Weed mat to kill lawn for prep? (Kikuyu lawn)

[Mimsy]

I just removed a relatively small area of sod (manually with a flat edge shovel) from my lawn in prep for a plant. Not only was it very hard work, which I don't mind but is time consuming, but I also had to dig down a bit to get through the rhizomes because the lawn is VERY well-established Kikuyu. I've got a map of approximate positions of most pipes/cables near me from the utility companies, but the location is approximate and I am a bit nervous digging. I'd like to try smothering the Kikuyu in areas with weed mat.
What is the best way to do this? Should I put down anything under the weed mat, like cardboard or extra soil, to help it along?

Here's 2 1/2 hours worth of work. It's about 70cm along the long edge. Phew!

 

[DirtMechanic]

Most people I know would spray it and save the delicate digging for the mulched area under the trees and shrubs.

 

[Oliver Buckle]

I don't know what sort of plant you are planting, or how rushed you feel about getting things done, but here is a thought if you don't mind substituting time for work. Find a nice big paving stone and a good big pot. Put the paving stone on the grass, the pot on the paving stone, and the plant in the pot. After about a year or so when the plant is starting to outgrow the pot, lift the paving stone, dig a hole in the dead square of grass and drop the contents of the pot in. You could turn over the rest of the dead grass, mulch it, and have a nice, neat square, an edge would keep the mulch in and keep it neat.

 

[cpp gardener]

Cut through the stolons and rhizomes around the area you want to plant in and spray with glyphosate (Round-up). This will kill the kikuyu in that area without damaging the rest of the lawn. You will have to treat new grass growth in the future, since it spreads by rhizomes underground.

 

[Mimsy]

Cut through the stolons and rhizomes around the area you want to plant in and spray with glyphosate (Round-up). This will kill the kikuyu in that area without damaging the rest of the lawn. You will have to treat new grass growth in the future, since it spreads by rhizomes underground.

How long does glysophate linger in the soil? I'm not averse to using a bit of herbicide, but I am nervous about unintended side effects.

 

[cpp gardener]

It is bonded to soil particles and not a threat within minutes. It doesn't move in the soil and won't be absorbed by plants. Essentially a non-issue.