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Bermuda Lawn: Weeds' response to urea application?

Posted by mistermango 7 (My Page) on
Sun, Jun 9, 13 at 15:17

I live in Knoxville, TN, and am in the slow process of deweeding a mostly Bermuda lawn. I am not 100% organic, but I prefer a non-chemical approach. I've taken a long view in my efforts to rid the yard of copious amounts of dallisgrass, content with the fact that it may take a couple of years to reach an acceptable lawn-to-weed ratio.

I maintain good cultural practices -- regularly mowing very low and watering deeply only when needed. At the start of the spring, while the Bermuda was still dormant, I applied glysophate to the lawn to attack the dallisgrass. It worked well, and the Bermuda is starting to fill in the brown spots created by the killoff. It is also very easy to pull what weeds are popping up in (or returning to) the dead areas.

Just last month, I applied my first round of urea (46-0-0), which is where my question comes in. As expected, the Bermuda responded very well to the urea. But within the last week or so, the weeds have started sending seed heads up like nobody's business.

Is the weed seeding activity because of the time of year, or because of the nitrogen application? The fertilizer application correlated to our first stretch of summer-like temperatures, so I'm assuming that's the cause. But, it'd be nice to know if the fertilizer I applied contributed to the unwanted plants' sudden desire to multiply.

Thanks for any insight you may have.

Follow-Up Postings:

RE: Bermuda Lawn: Weeds' response to urea application?

Can you post a picture of the weed seeding activity?

RE: Bermuda Lawn: Weeds' response to urea application?

The first of a few photos to come is attached. I mowed about 24 hours before these photos were taken. Before mowing, I snipped several dozen tall seed heads off the dallisgrass to prevent broadcasting the seeds. During mowing, I probably mulched another dozen or so that I had missed. What's in the lawn now are likely younger than 24 hours old.

What I noticed last summer--my first season in the house--was that the seeds became apparent, it seems, only when the dallisgrass stalk shot higher than a couple of inches tall. These are growing prostrate, making the ability to trim them before mowing problematic.

I don't think these seed heads are necessarily unusual. I just think the timing of my first nitrogen application a week or so before their sudden (and prolific) emergence may be more than just a coincidence.

RE: Bermuda Lawn: Weeds' response to urea application?

Another photo.

RE: Bermuda Lawn: Weeds' response to urea application?

And another.

RE: Bermuda Lawn: Weeds' response to urea application?

"regularly mowing very low"

I know you said you regularly mow very low, but in the pictures it looks like you haven't mowed in a while.

The fertilizer will make everything grow faster including the weeds, which will form seeds if you let it grow too high as you have noticed.

You need to be mowing twice a week or so depending on how short you are really mowing. This will cause your bermuda to want to grow horizontal instead of vertical and can choke out most weeds. Also, most weeds (not all) don't like being cut short often, which can kill them off eventually.

How short and how often are you really mowing?

RE: Bermuda Lawn: Weeds' response to urea application?

" I mowed about 24 hours before these photos were taken"

I just noticed you said you mowed 24 hours before the photos were taken. In that case it doesn't look like you're mowing very low.

Bermuda likes to be cut very short. Anywhere from well under an inch to 1.25 inches.

I keep my front lawn under an inch with a manual reel mower and about 1.25 in the back with a rotary mower.

How low are you mowing?

RE: Bermuda Lawn: Weeds' response to urea application?

I have my mower set to the next to lowest deck setting. I can't set it at the lowest setting, as my yard isn't level enough to pull it off. I mow twice a week, typically.

This last week was an exception, since we had many days of rain that prevented me from mowing for nearly a week. In the mow before these photos were taken, I had the deck set on the third-from-lowest setting, as to not take off too much at once.

RE: Bermuda Lawn: Weeds' response to urea application?

Sounds like you're doing what you can, then.

I'm pretty sure I've had that weed in your pictures in my lawn before and it had seeds even though it was cut very short. It was all growing outwards horizontally, which is how it avoided the lawnmower blades. I only had a few and pulled them easily.

If you don't have too many maybe you can pull them.

Also, just to clarify, my statement about cutting height is for hybrid bermuda. I get the feeling you may have common bermuda, which should not be cut as short as hybrid, but I'm not sure how short. You can find the info easily by searching.

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