Why the turf sucks on our local sports fields (not including golf)

The area where I live has some of the worst sports field turf that I've seen. Drive across the province and you will see a ton of amazing school and municipal sports fields. Even in the driest parts of the province, the grass is pristine. Enter the "Rainforest" on the coast and the grass quality is terrible. It has absolutely nothing to do with with the skill of the turfgrass managers, the amount of fertilizer they use, or the mowing frequency. It has everything to do with WATER.

In a recent post I discussed how we can determine how many "good days" we have each year for growing grass. That is the number of days where the growth potential is above 20% AND the 7 day effective precipitation (EP) divided by the 7 evapotranspiration (ET) is greater than 60% (60% is the crop coefficient for turfgrass).

Most people would be surprised to learn that the PNW is a pretty bad area for naturally (no irrigation) growing grass. We either get good temperatures for growing grass OR good rainfall for growing grass, but we rarely get both at the same time. This is good for golfing because you don't want it to rain when it's warm enough for golf but it's bad for actually growing grass. This year this was especially apparent with us having the worst growing conditions possibly ever but some of the best golfing weather, especially this fall.

The following table outlines this nicely. We had fewer than half the number of good growing days this year than in previous years. I don't know about you, but I can't produce a good turfgrass surface for the entire year with only 14 good days for growing grass.

Luckily for the golf courses on the Coast, we all have our own water supplies. We can irrigate our turf to make up for the shortfall of rain as long as we have good enough temperatures for growth. The following table outlines the number of days where we have good temperatures for growing grass but ignores rainfall.

Wow, we actually have quite a few good days when the temperatures are good for growth. This year wasn't great, but it also wasn't drastically worse than previous years. We can refine the effects that temperature have on growth by calculating the GP sum for the year. The GP sum is the sum of the daily growth potential numbers. If we have 30 days with a perfect growth potential of 100% or 1, we have a monthly GP sum of 30. If we have 30 days where it's 50% we have a GP sum of 15. The table below outlines the GP sum for the past 4 years.

While this year had fewer total days where the GP was greater than 20%, we had a slightly above average GP sum for the year. This was because we had an extended warm and dry Fall period. The table below shows the cumulative GP sum for each year and you can see that we didn't get caught up to previous years until October! We had a slow start but finished strong temperature wise.

So the moral of the story here is; We had a good year for growing grass IF you were able to irrigate. To figure out how much we needed our irrigation system (roughly, the best way would be to use a water budget taking into account the soil moisture holding capacity but for this calculation we will keep it simple but slightly less meaningful) we can subtract the number of Good Days from the number of days where the GP was greater than 20%. This is outlined on the following table.

Yep, I had the feeling it was a tough year for irrigating, this data sort of shows that. It's important to note that it doesn't show how intensely we were irrigating, but it shows for how long we needed to apply water throughout the season. It wasn't actually that bad this year as most of the days where irrigation was required was in the Fall when ET rates were relatively low. But in the end, insufficient water is still insufficient, no matter how low the daily ET is. The following table outlines our water use per Ha for the year. I would say it was an average year for total water usage.

So it's pretty clear that if you had irrigation, you probably had good grass. It wasn't easy, but it wasn't insanely hard either.

Back to the local sports fields. With the exception of the School District fields, everyone has irrigation systems that mostly use potable water (The School District doesn't have irrigation for the most part). The problem is that our potable water source isn't sufficiently sized for the demand and we routinely go into stage 2 (no watering grass) each year. This year we started stage 2 restrictions on July 25. To make the math easier lets just say it started on August 1.

From August 1 2022 onward we had 82 days of good temperatures for growth or over half of the total days in 2022. We only had 1 day of good growing conditions in the time span so we required irrigation for 81 days. This means that without an irrigation system and with water restrictions, we lost out on half of the good growing weather for the entire year on our sports fields.

On the golf course this is very apparent as we don't irrigate our driving range (due to water supply issues of our own) and it is still summer dormant brown. There was no rain when it was warm enough to break summer dormancy. It's basically 4ha of dirt at this point. The Coast's sports field aren't much better. Worse for them however, is that the majority of their use and traffic occurs during the Fall, Winter and Spring months when the temperature aren't sufficient for recovery. Combine this with no recovery in the summer and it's almost certain that failure is the only option.

The unirrigated driving range "turf" is the shits

To use the leaky bucket analogy, without the ability to irrigate, the local sports field turfgrass managers had a hole halfway up the side of their bucket (They only have access to water for half the days where temperatures are sufficient for good growth). The BEST they could hope for was 50% of what the weather allowed. If you have a hole in your bucket the only way to be able to fill it up to its full potential is to plug the hole. In the case of our local sports fields, the hole is the lack of irrigation during water restrictions. Any efforts to make things better will still only get you half way there and likely worse, you are only getting 50% of the value off of any investments you are able to make on your fields.

For unirrigated turf (school district) it's even worse. We had 14 days with conditions for good grass out of a total of 160 days where temperatures were good for growth. That's only 9% of the potential for the year.

In the golf business, 50% is not good enough. 90% barely cuts it! There is little point in trying to maintain assets (or expecting them to be reasonably functional) with only 50% as the best possible outcome. They have had many people offer opinions on what needs to be done to make their fields better but the data is clear. Water!