Subject: Re: Iron salts as slug killers From: "Bill Robinson" <roseguy@gte.net> Organization: Date: Wed, 21 Apr 99 08:48:54 Message-ID: <MOD$990420.13029@rec.gardens.ecosystems>
I had posted that, "Iron is one of the essential plant nutrients. As
is the case with all of the other mineral nutrients, iron needs to be
present in the soil at certain levels. That is, you can have too little
and the plants become iron deficient or you can have too much
and reach the toxic level. There isn't a whole lot of slack between
too little and too much."
G. Matson then posted, "As far as too much iron in the soil, I
cannot understand where that concept comes from"
"The Nature and Properties of Soils" by Nyle C. Brady and Ray R.
Weil, ISBN 0-02-313371-6, is one of the classic Soil Science texts.
It says, "It is axiomatic that anything can be toxic if taken in large
enough amounts. At low levels of a nutrient, deficiency and reduced
plant growth may occur (deficiency range). As the level of nutrient is
increased, plants respond by taking up more of the nutrient and
increasing their growth. If a level of nutrient availability has been
reached that is sufficient to meet the plant's needs (sufficiency range),
raising the level further will have little effect on plant growth, although
the concentration of the nutrient may continue to increase in the plant
tissue. At some level of availability, the plant will take up too much of
the nutrient for its own good (toxicity range), causing adverse
physiological reactions. . . . For macronutrients the sufficiency range
is very broad and toxicity occurs rarely, if ever. However, for
micronutreints the difference between deficient and toxic levels may
be very narrow, making the possibility of toxicity quite real."