What garden filler before top soil and turf?

[AmandaV]

I live at the top of a very rocky hill in the Northern Beaches. After buying the property, I had to tear out many of the small natives in our front garden due to years of neglect which had turned a 10m x 14m garden space into an overgrown mess. Then I had to rip up all the chicken wire that had been laid to deter brush turkeys (didn't work- don't recommend). The area is not level - there are holes and undulations and a fairly steep slope in places. It has extremely poor soil (clay and rocks) that has eroded quite a bit, and we get a lot of leaf fall from the surrounding gums. I also recently discovered the previous owners laid plastic matting under the soil.

So in all, not a great starting point. Oh, and the only access to this part of the garden requires a large crane.

My questions:

1. Before I bring in tons of new topsoil and lay turf, I would like to smooth out the slope as much as possible - what filler should I use before adding the topsoil? 

2. Given that the existing soil is rubbish, how much topsoil is required? I have seen suggestions ranging from 100mm to 150mm to 200mm. Given the size of my garden area, that is a big price difference at roughly $80 per cubic metre. 

3. Once I have added the topsoil, and before I lay the turf, should I add anything to the soil to enhance it?

4. Finally, to kill the weeds in my existing soil before adding the topsoil, can you recommend a weed killer that is environmentally friendly? I won't use Roundup or any other pesticides with forever chemicals in them.

Thanks!

AmandaV

[MitchellMc]

Hi @AmandaV,

To level and compact the area so it doesn't erode, I recommend using ANL 1 Tonne Loose Roadbase. You can then follow that up with 100mm of ANL 1m³ Organic Garden Mix, which you'll also compact, and then 50-100mm of ANL 1m³ NSW Premium Garden Mix—Bulk Bag.

200mm of soil would be a good amount over extremely poor substrate. You could go for less, even up to 100mm, but after natural compaction, you risk the layer of soil being too thin to sustain the grass.

To enhance the soil, it would be a good idea to add some Lawn Builder 4kg Scotts Starter Slow Release Lawn Fertiliser before your turf.

If you'd like to use a glyphosate-free weedkiller, I recommend Seasol 3L EarthCare Organic Weedkiller.

Please let me know if you have any questions.

Mitchell

[AmandaV]

Thanks very much for such a thoughtful and detailed answer.