Soil Decision Making
Animal Forage, Food Plants - Annual, Food Plants - Perennial, Fungi, Plant Systems, Rehabilitation, Soil Biology, Soil Composition, Soil Conservation, Structure, Trees — by Campbell Wilson June 15, 2011
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| Winona paddock Pasture cropped & time control grazed |
Adjoining paddock Traditional Crop and set stock grazed |
When you are trying to decide which method of soil improvement to take, sometimes it seems like there are as many different approaches as there are bacteria in a teaspoon of healthy soil.
This isn’t necessarily a huge problem when you’re talking about a suburban backyard scale. It’s easy in that situation to: do some aerating with a broad fork; balance the Calcium:Magnesium ratio and whatever trace minerals your soil test says are missing; build and add compost and worm castings; brew up some compost tea; add some seaweed extract, a handful of basalt rock dust, a bit of Charlie carp and the humified eyeballs of some rare mountain lion to top it off.
But what about the farmer who is planting 1000 Ha of Wheat and Rye so the armchair permaculturalists of this world can munch their organic sourdough toast while checking the next important forum posting written by someone else sitting at a computer at 10.30am. That farmer would quickly go broke if they did all the things a backyard gardener can do. So how to decide?
The farmer’s goal should be to turn subsoil into topsoil. That is, to be able to walk anywhere on his or her land, sink a post-hole shovel and find something resembling chocolate cake. If you’ve got chocolate cake, you’ve got good crops, whether it’s pasture, grain, fruit or veg. CSIRO scientists still say it’s impossible but I’ve seen it happen under the care of a number of our country’s best farmers (Col Seis and Ron Smith to name a couple) to know that it’s very achievable (and we’re talking years, not centuries, as you may have been led to believe).
What’s the secret? It’s plants and microbes working together.
It seems that Nature got sick of applying bags of NPK to all the different plants on Earth and equally sick of spraying out molasses and fish hydrolysate to feed the bacteria and fungi in the soil and decided to read Mollison’s Intro to Permaculture. Principle 1: Relative Location made a bit of sense, so she conducted a Needs, Functions & Products Analysis, and in doing so recognised that plants produced more than enough sugars through photosynthesis, but needed nutrients to do so, and meanwhile bacteria and fungi were easily the most efficient critters on earth at grabbing hold of nutrient, but had a hard time finding carbs to fuel their bodies. It was a match made in heaven. The plants were put next to the microbes and have been symbiotically trading root exudates (sugars) for nutrients ever since.
What does this have to do with building soil? Those sugars passing from the plant to the soil critters are liquid carbon. Let’s take one of the exudate recipients, mycorrhyzal fungi, as an example (they attach themselves to plant roots in a symbiotic relationship). They use these sugars to produce glomalin, a protective coating for their hyphae, which is sloughed off into the soil when the hyphae dies. The glomalin is a very persistent carbon compound that ‘sticks around’ in the soil for a long time (it’s one of the main things that holds soil aggregates together).
What encourages hyphae production? You need to feed them for as much of the year as you can, and this is only possible when a plant is actively photosynthesising. That is: maximise root exudates by maximising yearly photosynthesis.
This means:
- In pasture, an appropriate disturbance/recovery regime to maximise the growth potential of pasture plants. (See Holistic Grazing Management for further info.)
- Different plants thrive at different times of year. A mix of C3 (cool season) and C4 (heat tolerant) plants will ensure you can take advantage of moisture and have something green and growing throughout the year (See Carbon Grazing by Allan Lauder for more info on this topic)
- Winter cropping C3 plants (ie. wheat, oats, rye) into dormant C4 perennial pastures or summer cropping (millet, sorghum, corn) into dormant C3 pasture (search for Pasture Cropping, Col Seis)
- A winter active groundcover under dormant fruit trees.
Using a combination of time-controlled grazing and pasture cropping, Col Seis has managed to go from the soil shown on the right of the image at top (this sample is from over the fence, 15m into his brother’s conventional agricultural paddock, who still farms the way Col used to) to the soil on the left in 15 years. (He could do it in 10 now he reckons.)
In doing so, his soil test in relation to what existed before is:
So let’s consider the management interventions related to the chemical, biological and physical aspects of Col’s soil that have lead to these results.
Chemical
The changes seen in the table above to the chemical nature of Col’s soil have been achieved without the addition of single bag of super-phosphate, nor a tonne of lime, nor any trace minerals, nor any sizable amount of compost, in 30 years. (He does continue to put out a small amount of DAP when sowing a grain crop, but has had good success with worm juice this year.) Soil nutrient amendments haven’t been the driver.
Biological
Col did put compost teas out for a little while, but then thought, “What the hell am I doing this for? Why am I adding foreign microbes from a compost pile when there is already a huge diversity suited to the conditions in the existing topsoil”. He then changed to feeding the existing microbes with molasses and fish emulsion, until he once again thought, “What the hell am I doing this for? Why am I putting food out when the plants create the best microbial food there is”. Biological stimulants haven’t been the driver.
Physical
A small aerating affect is achieved with the tines on the direct seeder that Col uses for pasture cropping, but they only impact down to about 70mm which doesn’t explain the dramatic increase in carbon down to 500mm. Soil cultivation hasn’t been the driver.
All this has been driven by the plants within Col’s pasture and cropping system. Here’s a brief summary of what they’ve done:
Biological
- As stated above, Col aims to maximise the photosynthesis potential on his property, and hence maximises root exudates; the fuel for the life in the soil. (Winter cereals such as oats are one of the highest producers of root exudates and really give the native pasture and soil a kick.)
- The pulse of disturbance created by time-controlled grazing, followed by a period of rest until plants have fully recovered (that is, the perennials have replaced root energy reserves) offers plenty more food to the soil food web in the form of root exudates, decaying root systems, litter, manure and urine.
Chemical
- Soil microbes fuelled by root exudates, in particular mycorrhyzal fungi, are able to access nutrients from the subsoil that were previously tied up in a plant unavailable form. They can then transport these nutrients through their network of hyphae.
- The test results above, which were taken down to 500mm, show not only an increase in Col’s Available nutrients, but Total nutrients have also increased significantly, suggesting the breakdown of parent rock material by the soil life.
- Increased carbon levels also result in a huge increase in the water and nutrient holding capacity of the soil.
Physical
The growing soil carbon levels fuelled by root exudates, along with the carbon pathways created by decaying root systems, as well as the improved structure provided by bacteria glueing their butts to the particles, the fungi wrapping themselves around everyone else and the worms and other larger critters creating tunnels through the soil as they relentlessly munch-on, all help to improve the aeration, root penetration, nutrient holding capacity, nutrient availability, water infiltration and retention etc.
So does that mean that the soil improvement methods handed to us by the various soil legends that have come before (ie. P.A. Yeomans who was physical-centric, William Albrecht who was chemical-centric or Elaine Ingham who is biological-centric) are unnecessary?
Not at all.
With the right management practices, plants can do the job, but the methods that folk such as these gave to us can help to speed things along. The key thought when you are deciding which one(s) you want to spend your money on, is to keep in mind what the goal is: for plants to maximise photosynthesis and drive the system.
Therefore the practice that you choose should address the major limiting factor that restricts photosynthesis. For example:
Physical: On an area of pasture that we are developing at the moment, compaction from past practices is the major limiting factor. It’s preventing decent root penetration as well as resulting in water sheeting off. So, in conjunction with time-controlled grazing, we are implementing an initial program with a Keyline Plow using Keyline Pattern Cultivation. Good grazing and pasture cropping once every 3-4 years should maintain it from there.
Chemical: On the property of a friend of mine, he has a heavy sodic layer down about 170mm which is inhibiting root penetration. In this case, he has had an expert in the Albrecht method of soil balancing give him some advice. He has been injecting liquid calcium down to the sodic layer, which has changed the structure of the soil and resulted in root penetration a further 30-40cm in 2 years. The plants can now start to drive the system.
Biological: As far as adding biology goes, tests have recently been done by a leading University on a number of different compost teas and microbial jungle juices. Basically the results showed that if you had a bit of decent topsoil already, the compost tea made no difference. If your soil is dead, for example it might have been plowed non stop for 100 years, or perhaps there’s been excessive chemicals used on the land, then it could be worth putting some critters on as an initial inoculation.
This is just my opinion, but rather than adding foreign microbes from a bottle or even a thermophilic compost pile (which is an incredibly different environment to field conditions if you think about it), why not get hold of some soil from under a few of the best pastures in your region. Perhaps grab some from under a healthy bit of native grassland that you know of too. In my opinion they could well be better suited to your conditions.
Here’s a good story related to this topic. John Weatherstone is an inspirational farmer who has planted many thousands of trees to compliment his grazing enterprise. He had a stand of Casuarinas that were yellow and weren’t doing well. John W had a long discussion with John Field from the Australian National University about whether it could be the clay or the salt below or etc. In the end John F said, why don’t you go and grab some duff (leaf litter and topsoil) from under a healthy old stand of Casuarinas and put it around their base. John W did this to half of them and they turned green and healthy within a month. What a difference the right biology can make. (The other half began to turn green too, marching progressively away from the inoculated stand due to the root grafting that takes place, as well through the fungi which connect plant ecosystems.)
So, here’s the short version:
- Aim for plants to drive the soil system by maximising photosynthesis.
- If you’re keen to spend money to speed things up, carefully consider what the major limiting factor is, and base your interventions around this.
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Cam Wilson manages the tree and hydration systems at Mulloon Creek Natural Farms, the home of The Mulloon Institute. If you are interested in participating in the upcoming intern program, please visit www.themullooninstitute.org
Comments (20)
The proof is in the pudding. I love the nice crumbly chocolate cake. Thanks for a great report Cam.
Comment by Craig Mackintosh PRI Editor — June 15, 2011 @ 5:17 am
Brilliant intro, to an awesome article!
Comment by Jason Gerhardt — June 15, 2011 @ 11:17 am
After years of thought, reading, and experimenting with soil improvement, I can say that this article could save many people years of thought, reading,and experimenting with soil improvement. Excellent.
Comment by JBob — June 15, 2011 @ 2:36 pm
Very enjoyable read, I’d like to note its 3.30 in the afternoon and I have just layed down some green manure for spring planting and cleaned up after a storm here on the North Coast
Im really intrigued now by the use of indigenous microorganisms after reading this report on the Rodale website http://www.rodaleinstitute.org/20040401/Hamilton and I saw a hint from Darrens blog from the rice and mango farmer he met in Yucatan Peninsula in Mexico.
The results do speak for themselves, but I still wonder if pasture cropping can be replicated over all the grain growing districts and still be able to maintain the current volume of grain harvest. Im sure if we had todays knowledge on soil life 100 years ago, we could at least maintain carbon levels and enjoy true sustainability. Farmers might need to return to the 7 year rotations that were common 50 years ago.
Nice job on getting the information out there, Cam. Look forward to more light reading.
Comment by David Mattinson — June 15, 2011 @ 3:48 pm
Good reading, thank you.
Comment by Joshua — June 15, 2011 @ 4:52 pm
Good one, Cam. Nice to see my PDC teacher in print. Hope you and Jess and the little nippers are OK.
Comment by Bev — June 15, 2011 @ 4:59 pm
I also wonder about potential risks of spreading microbes from far off places/laboratories. Given we don’t know the half of what happens in soil, avoiding disrupting local soil ecologies has to be something to think about.
Comment by Tom Chambers — June 15, 2011 @ 8:36 pm
Great article!
Comment by Isaac — June 16, 2011 @ 2:03 am
Hi Cam,
Thanks for a great article. I look forward to more news from Mulloon.
Harry
Comment by Harry Wykman — June 16, 2011 @ 4:11 am
Great article Cam. Love it. Concise and eloquent.
Col is running a couple of workshops coming up in October through RegenAg including one in North Queensland and a rare opportunity to here him on his own place Winona.
http://regenag.com/web/upcoming-courses/categoryevents/3-pasture-cropping.html
Comment by Nick Ritar — June 16, 2011 @ 2:15 pm
Great article Cam.
What’s the reference on the compost tea study? I’m not surprised that they found that. I’ve become fairly reserved about some of what Elaine Ingham says, as much as I loved doing the course and love looking down the microscope. There’s little evidence that compost teas help with disease control as foliage sprays for instance.
Although I have got a lot from reading Albrect, there are criticisms of some of his experiments, and critiques of the whole ideal mineral balance concept. This wikipedia article, though written by one person looks like a well referenced critique.
http://en.wikipedia.org/wiki/Base_Cation_Saturation_Ratio
(There is nevertheless evidence, and it’s widely accepted that Mg can cause dispersiveness in clays, so adding low magnesium lime or gypsum helps with this, so the Ca:Mg ratio is still relevant.)
Comment by Adam Grubb — June 16, 2011 @ 5:35 pm
I should say the wikipedia article also disputes the Ca:Mg ratio. This is a study that supports it though, concluding: “the research presents evidence that it is beneficial to manage soils to high Ca:Mg ratio if they are prone to sealing.”
http://www.tucson.ars.ag.gov/isco/isco10/SustainingTheGlobalFarm/P057-Dontsova.pdf
(I will add it to the wikipedia article)
Comment by Adam Grubb — June 16, 2011 @ 5:59 pm
Great article. Absolutely loved it.
Comment by Dan Smith — June 17, 2011 @ 8:51 am
Hey Adam
The findings of the compost tea study I mentioned aren’t published yet. I got the inside word from one of the professors involved. Will happily send it on once it’s made public.
The article you mentioned here: https://www.agronomy.org/publications/sssaj/articles/71/2/259 is a good one. I imagine it would cost an absolute fortune to try to balance the soils in most places in Oz.
One of the insights I’ve had in recent times is that rather than trying to add all the P or Ca or whatever is deficient in that particular soil, the aim is instead to add just enough in an available form to kickstart the microbes that make that particular nutrient available. They can then start mining the subsoil, and parent material for the nutrient which is often in abundance but in an unavailable form.
In the case of the example mentioned in the article, the addition of Calcium to displace excess Sodium molecules, thereby reducing the shrink swell nature of the base cations is pretty well tried and tested by mainstream science. The liquid injection process he uses gets the Ca down to the sodic subsoil faster than gypsum will if applied to the surface.
Comment by Campbell Wilson — June 17, 2011 @ 1:38 pm
Compost, manure, mineral amendments etc are still appropriate approaches to intensive vegetable production though yeah?
Comment by Nathan Edwards — June 18, 2011 @ 1:27 pm
Great post Campbell.
I wonder how you would go about soil testing. Assuming at least some chocolate cake topsoil, would there be any value in a microbiological soil test at all?
e.g. In your physical limitation example above (compacted pasture) odds are that fungal ratio is far from ideal, I doubt you would need a biological soil test to show this. Would you rely on the fungal biota to repopulate the soil in conjunction with improved management practices (keyline/HM etc.) or add biota from “best pasture” locally.
Would it not be advantageous (in this example) to make a batch of fungal fed ACT using the “best pasture” or local mature forest (or a mix of both) as the source material, and apply that in a single pass with the keyline plough, skipping the microbiological soil test all together? Or maybe feed the biota directly in the soil in a single pass with the keyline plough skipping the testing and brewing all together?
Looking at the myriad of available soil tests (and the costs) I wonder what regime you use beyond standard chemical analysis.
Comment by Pete — June 18, 2011 @ 6:21 pm
Beautifully told Cam. With this article and others you’ve demonstrated great talent as a teacher and storyteller, explaining complex topics in an interesting way using language almost anyone can understand. Really great work, well done.
Comment by Peter I — June 19, 2011 @ 6:38 pm
Really enjoyed reading this. Will give it some thought.
Deano
Comment by Deano — July 5, 2011 @ 7:43 am
A good well researched & Written Article Cam, I agree with most of your statements & have had great success following a similar path as Col has, competition from annual grasses in our cool soft environment (Northern Tableland) made pasture cropping without a knockdown spray (Roundup) almost impossible. Annual applications of Lime 100kg/ha in composted manure has worked well to lift PH far more than should be possible on several propertes around here. The tools of Planned grazing, rest, stock density, water & wire and patience are a very powerful way to make very degraded land into productive pastures as well as to rapidly increase organic matter & soil carbon.
Comment by Cam Banks — July 23, 2011 @ 12:38 pm
An excellent article and beautifully told.
The bringing together of the physical, chemical and biological components of healthy FUNCTIONING soil is the key…this is holism at its best and demonstrates what Colin is so skilled at doing -
getting out of Nature’s way so she can do what she does so well.
The old saying of “don’t just stand there, do something!’ is turned ’round by Stuart Hill……’don’t just do something, stand there’ [and let Nature take her course] is sage advice.
Comment by bush goddess — July 27, 2011 @ 9:54 am
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