Agriculture Reference
In-Depth Information
themicro trace elements to start with (those at the very bottom ofAgricola's chart),
and ordinary soil tests don't measure them anyway.
The laboratory may also estimate the
CEC
(cation exchange capacity) and the
base saturation percent
of Calcium, Magnesium, Potassium, Sodium and
Hydrogen in your soil sample. Unless you know that the method the lab is using to
calculate CEC is the same one described in this topic in the appendix on
Calculating TCEC
, it would be best to calculate it yourself based on the amounts
of Ca, Mg, K, and Na and soil pH at 1:1 soil:water by weight.
If the soil pH is above 7.0, the soil probably contains free, undissolved Calcium
and/or Magnesium carbonates, and both theAA7.0 test and the Mehlich 3 test
are likely to dissolve them and give too high a reading for Ca and Mg, leading to
an overestimate of CEC. For soils above pH 7.0, theAmmoniumAcetate pH8.2
test (AA8.2) is recommended for determining CEC and base saturation
percentages only. You will still need the Mehlich 3 test results for all other mineral
elements. See Chapter 9 on Calcareous and High pH soils for more detail.
In high doses, many mineral elements can be toxic to people, animals, plants and
soil organisms. This is true regardless of whether they are in a naturally occurring
or purified, concentrated form. Keep them out of ponds and streams.
Any
mineral,
if used in excess, can throw things out of balance, so take it easy. It is much easier
to put them in than to get them back out of the soil.
Caution When Applying Mineral Amendments
High levels of some minerals in the soil may inhibit sprouting of seeds. Boron is
definitely known to do this. High levels of free minerals (not biologically
assimilated) can also “plug up” the vascular systems of young plants, stunting
their growth. Seeds may sprout fine but stall out after the first set of true leaves.
This seems to be particularly true after adding high amounts of Calcium. For these
reasons it is best to wait until the minerals are chemically and biologically a part of
the soil before starting seeds in it. Transplants usually do fine if you wait a week or
so after adding large quantities of minerals before replanting them, and we have
seen no problems with established plantings, trees, or pastures.Adding minerals
in the fall or in the early spring works best.
If minerals are added directly to potting mixes the mix should be moistened after
mixing in the minerals, and it is best to give it a little time, a week or so, to “settle
in” before the potting mix is used.Adding a biological activator such as beneficial
bacteria or fungi to the mix can greatly speed up the process.
The mineral concentrations shown on this chart are perfectly safe for plants once
they are assimilated into the living soil. If the chart's guidelines are followed you
won't end up with too much of anything-many soils naturally contain higher levels
of available minerals than the chart calls for.
