how do I raise the cation capacity of soil without adding potassium?

My soil is a heavy clay, with a cation capacity of 39.5

The cations are Calcium 84
Magnesium 9
and Potassium 7

The ideal for this soil would be 76, 10, and 5

So it would seem that I need to increase the cation capacity, to lower the overall saturation of magnesium.

But organic matter has tons of Potassium in it, which will mess up my soil. How to fix this?

In a related problem, the Potassium in the soil is at 1011 ppm, and the phosphorus is at 71 ppm. The soil test says that the phosphorus is excessive. However, to have a balanced soil, the potassium and phosphorus levels should be roughly equal. So do the soil test people just not know what they are talking about, or is there some way to lower the amount of potassium?

Unfortunately, I added manure and wood chips to the soil surface, which are probably messing things up further.

Hi Gilbert,

I've been reading the "intelligent gardener" by steve solomon and have been inspired by the notion of soil balancing.

39.5 cec sounds dreamy...

just wondering why you don't try and buffer the cations with some sulphur?
from what i gather the excess cations will tie up as sulphates.
same may be achieved with nitrogen to nitrates, i gather.

my ground is the other end of the scale - low in available magnesium and very loose.

how's the soil life and fungals they might help you buffer the cations too.

g/l

Some quick thoughts.

I suspect you goal is to grow plants sustainability... is it working? If you are getting good performance, than reaching a numerical ideal might not be important. I suspect that how soil nutrient analysis leads to individual plant healthy is actually less accurate, precise, and direct than the numbers might suggest. Different plants will respond differently, and no soil is perfect for all plants. Soil amendment suggestions are loaded with assumptions and generalizations.

My understanding is that when CEC is high and pH near neutral, that means there are lots of cations available, and so the exact balance of cations becomes less critical that were CEC to be low (sandier siltier soils). I have never heard of anyone wanting to reduce CEC... usually its the other way around.

The way we tinker with Ca:Mg balance around here is in the ratio of Carbonate Lime to Dolomite Lime... and that is because we are liming regularly to manage pH in leached soils... what is your pH, as that will affect how you tinker with cation balance. (sorry can't help you much there.. but I bet the sulfate based rock are more in line... SulPoMag, Gypsum... etc.

Ph of 7.8. So I don't want to add any lime, that is the problem. And I want to raise the cation capacity so that the Calcium is less of the total.

Hi Gilbert,

I ran your numbers from the other thread through my interpretation of the excess cation worksheet
now take my calculations with a grain of salt as i'm doing this more as an exercise for me to help understand the connections.

you say your ideal soil would be 76,10,5 (Ca,Mg,K) = 91% of cec...I've been working on 80-85% total cations & 76,8,4
there was no sodium level in your post so i used Na = 0.

i calculate you at roughly 80, 5, 12 = 97% of tcec
but what i get from it is your soil is in Potassium excess by 1011-323 = 688ppm (323 ppm ideal via my take on the excess cation worksheet)

i'd be buffering the cations with anions (Sulphur & Phosphorus) and nitrogen

you say you've added some manure and woodchips... they'll be a store for Sulphur, Phosphorus and Nitrogen until it breaks down.
so the benefit of those additions might not show for a season or so until they've fully composted and start to give back the initial drawdown.

manganese, calcium, and boron will be tied up by the excess potassium, so look for those deficiencies as potential clues.

red clover grows well in excess potassium apparently, maybe you could intentionally mine the excess potassium via red clover and feed it to the chooks and make use of the eggs offsite.
the roots of the clover will give some nitrogen back.

g/l

Brian

The natural cec of the soil (sand) around here is around 5. Good for grass, pine trees, and this prickly thing called fireweed (DO NOT step on it barefoot). I add compost, leaf mold, grass clippings and wood chips. The leaves and wood create a rich volume of humus. It's the humus that boosts the cec.

Hau, Gilbert,

The easiest method to increase the CEC of just about any soil is by the addition of a Biochar that has been blended with compost.
One other issue is the amount of K in your soil, it is possible to use an amended Biochar to help with this issue at the same time.

Biochar enhances soils. Research is now confirming benefits that include:
•Reduced leaching of nitrogen into ground water
•Possible reduced emissions of nitrous oxide
**•Increased cation-exchange capacity resulting in improved soil fertility**
•Moderating of soil acidity
•Increased water retention
•Increased number of beneficial soil microbes

Biochar can improve almost any soil. Areas with low rainfall or nutrient-poor soils will most likely see the largest impact from addition of biochar.


“Making compost from litter and excretions has been common in Japan for a long time. In the
1980s, charcoal compost was made from fresh chicken dung and palm shell charcoal; the
more charcoal used, the faster the composting process. Under aerobic conditions the
Bacillus group became dominant and produced antibiotics that inhibited growth of soilborne
pathogens and suppressed root diseases. Charcoal compost is now sold in Japan as
a biological fungicide. Various other organic composts are now being been produced from
livestock excretions and charcoal and sold commercially.” (Ogawa, 2009).

Another example from Japan is bokashi, an organic fertilizer made by combining “effective”
microbes, molasses, biochar, bran, and animal manure with water, and incubating under
anaerobic or partially anaerobic conditions (there are variations of this recipe and some do
not include charcoal). This amendment was developed by the Japanese philosopher Mokichi
Okada in 1935 (Reap Canada), and is now made and used in many developing countries
around the world, often incorporating native micro-organisms in addition to the “effective”
micro-organisms. The biochar can be made from any convenient source of biomass, such
as sugar cane bagasse.

In addition to these benefits, you can increase mineral content by including some biochar created by converting bones into biochar. Another method of introducing better mineral content of soils is by the addition of rock dust.
Both of these can be effectively incorporated into a biochar blend then applied to the soil.

The ability of biochar to increase the water holding capacity of soils has, at this time, not been fully documented. It will however, by the very nature of the biochar, hold onto at least some water.
This year I am doing a study on water retention of one area of Buzzard's Roost Farm to see if I can add to the current documented studies on this aspect of biochar.

Biochar is not a be-all end-all solution but it is a well documented, used for thousands of years, soil improver. It is something that I use more as a carrier of nutrients at this time, I have a couple of areas that are red clay, the additions of compost/biochar I made last year are already showing signs of turning these areas into better, more friable soil. I will add the same amendments again this year to continue the documentation of this particular clay soil study I am performing.