permaculture

["Lawrence F. London, Jr." <venaurafarm@bellsouth.net>]

On 11/14/2011 3:11 AM, Alia Tsang wrote:
> Dieter, you can always edit the wikipedia page. ;)
>
> One thing that humus does for a soil is increase cation exchange capacity.
> This provides sites for mineral nutrients (such as ammonium released by the
> breakdown of new organic material) to bind to so that it doesn't get washed
> out of the soil. It also makes the soil a better buffer, keeping mineral
> and pH levels more stable, and helps the soil clump into nice, water
> holding, microbe sheltering aggregates. These effects are a big part of how
> humus boosts soil fertility.
>
> John, speaking of hormone-like chemicals, a lot of microbes excrete plant
> hormones. I'd bet the increased microbial activity in high organic matter
> soils means there are some bacterial or fungal hormones boosting plant
> growth too. Or maybe these hormones even become part of the humus.
>
> And good point about burning - think about how much carbon they're losing
> in that smoke! They're starving their microbes...
>
> And just a little trivia for you, the structure of humic acid and fulvic
> acid (two components of humus) aren't defined by a chemical formula,
> they're "operationally defined" by how they're separated out of the humus.
> Humus is treated with NaOH (lye, or another strong base) and they separate
> the what's in the resulting liquid by acidifying it. Everything that
> dissolves in the NaOH and stays dissolved when it's acidified is fulvic
> acid, everything that was dissolved but falls out of solution when it's
> acidified is humic acid. The actual chemical components of all this are
> still being explored.
>
> Alia

What great information, Alia. Thanks very much for clarifying what we 
need to know about humus. From what I have learned in this and a few 
other lists is that the ability of humus to increase soil CEC is very 
important to balancing minerals and making nutrients available to 
plants. The notion of balanced soil minerals, complete arrays of those 
required by plants and thereby for maximum human nutrition, nutrient 
dense and other related concepts all seem to rely heavily on adequate 
soil CEC and amending farm soil with organic matter to help achieve this 
healthy condition.

Dieter and John know which discussion list I am referring to as we 
engaged in considerable dialog on this important topic there. Thankfully 
that discussion is happening here now.

Thanks again for you very valuable feedback.

Lawrence