Agriculture Reference
In-Depth Information
roots of most crops to reach. In highly leached soils such as this there is often a
Calcium deficiency in the topsoil; that tends to attract extremely deep-rooted plants
such as dandelion and Canada thistle. These plants have a long taproot that
reaches down to the Calcium layer and pulls the Calcium back up to the topsoil. If
you have a dandelion problem in your lawn or garden, suspect Calcium deficiency.
In more arid climates such as theAmerican Southwest, the depth of the Calcium
layer will be much less, usually 30 to 90 cm (1-3 feet) deep. Because there is
seldom enough rain in these arid climates to carry the Calcium any deeper, it often
forms a hard, whitish-colored layer that is impervious to water, known as caliche.
This caliche layer is akin to concrete and must be broken up to allow deep-rooted
plants such as fruit trees to extend their roots into the subsoil and to allow drainage
of irrigation water.
Agricultural Sulfur (90-100% S) must be converted to the sulfate (SO
4
) form before
it can be used by plants. This is done by Sulfur converting bacteria which naturally
occur in soils. The soil temperature must be above 13°C (55°F) for the bacteria to
do their work. During the conversion, 4 atoms of Oxygen will be taken from H
2
O to
form SO
4
, leaving 8 atoms of free Hydrogen H+, which is acidic and will lower the
soil pH. When Sulfur is applied as Ca, Mg, or K sulfate it generally will not affect
the soil pH much. Ferrous sulfate (Iron sulfate) will lower the soil pH.
On the next page is the soil report that we are working with, showing the
requirements for Calcium, Magnesium, Potassium and Sodium that we have
determined in this chapter.
