SOIL PARTICLE SIZE QUESTION

[August44]

I am finally getting around to asking some questions that I have had for some time but have been to busy to get it done. I am showing pictures of a mix that I have been using but not at all sure it is the best for my situation. The mix has particles from 1/8th - 7/16. The fines were screened out long ago and everything falls through a 1/2" screen. Mostly pumice, with some lava, charcoal, and some bark. I am reclaiming this from repotting trees for several years. I am more concerned about the particle size and the variable/different sizes in one mix. I mainly use this for collect conifers, smaller up to pretty good size. Suggestions and opinions are appreciated. Thanks

 

[The Barber]

I'm no expert and others may chime in and give a more in depth response. Larger particle size allows for more air exchange, it also will dry faster. Smaller particles take up more space and allow for less air exchange in the soil, and will dry at a slower rate of speed. Smaller particles are well suited to small pots that have a low volume of soil that you don't want to dry out too rapidly depending on how often you want to water. A mix of smaller and larger particles are fine, the smaller will fill voids between the large particles. If you're wanting to have a more consistent particle size, you can get different size screens and sort them out. Not sure what the actual question you have is though to be honest, but hope this helps.

 

[cheap_walmart_art]

The consistency of soil in both pics appears to be fine to me. The only time I ever really worry about differing sizes in my mixes is when I put a tree in a “finished” pot, I’ll usually try to add a drainage layer of the same soil mix, but consisting of the larger particles I filtered out of the main mix.

 

[August44]

I'm no expert and others may chime in and give a more in depth response. Larger particle size allows for more air exchange, it also will dry faster. Smaller particles take up more space and allow for less air exchange in the soil, and will dry at a slower rate of speed. Smaller particles are well suited to small pots that have a low volume of soil that you don't want to dry out too rapidly depending on how often you want to water. A mix of smaller and larger particles are fine, the smaller will fill voids between the large particles. If you're wanting to have a more consistent particle size, you can get different size screens and sort them out. Not sure what the actual question you have is though to be honest, but hope this helps.

Thanks for the response. My main concern is the particle sizes. I have read many times that one wants to use soils that have the same size particles throughout. I was never sure why that it was important that they all be the same size, so I just blew it off and ended up with a mix like this. I live in a remote area where there are no bonsai shops or anybody at all close that sells substrate, so I spend a lot of time reclaiming soil. If there is a benefit to having all one size, 1/4" or otherwise, I'd like to know that, and I will shoot for it. If there is no benefit then I will continue with what I am doing.

 

[The Barber]

Thanks for the response. My main concern is the particle sizes. I have read many times that one wants to use soils that have the same size particles throughout. I was never sure why that it was important that they all be the same size, so I just blew it off and ended up with a mix like this. I live in a remote area where there are no bonsai shops or anybody at all close that sells substrate, so I spend a lot of time reclaiming soil. If there is a benefit to having all one size, 1/4" or otherwise, I'd like to know that, and I will shoot for it. If there is no benefit then I will continue with what I am doing.

If you were using a clay/soft substrate like akadama or kanuma then maybe it would matter more as same particle size would break down at a similar rate, but I don't think that would pertain to stone type substrates such as pumice, etc.

 

[Deep Sea Diver]

It’sa pretty wide range mix August…. And less porous and likely wetter than conifers would like best. Would refine the mix to sieve out the smallest particles.

A couple things to remember, some grace been mentioned that m might help you.

In general:

The more uniform the particle mix, the more oxygen/water/CO2 exchange.

The larger the sorted mix the dryer the mix will be

That said, we use certain particle size bands to accomplish different goals. For example

5/8-3/8 for development.- more root spaces, coarser roots. This is a dryer mix.

5/8-1/4 for near refinement and refinement trees.

1/8-1/4 older trees esp. deciduous. This is tuff most moisture holding mix.

Each type of particles has different moisture holding characteristics. For example akadama and Biochar can hold a lot of water, while lava less.

On the road now. Will send you a link with more info upon return.

Cheers
DSD sends