PERMACULTURE | Designing 30,000L of SWALE! – The Tree Willy


Dealing with Drought

A few comments on Red’s video:
Here in Australia if it’s hot and I haven’t had rainfall such that the upper soil (10cm) moisture drops below 4% then I tend to begin deep watering or fertigating by adding nutrients to water to make the most of that water when I do water, especially if I’m hand watering.
Over summer it took 10-12 days on average for the soil moisture to drop below 4% after a rainfall event where I live, and after February it stayed there until the end of March. The garden was parched.
I use our governments Australian Landscape Water Balance site to help determine that 4% for my soil type, but I could otherwise use an accurate soil moisture meter or learn to read my soil by hand.
Below 4% is important because soil microbiology begins to go dormant and die, and because microbial mucilage glues soil aggregates together, those aggregates then begin to break down. This lack of soil moisture also exposes the soil to oxidation from organic acids, and when rewet makes soluble nutrients available to microbes and plants.
On the left is an example of an organic acid test I did on my prismatic clay subsoil with lemon juice, on the right, water. If you look closely you can see how many days it took for the water to evaporate by counting the brown iron oxide rings.
Organic soils contain many organic acids such as humic and fulvic acids that perform a similar function.
clay rock vs eggshell+lemon.png
Organic acids in the topsoil and oxidation is why plants grow like crazy  after a bit of a dry spell and then rain.
Microbes feed on these soluble nutrients and create CO2 respiration bursts at ground level that plant leaves can then transpire and help accelerate plant growth.
However these CO2 burst nutrient “priming effects” don’t happen if soil moisture is kept just above the 4% soil moisture (see (b) above). So short, regular watering will prevent these bursts, and maintaining a soil moisture below that needed for basal respiration levels will also mean soil microbial activity and respiration is below that required for adequate nutrient cycling. Meaning you either water and water regularly to maintain basal respiration, or you let the soil dry and deep water when it reaches that 4% to get a burst.
Here in Australia to restore nutrient cycling in pasture researchers are artificially performing a similar function by drying & photo-oxidizing strips of soils by bringing them to the soil surface with tools like the SoilKee renovator, this has a similar effect.
In India they take subsoil and dry it.
Clay particles that are oxidized also exchange aluminium (toxic to most plants) for ferrous iron in soils, which is needed for plants to produce phytochromes such as in blueberry plants and many fruit trees. When you change the soil pH to grow blueberries with epsom salts (magnesium sulphate) or iron sulfate, this ferrous iron (Fe2+) is what you’re making more available by lowering the pH. And these phytochrome pigments control growth and flowering in some plants.
On the topic of fertigating, last year scientists from Japan also found a drought pathway in plants for acetic acid (vinegar) that I’ve keep meaning to trial, but the paper is paywalled and I didn’t know the concentrations until now when I found this figure.
I’ve just looked up common $1.20 supermarket 2L white vinegar here in Australia. It’s about 4-4.2% glacial acetic acid and I calculate that diluting it 1 part to 140-145 parts water may give near 20 mM (milliMole). So a 2L bottle should be enough for 280L of water depending on your water quality if you wanted to try it.
It would be interesting to trial adding the vinegar before or after wilting point. Either way, if rain isn’t forecast, a watering with vinegar may help plants survive until there is another rain event, and it may be best applied when soil moisture hits 4% to also get a CO2 burst from the water.

Unpowered Measured Irrigation Controller

Looks like Bernie’s adapted the magnetic valve as used in the Aqualone irrigator that never seems to ever have stock.
The Tropf Blumat is another unpowered alternative that senses soil moisture rather evapotranspiration.
If you know of any other unpowered automated irrigation systems, leave them in the comments!

Adaptive Keyline Swales and Erosion Control with Vetiver grass and Pinto Peanut, Ecuador


If you look closely you can see a saddle dam at the top of the ridge where the grass is very green. A stark illustration of how storing and sinking water can change a landscape. If you look VERY closely you can see where the excess water from the saddle dam is travelling down into the valley towards the pond where the grass is greener and vetiver grasses have been planted.

To the left of the saddle dam in the valley you can see a line of trees leading to a pond. Where those trees begin at the top of picture is an ideal water collection point for another dam, and is known as a keypoint between ridges. Using swales, ditches or deep ripping from that point can distribute excess water to other areas of the hillside, thereby slowing the travel of the water down the hillside.
Swales or ditches don’t always have to be on contour. Often you want to distribute excess water where land naturally funnels it to other places. So the higher in the hillside you can slow, store and distribute water from, the better.
Let gravity distribute it for you.

Red Tide – Phytoplanktom Blooms, and One-Rock Filter Dams

Phytoplankton are Earth’s life raft!

Near the end of this Walde Sailing video they show a red substance in water.
This is commonly known as red tide. Red tide is likely an iron-rich phytoplankton bloom. When nitrogen and iron are added in combination from sediment run-off or pollution to waters then chlorophyll a concentrations can increase 40-fold leading to diatom proliferation, and reduced community diversity.
Nutient addition like this can also lead to coral bleaching and die off.
After blooming these organisms die and sink in the water column where microbes consume them and deplete the oxygen resulting in dead zones with little sea life. A dead zone the size of Scotland in the Gulf of Oman was recently discovered by robots exploring the Arabian sea, previously unknown because the area wasn’t safe for humans to do the sampling.
Still waters and a lack of mixing with air exacerbates these dead zones especially at lower depths.

Scientists also recently concluded that the last massive extinction event in earths history was the result of anoxia.

Oxygen is the byproduct of phytoplankton and they are responsible for the bulk of atmospheric oxygen when the cycle is regulated. We don’t want them dieing off in these explosive life raft blooms!

We can minimise anoxia in our oceans while still benefitting from phytoplankon oxygen production by reducing nutrient run-off in sediment from land with techniques like simple one-rock high filter dams seeded with plants to grow in the sediment and act as biofilters. This applies not only to our oceans but also inland waters, where even our water supply is at risk from sedimentation and a reduction in water volume in fresh water reserviors we get out drinking and irrigation waters from.

Here’s a Great Barrier Reef rock gulley success story.
Here are one-rock high filter dam pictures

one-rock gulleyone-rock