Biochar to improve soil water retention.

[Gary Prentice]

Has anyone any experience with using biochar to improve water retention when tree planting.

 

I'm currently involved in a site where hundreds of tonnes of sandy/clay shale has been tipped and then compacted. Initially we had concerns about the permeability of this soil - thinking that tree pits would turn into sumps. 

 

In an attempt to assess permeability, I dug a trial pit 600mm deep. For a percolation test, you're meant to fill this with water and allow it to drain for 24 hrs, then refill and time how quickly the level drops over a set height of water.

 

For the first fill, I poured in 25 L - it disappeared!

 

I left the pit covered for 24 hrs and returned this morning with 75 L of water. The pit was still damp to the base and sides, to the height of the first part fill. I poured in three 25L drums simultaneously, but by the time I picked up my tape measure to measure the height it had drained away. 

 

Acknowledging that we've had no rain since this 'soil' was tipped and the moisture content is likely to be very low, I can still only come to a conclusion that the soil is free-draining/very free draining, so the tree planting problem isn't about draining tree pits but improving their water retention capability. We're looking at group plantings of three trees to a planting area, I haven't calculated soil volumes as yet as agreement of species is yet to be reached. 

 

I can talk to the Carbon Gold people, and it will be the best thing since sliced bread , but I wondered if anyone here had any experience, or alternatives?

[Khriss]

Never tried it - go with customers spec'  and add a backup irrigation scheme ? K

[Khriss]

( Leaky pipes n ISO tanks )

[tree-fancier123]

A bloke near me was making biochar, used to let me dump brushwood. I read up on it and couldnt believe the ebay prices for a kilo. A lorry of decent topsoil and a digger?

[Stere]

Try downy birch they can grow/seed naturally with zero soil on slate tips.

 

Or a more science  approach:

 

https://www.researchgate.net/publication/237662955_RE-CREATING_WOODLAND_AND_HEATHLAND_ON_SLATE_WASTE_IN_WALES

 

 

 

 

 

 

[Gary Prentice]

17 minutes ago, Khriss said:

Never tried it - go with customers spec'  and add a backup irrigation scheme ? K

If only it was the customers spec 

 

Let's just say that there's a complicated backstory involving 20,000 tonnes of excavation waste tipped around a trees with a TPO! Initially the council were claiming irremediable damage to eighteen mature trees.

 

I'm currently acting on the clients behalf to provide method statements for removing tipped soil, mitigation planting for trees that are unsalvageable, planting to replace trees that should have been removed prior to tipping etc, etc etc.

 

So I'm writing the specs... 

[Gary Prentice]

20 minutes ago, tree-fancier123 said:

A bloke near me was making biochar, used to let me dump brushwood. I read up on it and couldnt believe the ebay prices for a kilo. A lorry of decent topsoil and a digger?

Groundwork lads are on site monday week, to move some of the tipped earth from around the trees, so I need to get the planting pits excavated while they are there. We'll get a good quality top soil for the pits and the surrounding areas that will be seeded or turfed, but my concern is that the subsoil is so free draining we need to look to retain moisture. TBH, I think that establishing grass might be problematic unless that get a decent depth of topsoil.

[Gary Prentice]

17 minutes ago, Stere said:

Try downy birch they can grow/seed naturally with zero soil on slate tips.

 

Or a more science  approach:

 

https://www.researchgate.net/publication/237662955_RE-CREATING_WOODLAND_AND_HEATHLAND_ON_SLATE_WASTE_IN_WALES

 

 

 

 

 

 

Thanks for the link, I'll have a read of that. Because of the site history, species selection can't be limited, there's going to be a requirement to plant a variety of species.

[openspaceman]

2 hours ago, Gary Prentice said:

I can talk to the Carbon Gold people, and it will be the best thing since sliced bread , but I wondered if anyone here had any experience, or alternatives?

No planting experience and I can't see it being a magic bullet, I'd go for a soil rich in organic matter and add some biochar for luck.

 

I'd not want to make Craig Sams any richer so would suggest you get some fines from a charcoal maker local to you or make your own from brushwood in a flame curtain device or trench.

 

[Khriss]

Bloody hell- I dont want yr monday Gary :P the D.birch sounds a good route to take - am doubtful the bio char will make a difference - wouldn't even bother with turf - good load of well composted chip around trees for water retention  , which will have the earthworms busy and again a drip irrigation system, in mind of the blinding weather we been havin , K