrition

A good superintendent knows his turf from the ground up; staying in touch with the soil can make the difference between a weak stand and a healthy stand. Biostiumlants come in a variety of forms and from different sources. They can help bolster that turf during the stressful summer months, but what kind of program will supply the nutrition your soil lacks?

It’s in a superintendent’s nature to want to start by checking it out from underground, but Dr. Bruce Branham, turfgrass researcher at the University of Illinois, says that approach might only get part of the answer.

“The question is more about how do you determine what the plant needs,” he says. “You could do a soil test, and that generally works for potassium and phosphorus. Things like iron, manganese and copper, we really don’t have a good way of looking at in the soil. It’s a better idea to take a tissue test.”

A tissue test of the plant will give a more accurate picture of what’s going on inside the turf at the time, and what’s getting picked up from the soil. This helps determine whether bionutrition will support the course’s goals, since each course has a slightly different concept of the ideal stand of turf. The wide variety of responses for turf makes best bionutrition levels difficult to nail down in studies and in regular soil testing, says Branham.

“In turf, it’s a lot harder to know what the optimal levels are, as turf is not a normal crop,” he says. “With other crops, you can correlate nutrition levels with yields. With turf, we don’t know what to evaluate for exactly. Quality is subjective.

“When it comes to bionutrition, it really becomes much harder to tell what turf needs. We want the plant to be maximally healthy, but it’s a subjective process. You can sometimes see results. A hard question is: Do you use it all the time? How do you decide what the turf needs? It’s not easily amenable to simple answers. We can easily tell whether a fungicide or herbicide controls a specific disease or weed, but it is much more difficult to determine if a biostimulant has increased turf stress tolerance.”

Whether or not biostimulants play out easily in studies, green is green for many superintendents. Rebounding from last year’s wet spring and blistering summer that gave disease a solid hold and dried up greens, some possible help for protection against the heat this year is welcome. Biostimulant programs, like those with seaweed extract, have been used to help support turf health and nutrition when the plant’s own natural resources are running low with an intense summer.

“What I tell people is they’ve been shown to enhance stress tolerance of turf,” says Branham. “If you’re expecting heat stress, they can be useful. It’s kind of like insurance for turf under stress. The hard part is trying to evaluate what it’s doing for the turf.”

Since many studies aren’t going to be able to speak directly to the needs of your turf, the best way to evaluate how biostimulants should be used is to ease into a program, either treating portions of the course or leaving some of the course untreated.

“That’s the one thing they should do is leave a small area untreated to visualize the effectiveness of the product,” says Branham. Testing the applications over time, perhaps a season before applying it to the whole course, can give the superintendent hard evidence to work with. “This can help convince skeptical board members that the product is worth the cost.”