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Carlos
I have pasted a few notes which may be of help, to you or others that
are interested. From a soil, plant, animal health point of view, the
base saturation figures would be some of the most important info you get
from your soil test data.
Total base saturation (%)
A measure of how full up the CEC is. The higher the Base Saturation the
higher the pH level will be.
Desirable Base Saturation levels are given in the table below.
Crop
K (%)
Ca (%)
Mg (%)
Na (%)
Agricultural
2 - 5
50 - 75
5 -15
1 - 2
Horticultural
3 - 6
50 - 75
7 - 15
1 - 2
Glasshouse
6 - 12
50 - 75
7 - 15
1 - 2
The proportion of the soils total capacity for cations that is actually
occupied by these nutrients, the Total Base Saturation, is calculated by
summing together the levels of calcium, magnesium, potassium and sodium
found in the soil and expressing this sum as a percentage of the CEC
value.
There is a correlation between Total Base Saturation and soil pH with
increasing Total Base Saturation being associated with increasing soil
pH. This can give another perspective on a soils requirement for lime.
Generally speaking the higher the BS is in the range 50 - 80 % the
better as the minerals are more available.
Over the 80 level and losses may start happening.
pH comments. No doubt you are aware that pH is not an indication of your
Ca levels.
Soil pH
Measure of the soil acidity.
Influenced by the `Base Saturation' of the soil CEC. As the Base
saturation increases so does the soil pH.
A soil with a high pH could still need liming if a low Ca Base
Saturation is shown.
- High pH & Low Ca level: Look for K and / or Mg to be high. Lime for
Ca Level, not for pH adjustment.
-Low pH: Look for Low Ca Level: Heavy metals may be high (Fe, Al, Zn,
Mn, etc) which can be Toxic to plant growth.
Remember these are for NZ soils, but may be a starting point for your
own soils. Look at the following especially in relation to Na.
Ideal Ratios
The Grass Staggers ratio*
Critical value for grass staggers ratio is 2. 2
(k / 39)
* -----------------------
(Ca / 20) + (Mg / 1215)
Other ratios:
Ca : Mg - 6 :1
Mg : K - 3 : 1
K : Na - 2 : 1
Copper, Molybdenum, Sulphur:
The availability of Cu in the feed is influenced by Mo and S levels.
High levels of Mo ( 3 -10 mg/kg) and S (0.35-0.5%) mean that higher
levels of copper may be required.
Iron, Copper, Zinc:
High Iron levels can affect Cu and Zn availability. Means that higher
levels of copper and Zn may be required.
Potassium, Sodium, Magnesium:
High K in the feed will not only suppress Na and Mg uptake by the plant,
but also the absorption of these elements by the animals.
What is your soil test regime?
As we have 4 distinct soil types on our farm, I have cut the farm into 4
blocks and from each block chosen the poorest performing fields from
each block to test. My thinking is that if these show good levels then
the better performing fields must have better levels. I usually sample
in September, a cold wet month for us in NZ, when the soil life is
either still dormant or swimming for their lives 8>). I usually do both
soil and herbage tests from the same field and we test every second
year. The thinking of testing in September is that if any deficiencies
are going to show up it will be when I am getting the least possible
help from the soil life to convert minerals into plant available forms.
We are rather fortunate as we have many years of soil test data to use
to compare and see any patterns.
I will comment on the Bd aspects in a separate post.
regards
Ian Buckingham
Maungatawhiri
New Zealand
Your biodynamic approach is what I think we need as long term producers.
Could we expand the discussion in that direction?
Our soils are actually very rich in organic matter. Our last Hills lab
tests show over 20% OM, 25 meq/100 g CEC, 6.6 pH. K and Mg are over the
high range. The other macro nutrients are high-medium. One thing I have
noticed, is that even though our soils are mid (0,33 meq) Sodium. Our
clover and grass analysis are low in Na (0,09%). My possible explanation
is that the high N and K are blocking the Na plant absorption. What
would you think? Is it worth it trying to add more Na?
