17-07-2005, 04:30 AM
|
|
|
wrote in
ups.com:
Now there is another evidence that John is mistaken about asphalt
and bad chemicals although it is not a fine example it is an
example none the less. What I am talking about is the growing
propensity of plants near asphalt roads. Perhaps the propensity is
that the asphalt road provides a large mulch for the trees
alongside the road. And whether any fruit from those trees next to
an asphalt road have bad chemical contents, which I suspect do
not.
Since I live in a dry climate, I believe I can provide a reason why
there is greater plant growth near roads. Well, two reasons.
1) Runoff from the road surface can double the amount of effective
rainfall a short distance from the road. That can make a big
difference in available water.
2) The fence that keeps grazers away from the road prevents the
plants from being converted to cow biomass. This can be very marked
in some areas, especially where ranching is practiced.
I think the trouble here is that John and many others are working
from a opinion and belief but not working from actual science
research. They opine that asphalt has bad chemicals and they opine
that those bad chemicals will transfer into the tree and its
fruit. But I get the sense that asphalt roads and asphalt roof
shingles that are untreated have mostly a great benefit to any
plant lucky enough to have them as a mulch. I suspect that by the
time the shingles degrade into the soil that they enrich the soil.
So we need a real science testing and research and not everyone
with their bias opinion saying bad chemicals.
I mistrust your confidence, there are a huge number of organic
compounds in asphalt, most of them not studied for plant uptake.
Most of them are likely very similar to humus compounds, and nothing
to worry about, but even though plants tend to be rather picky about
what they take up, there is the chance that your tomato plant may
have some harmful chemicals in it that while not hurting the plant,
may cause eventual illness in people.
You could try to measure uptake, you would have to grow something
with and without asphalt based mulches, and test them for
differences.
Asphalt is "mostly inert" but that doesn't mean that it is
"completely harmless".
Sean
|