Tuesday, October 13, 2020

Compost Tea - With and Without Aerator

We're brewing compost tea, partly to go with our biochar.  We wanted to find out whether it's effective to aerate the tea by simply stirring it every day, so we started two batches of tea in 5 gallon buckets - one with a pump aerator and one without.

Why does aeration matter?  In theory, the beneficial microbes we want to cultivate in our tea are aerobic (oxygen-loving), whereas anaerobic (not oxygen-loving) microbes that would grow in the absence of oxygen tend to be parasitic or pathogenic to plants (and people).  Our pump aerator consists of an aquarium air pump connected to a loop of 1/4" soaker tubing, which you can see in operation in the image below.


The ingredients we used are:

- 4 gal dechlorinated water

- 6.5 oz compost

- 1 Tbsp kelp juice

- 1 Tbsp molasses

Normally we wouldn't have to measure this precisely, but in this case we wanted to make sure the only difference between the two batches was the presence or absence of the pump aerator.

Then we let the tea sit for three days, stirring one bucket every day and leaving the air pump on constantly in the other.  After three days, we got out the microscope and captured the videos below.

Aerated by stirring:

Aerated by pump:


The differences between the two buckets, in terms of quantity of individuals and species, were so dramatic I felt compelled to check three different slides from each bucket to confirm.
The pump-aerated batch was filled with cocci.  I don't know enough to identify the species, but it stands to reason they are aerobic and beneficial.
The stirred batch was filled with protozoa.  I also observed two shapes of bacteria: cocci and bacilli.  Again, I don't know enough to identify the species, but they're most likely anaerobic.
From now on, we'll be brewing all our compost tea with a pump aerator.

Saturday, October 3, 2020

Our First Batch of Biochar

There's much to catch up on: how our practices, theory, and philosophy continue to deepen; lessons we've learned from our second food forest area; what our chickens have taught us; new ways we've learned to prepare and eat onsite crops; and processes we've designed to fill a vacancy opening up later this year.  But for this little blog entry, I'd like to focus on our first batch of biochar.

Biochar is an organic, charcoal-like soil amendment that has a surprising capacity to hold water, soil microbes, and nutrients and prevent those nutrients from leaching from the soil.  We made a small batch (it'll probably crush down to 2-3 gallons) in a cone-shaped pit.  This approach required little time and effort, but it did require constant attention and careful timing to expel and burn the volatile compounds from the wood and pyrolize the cellulose without burning the resulting carbon.  We started burning a small amount of wood at the bottom of the cone, and continually added fresh wood at the right rate to keep the surface burning, while denying oxygen to the charred layers below, just in time to prevent the carbon from burning.

Once we had enough char for our first trial, we filled the pit twice with water (making huge billows of steam), which cooled our biochar and prevented it from slowly smoldering into a pile of white ash.

What Went Well

Extent of burning and pyrolysis - We did have a little white ash at the bottom of the pit (overburned), and a few of the larger sticks at the top were still brown in the center (underburned), but the rest of the batch was solid black as obsidian and brittle throughout - perfect.

Arrangement of sticks in parallel - Usually when you're building a wood fire, you want to criss-cross the wood for ventilation.  But because we wanted to minimize ventilation, we laid the sticks in parallel.  I don't have a control group to compare against, but I suspect that helped to halt combustion at lower levels.

Synchronic layering - The instructions we found suggested using discrete layers, in sort of an iterative but diachronic pattern of add, pause, add, pause ...  But instead, we continuously added wood at a deliberate rate, keeping an eye on the size of the flames and watching for white ash.  Again, I don't have a control, but I suspect this approach accelerated the process and gave us more even results.

What to Do Different Next Time

Cut more sticks ahead of time - While the fire burned, I spent much of my time quickly cutting sticks to length.  Next time, I'll cut sticks to length ahead of time so I can pay more attention to the fire.

Next Steps

We'll crush our biochar to smaller bits, adjust the pH of the ash we unintentionally produced (using some vinegar we accidentally made while brewing kombucha), and use various methods to load it up with microbes and nutrients.  One method we'll use is to scatter biochar in our chicken coop, where it will not only reduce odor, but also absorb ammonia and nitrifying bacteria.  Another method we may try is to mix it with compost and flour from mesquite pods that are no longer suitable for human food.

Thursday, January 16, 2020

Two Paths into the (Food) Forest - Part 3 - Philosophy and Strategies

In part 1 and part 2 I gave two different conceptions of the term "food forest" that I have held and described how the difference in definition resulted in different approaches to starting the food forest.  Now I'll describe some experimental strategies we used in our second section of food forest and list our plant palette of support species.

But before I do that, here are a few brief philosophical observations about the these two approaches.

I would say our second approach focuses more attention under the surface of the soil.  I don't mean this as a categorical distinction, but more as a matter of relative degree.  The first approach also relies on and intentionally cultivates subsurface life, but it puts a greater emphasis on supersurface production from the very beginning, where the second focuses more below the soil first and defers (again, relatively) focus on production.

The second approach shifts more of the work (e.g. importing mulch, applying fertilizer) and more of the "determination" (e.g. what to plant where and when) from the humans to the plants.

The first approach involves more development by building, and the second, more development by growing.  Again, this is a matter of relative degree.  In the first approach, parts (trees) are developed (partially anyway) offsite and then assembled onsite; fertilizer (at least the first application) is generated offsite and then imported and applied; and the the placement of all plants is effected by a human agent.  In the second, all parts at all scales are developed simultaneously in situ, and the placement (after thinning) will be influenced - even if not strictly determined - by how seeds land and which locations offer ideal growing conditions.

I often make the point that development by growing results in a product that emulates a living (biological) system, but more than that, I think it's a requisite to mastery.  Not that I'm a master at cultivating a food forest or even at gardening, but I can master being while I commit myself to the act of cultivating a food forest, thanks to development by growing, and thereby approach mastery of the act.

I said "brief" so let's get on with strategies.

Bermuda grass grows very quickly throughout most of the year in our climate.  For better or worse, we take intentional strategies to grow in spite of it.  Here are some strategies we have used at Sage Gardens, ordered from most passive to most active:
 - Deny it water (and cut it when it grows long)
 - Shade it out with plants
 - Smother it with mulch
 - Dig it out

By the way, two other strategies to deal with grass that I like but haven't practiced at Sage Garden are grazing and solarizing.

In the area surrounding the second section of food forest, we'll simply deny Bermuda grass water, and inside the food forest, we should have a canopy to shade it out pretty quickly.  The anticipated problem is along the edge, where grass can send leaves to get sunlight from the outside and send roots to get water from the inside.  Without some strategy for the edge, Bermuda grass might rob the trees of water and nutrients.  We used two "edge strategies" to avoid this.

Edge strategy 1: smother
Along a 17 ft portion of the edge is where a future arroyo is planned.  In order to get the food forest seeded right away (to take advantage of forecasted rain), we postponed digging the arroyo and "reserved" the space using contractor paper - a trick I took from James Prigione's food forest videos on YouTube.  We covered the paper with straw mulch to weigh it down and make it look nice.

Edge strategy 2: shade

Along the rest of the edge, we heaped sweet potato vines.  This time of year we have an overabundance of sweet potato vines going dormant.  If some of these survive the winter (when the Bermuda grass is also dormant), they should sprint into action in the spring, shading any grass within several feet, and providing edible leaves and tubers.

Strategy: drip tube and valves
We tied into an existing irrigation line we were already using for more frequent watering, and ran two lines of drip tube, each 15 ft long, over the new forest area.  The drip tube has 0.6 gph emitters spaced at 1 ft, so in the two hour duration that we run this irrigation zone, this 70 sq ft area will get about 36 gallons.  Each of the two drip tube lines has its own shutoff valve (a simple 1/2" inline manual valve) to give us options if we want to cut the water volume in half later, or plant a "row" of veggies along one or both of the tubes.

Strategy: early canopy
I mentioned in part 2 that we're planting very densely with some fast-growing plants in order to form a low but tight protective canopy within 3-4 months.  This strategy is taken from Geoff Lawton's video "Establishing a Food Forest."

Strategy: plant by seed
Eight of the nine species of plants we planted in the new section of food forest were planted by seed.  Four of those species are from seeds we collected onsite (for free).  This strategy allows us to plant potentially (dependent on germination rates) 500 plants for a cost of about $25.  This makes it economically feasible 1) to employ our "early canopy" strategy, and 2) to overplant in compensation for my inexperience.  As I gain more knowledge and experience, I'll be able to get the same results with fewer seeds, but for now, I'm starting as I am.  We had a mix of large seeds of small quantities and small seeds of large quantities, so we first planted the large seeds under the surface, and then scattered the small seeds, to be covered later with straw mulch.  We used this order to avoid accidentally picking up small seeds on our shoes while we planted large seeds.

Strategy: let the plants do the work
We're relying heavily on our pioneer plants to 1) convert atmospheric nitrogen and other gases into bioavailable subsurface fertilizer, 2) convert water and atmospheric carbon dioxide into woody mulch, 3) regulate soil temperature and moisture by physically covering it, and 4) aerate the soil.  This strategy is inspired by the permaculture principle that "everything gardens."

Strategy: no dig, no amendments
We didn't till or amend our soil in any way.  We selected pioneer plants that can grow quickly in poor soil.  Honestly, the labor and cost to till and add amendments isn't prohibitive on this small scale, but we want to learn a way that can be upscaled.  This strategy is inspired by Masanobu Fukuoka's concept of do-nothing farming.

Strategy: legume seed + inoculant
Seven of the nine species are legumes planted by seed (and an eighth, moringa, although it isn't technically a legume also forms a symbiotic association with nitrogen-fixing bacteria).  We coated these seeds before planting with inoculants containing high concentrations of the rhizobium bacteria that will later cooperate with their roots to fix atmospheric nitrogen in the soil.  These bacteria are naturally occurring in the soil, but by inoculating the seeds, we hope to jump-start the nitrogen fixing process.

Strategy: fungus selection
I don't know yet whether this will work, but we intentionally started mushrooms of a species that 1) can thrive and hold its own in a Phoenix urban forest microclimate (without being picky about what it eats), 2) isn't parasitic, and 3) has delicious fruiting bodies.  For us, that translated into oyster mushrooms.  Since this species is saprophytic, it will start its life eating our straw mulch and later eat pruned branches.  And whatever it eats it will turn into food, either for humans or for subsurface organisms that will feed the trees.

Strategy: plant selection
Here are the criteria we used to select plants:
 - Must grow in poor soil
 - Must have mix of forms: some trees, some bushes, some ground covers
 - Prefer nitrogen-fixing plants
 - Prefer fast growers
 - Prefer native plants, followed by desert adapted
 - Prefer seeds we can collect from existing plants onsite
 - Prefer trees that can be pollarded or coppiced

All of which led us to the following plant selection for this section of food forest:
Plant Form Native Species Adapted Species Other Species
Tree 10 sweet acacias
Acacia farnesiana
35 leucaenas
Leucaena leucocephala
15 moringas
Moringa oleifera
Bush 35 pink fairy dusters
Calliandra eriophylla
35 baja fairy dusters
Calliandra californica
Ground 200 lupines
Lupinus arizonicus
25 trailing acacias
Acacia redolens
200 common vetch
Vicia sativa
8 sweet potatoes
Ipomoea batatas