Sterilizing compost?

Has anyone tried to sterilize compost? - and how do you do it?

My OH looks after the compost heap ( and lawn, for his sins!) and I have to admit that I have a habit of putting some perennial weeds on there.I know I shouldnt but...

This year I decided to try his compost from the heap with some of my seedlings after pricking out and they have done slightly better than the ones in the usual multi purpose. Problem is of course the weed seeds and I have lost a few seedlings to something chomping them.

It would save alot of money if i could sterilize it as we do make loads of the lovely stuff.

 

I'd like to be able to do that too!

When I worked on a comemrcial nursery we had steam pipes (long ridgid metal perforated pipes that clipped together) that hooked up to the boiler, and we piled the earth in furrows over the pipes, and them large tarpaulins over that. Can't remember how long we left the steam running for, but we were growing "virus free flowers" in plastic tunnels, and the hygene was very important, so I assume that steam was regarded as the best route ... although it was 30 years ago ...

For very small quantities (e.g. a flower pot amount) I reckon you could microwave it - but I don't know if that will de-nature any of the good stuff in the compost? The bugs will be cooked for sure! and I expect any weed seeds too. How long for? Dunno :( You could put some in for one minute, then another batch for two minutes ... and see what grows in each batch.

 

MMM.......sounds very interesting!

Maybe I will try microwaving some for varying times and putting a seedling in each....

I read somewhere that you need a temp of 160 deg to sterilize it - but I may well be wrong on that one!

Ah well, back to the microwave! lol

will let you know how i get on!

 

A steam wallpaper stripper would be a good option for wet heat, the microwave would probably dry the compost out completely :wink:
I think you`re right with the temperature of 160F, i read somewhere if you take it too high 212F (100C) it would be toxic for planting, so you`d need to wait for the bacteria/flora/fawna to re-establish to deal with it.

 

Now don't laugh, but I think a friend used to boil garden soil in a saucepan on the hob when she needed "compost" to plant something, as the cats had usually widdled all over that area of the garden. She just stirred it round in an old saucepan on a low heat and it seemed to work.

 

Do you reckon sterilising would kill the herbicide used in lawn weedkillers?

 

I doubt that sterilising will denature herbicide, but it might, however I believe that lawn herbicides breaks down in about 6 months (I think that's what I've read on the packet).

(There are far more persistent weedkillers used by farmers on meadow land used for grazing and hay-making, which then persist in manure etc., but I presume you aren't meaning those when you say "lawn weedkillers")

 

I use a microwave I have in the shed 1kg in a polythene bag (tied) nuked for 2min 750-850w it works great and doesn't dry out,I have used a wallpaper stripper it is very messy,I know someone who uses the boil in a fine cloth bag method ok for small amounts,temperatures around 160f is about pasteurisation temperature and will kill most bacteria, moulds and yeast.

 

"I use a microwave I have in the shed 1kg in a polythene bag (tied) nuked for 2min 750-850w it works great and doesn't dry out"

Perfect ... our microwave is well past its best for the kitchen, I think I might relegate it to the garden shed!

 

wow thanks everyone! some great ideas there.

I think i shall try microwaving and see what happens. I will keep you posted!

 

Good excuse to buy a new one for the kitchen then:D

 

but if your killing all the bacteria, surely your killing all the goodness as well

 

Its the nutrients that the plants need, and they won't be effected by sterilising, normally. I don't think that microwave, or steam-pipes, will de-nature the nutrients.