Sod and Pre-Emergents?

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cjac9chris
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Joined: December 27th, 2020, 12:46 am
Location: North Central San Antonio, TX
Grass Type: St. Augustine
Lawn Size: 1000-3000
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Sod and Pre-Emergents?

Post by cjac9chris » March 14th, 2021, 6:43 am

Hi,
I currently have a two-faced lawn in my backyard.

There's an existing 700 sq. ft. patch of St. Augustine that has been there since I bought the house plus a temporary annual ryegrass lawn that's about 400 sq. ft. In between them is a nice little patch of poa :x

When my soil temps hit 55* in January, I ran out and put pre-emergent on everything not realizing that that would effect sodding in the future.

My question is: if I cut out the ryegrass and poa with a sod cutter will that break the pre-emergent barrier and allow me to lay down St. Augustine sod next month?

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MorpheusPA
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Re: Sod and Pre-Emergents?

Post by MorpheusPA » March 14th, 2021, 4:12 pm

Well, it'll help. Since you're going to have to cut out the old grass anyway, that's a good thing.

Sod isn't going to react to pre-emergent like seed would. Sod is a living, already-sprouted plant, so it won't die. The root penetration might be a bit slower, but it'll get there. And yes, root trimming is a thing, too.

But what's done is done and there's no easy way around it.

cjac9chris
Posts: 46
Joined: December 27th, 2020, 12:46 am
Location: North Central San Antonio, TX
Grass Type: St. Augustine
Lawn Size: 1000-3000
Level: Some Experience

Re: Sod and Pre-Emergents?

Post by cjac9chris » March 14th, 2021, 10:11 pm

So you're saying there's a chance!?

Would you mind elaborating on what you mean by "root trimming is a thing"?

Thanks!

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MorpheusPA
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Re: Sod and Pre-Emergents?

Post by MorpheusPA » March 14th, 2021, 11:16 pm

More than "a chance," it'll work. You won't lose the sod, it just won't establish quite as quickly.

Root trimming is the tendency for the smaller feeder roots to be unable to grow in a pre-emergent layer due to the desiccation effect of the pre-emergent. The structural roots have no problem. So the sod's not going to establish good feeder roots (those really fine hairlike roots that absorb nutrients and water incredibly efficiently) until after the pre-em dissipates. But it's not going to be totally unrooted and can certainly send structural roots, and feeder roots of modest size without problems.

Pre-emergents only kill seeds. They're unable to kill anything even a few days old. It's not going to kill sod, particularly if you keep it moist, as you should. And you do need to cut out the old grass anyway, you can't simply lay sod atop the new stuff, and scratch up the soil where there is no grass.

The pre-em layer isn't very thick anyway and will be gone by summer (probably, if you let me know what and how much you used, I can tell you more accurately). St. Aug won't have any trouble laying down feeder roots then, and in fact, it probably really won't until then anyway.

cjac9chris
Posts: 46
Joined: December 27th, 2020, 12:46 am
Location: North Central San Antonio, TX
Grass Type: St. Augustine
Lawn Size: 1000-3000
Level: Some Experience

Re: Sod and Pre-Emergents?

Post by cjac9chris » March 15th, 2021, 9:16 am

Okay, that makes sense. I wanted to cut out the old grass so the new sod would be more level with the existing grass. I thought the pre-m disturbance would just be an added bonus.

I applied 3 lbs./1k sq. ft. of Sunniland Dithiopyr 0-0-7. I was out in the lawn yesterday and I swear I saw prills that still hadn't broken down (despite being watered in, watered several times since and rained on.)

I would imagine most would be gone by April when I'm sodding since I think it lasts about 30 days per pound from what I've read.


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MorpheusPA
Posts: 18131
Joined: March 5th, 2009, 7:32 pm
Location: Zone 6 (Eastern PA)
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Re: Sod and Pre-Emergents?

Post by MorpheusPA » March 15th, 2021, 5:47 pm

The prills are usually just the carrier; the active ingredient gets washed out after getting wet. Usually that prill is clay or something else and you don't need to worry too much.

So yeah, if you applied in early March, it should be gone by early June. Since you should still be working with the sod by that time, to some extent, you should be just fine.

cjac9chris
Posts: 46
Joined: December 27th, 2020, 12:46 am
Location: North Central San Antonio, TX
Grass Type: St. Augustine
Lawn Size: 1000-3000
Level: Some Experience

Re: Sod and Pre-Emergents?

Post by cjac9chris » March 15th, 2021, 9:33 pm

Ah, got it. Thanks!

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