Horticulture grit vs sand?

SnowyMuckish · 19-09-2020 9:51pm #1

We have heavy clay soil which I’ve been adding plenty of organic matter to over the past 5 years (bark, compost and manure) but I want to improve the drainage more to plant tulips, alliums etc as living beneath a mountain in the NW means we have our fair share of rain! so I ordered what I thought was horticulture grit from a local pit.

Now I was expecting something like the potting grit you’d get in Homebase (10mm washed chips) but when it got here it looked just like normal sand. The OH called it sharp sand. Rang the pit back, they explained that that is what all the farmers add to their land to improve drainage.

So thought no more of it and spent the day adding it to my boarders. Came in later went onto Google which said that adding sand is at best ineffective and can turn clay to concrete :eek: :mad:

I’ve probably undone my years of good work! Any thoughts?

The Continental Op · 19-09-2020 11:40pm

Nah don't worry about it. Almost anything that isn't clay in a clay soil will improve it.

Do a bit more googling and see what you come up with adding lime - key word is flocculation. Most useful if your soil is acidic which with that rain you mention will probably have leached most of the lime out of the soil creating acid condition.

Your biggest issue is damaging the soil structure by working on the soil when its too wet.

magicbastarder · 20-09-2020 8:08am

There's a difference between sharp sand and builder's sand. Adding sharp sand to clay should help you. The sharp sand is spikier and should allow more micro channels for drainage.

Bill Hook · 20-09-2020 9:20am

I have Joyce Russel's Polytunnel book out of the library at the moment and there is a bit about making your own potting mixes where she says that you could use building sand but to check it first by rubbing a bit of sand between your finger and thumb: if it feels silky it's no good but if it feels gritty and 'sharp' it's probably OK.

I have been using builders sand in all my potting mixes and when I plant things like sage that need good drainage. I left a pile of it outside on concrete and the rain washes the powdery bit to the bottom of the pile leaving nice gritty stuff on top. I put the gritty stuff in a bucket and keep it in the shed until I need it.

SnowyMuckish · 20-09-2020 11:06am

I’ve often added sand to potting mixes for better drainage, this is the first time I’ve added it to my boarders on a large scale. It seems adding sand to other soils is ok. What I was reading on a few sites mentioned the structure of clay soils, apparently the clay particles are very small in comparison to the other components of the soil and adding sand can destabilize the structure?amongst other things. Hopefully the sharp sand is better!

Anyway what’s done is done, I can’t undig it! Maybe I’ll have perfectly drained soil for my bulbs or maybe I’ll have concrete, I’ll know come spring!

The Continental Op · 20-09-2020 11:42am

Lime can help rebuild that structure, sorry can't post links but there is plenty on the web about it.

The old way in the veg garden was to rough dig a clay soil in the autumn leaving big lumps and then cover in lime. The action of the weather including rain and freeze thaw in the winter breaks the clay down which then reforms with a better structure around the lime, a process know as flocculation.

How effective lime would be in a border I don't know but can't see it making things worse provided your soil needs lime anyway.

SnowyMuckish · 20-09-2020 11:57am

Must give that a go too, going to add plenty of cheap aldi compost to it too in spring!

Horticulture grit vs sand?

Comments