How much soil to move

[rary]

I have a raised bed in the greenhouse which I use for growing tomatoes the soil depth is 12inches it can take 15in. if I am putting fresh soil into the bed what depth of soil would I have to remove before adding the fresh soil?

[veggiechicken]

Remove soil??
You old people have nothing better to do with your time than make work for yourself!!
Why don't you just top it up?

[Snoop Puss]

Rary, are you removing soil so that you can grow tomatoes in the same bed next year in what is effectively fresh soil?

[SarrissUK]

Yeah I'm with VC - I wouldn't remove any, if there's a few inches to spare at the top. Just top up with manure and you're done

[quanglewangle]

Wow: interesting thread for me as a new greenhouse operator. I was expecting to dig out best part of half a cubic metre of compost/topsoil mixture and repace it.

Is the consensus that I don't have to? What about pathogens?

[veggiechicken]

What's the difference between growing in open ground and in the GH?

Do you remove half your "open ground" bed and replace it each year?

[Bren In Pots]

I dig a good size hole fill it with dalek compost then plant my tom into that, seems to work fine for me.

[quanglewangle]

What's the difference between growing in open ground and in the GH?

Do you remove half your "open ground" bed and replace it each year?

Not sure this is a fair comparison. Outside you get lots of UV, fresh air, a wider range of invertebrates, birds, and hoeing, to keep pathogens and other nasties in check.

Really don't want to dig out my greenhouse bed but need more convincing arguments.

[ameno]

What's the difference between growing in open ground and in the GH?

Do you remove half your "open ground" bed and replace it each year?

You rotate crops in open ground, so pathogens never get a chance to build to problematic levels.
In the greenhouse, though, especially a small one, you would grow the same crops in the same soil year after year.

[rary]

Remove soil??
You old people have nothing better to do with your time than make work for yourself!!
Why don't you just top it up?

I have some bags of seaweed and also a compost bin to empty plus I want to change the soil in my trombo bed as thats 2 years i have been growing them in the same soil though seaweed and manure was added this year
and that enough of the old people bit, it me, rary, you are referring to not yourself

[veggiechicken]

I'm not a believer in crop rotation either.

I grow my tomatoes in bottomless pots in fresh compost resting on old compost. At the end of the year I empty the pots onto the same bed and grow winter veg in it.
The following year, I do exactly the same, toms in bottomless pots resting on the previous+++ year's compost. It works for me.
I wouldn't know a pathogen if it jumped up and bit me.
I'm just a simple chicken who's been growing in GHs this way for 40+ years.

[rary]

Rary, are you removing soil so that you can grow tomatoes in the same bed next year in what is effectively fresh soil?

That`s correct Snoop the raised bed sits on a concrete floor in the greenhouse and as I have said to VC there is an other bed I want to change, but going with the comments I will be leaving a 3 inch bed of old soil at the base I have started to dig the soil out and about 3 inches below the surface the soil is moist and that is after about 2 weeks without watering and temperatures of over 35c the past 2 days so quite pleased with that plus the soil is alive with worms which is great to see

[quanglewangle]

[...]in bottomless pots in fresh compost[...]

Hmm. Interesting. So you really are growing in fresh compost, just not very much, you wily chicken you.

If, as you say, this has been successful for you perhaps we can conclude that the pathogens (there really are such things VC) don't attack plants from the deeper roots - the ones that stick out of the bottom of your bottomless pots.

[veggiechicken]

QW, I believe you when you say that pathogens exist but, until one comes along and introduces him/her/itself to me, I shall feign ignorance.

Like rary (I do really - he's old so I respect him), my GH beds are on a solid floor and the beds are only a few inches deep - but comprised solely of old compost from earlier year's tomatoes. Each year it builds up another inch or so. In the oldest GH its about 6" deep and I grow root crops in it overwinter. That compost has been there for at least 20 years.

Photos at
https://www.growfruitandveg.co.uk/gr...ml#post1667967

[rary]

I'm not a believer in crop rotation either.

I grow my tomatoes in bottomless pots in fresh compost resting on old compost. At the end of the year I empty the pots onto the same bed and grow winter veg in it.
The following year, I do exactly the same, toms in bottomless pots resting on the previous+++ year's compost. It works for me.
I wouldn't know a pathogen if it jumped up and bit me.
I'm just a simple chicken who's been growing in GHs this way for 40+ years.

As a general rule I would do the same VC but as I grow in what is basically a closed pot (poly lined raised bed on a concrete floor) and as I want to add the bags of seaweed I need to remove some of the soil
As for the simple chicken bit, who are you trying to kid and as for the 40+ years, people generally put the higher number first rather showing it like you have, as a + sign