‘I’ve two queries relating to soil and the initial establishment of garden beds on grass.’

Here’s the full question:

‘What a wonderful project you have here! I’m finding this site a helpful learning tool, the videos in particular, and great to have alongside whilst heading to that stretch of green out back to coax it to become edible.

I’ve two queries relating to soil and the initial establishment of garden beds on grass. From your video on soil, I understand that a good garden mix is ideal for raised beds. We have at our fingertips mountains of horse manure that’s been composted with sawdust for several months. I’ve seen a few worms crawling through the composted material but remain uncertain whether we might plant directly into it? If we were to build beds, would you suggest planting directly or composting the manure instead? In terms of establishing the garden beds, I’m wondering what to do about the grass. My initial inclination was to build a series of hot composts, perhaps one/two a fortnight, to ‘cook’ the grass beneath and plant directly once done. The aforementioned manure could be useful here. However this process will take time and my flatmates are eager for summer bounty, so I’m wondering if there’s a ‘short cut’ (we are afterall into spring already). Should I dig? Should I simply create a raised bed and sheet mulch with cardboard above the grass? Long term, what do you consider the best option?’

Our response:

Great that the compost has worms in it. If the manure and sawdust have turned into a dark loam and you can’t recognise either component, it’s probably ready to use. It may still need to have some other nutrients (like seaweed or other organic material) added though as the manure and sawdust may lack some of the important elements necessary to grow many of the fruiting summer veges. Sawdust, especially pine, gum and macrocarpa can be very acidic, so a good dressing of lime can improve the soil quality.

Is your grass an invasive one like kikuyu? If it is, the best method if you want to get growing soon is to cover the grassed area with thick cardboard and newspaper and build the bed on top of this layer (this is sheet mulching which you mention). After a year, the grass should have died down and the bed can be aerated.

Options that take a bit of time are the hot compost one you mention, and also laying a clear plastic sheet over the grass and allowing the summer sun to burn the grass off. Both will take around 6 weeks.

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