Agriculture Reference
In-Depth Information
ratio or any other ratio we want.
The complete soil report is at the end of this
chapter.
Exchange
Capacity
Calcium ppm
found
Magnesium ppm
found
Potassium ppm
found
Sodium ppm
found
11.4
1250
116
89
26
First we will determine the percentage of base saturation of each of these
elements, and then figure out if we need to add more and if so, how much.
The soil's exchange capacity is 11.4 meq. Starting with Calcium, we multiply each
element by the amount needed (in ppm) to saturate that 11.4 CEC 100%:
Ca; 11.4 x 200 = 2280 ppm
Mg: 11.4 x 120 = 1368 ppm
K: 11.4 x 390 = 4446 ppm
Na: 11.4 x 230 = 2622 ppm
The table above shows how many parts per million the soil test found. To find out
the percent base saturation for each element in our working example, we divide
the amount measured by the lab test by the amount needed to saturate 100%:
Ca: 1250 / 2280 = 0.548 or 55%
Mg: 116 / 1368 = 0.0848 or 8.5%
K: 89 / 4446 = 0.020 or 2%
Na: 26 / 2622 = 0.0099 or 1.0%
Percent Base Saturation of Worksheet Sample
Calcium
Magnesium
Potassium
Sodium
55.0%
8.5%
2.0%
1.0%
Recall we want 68% Ca, 12% Mg, 4% K, and 1.5% Na. To calculate what that
“ideal” ratio would be in this soil we simply multiply the exchange capacity
(11.4meq) by the amount needed to saturate 100% of 1meq, and then multiply that
result by the percentage of saturation desired.
