when to add soil/compost to new raised bed?

[chilli_grower]

Ok, so I have dug out a new raised bed, frame going in soon....

Question is, when should I fill it with top soil/compost? (Silly question possibly)?

If I fill it now, wouldn't a lot of the 'goodness' get washed away?

THank you

[chris]

Just grow the soil now, they'll be nutrients in it already. You could cover it if you like, or lay a layer of compost on top now- worms will drag it down. When you've harvested your crops just mulch again- you'll slowly build the depth up.

That's what I'd do anyway!


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[BertieFox]

Soil and compost are entirely different things. 'Soil' is the basic material of rock and organic materials into which your plants root, and need not be particularly fertile, while the surface layers are the ones which should be full of plant food and humus, breaking down to produce trace elements and minerals. So you should fill your bed with soil at any time, making sure the mixture produces the right balance of acidity and alkalinity, and proper drainage, and only mix in your compost or plant food in the spring when it is less likely to be washed away and the plants can make most use of it. Slow release composts made from composted garden waste, and organic fertilisers like blood, fish and bone, are slow release and will last throughout the season. I would always apply these in the surface layers, and we NEVER 'dig in' compost, other than organic matter to retain water in very dry ground.

[chilli_grower]

ok guys, thanks for the detailed replies.

I will fill with soil shortly, and add the compost and fertiliser early spring.

I do not quite understand why the soil etc where the roots are, do not need to be very fertile?

I would have assumed that this would be where the nutrients were needed most? As opposed to compost/fertiliser being on top.....



Cheers

[kathyd]

I wouldn't have thought it'd make a huge difference when you fill it with soil or compost to be honest, as long as you keep it covered with something. It's no different really from an existing bed where the crop's been harvested - what do you do to protect it during the winter? Some of my raised beds have winter crops in eg leeks, parsnips, brassicas and some green manures. Others I've covered with wet cardboard, and am gradually chucking green stuff on top as it becomes available. On others I've thrown down my fairly grotty half rotted compost from my compost heap. I've even left a couple full of weeds which I'll deal with in the spring... So I'd just do it when it's most convenient for you .

[mothhawk]

I agree with Chris and Kathy. Also, if the area has been grass for quite a while, it's probably a bit nutrient poor and so also poor in soil fauna (bacteria, worms etc), especially if you collect the grass clippings rather than leave them on the ground and haven't spread any compost/fertiliser on it.

Either put in the top soil and then cover with a deep layer of H/M compost, or as Chris says, just a thick layer of compost, and let the raised bed gradually fill over time as each year you add more compost. Then cover the whole bed with cardboard, which will warm it a little, and encourage worms and other beneficial fauna to the bed to start mixing up the compost into the soil and generally doing what they do, so by spring when you remove what's left of the cardboard you should have a fertile, easily worked soil ready to plant.

[chilli_grower]

thanks Mothawk, sounds like a plan....

[mothhawk]

Don't worry about nutrients washing away. The most water soluble nutrient is nitrogen, in plants it's found in green leafy stuff mostly, which is why folk grow green manures on bare ground, so the nitrogen is taken up into the plants, then the plants are chopped down and the nitrogen released again back into the soil.

If you put on plenty of organic compost, there will be lots of nitrogen and other nutrients in that. Heavy rainfall over a prolonged period may wash the nitrogen and other trace elements and nutrients deeper into the soil, but it will still be there for plant roots to use and so draw back upwards when they reach it.

Microbes in the soil help to retain nutrients too.

[BertieFox]

"I do not quite understand why the soil etc where the roots are, do not need to be very fertile?"

The next time you pull out a cabbage or sprout plant, look at the roots. The deep roots penetrating into the soil are large and corky, and are used to reach moisture. The 'feeding' roots around the base of the plant, principally, are small and hair-like. Some minerals may be in the ground water or lower parts of the bed, but most are nearer the surface where organic matter breaks down. I guess the 'double diggers' who believe in burying compost two spits down will claim that that will make more feeding roots, but I would argue that you should follow nature, not try to change the way things happen. Many argue by digging stuff in, you change the soil structure and disrupt other natural activities, some as worm behaviour, which also enhances soil fertility.

[chilli_grower]

thanks for the detailed explanation Bertie.

[Two_Sheds]

blood, fish and bone, are slow release and will last throughout the season.

The packets usually tell you to reapply every six weeks or so

[Two_Sheds]

If I fill it now, wouldn't a lot of the 'goodness' get washed away?

Most plants will grow in most soils. Of course there are exceptions, but what I always say to beginners is to forget about all the "rules" for the first year, and just use the soil you have.
You will learn by doing, what your plants need, and what your soil is like.

Garden centres are full of products specially designed to separate the gardener from his/her money

[chilli_grower]

well, here we are so far....

[Sheneval]

well, here we are so far....

Looks good to me - the experts on our site, even those who have had their allotments for the last 5 years since they started, added a layer of compost on top when sowing their seeds on raised beds.

Learning from experience over time is fine if you are starting growing in your 30s, 40s, or even 50s and have plenty of time to build up the fertility of the soil over time, but if in your late 60s as I am, you want results asap.

Personally, I added compost to every bed this year and was well pleased with the results - I also limed where appropriate, and as an experiment added Biochar and Rock Dust; I also used Blood, Fish and Bone as a feed and will be doing all of these things this coming year. Some of my friends swear by chicken pellets and some use growmore.

Do whatever you are happy with that suits your purse and enjoy

[chilli_grower]

Thanks for the tips Sheneval.

I am early thirties