This will make you rethink what you throw in the spray tank

In 11 attempts, Si failed to increase green speed every single time

Beth Guertal wrote to me a couple weeks ago:

“I liked your Si blog post of recent date. It made me go back and find some data I collected once upon a while.”

As you probably know, I think it is ridiculous that more silica in leaves would somehow make greens faster, or that it would make for a cleaner cut of the leaf. More about that later.

I also think it is ridiculous that green speed data are so easy to generate, but there is no data to show that Si increases speed. Why? I have speculated that the lack of data means people have tried to do it, but haven’t been able to. So I was glad to receive this report and data from Beth.

There were three treatments applied to a Tifeagle green. Control of nothing applied, Si treatments that also included N and K, and an N and K treatment to match the rate applied in the Si treatment.

The N rate was 0.1 lbs N/1000 ft2/week (0.5 g N/m2). Treatments were applied weekly for seven weeks. Green speed was measured 11 times. Here’s the results.

si speed chart 11 dates

On 11 times the green speed was measured, the Si treatment had the fastest speed on 0 of them.

And that is no surprise, when you think about it. Zoysia species are known for having a high silica content of the leaves. They are also known for being difficult to mow cleanly, because of that high silica content of the leaves. And they are also known for having a slow green speed compared to other grasses receiving the same maintenance, also because of the stiffness of the leaves.

Which green is going to have a faster green speed? Fine fescue at 5 mm? Or korai at 5 mm? Once one thinks about that, it is pretty obvious that the silica content of the leaf, in terms of making the leaf more rigid, is certain to slow, rather than speed, the ball roll.

And I expect I may hear some responses like this:

“I know the label says ‘increases green speed’ or ‘allowing for a much cleaner cut’, but I think that is nonsense. I’m applying it to boost plant defense against stress and pests.”

Ok, fine. High silica content of zoysia leaves still leaves the grass susceptible to decimation from insects and diseases. Here’s some armyworm activity on Zoysia japonica in Chiba.

noshiba armyworm damage

Here is the wonderfully-named dog’s footprint on Zoysia matrella in Hilo.

inu no ashiato in Hilo

Maybe Si helps with something. But I’d prefer to manage turf without adding any extra.

For more about this, see:

  • Silica and green speed, in which I ask, “So if silica does make greens faster, shouldn’t zoysia greens be lightning fast?”
  • The first half of this post on N & MLSN, in which I wrote “We’ll get to the N below. But wow! I didn’t know silica was such a hot topic!”
Micah Woods
Micah Woods

Scientist, author, consultant, and founder of the Asian Turfgrass Center