Exerpt from: Secrets of the Soil (wonderful book!)

K N and P J Harris ecoli at cix.compulink.co.uk
Wed Apr 23 12:47:25 EST 1997


> ==========
> bionet/plants #4052, from animaux at ix.netcom.co, 1268 chars, 10 Apr 
1997 14:03:40 
> Comment to 3982.
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> From: animaux at ix.netcom.com(Mark & Victoria)
> Newsgroups: bionet.plants
> Subject: Re: Exerpt from: Secrets of the Soil (wonderful book!)
> Date: 10 Apr 1997 14:03:40 GMT
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> In <E8DB6z.5qH at cix.compulink.co.uk> ecoli at cix.compulink.co.uk ("K N 
and
> P J Harris") writes: 
> >
> >The humus in soil IS important but hardly ever as a source of plant 
> >nutrients itself. It has great significance for nutrient retention
> (most 
> >of which is in an inorganic form), for water retention and for soil 
> >structure but the great age of most humus (say 1000 years) means that 
> >its turnover rate is too small to yield nutrients.
> 
> How do you explain forests which are never artificially fertilized, 
nor
> do they receive anything other than the rotting bodies, (which are
> turned into humus by the microbial activity) of animals and plants?
> 
> Forests which live, say, thousands of years...
> 
> Victoria
Hello Victoria,
Sorry for delay but I've only just got back from China where they really 
know how to chuck the synthetic stuff around at levels that make even my 
eyes water.
Your point about forests is a good one. My answer is that forests, and 
particularly the vulnerable rain forests, have very little nutrients in 
them and they are in a very tight cycle. The available nutrients in the 
falling leaves are back into the fungal-root system very quickly 
otherwise they would be leached away. The "humus" in the soil is only a 
small backwater holding mainly carbon and not much else. Hence, when the 
forest is chopped down you have an infertile desert in no time. All the 
nutrients in the system were conserved in the living canopy.
The tragedy is that people look at the fantastic living mass that is a 
rain forest and make the mistake of thinking that this must be very 
fertile - if we chop it down we can grow fantastic crops. Wrong - wrong 
- wrong. An understanding of soil science and soil microbiology in 
particular would convince them that it is a special system.
Peter Harris,
Department of Soil Science,
The University of Reading, U.K.





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