From d.richardson@mail.utexas.eduWed Mar 22 22:28:39 1995 Date: Wed, 22 Mar 1995 19:55:11 -0600 From: Dick Richardson To: sanet-mg@ces.ncsu.edu Subject: Re: Humus -- rural -> urban -> rural Thomas Hansmeyer poses the question we all need to ask, namely: > [snip] ... I guess I am asking if the Luebkes >needed to import Carbon from other sources? Which gets into further debate >as to whether enough carbon exists within the current system to allow all >of agriculture to increase the OM to healthy levels, 5% or so. Composting is fine, and avoids lots of problems that have regulations tied to them, but actually, it's even better if the composting occurs in the soil. Lots of benefits are lost in having the composting first as a "treatment" of the organic materials in order then to produce a soil amendment. The microbes in the compost pile are also needed in the soil. Another case in point is with the use of urban sewage. We call it "waste" and much is sent to the landfill. If we called it a "resource" we'd be working on improving the quality, and thereby reduce some of the potentially harmful components of organic and inorganic types. Even the legally required anaerobic digestion could be avoided if society was properly aligned with the needs of recycling the carbon, as Thomas Hansmeyer mentioned in his post, where the carbon is food supplied to the microbes and other "soil" organisms like dung beetles. As it stands, some sewage (or treated, "biosolids") is fine for land application, before or after composting, and other sources are fine in certain soils -- as for example, alkaline soils when there are somewhat more heavy metal components in the sewage (or biosolids) than one would use in an acid soil. However, there is a strong engineering perspective (bias) in the treatment and use of such resources, and there are ecologically sound alternative perspectives we need to begin using. I have not done the calculations on how it all adds up, but as a matter of principle, there needs to be a complete cycle of organics (and inorganics also) leaving the land where food is produced and its return from the areas where it is used in foodstuffs (whether eaten first, or discarded uneaten), building materials, clothes, or whatever. That is, it is not a negative feature to bring materials "back" to the land from "outside". It's all one system, and should include the urban part along with the rural part. On another "curiosity info" note, there is a rumbling in our current Legislature that one should not label compost as a "fertilizer" or a "plant nutrient", but as a soil conditioner/additive. This is from the commercial fertilizer interests, who don't acknowledge that the NPK of commercial fertilizer does little good (or should be) for feeding the microbes, which in turn feed the higher plants AND condition the soil. If we reacted as strongly against some commercial fertilizers with regard to "heavy metals" (including "trace minerals") as we do when they are in the sewage, we'd likely be banning the "fertilizer" to the landfills and bagging the sewage! ;-) Cheers, R. H. (Dick) Richardson Office: 512-471-4128 Zoology Dept. Home: 512-476-5131 Univ. of Texas FAX: 512-471-9651 Austin, TX 78712 From ACLARK@CROP.UOGUELPH.CAThu Mar 23 10:32:49 1995 Date: Thu, 23 Mar 1995 09:57:06 EDT From: "E. Ann Clark, Associate Professor" To: sanet-mg@ces.ncsu.edu Subject: Re: Humus -- rural -> urban -> rural Responding to Dick R. on the issue of composting. Just curious about the comment that it is better if composting occurs in the soil. Just finished an M.Sc. student doing a study on composting and we didn't come across this idea in the lit. I'd be interested in learning what it is that is more beneficial about composting in-situ - in the soil - as against ahead of time. Evidence from the literature? Conventional organic wisdom hereabouts sees placement of raw manure directly into the soil as a net negative, because of a) rapid release of N which destabilizes cycling, b) VFA's which can be caustic, and c) potential for anaerobic decomposition when high moisture substrate (whether animal manure or direct cut red clover) is plowed into the soil. As an example, they recommend cutting and wilting red clover plowdown before plowing it in, to avoid this problem. Good points on "waste" management at landfills! Ann ACLARK@crop.uoguelph.ca Dr. E. Ann Clark Associate Professor Crop Science University of Guelph Guelph, ON N1G 2W1 Phone: 519-824-4120 Ext. 2508 FAX: 519 763-8933