Re: Research on fertiliser runoff
At 05:41 PM 1/24/97 GMT, you wrote:
>I am looking for research that gives some idea of possible
>runoff od chemical fertiliser applied as a top dressing
>and the same for organic growing using compost or
>composted manure. Does anybody have ideas as to
>where to look for such data?
A very important distintion in more sustainable ag. is the application of
compost verses other sourses of nitriogen. In compost the Nitrogen is
generally stable. Some may have volitillized out in the process of turning
the raw materials into compost, the rest is tied to carbons or chemically
less water soluable. Manures are intermitant, and generally fresher manure
has more soluable nitrogen. N concentration varies from species to species
and in farming by handleing method. In a pasture situation, especially one
where soils are active with decay organisms and some insects, fresh manure
will be rapidly dispursed and incorperated into soils. This is basically
micro sheet composting, with N also being taken up by the plants, reducing
runoff potential. Pastoral soils will also gennerally have better
infiltertion than crop ground and less run off. Issues also arise
where minerals are fed to animals at high rates. Phosphous and calcium are
fed at pretty high rates to our dairy animals and this is reflected in the
manure and urine. A consideration also is that added P may help capture N
that would other wise volitilize, making stronger compost. Lots of other
issues to the topic of compost, bottom line is that its great, predictable
life giving material and its worth doing.
Chemical fertilizers are a mixed bag. By chemicals I have to include
things like gypsum (calcium suphate) and lime, both excellent soil
amendments in their place. Also included Anhydrus Amonia, pure liquid
amonia gas which is a highly reactive chemical and kills soil life like
crazy while burning up humas. Comercial N fertilizers all volitilize
and/or disolove in water. Most others disolve and run off to some degree.
Theres lots of good agronomy data on it in the Ag. collages of the world.