[KaySee]

I'm in the process of pulling up my tomatoes, peppers and chillies. They have been growing I raised beds filled with "Mel's Mix" from the square foot gardening book. When I pull the plant up the roots are very fibrous and mat the soil into a large clump about the size of the whole bed. I can shake most the soil out of the roots but it leaves a lot of small fibrous strands. I can sieve the soil but it's a very slow process and doesn't remove them all anyway.

Now given that I will rotate the plants into different beds next year, the cost of replacing the soil each year would be prohibitive.
How much effort should I put into this? i.e. should I just pick out the biggest bits and leave the rest?
Is the sieving necessary?

[Eblana]

I just take out the bigger ones and the rest seem to compost off into the soil themselves.

[mumofstig]

I just take out the bigger ones and the rest seem to compost off into the soil themselves.

The small roots rotting away help keep the goodness in the soil, are the beds open to soil at the bottom?

[BabbyAnn]

They have been growing I raised beds filled with "Mel's Mix" from the square foot gardening book.

I presume the soil has indefinite depth and not restricted by a base.

Now given that I will rotate the plants into different beds next year, the cost of replacing the soil each year would be prohibitive.
How much effort should I put into this? i.e. should I just pick out the biggest bits and leave the rest?
Is the sieving necessary?

If the roots are small then they will eventually rot down and add biomass to the soil.

Although I don't do square foot gardening, I thought it was intentionally to grow as much as you can in a small space in a season.  This means a lot of the nutrients required for healthy plant growth and cropping will have been taken up by your crops, so you need to replace the nutrients (not the soil)  I think you will still need to add something like compost though

[KaySee]

Thanks for the answers.

The beds are on a weed barrier, which sits on very hard compacted clay soil.

It makes sense to leave them to rot, and I suppose that is the point, I was more concerned about disease from the tomato's, I keep reading that you shouldn't compost tomatoes and potatoes etc.

[mumofstig]

I'd remove the weed barrier so that worms can get into the compost they'll do a good job, if a slow one, of mixing compost and soil together to give you a good growing medium, that will only need the occasional top up.
Most veg will grow better if they can get to nutrients and moisture deeper in the soil.

[snow white]

I have been doing lots of reading lately about square foot gardening and raised bed gardening.  Mel recommends taking the roots out but raised bed people say leave the root in so it composts into the mix.  If it was me, I would take the big bits out and leave the rest.  As long as you are not putting tomatoes or potatoes in the same bed next year, I can not see a problem.  You will  need to refresh some of the compost anyway with fresh.  It is your garden, so do what is best and easiest for you.  It is far to expensive to keep adding a whole raised bed worth of fresh mel's mix.

I would also remove the membrane as mentioned so that the worms can assist in breaking down the compost and adding their own special brand of manure.