Soil mix.

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Colin2016
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Soil mix.

Postby Colin2016 » Fri Nov 04, 2016 3:39 pm

Just gone out & got 5 bags of compost & 200 litres of Vermiculite which I want to mix with soil that is discibed as freely draining slightly acid loamy soli, with low fertility & low carbon.

Any suggestion on what ratio to mix it up and what is the easiest way of testing it once done?
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Geoff
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Re: Soil mix.

Postby Geoff » Fri Nov 04, 2016 5:58 pm

The benchmark for soil based composts are the John Innes formulations. For a deep bed you would use the potting formulation which was originally 7 parts loam, 3 parts peat and 2 parts sand. The difficulty with this was always defining loam, the best form was supposed to be rotted down turves which I would guess would have a slightly higher organic content than unimproved garden soil. Assuming by compost you mean a modern peat free formulation that has no soil content I would suggest using something like 2 parts soil, 1 part compost (to boost the organic content a bit from 7:3 ratio) and just over ½ part vermiculite, assuming you are using that instead of sand (not sure why you have chosen it, I would prefer sharp sand). You can usually tell if a mixture feels right, too sticky or too gritty, so mix some then perhaps change it a bit.

The other thing to consider is the fertiliser requirements. A deep bed would require the richest formulation JI3. In the original formulations this would require the addition of 0.6 kg ground limestone, 3.6 kg hoof and horn, 3.6 kg superphosphate and 1.8 kg potassium sulphate per cubic metre of mixture. You probably wouldn't do it this way. You could buy a base fertiliser and use it as instructed but this is usually an expensive option. The above mixture has an N:P:K of about 5.2:7.7:10, compare this with fish, blood and bone at 5:5:6.5 and you come to the idea of using about 10 kg per cubic metre of FBB with perhaps a little extra superphosphate and the limestone. You could use a bit less than this on the basis that nearly a quarter of you mixture (the compost) should already contain some fertiliser.

Not sure you can really do a quick test at this time of year, you'll just have to see how it goes. Good luck.
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Colin2016
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Re: Soil mix.

Postby Colin2016 » Sun Nov 06, 2016 2:17 pm

Thank you very much Geoff for your detailed reply.

Yes using peat free compost and went for vermiculite as I have read this retains moisture better.

Have read chicken manure is good so if I add fish, blood & bone would there be any benefit in adding chicken pellet manure?

Thanks again for your help.
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