Agriculture Reference
In-Depth Information
Base Saturation
The first main test we probably want to get done is called a base saturation test. It gives
us an indication of the percentage of base cations, or positively charged ions — calcium,
magnesium, potassium and sodium, possibly aluminum and importantly, hydrogen — in
our soil. The significance of the base saturation test is that it includes hydrogen, which
makes things easier for us. If you can't get a base saturation test, another test is called an
exchangeable cation test and it doesn't include hydrogen. This makes it rather time-con-
suming and difficult to interpret properly.
Much of the initial research that produced the numbers that follow comes from decades
of work started in the 1920s by Dr. William A. Albrecht at the University of Missouri. He
actually started working there as a microbiologist and I believe he was initially studying in-
oculation of legumes with various Rhizobia bacteria. He came to the conclusion that the
nutrients in the soil were having an impact on the quality and yield of the food crops, so he
started researching the impact of nutrients and nutrient ratios on the crops.
He perfected the use of the base saturation test. A total base saturation of 75% means the
CEC sites in our soil are occupied 75% by the bases and 25% by hydrogen. But more im-
portant to us are the specific numbers, and here's the magic formula. The ideal results are
60-75% calcium, 7-15% magnesium, 2-5% potassium, 0.5-3% sodium, and 10-15% hydro-
gen, and a few percentage points for all of the other micronutrient cations, such as iron and
copper. We don't know precisely why nature has settled on these numbers. What we know
is that often, the closer the soil gets to these numbers, the healthier the soil and plants be-
come.
When I say we, I don't mean everyone. Some people disagree with this method, claiming
there is not enough research proving its effectiveness. Their other main argument is that all
soils are different and there is no one formula that fits them all. This is certainly true. We
could use more research. What is also true is that this method has worked for thousands
and thousands of people over at least the last 60 years.
It has worked for me, as well, because I've used a lab that is doing it right, using Al-
brecht's system or something similar. The soil labs mentioned previously are doing it right,
as is Kinsey Agricultural Services. Neal Kinsey, co-author with Charles Walters of
Hands-
On Agronomy
, has helped bring Albrecht's system to us. There are other labs doing a base
saturation test without using Albrecht's system, and making fertilizer decisions based on
those results may not be as effective. The only research I've seen that disproved the effect-
iveness of using the base saturation test for fertility management was poorly conducted, not
even using Albrecht's system, among other issues. Albrecht's system does work in the
hands of a good lab.
