On the surface it looks just like a fine sand but unlike sand there must be something about the micro-structure of this material that holds much more water than expected.
Pore space for water holding and cation exchange.
palagonitic dust, which contains hydrated and hydroxylated volcanic glass of basaltic composition, accommodates significantly more H2O under comparable humidity and temperature conditions than do the smectites nontronite and montmorillonite.
What’s in Palagonite?
How is it formed?
Does it make a good soil amendment?
Overview of Palagonite for Organic Farming
Personally, when used as a soil amendment, I’d prefer something with lower levels of Aluminium Oxide and Titanium Dioxide, Sodium Oxide is borderline too, but you can’t argue with the results when mixed with compost.
Composting with Palagonite:
During it’s formation gasses become trapped.
This 3-D rendering, produced using X-ray microtomography at Berkeley Lab’s Advanced Light Source, shows a cube-shaped sample of pumice (blue-gray) and pockets of trapped gases (other colors). The X-ray studies helped scientists uncover how gas becomes trapped by surrounding liquid, causing pumice to float on the ocean’s surface for prolonged periods.
Credit: Berkeley Lab, UC Berkeley
Add 1.5% biochar to a 3.5% (0-100mm sampled) soil organic carbon soil, wait 9 years and it begins to positively prime. Clearly they didn’t add enough to reach a tipping point faster, or depending on your perspective and availability, adding biochar to low carbon soils is a long-term investment. I assume it was surface applied as the study is paywalled.
Paywalled: Biochar built soil carbon over a decade by stabilizing rhizodeposits : Nature Climate Change : Nature Research
Nutrient cycling may suffer even when those soil microbiomes grown in high phosphorus soil are then later used to inoculate other soils.
Laura Kaminsky: Phosphorus and the soil microbiome of alfalfa
When the microbes aren’t doing the work because they’re not being watered, housed and fed well, some farmers do that work for them.
In the video from India they explain how they use dried topsoil and subsoil for fertigating their crops via foliar spray. This has multiple effects, the first is providing soluble and insoluble nutrients to the plant surfaces for plants, microbes and sunlight to break them down, and second is adding to existing topsoil where more active microbes may utilise them.
However care should be taken as many clays from subsoils are known to have antibiotic effects, even on superbugs, and the application of foliar sprays with these clays has been shown to eliminate some plant pests and diseases. Many subsoils also have low pH that make kill some microbes.
So on one hand applying subsoil may be supplying nutrients and could increase productivity, and this appears to be the case in India. On the other and depending on the soil it could initially be killing the plant and soil microbes that produce them. This can potentially break the natural cycle and make this a system that requires continuous human intervention.
In the video they recommend 3:1 dried topsoil to dried subsoil in their foliar spray, with that increasing in subsoil content to 1:3 for disease eradication.
Every 10 days or even weekly…
They are effectively mining the soil to liquid feed the plants for continuous cropping.
Whether this is sustainable or even regenerative is a good question.
Does this practice build soil over time? Could it? Is that building as much as they excavate and does it compensate for the energy used to distribute those nutrients? They do mention increased plant nutrients, but I’m not sure if they also tested the soils.
On one hand the drying of soils is effectively hunting and killing microbes and their mucilages for their nutrients, on the other you get increased productivity. It’s like robbing Peter to pay Paul, which is the best investment? The same applies to killing off plant predators with foliar spraying, effectively feeding the plants with dead microbes and dead soil.
But perhaps this produces more plant exudates that produce more symbiotic root microbes to kickstart nutrient cycling above the level in the root zone needed to build soil rather than consume it?
If done in combination with diverse cover cropping and chop and drop to provide a cover and food for the soil I can see it being a useful tool to help get back to letting nature do the work, instead of the farmer.I think of this in the same way as I think of tillage. Initial minimal tillage can kickstart a system faster towards a regenerative approach by decompacting soils and releasing nutrients for plants to establish and grow and photosynthesise thereby feeding more microbes that build soil and reduce soil density.
It’s important to keep in mind too that tilling kills off fungi and earthworms, and so using any technique that disturbs soil should be minimised.In situations when access to organic matter is limited I can see these approaches helping get an initial crop in the ground to then be regeneratively managed. On the other hand where there is plenty of organic matter and soil moisture a no dig approach may be more appropriate.
Not very permaculture aye? Lots of mystic hand waving? Well… read on.
Ever wanted to know how “Preparation 500” is prepared? Or what’s in the end product?
The material was found to harbor a bacterial community of 2.38 × 10-8CFU/g dw dominated by Gram-positives with minor instances of Actinobacteria and Gammaproteobacteria. ARISA showed a coherence of bacterial assemblages in different preparation lots of the same year in spite of geographic origin. Enzymaticactivities showed elevated values of β-glucosidase, alkaline phosphatase, chitinase, and esterase. The preparation had no quorum sensing-detectable signal, and no rhizobial nod gene-inducing properties, but displayed a strong auxin-like effect on plants. Enzymatic analyses indicated a bioactive potential in the fertility and nutrient cycling contexts. The IAA activity and microbial degradation products qualify for a possible activity as soil biostimulants.
Of the bacterial species, two dominated 90% of the culture. Half was Bacillus megaterium a plant growth promoting rhizobacteria (PGPR) known to produce Cytokinin. While the other half was Bacillus safensis another PGPR known to produce Auxins.
Cytokinins promote cell division and act in concert with auxins that promote cellular expansion. And, for example, the ratio of auxin to cytokinin in certain plant tissues determines initiation of root versus shoot buds.
Sounds like it should be called PGPR 500.
Microbes and soil respiration.
In field trials shown below in the video, CO2 respiration also shows a correlated rise in nitrogen removal and yield by plants.
Does that mean you are better off cycling between dry and wet conditions compared to a consistent moisture level for mineralisation? Probably not as indicated in the cumulative mineralization rate in the diagram above. My own gardening experiment with a wicking tray vs periodic watering system seems to bare similar results to those shown.
Temperature is also mentioned, with CO2 respiration at least doubling with every 10 degrees Celsius. That has me thinking about soil carbon priming vs CO2 respiration and how much and what type of mulch would best keep the soil microbes happy and in goldilocks temperature zone respiring CO2 while sequestering carbon.
It’s in French but you don’t need to understand a word he says to understand what he does… at least until he plants his antenna. ;^)
The termite infested wood is a nice touch.