Fertigation with Teas during Drought.

Living the Good Life with Rushka

Rushka and Emma discuss drought problems and planting mistakes in South Africa. In passing Emma mentions watering her trees with Comfrey tea. Comfrey is high in potassium and that helps plant stomata regulate moisture, and encourages fungal colonisation. Go Comfrey. You can generally find potassium in skins/rinds of fruits too.

Stomata open vs closed and the role of potassium ions in closing:


I don’t have any Comfrey here, however to make the most of scarce water when it’s dry here in Australia I’m trying organic fertigation rather than simply watering, especially for younger plants. I’ll make up an organic soup if it hasn’t rained for a couple of weeks or we’re expecting a long stretch of hot weather, and apply that and not water unless plants are still drooping in the mornings before it heats up.

A study I read showed that microbes start to go dormant and die after 2-3 weeks of drought in some climates, and when that happens some of their soil aggregate glues break down and begin to leach nutrients when you do water or it intermittently does rain. I recently learned that the rate of soil aggregate breakdown or growth is exponential too, so keeping microbes happy in the goldilocks zone is important. Mulch and feed them!

My process is to take soft green cuttings from plants/weeds that are growing well and chop or blend it finely into a bucket as this chopping adds useful surface area and edge and aids the breakdown and dissolving of nutrients. Herbs can be used for their high nutrient density, however be warned that their oils could impede fungal growth.
Then I add a couple of tablespoons of the least processed sugar I have, ideally that’s a piece of crushed fruit or a syrup. Not all sugars are equal. Compare Maple and Panela(Rapadura/Unprocessed Jaggery/Cane sugar) with centrifugally spun raw and refined sugars that are mostly carbon.

maple syrup.png

panela (rapadura).png

I add to that 1 part aged urine and 5 parts water and add a handful of good moist topsoil for indigenous microbes or compost. Optionally, if you have some moist crumbly wood that is covered in fungi, add that too, otherwise ground up rough bark can work, as this can help add fungi and nucleation points I’ll get to below. The fruit adds sugar and potassium (for fungi and plant stomata that control plant moisture), and the urine adds nitrogen which helps speed the breakdown of carbon compounds in the plant material, while both also add soluble compounds. Stir well with forward and sudden reversing motions for 5 minutes and then steep for up to 6-8 hours. The mixing is very important. Ideally the mixing container is larger than the amount you want so you can easily stir at speed and change direction to mix it well while not making a mess. Get out your drill and make a wire stirrer, or kitchen beater if you’re lazy. 🙂 You want to really froth the water with forward and reverse action to help mix and aerate it like your washing machine might. All the particles in the water will end up covered in tiny bubbles that form nucleation points that way, and become feeding stations with air, nutrients and water at their boundaries that should last long enough to stay mostly aerated for our needs.

You should get something like these carbon dioxide bubbles forming in solution around a finger, but in our case those bubbles would be on all the particles suspended in the water.


Studies I’ve read show it takes about 6-8 hours for most labile minerals to dissolve so I don’t bother going much longer than that. And while this process will culture microbes too, that isn’t the main goal here.
If I have charcoal I’ll grind that into a powder and add that to my soup too, as it helps aerate with lots of pores, and hold onto the nutrients in the soil and partially dissolves to feed soil organisms. Porous material that will partially float like crushed expanded clay balls are another good addition as they hold air and nutrients in the water column. Eggshells, oyster shell, limestone, etc, baked, crushed, then soaked in vinegar is also optional for calcium. Like us, calcium is used in the skeleton of plants. A source of silica is also important as plants take it up during drought in place of carbon. The porous diatomaceous earth made from tiny diatoms, a type of phytoplankton, is one source. Oats, millet, barley, potatoes, banana peel and bran cereal are others.


I either make my soup in the morning and apply at night, or at night for steeping overnight and applying in the morning. That’s it. You can test with a pH and Electrical conductivity meter to see how well you did, or just apply it and see what results you get.

The simple version is simply aged urine, water and sugar, this stimulates carbon priming from mulch materials accelerating their breakdown.

The more complex version is as complex as you want to make it.

It should be noted that some minerals require acidic environments to dissolve, and fermenting for long periods can help, so it all depends on your goal here. Should you ferment for longer periods, ensure that none of the material you add is high in heavy metals.

It’s worth noting that fungi are drunks. They exude alcohols and acids to break down matter. They also move water along their hyphae network at up to 75mm (3″) a day and can share it among friends. This is why they’re so valuable to drought areas and should be encouraged.

Water Solubility.png


  • Enough soft chopped greens to fill half a container, or less if using plant-based meal (ground up plant material)
  • 1 part fruit (2 tablespoons of sugar or syrup)
  • 1 part handful topsoil (or compost)
  • 1 part aged urine (at least 1 month at room temperature)
  • 5 parts rain water (non-chlorinated water)

Optional extras:

  • 1 piece of fungi covered crumbling wood (optional)
  • Micronised charcoal (optional)
  • Crushed clay balls as used in hydroponics (optional) (Or cook come clay and flour with fire to 200 Celsius then crush)
  • Baked crushed eggshells soaked in vinegar (optional)
  • Bonsai medium like crushed bark as used in potting mixes (optional)
  • Silica/Crushed Diatomaceous Earth (optional)

Bonus: Why use mycelium covered crumbling wood? Water holding and Liquid Mycelium!


My Terra Preta “black soil” Recipes.

The mysteries of Terra Preta aka “black soil.” How was it formed?

Thought I’d have a stab at my own recipe. Untested as yet.

I actually came up with a couple of recipes depending on whether amendments are made in a village or field.

Firstly, in village areas I think most of the material is cooking & construction material burnt and then thrown into a hole, garbage or compost pile. I haven’t seen any baked soil layer in photos that would be reminiscent of growing on top of a deep fire pit. But I haven’t looked hard.

Materials including wood ash, charcoal, bones & egg shells were likely cooked with fire. And although it takes 842C to create calcium oxide, cooking can help expedite the breakdown of the bones that then form an excellent soil amendment.

Any cooking liquid waste like from tea, soup, broth can go on the pile too. Humanure and urine? Up to you.

This mess was probably then left to compost with other wastes like animal carcasses, plant materials, and all their clay pottery failures!

Basically the bulk of waste material the villagers would have created in daily life.

How much if any processing like crushing or grinding of the material was done is a good question, as is the kind of domesticated animals they may have kept too. Images of tribes suggest pig, fowl, and possibly bovine. Perhaps they ran the animals over the burnt wastes to crush and inoculate it with manures for them, or collected the manures for the waste pile?
However they did it, they likely had a variety of ground charcoal and rockdust for decorating themselves and their environment, so I’ve included those.

My Village compost recipe:
15% Wood ash,
5% Pyrolised Calcium (Bone, egg shell, etc),
50% Assorted fresh plant and animal material waste for microbes,
10% Ground Clay+Rockdust, Optional: River silt.
+Cooking & water waste.


To make it easier to remember my recipe I decided to simplify the proportions by starting with any amount of plant/animal matter, then adding half as much in charcoal, and keep halving with wood ash, then clay+rockdust and finally pyrolized calcium. I remember it as adding from dark to light coloured material.
I’m calling it Half Terra Preta because I was also thinking about the other half in the fields, and how they may have amended those extensive raised beds shown from air in the documentary.

I’m thinking something like large in-situ hugelkultur biochar soil mounds. Where they would slash land, let the greens rot down into the topsoil or possibly let animals on to forage and fertilize it in, then collect the larger brown materials in long and wide  hugelkultur-like mounds.
Hold a feast along it, cook up animals, burn the material and bones, maybe cook in big clay vessels and have some firewalking too. 🙂
Then cover using subsoil creating those irrigation trenches on either side, while also saving the topsoil for later.
With the coals still hot it will bake the subsoil placed on top of the charcoal and keep the fire in check. Kinda like this:

The heat would likely kill those soil microbes however. Heat also changes the soil structure in a way that reduces clay dispersion from rain, important in the tropics! See:

So I thought it would then be a good idea to wait for the coals to stop burning and cooking the soil, at this point you could crush and mix the two before mounding the living topsoil back on, or just mix the lot.
You’d end up with a charcoal+bone base, baked subsoil middle, then fertilized topsoil, all ready to mix before planting out.
I call this half the Half-baked Terra Preta, and it could be the source of the village charcoal used for cooking too.