Agriculture Reference
In-Depth Information
The Ideal Soil Chart (Agricola's Best Guess v 2.0 January 2014)
Based on a Soil Test using the Mehlich 3 method
Organic Matter (OM)
2% — 10%
Depending on climate
pH 6.4 - 6.5 Balance the minerals and pH will
take care of itself
Primary Cations as % of Cation Exchange Capacity (CEC)
See appendix “Calculating TCEC” p 125
Calcium (Ca)++ min 750ppm
60% — 85%
(Ideal 68%)
Ca & Mg together should add to
80% of exchange capacity in most
agricultural soils pH 7 and lower
Magnesium (Mg)++ min 100ppm 10% — 20%
(Ideal 12%)
Potassium (K)+ min 100ppm
2% — 5%
(Ideal 4%)
See Phosphorus (P)
Sodium (Na)+ min 25ppm
1% — 4%
(Ideal 1.5%)
Essential for humans and animals
Hydrogen (H)+
5% — 10%
(Ideal 10%)
Alone proton. The “free agent”
Primary Anions
Phosphorus P- min 100ppm
P =
Ideal
K by weight (ppm)
BUT: phosphate
(P
2
0
5
) should
be ~
2X potash (
K
2
O)
Needs a highly bio-active soil to
keep it available.
Sulfur S - - min 50 ppm
1/2 x
Ideal
K up to 300 ppm
Need for Sulfur amino acids
Conserves soil N and Carbon
Secondary elements
Iron(Fe) + min 50ppm
Manganese(Mn) + min 25ppm
Zinc (Zn) + min 10ppm
Copper (Cu) + min 5ppm
Fe: 1/3 to 1/2 x
Ideal
K
Mn: 1/3 to 1/2 x Fe
Zn: 1/10 x P
(up to 50ppm)
Cu: 1/2 x Zn (up to 25ppm)
Iron and Manganese are
twins/opposites and synergists, as
are Copper and Zinc.
Boron B
3+ or -
(cation or anion) min
1ppm
1/1000 of Calcium (max 4 ppm)
Essential for Calcium utilization.
Calcium transports sugars
Chlorine (Cl)- min 25ppm
1x to 2x Sodium
Essential, but ages clays rapidly
when used in large amounts
Silicon Si
4 + or - (
cation or anion)
Ideal unknown. Si is the most abundant mineral in most soils. Active
soil biology and balanced mineral chemistry will ensure availability.
Micro (trace) Elements
Chromium Cr-
Cobalt (Co)+
Iodine (I)-
Molybdenum Mo-
Selenium (Se)-
Tin (Sn)+
Vanadium (V) +
Nickel (Ni) +
Fluorine (F) -
All of these are essential in small
amounts. 0.5 - 2ppm is
enough.
Some of the micro elements (e.g.
Mo, Se) can be toxic to plants
and soil organisms in quantities
above 1-2ppm. Use Caution
when applying micro/trace
elements in purified forms
There are probably 30 or so other
elements needed to grow fully
nutritious food. Sources are
amendments such as seaweed,
rock dust, ancient seabed or
volcanic deposits, rock phosphate,
greensand etc
Plants need at least 17 of the 23 elements listed above, as well as Nitrogen, Carbon,
Hydrogen, and Oxygen.
