Below the surface

Managing soil health is an important component in any turf manager’s agronomic program. In order to do this effectively, superintendents need to, among other things, consider the soil composition on different playing areas of their courses; test chemical, physical and biological properties of their soils; and incorporate slow-release fertilizers.

In an interview with GCI, Dr. Cale Bigelow, professor of agronomy at Purdue University, shared these tips and other information related to soil health and composition. Here’s what he had to say:

GCI: Is soil composition a topic turf managers have a firm grasp of?

CB: I’m going to say some yes, some no. That’s probably the easiest way to answer that. I think that when you talk about soil composition, particularly on the golf side of things, so many people are very focused on their sand-based root zones. So that would be their putting greens or tees. The reality is, they’re managing much, much more acreage, and I think that their appreciation of what they have there is lower. And that’s sand, silt and clay, soil texture, soil structure, all those things, I think that’s an area that they are probably not as confident in.

How is soil composition tied to overall turf health?

Bottom line, it has a strong influence on the soil physical properties, so how much pore space would be there, but it also has a very strong influence on the microbiological properties as well.

What is the correct soil composition for golf course turf?

There’s an optimal or an idealized soil, which would be 50 percent solids, with some of the solids being some amount of organic matter, and then there’s 50 percent pore space, which is evenly balanced between water-filled pore space and air-filled pore space. That’s the standard, sort of textbook pie chart. But when you think about ideal soil, it might depend upon the playing area, as well. For example, on something like a putting green, you’re really striving for a very strong sense of surface firmness. Fairway is maybe the same thing, tees maybe not quite as much.

How does soil testing factor into assessing soil health, and overall turf health?

I think that a lot of managers that have been around it and experienced for a while, they have a pretty strong appreciation for the differences between testing for physical properties, which would be pore space, drainage category, soil composition in terms of sand-silt-clay ratios. And then you have your chemical properties, which would be your nutrients. The other thing that we are starting to see a few people doing is you can actually do some tests now for the microbiological activity, which ties into the soil health conversation.

What is the importance of slow-release nourishment for golf turf? For example, because of what the turf must endure – mowing, aerification, high traffic/play, pest pressure – are those needs different or heightened?

I think that when you have a conversation about any sort of nutrition, it’s a regular release of nutrients to meet the plant’s demand. So with that, you’re looking at something that is not going to have a lot of peaks and valleys, you’re not going to have the flushes in growth, you’re going to be able to promote steady vigor, but you’re not going to have a situation where you’re not going to get a lot of succulent growth. So that’s where sometimes people use the term ‘controlled-release’ type material. And that ties back a little bit to that idealized soil that you were mentioning because with some of the organic matter that might be in there or that you might create over time, that’s going to contribute to that background nutrition.

How does a strategic fertilization directly impact spring green-up and summer recovery?

It comes back to making sure that sufficient nutrients are there so that the plant’s needs are met. Typically with cool-season grasses, we still focus to a certain extent on some fall fertilization to make sure that the plant is essentially pre-loaded and ready to go for that growing season. If you experience a summer like we just did in 2016, your nutritional program might be slightly different because there was quite a bit of summer stress for people, particularly late in the season where, in some situations, the nutrition might have run out. It was warm, it was hot, it was wet, and some of the plants that got stressed out — it’s possible that they needed a little bit more gas to get through the race.

Is there anything else that you would like superintendents to know about soil health or soil composition?

It’s a systems approach. And by that I mean that there’s probably some sort of soil cultivation involved, there’s some sort of a testing aspect where you’re trying to benchmark or gage where your starting point is and where you need to go. There’s also going to be probably some incorporation of some sort of carbon based amendments. Those could be composts, those could be natural organic fertilizers. That’s where we oftentimes see some deficiencies, particularly on heavily disturbed sites — not necessarily on golf greens, but on golf course fairways, roughs, some of those kinds of areas that are of more native soils and not synthetic soils.

Check out EarthWorks Website -- www.earthworksturf.com -- for more information.