Grinding Biochar--necessary or not?

[maikeru]

Originally Posted by Mukrakiish

What sorts of innoculation/fertilization are you doing to your char/biochar other then using compost and manure? Any set ratios or amounts? (maikeru but whomever can reply with their experiences)

Is anyone making particular points of crushing before innoculating? Is anyone leaving it to evaporate all moisture off before using or are they draining (which would bring its own problems if you crushed it to a powder).

To stay semi-on topic...I'm definitely in agreement that you should be grinding it down to a powder to access as much nutrients and micro-organisms as possible. I can't see much reason unless you'd specifically want large chunks mixed in (for some specific reason) otherwise, grinding would be ideal so long as it was mixed in after and not on the surface.

Edit: just realized how old this thread is. But the questions are still up unless I just need to use the search engine a little harder

Not at all. I still play a lot with biochar and new mixes.

When I first played with biochar, it was simply buying cheap wood charcoal, putting it in a wet burlap bag, and jumping on it. Trust me this is inefficient. It'll break your legs and back. But I was inquisitive then and couldn't wait... This was dry. I still want to and need to produce my own biochar from coffee grounds in a terra cotta cooker. That's like my other weird science project for the summer.

Chunky, grainy, and powdery biochar all have their purpose in a mix, IMO. Although powder yields the most surface area for nutrient retention, chemical reactions, microbial habitats, and water retention, it also is more likely to become compacted, clay-like, and to cut off oxygen and airflow, which we know is critical for the rhizosphere and plant roots. Therefore, I think a general mix of all sizes is the most beneficial, but it also depends on what else is in the soil, such as if you have sherds, pebbles, sand, or what not, and amount you want to add. I made biochar mixes going from 10-40% charcoal in the total soil and generally without terra cotta sherds, although I think now I would definitely add them, like the original Amazonian makers did. Chunks and larger grains promote airflow, drainage, and prevent compaction. Also, as I understand it, biochar's surface can gradually oxidize due to chemical reactions from microbes, plant roots, air, etc., which improves its cation exchange capacity (CEC) and water and nutrient retention. You want this to happen, so make sure that the mix allows air and water to penetrate. You will notice that the soil ages and changes in fertility. I still am seeing this with biochar soils made from my first batches.

From my microbiology classes and my plant course two semesters ago, I remember that mycorrhizae help plants acquire more nutrients like phosphorus and may be retarded by the addition of excess phosphorus, especially in the forms of superphosphate. Synthetic chemical fertilizers high in N can also harm or kill N fixers, mycorrhizae, and other soil microbes. So if you use synthetics or chemicals, go easy or limit the use of N and P. Gradual or slow dope. In my first mixes, I became impatient and used a heavy dose of MiracleGro, but I probably wouldn't do that again. It does work, and the biochar limits toxicity to the plants, but I favor less chemicals and more complex, nutrient-rich organic fertilizers now. I think it's really important to get trace elements and minerals into a mix, and chemical fertilizers just don't do that.

I'd go for more organic means like soybean meal, vermicompost (which is rich in beneficial microbes and N, P, Ca, etc. but not overwhelmingly so and makes these nutrients readily available to plants/microbes), blood (rich in N and Fe) or bone meal (less N but more P), fish bones, seaweed (rich in trace elements and respectable N), or even coffee grounds, urine (if you're cool with this, it is rich in nutrients of all kinds), weed waste (good use of unwanted guests), green manure (clover, alfalfa, straw, etc.), or grass clippings (which are N rich). I use algae-rich water as a light organic fertilizer now for many of my herb plants in biochar. (Simply leaving a glass jar w/ water on the window. Wait until green and scummy.)

Do you want your inoculant/fertilizer for the biochar sterile or fairly so, so that it wouldn't compete with any desired or cultivable fungi? All the ones I mentioned above basically let whatever's present to grow willy-nilly.

I think how inoculants/fertilizers should be applied depends on kind and how long you have. For example, you could do something like soaking biochar with chicken manure or MiracleGro for a few days, and that would heavily dope it. In my case, I was able to add about 2-3 times the recommended dose listed on the back of the box straight to the plants in biochar I was growing. You could also put in slow-release fertilizer like Osmocote.

In my biochar garden outside, I did not really dope the soil, because I'm growing white clover as green manure and for N fixation and have added a lot of spent coffee grounds. Hoped the spent coffee grounds would gradually release their nutrients and dope the charcoal as they decayed. Also, since I'm using a lot of topsoil in the garden, I'm assuming the sand and clay in it has micronutrients which will become more available to plants, fungi, etc. as soil microbes flourish and multiply. I see clay, sand, pebbles, and rocks as "nutrient reserves" which will gradually weather and feed the soil system.

Indoors, with my plants in containers where topsoil/sand is not used, I've used coffee grounds, seaweed, tea leaves, some vermicompost, fish bones, fish water, shrimp shells, and blood and bone meal as inoculants/fertilizers with great success and to supply macro- and micronutrients needed. (I eat a lot of seafood, so that's why fish bones, fish water, and shrimp are all on the menu for the soil. )