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We moved into our new house in late March and started with mud. The builder put down seed with a hand spreader and put straw down on the sloped parts of the yard. He then told me to only water it every few days but not if it rains. I moved from a condo so I took him at his word.

My lawn is a wreck now, and despite doing a ton of research, I don't feel 100% confident in a good plan on how to deal with it.

The parts of the yard that did not have the straw down are seemingly 98% crabgrass. It's horrible. There are also lots of weeds, which I think are categorized as "broadleaf weeds" all over. From what I understand, weeds are common when you have soil brought in, and crabgrass when there's a low density of good grass and high heat and/or no shade. I've been cutting the grass at 3" for the last few months to give the grass a chance to survive, but it means I only have a non-embarrassing yard for 3 or 4 days and I've been mowing weekly throughout the summer just to keep the crabgrass length down.

My yard has zero trees, is pretty flat in the front and back, and slopes down maybe a total of 8-10 feet as it goes from the front of the house to the back.

After I bury some irrigation pipe for drainage from my downspouts next weekend, here's my plan:

  • [power]rake to clear up debris (straw is everywhere!) from the soil
  • rent an aerator and run it over the yard and dump in new seed
  • water aggressively for a few days, then daily for a couple weeks
  • fertilize in mid to late September
  • continue watering regularly
  • fertilize in November

I have no idea if this will be effective. I also don't know if I should aerate and seed again in the spring or if that would just damage the new seedlings.

What advice would you give to me?

TL;DR - new lawn is a mess of crabgrass an broadleaf weeds. What's the best strategy heading into the fall and next spring?

  • I would suggest you water deeply; that will encourage deep-rooted grass, not shallow grass, which will beat out weeds in hot weather. – ashes999 Aug 17 '13 at 18:10
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I agree with Randy that a soil test is essential but a few simple tests now will help guide your decision:

  • go to your lawn and dig a few holes and take a cup sized sample from each
    • when the soil is neither really dry or really wet take the sample in your hand and make a ball of it. Does the ball crumble apart when you open your hand ( sandy) or sit like a lump of....clay?
    • get a transparent jar and fill half to two thirds with water. Add a soil sample, shake and let sit overnight. Do you observe any layers in the soil? Rich soil will have the heavier clay type particles at the bottom, sand and silt on top with organic matter floating at the very top.

The most likely problem is an absence of organic matter because the developer has given you subsoil to work with. Other possible issues are that there is a heavily compacted layer of soil underneath the soil the developer added.

To get nice looking turf you need sunlight, a good soil profile, water, grass or mixture of grasses adapted to your area and good lawn care practices. Here are some solutions from previous questions:

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I wonder if you topsoil was removed? Possibly even sold to someone else. Regardless, it seems as though your topsoil is not what topsoil should be. You may start with a soil test. Here is an especially bad report I found online that I'll use for illustration purposes.

enter image description here

Not much of anything would grow on this "lawn", except a few weeds here and there. It was a newly constructed house in the Atlanta area.

The 1st thing we notice is the "total exchange capacity" is far to low to support life. In the southeastern states, a 10-15 number would be good. In the midwest, you could double that. This soil could greatly benefit from some organic matter as the humus would raise the TEC number significantly.

The 2nd thing is the ph is far too low. 5.5 can be considered low for many grass species, but 4.6 is crazy.

Next we skip down to the "base satuation" category and see there is 23% Ca where there should be 60-70%. And then, there is 53% H where there should be 10% (hence all the acidity).

This is an extreme example, but might not be too different from what you're dealing with. To put grass seed on this soil would be a total waste of time and money. Aeration will do nothing to fix the problem. The 1st and most important thing to do here is lime, lime, lime and more lime. Then after a few months of that, get another test and see where the other cations are lining up. H should go down and Ca will go up. If Mg is low, switch to dolomite lime. It often takes a year or so before lime works down into the soil, so if tilling or somehow mechanically mixing the lime into the soil is an option, that will speed up the process.

Anyway, its difficult to know what you're dealing with for sure, but almost certainly you're missing Ca. Especially if you live in an area that receives more than 20-30 inches of rainfall annually. Calcium is by far the most leached nutrient from soils. A soil test may be the wisest thing you could do at this point.

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