home made fertilizer

Scott Pittman pci at permaculture-inst.org
Tue Mar 20 14:33:13 EST 2001

Toby could you send me your email address so I can pick your brain off line?
I am looking for a good simple book on CEC in soil.


At 10:00 AM 3/20/01 -0800, you wrote:
>on 3/19/01 10:51 PM, Evan Davies at evangardener at hotmail.com wrote:
> > The reason there is no smell using the sawdust method to store urine, is
> > that sawdust, or wood shavings(sawdust will absorb the liquid a lot
> > quicker)is a large proportion carbon
>For those who are interested, that's one of several reasons. BTW, I prefer
>using fine shavings unless I can get coarse sawdust, because the sawdust
>from all but the big mill saws is too fine, and often packs down into a
>gooey, anaerobic lump that gets really foul in the center and is hard to
>spread out evenly in a compost pile. Which leads me to additional reason 1:
>Using shavings or sawdust, which have lots of  air between the particles,
>results in aerobic fermentation of the urine, while a bucket of liquid will
>quickly become anaerobic. Anaerobic processes are far more stinky than
>aerobic ones. Aerobic fermentation will yield more nitrate (NO3), not a gas,
>while anaerobes, lacking those oxygen molecules, are forced to make gaseous
>ammonia, NH3. Bye-bye nitrogen.
>  Also, shavings and sawdust have lots of surface area, allowing quick
>colonization by huge numbers of microbes, which will metabolize the ammonia
>and other volatiles in decomposing urine before much of it can outgas. Any

>gases from the puddle in the bottom of the bucket must rise up through this
>fluffy bacterial filter before they can escape, and get absorbed. And third,
>wood has an extremely high C/N ratio, 400-800 to 1, so any nitrogen in the
>urine will be quickly gobbled up by microbes to be bonded to the
>overwhelming amount of carbon they get from the sawdust. The bugs are
>building molecules of roughly 12:1 C/N, so they'll lock up nitrogen quickly
>to do that (which is the opposite situation we hope to have when we're
>fertilizing, where we want to release nitrogen--slowly--rather than tie it
>I like to build my compost piles on the woody side, more like 40:1 C/N.
>Nitrogen is lost rapidly even in compost piles that are built to the ideal
>25:1 ratio. In a fast, hot pile of 25:1, the rapid metabolisms of the
>microbes often lurch into anaerobic processes and give off a lot of ammonia.
>You can catch that ammonia by adding gypsum to the pile (the CaSO4 of gypsum
>reacts with ammonia to give non-volatile ammonium sulfate) or, if there
>aren't lots of seeds to sterilize in the pile, I just make a woodier 40:1
>pile and let it moulder more slowly. This cooler pile seems to leave more
>nitrogen in the compost. At least the resulting soil tests higher for
>nitrogen, so I assume that's what's happening.
>Hope this isn't too tedious. Thanks, Evan, for giving me an excuse to
>blather about soil chemistry, one of my pet subjects.
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