learning about compost

Hoping to make use of the white, frozen-piped days, I try to learn stuff.

It’s not always easy to find gardening information that really perks the senses. So much of it is re-hashed opinions and common knowledge. That’s why this sentence on composting from Organic Gardener’s Composting by Steve Sullivan sat me right up:

Decomposition must be rapid and aerobic, but not too aerobic. And not too hot.

Interesting. My logic always told me to burn, baby, burn. Let it fry. But maybe I just learned something. (To put it in context, Steve is writing about Sir Oliver Howard, originator of the Indore Method of composting in the 1920s, named for the area in India where he was experimenting):

Quite intentionally, Indore compost piles were not allowed to reach the highest temperatures that are possible. During the first heating cycle, peak temperatures were about 140°. After two weeks, when the first turn was made, temperatures had dropped to about 125°, and gradually declined from there. Howard cleverly restricted the air supply and thermal mass so as to “bank the fires” of decomposition. This moderation was his key to preventing loss of nitrogen.

Moderation is Da Man! I have to admit that I’ve never gotten my piles much past 140° anyway, but anal-retentive gardening? Yeah baby.

Provisions were made to water the heaps as necessary, to turn them several times, and to use a novel system of mass inoculation with the proper fungi and bacteria…Howard was pleased that there was no need to accept nitrogen loss at any stage and that the reverse should happen. Once the C/N had dropped sufficiently, the material was promptly incorporated into the soil where nitrate nitrogen will be best preserved.

Ok, that’s not completely helpful (all the ‘sufficiently’s and ‘as necessary’s) but gardening’s all about doing things that jive with what you know is true. It hasn’t been long that I’ve understood that adding even nitrogen-rich organic matter to the soil can temporarily deplete soil nitrogen, so this is scarily making sense.

Maybe composting a little longer at slightly lower temperatures means that the soil doesn’t have to work so hard at processing nitrogen that it’s actually depleting nitrogen. Maybe the quick-compost schemes are like most other quick things…not as good.

But the soil is not capable of doing two jobs at once. It can’t digest crude organic matter and simultaneously nitrify humus. So compost must be finished and completely ripe when it was tilled in so that:

“. . . there must be no serious competition between the last stages of decay of the compost and the work of the soil in growing the crop. This is accomplished by carrying the manufacture of humus up to the point when nitrification is about to begin.”

Garden Nerd Love to you, Steve.  I hope to be ‘carrying the manufacture of humus up to the point when nitrification begins’ really, really soon.

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11 thoughts on “learning about compost

    • Thank you! I have a home test kit and last year had a sample analyzed by the Extension Service. It cost $25 but the information they supplied was well worth the money.

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