Xref: utzoo sci.bio:3918 sci.chem:2524
Path: utzoo!utgpu!news-server.csri.toronto.edu!cs.utexas.edu!sdd.hp.com!elroy.jpl.nasa.gov!jarthur!uunet!mcsun!ukc!newcastle.ac.uk!lorien!william
From: william@lorien.newcastle.ac.uk (William Coyne)
Newsgroups: sci.bio,sci.chem
Subject: How does soil stay fertile?
Summary: How does crop rotation maintain soil fertility?
Keywords: soil fertility crop rotation
Message-ID: <1990Nov19.130439.9168@newcastle.ac.uk>
Date: 19 Nov 90 13:04:39 GMT
Sender: news@newcastle.ac.uk
Organization: Chemical & Process Engineering Dept, University of Newcastle, UK.
Lines: 15

In the past crop rotation without the use of artificial fertilizers
was used to maintain the productivity of fields.

How did this work?

The soil requires various elements - nitrogen, sulphur, phosphorus. 
Now the nitrogen can be obtained from the atmosphere by growing certain
plants in the field(eg clover), but where do the other elements come
from to replace those amounts of them used in the previous seasons?
 
email replies can be sent -

JANET: W.P.Coyne@uk.ac.newcastle
UUCP : ...!ukc!newcastle.ac.uk!W.P.Coyne
ARPA : W.P.Coyne%newcastle.ac.uk@nss.cs.ucl.ac.uk