3.5: Percent Base Saturation
- Page ID
- 34623
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\(\newcommand{\avec}{\mathbf a}\) \(\newcommand{\bvec}{\mathbf b}\) \(\newcommand{\cvec}{\mathbf c}\) \(\newcommand{\dvec}{\mathbf d}\) \(\newcommand{\dtil}{\widetilde{\mathbf d}}\) \(\newcommand{\evec}{\mathbf e}\) \(\newcommand{\fvec}{\mathbf f}\) \(\newcommand{\nvec}{\mathbf n}\) \(\newcommand{\pvec}{\mathbf p}\) \(\newcommand{\qvec}{\mathbf q}\) \(\newcommand{\svec}{\mathbf s}\) \(\newcommand{\tvec}{\mathbf t}\) \(\newcommand{\uvec}{\mathbf u}\) \(\newcommand{\vvec}{\mathbf v}\) \(\newcommand{\wvec}{\mathbf w}\) \(\newcommand{\xvec}{\mathbf x}\) \(\newcommand{\yvec}{\mathbf y}\) \(\newcommand{\zvec}{\mathbf z}\) \(\newcommand{\rvec}{\mathbf r}\) \(\newcommand{\mvec}{\mathbf m}\) \(\newcommand{\zerovec}{\mathbf 0}\) \(\newcommand{\onevec}{\mathbf 1}\) \(\newcommand{\real}{\mathbb R}\) \(\newcommand{\twovec}[2]{\left[\begin{array}{r}#1 \\ #2 \end{array}\right]}\) \(\newcommand{\ctwovec}[2]{\left[\begin{array}{c}#1 \\ #2 \end{array}\right]}\) \(\newcommand{\threevec}[3]{\left[\begin{array}{r}#1 \\ #2 \\ #3 \end{array}\right]}\) \(\newcommand{\cthreevec}[3]{\left[\begin{array}{c}#1 \\ #2 \\ #3 \end{array}\right]}\) \(\newcommand{\fourvec}[4]{\left[\begin{array}{r}#1 \\ #2 \\ #3 \\ #4 \end{array}\right]}\) \(\newcommand{\cfourvec}[4]{\left[\begin{array}{c}#1 \\ #2 \\ #3 \\ #4 \end{array}\right]}\) \(\newcommand{\fivevec}[5]{\left[\begin{array}{r}#1 \\ #2 \\ #3 \\ #4 \\ #5 \\ \end{array}\right]}\) \(\newcommand{\cfivevec}[5]{\left[\begin{array}{c}#1 \\ #2 \\ #3 \\ #4 \\ #5 \\ \end{array}\right]}\) \(\newcommand{\mattwo}[4]{\left[\begin{array}{rr}#1 \amp #2 \\ #3 \amp #4 \\ \end{array}\right]}\) \(\newcommand{\laspan}[1]{\text{Span}\{#1\}}\) \(\newcommand{\bcal}{\cal B}\) \(\newcommand{\ccal}{\cal C}\) \(\newcommand{\scal}{\cal S}\) \(\newcommand{\wcal}{\cal W}\) \(\newcommand{\ecal}{\cal E}\) \(\newcommand{\coords}[2]{\left\{#1\right\}_{#2}}\) \(\newcommand{\gray}[1]{\color{gray}{#1}}\) \(\newcommand{\lgray}[1]{\color{lightgray}{#1}}\) \(\newcommand{\rank}{\operatorname{rank}}\) \(\newcommand{\row}{\text{Row}}\) \(\newcommand{\col}{\text{Col}}\) \(\renewcommand{\row}{\text{Row}}\) \(\newcommand{\nul}{\text{Nul}}\) \(\newcommand{\var}{\text{Var}}\) \(\newcommand{\corr}{\text{corr}}\) \(\newcommand{\len}[1]{\left|#1\right|}\) \(\newcommand{\bbar}{\overline{\bvec}}\) \(\newcommand{\bhat}{\widehat{\bvec}}\) \(\newcommand{\bperp}{\bvec^\perp}\) \(\newcommand{\xhat}{\widehat{\xvec}}\) \(\newcommand{\vhat}{\widehat{\vvec}}\) \(\newcommand{\uhat}{\widehat{\uvec}}\) \(\newcommand{\what}{\widehat{\wvec}}\) \(\newcommand{\Sighat}{\widehat{\Sigma}}\) \(\newcommand{\lt}{<}\) \(\newcommand{\gt}{>}\) \(\newcommand{\amp}{&}\) \(\definecolor{fillinmathshade}{gray}{0.9}\)Percent Base Saturation
The Percent Base Saturation is a measure of how much of the CEC is filled up, or saturated. It measures what % of the available sites are full, either with a H+ or a nutrient cation.
The term “base” saturation is somewhat confusing because bases are technically molecules that have a negative charge so that they can accept a proton with a + positive charge. It turns out that the cations mentioned above, Ca++, Mg++ , K+ as well as sodium (Na++) all are associated with compound molecules in the soil, for example, CaCO3 (calcium carbonate), Mg CO3, K CO3 and Na CO3 . Each of these compounds acts slightly more negative (-) “basic” than positive (+) “acid”. So, they act as “bases” in this saturation measurement.
There are ideal levels of each nutrient saturating the soil particle (CEC) sites to produce the best plant growth. Returning to the bank analogy, pretend we can have $100,000 in total in the bank (the CEC). In order to have the highest levels of productive economic activity, experts have determined that we should have the money in the following denominations: $1.00 bills = 70-80%; $10 bills = 12-15%; and $100 bills = 3-5%.
Similarly, experts have determined that the plant nutrient requirements for an ideal soil will have the following saturation levels in its nutrient bank (CEC) in the following ratios:
- Calcium base compounds occupy 70-80% of the soil bank,
- Magnesium base compounds occupy 12-15% of the soil bank,
- Potassium (K) base compounds occupy 3-5% of the soil bank,
- Sodium (Na) base compounds occupy 0% of the soil bank.
|
Ca |
Mg |
K |
Na |
|---|---|---|---|
|
$1.00 bank bills |
$10.00 bank bills |
$100.00 bank bills |
pennies |
|
(Georges) |
(Alexanders) |
(Benjamin’s) |
(person's face on the denomination)
|
|
Ca compounds |
Mg base compounds |
K base compounds |
Na (sodium) compounds |
|
70 - 80% |
12% - 15% |
3% - 5% |
0 % |
55 – 60% |
25 - 40 % |
5 - 8% |
Most typical soils |
Unfortunately, these are not the % base saturation levels found in most soils in the temperate climate of the United States. More typically, levels of base saturation are a bit too high in potassium, moderately too high in magnesium, and moderately too low in calcium. This means that the plant may be getting adequate nutrients, but it could, if the base saturation numbers were improved, get great levels of just the right nutrients to produce a bumper crop.
Sometimes, the total of base compounds does not reach 100% saturation. In other words, our bank may have enough room for $100,000 in total currency, but only $75,000 dollars are available. The economy is only using 75% of its “power”. Likewise, we may only see 60% Ca compounds, 25% Mg compounds, and 5% K compounds. This only adds up to 90% base saturation when we could have had 100% under the right conditions. An extra 10% of nutrients would have helped our crops grow that much better.
There is a strong relationship between pH and % base saturation. If the % base saturation is less than 100% (like the 90% in the example above) then increasing the pH can increase the amount of calcium and magnesium in the soil solution and the amount of base compounds saturating the sites.
This is good news because according to Henry Foth “many studies have been conducted that relate increases in plant growth with increases in the percentage of calcium in plants and with increasing pH or % base saturation”.
There is a strong, continuing debate between University researchers and the organic and sustainable farm community on calcium and whether it is a nutrient that limits plant growth because of its availability. It has yet to be resolved; the university says that calcium is not a limiting factor while farmers claim they have good results when balancing their soil calcium levels with pH and magnesium levels. This debate will likely go on for a few more years until soils, CEC, and % base saturation are better understood.