Raised Bed - Soil/Compost Life.

[MichaelD]

Hey, apologies if the title of the thread is somewhat confusing. I'm not really familiar with gardening terminology as yet.

Lets say I build a raised bed and fill it with soil/compost, ie whatever is needed.

How long can I then keep growing in it? Will I need to change it every every few months, 12 months, longer?

Regards
Mike

[burnie]

Are you putting the raised bed on soil or onto a solid base like concrete? If it's on soil then it will not need changing, just topped up with compost or manure depending on what you grow in it. If you build onto a solid base you can find the soil can become depleted faster and may need changing, you may also need to change soil in a greenhouse after a time too.

[ameno]

Even on a solid base, if the capacity is large enough, it should never need changing due to depletion. Just feed the soil every year with something which gives a wide range of nutrients (not just NPK) and you'll be fine. I use pelleted poultry manure. Fish, blood and bone would probably work well, too. Artificial fertilizers lack micro-nutrients, so are no good for a bed with a limited capacity of soil. And horse or cow manure is a little too bulky.

[lolie]

I grow most of my stuff in small raised beds which have a base. I used to empty them out and change the soil but now I just top them up each year and add amendments.

I also do the same with my large raised bed which doesn't have a base.

I would probably only change the soil now if there was some issue which needed a quick solution. In the past I found beds containing a lot of coir repelling water over time. It was definitely quicker to replace the soil. If I eventually put my blueberries into beds, I'll probably replace the soil rather than amend it.

[Bren In Pots]

Mike you've had some good advice so all I'll mention is crop rotation there's lots of info on line but its basically don't plant crops such as cabbages, onions or potatoes in the same place each year. It helps prevent problems building up in the soil.

[ESBkevin]

I'd say you've been given good advice so far, can I add some other information?

Essentially in the UK top soils there are enough trace elements unless you are on some sand/heathlands, the problem is making them available to the plant roots. This is where nature is your friend, the various micro life forms and fungi make those 'digestable' by the root systems that feed your plants. You can force feed potasisun and nitrogen etc. with man made chemicals, but those chemicals too are a bi-product of the breakdown or organic material.
So in simple terms adding more composted material as a mulch (or dug in if you really must), will create a harmonic production line of available nutrients for whatever you plant in there. Nothing is instant, but the soil will contain all the microbes needed and suitable for your localised soil type within itself (billions in a single spade full). When we feed the soil life, it multiplies to the available food source just like nature does with anything. The various stages of decomposition use differing organisms or fungi and each bloom at the appropriate time to reproduce and create thier contribution. The result is the soil food web feeds your plants an dthey feed you so you feed the soil and so on.
The great news it that the soil food web regulates itself and you hardly have to think about it other than slpping more compost/mulch on there.

[Kirk]

Shouldn't have a problem, just every year or so you will need to add additional nutrient in one form or another.

Will "warn" you that adding it as manure will slowly fill the bed up - I have found that to occur and it is/can be a bit of a problem. Eventually the bed is not high enough.

I have about 2 inches spare height now and this year I will add a bucket of pelleted chicken manure. I can add another 2 inches fairly easily after that no way to add additional. You may want to consider the chicken manure idea eventually.

Always seems a good idea to fill the bed to the top, it isn't.

How high is the bed ?

[MichaelD]

How high is the bed ?

I haven't actually built it as yet, however i'm thinking about 2-3 feet.

[veggiechicken]

You'll need a lot of compost/soil to fill a bed 2-3 feet deep!

[MichaelD]

You'll need a lot of compost/soil to fill a bed 2-3 feet deep!

Will one foot deep be enough to grow in?

[veggiechicken]

Are you building your beds on soil? If so you have plenty of depth already.

[SarrissUK]

The depth required will depend on what you want to grow too, Michael. Lettuce and radishes for example have very shallow roots, as do most cabbages so they wouldn't need even a foot of depth. Other crops such as carrots, parsnips and all fruit bushes, raspberries etc will need more depth than that, and I would say, best in raised beds that are on top of the ground, with no base.

Depth is also good to provide a more stable water availability for the produce - the less depth and width, the more regular watering is required.

[MichaelD]

Are you building your beds on soil? If so you have plenty of depth already.

They will be yes. Wont I need to dig the soil before hand though? I don't really want to if I'm honest, however I will if needed.

[veggiechicken]

Have a look at Charles "No Dig" Dowding's website......................https://charlesdowding.co.uk/start-here/
Its great place to start learning about gardening.

[ameno]

They will be yes. Wont I need to dig the soil before hand though? I don't really want to if I'm honest, however I will if needed.

Only if it's very compacted (for instance if it has had heavy vehicles driving across it a lot). Otherwise, it will be fine just covered by the raised bed.
And on soil, frankly you don't even need one foot depth for a raised bed. Six inches is plenty. Raising it further means it's easier to reach, but you will also need more soil, compost, etc to fill it.