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Keyline Plowing with Compost Tea Application

Read the first installments here.

Part IV: Re-Inventing the Herbicide Tank – Giving Destructive Equipment New Purpose

Compost tea brewing requires the use of specialist equipment. Especially when you intend to apply tea to hectares of paddocks. In my case, I’ll be making tea using a 1000L brewer supplied by Trust Nature Pty Ltd. The brewer tank is a little large to mount on the keyline plow, so an ‘application’ tank is required. This is a smaller tank, fitted with a pump and plumbing necessary for application during keyline plowing.

I’ve opted to retrofit an old herbicide spraying unit, giving it a new life in the plant friendly business. As this tank has been previously used with poison, it is necessary to sterilise it. Otherwise our precious microbes will not survive their journey into the soil. To accomplish this, we dilute a 50% hydrogen peroxide (H2O2) mix – 5% solution to water. That is, 5 lts of H2O2 solution (50% mix) with 100 lts water. Running through the pump and tank, and then flush with clean water. The unit is now ready for retrofitting.

A few specifications to begin. The tank is a 200L herbicide stray unit, fitted with a small ‘Shurflo’ 12 volt diaphragm pump that is capable of discharging (with open flow) 5.3 lts of tea per minute under 60psi. The existing tubing I have chosen to completely replace, plumbing an entirely new set of lines optimised for the plow. While I’m still in the construction stage, it’s currently impossible to tell whether this pump will have the necessary capacity. Only testing will determine this. It’s a standard kind, and upgrading the pump doesn’t present any issues.

Since the original unit was fitted with only a single hose with trigger gun applicator, I’ve had to reconsider the tubing completely. With seperate tube lines running to each shank and a ground spray line, it is necessary to fit each line with its own flow control tap. This will be necessary to adjust the pressure between secondary lines off the main flow line. Otherwise some tube lines would receive greater flow than others.

For this flow control system, I’ve settled on inexpensive garden variety irrigation valves (available from any hardware store), plumbed on 12mm plastic tubing. One for each keyline plow shank, and another for an above ground foliar spray line. I’ve also plumbed a tank return line for master flow control (should I have too much pressure).

The next stage will involve running a sequence of tests to ‘calibrate’ the flow valves. Once set, they will distribute the correct dose of compost tea for each shank into the soil and over foliage. Setting these taps involves running the unit while timing the output and volume for each tube line. When they all output the same volume in the same time period, the system is calibrated.


Part V: Farm Like a Gardener

A wise piece of advice; “garden like a farmer and farm like a gardener”. That’s great, but how does one do this on a practical level?

If you are an organic gardener who tends to a modest 10 x 10 meter vegetable garden and you hear that a little soil inoculum in the form of ‘compost tea’ would do your patch wonders, I’m sure your response would be something along the lines of “what a good idea!, I might just do that…”

But what if you are a farmer with 100 acres of pasture, and you hear the same suggestion?


One answer to this common silence is now clear. While this method certainly isn’t the only means of ‘farming like a gardener’, it is an invaluable tool in the box. As Paul Taylor says “… [keyline + compost tea] is cutting edge technology that has the potential of being [one of] the most advanced systems to date”.

This is exciting farming and land stewardship. On a personal note, I hope you’re enjoying this series of articles. For this entry, I’ll simply finish with a sequence of photos from my work today…

Healthy Soil : Accept No Substitutes.

Bubbling Away

You might notice the addition of the Yeomans ‘seed boots’ which has been employed to deliver the precious soil inoculant. These are steel tubes mounted on each shank tool groove, as seen clearly in the photo below.


Part VI: The Final Prototype – Direct Injection

The keyline plow / compost tea injection system is now undergoing trials. The plow rig can be seen in the photo below. While I’m already planning several enhancements to this system, I’m very pleased with the current outcome.

Injecting Compost Tea Directly into the Rhizosphere

Establishing Injection Depth

An important consideration of keyline plowing is present root depth. This can be assessed by simply digging a hole with a shovel. Once we establish the depth of the pasture root systems, we can ‘dial in’ the shank digging depth to penetrate the soil just beneath the current root depth. This progressive deepening of the soil profile over successive treatments is what keyline plowing is all about. Re-activating and converting the subsoil material into fertile topsoil in step with plant growth.

When including compost tea injection in this method, we’re also able ‘dial in’ the shank boot delivery tube to inject compost tea directly into the rhizosphere (even has the shank’s actual digging tip cuts below this zone). The rhizosphere is a ‘narrow region of soil that is directly influenced by root secretions and associated soil microorganisms’ 1.

Re-populating the Soil

In this way, our efforts to re-populate the soil with beneficial organisms are given the best chance at success, since this region of the soil profile is the most active biologically and in terms of nutrient exchange, the most vibrant. Conditions critical for healthy plant growth and the propagation of soil life.

Additionally, by carefully accessing soil conditions and choosing the right time for treatments, our introduced biota are given a superb start in their new enviroment. They quickly establish themselves and set about stablising the ecology of the soil – something that is essential for the soil to function correctly if our expectation is vigorous plant growth.

The Keyline Plow : As Seen In Action

Thanks for your interest in keyline & compost tea. To view more photos and watch a video of the plow system, please visit the following address :


  1. I’m just wondering. Will the keyline plowing will be any good for very sandy soil (literaly no clay or silt). I’m wondering will it be appropriate for Poland (USDA zone 6; 20 inches of annual rainfall).

    Great post

  2. Keyline Planning and Plowing of all land will benefit all soil types and the compost tea is the Jewel in the Crown for Permaculture everywhere. Just do it.

  3. What a fantastic setup! I’d love to see a follow up to this post showing the land 3 months after the yeoman/compost treatment.

    Just finished reading “Teaming with Microbes” – a book that describes in detail what goes on in the soil food web and why/how aerated compost tea is such an important tool in our Permaculture toolbox. Link for the book:

    I also recommend an extended visit to the “Taranaki Farm” site to anyone, a valued source of practical information for me. (

    Thanks for this post.


  4. Putting compost tea in the soil while keyline plowing is a truly great idea. Hoping the results are much better than expected. ……….One might also use a simple high pressure water sprayer (tractor mounted and run through the keyline plow tines under pressure) if one wanted to enlarge the subsoil air chasm laterally . ( assuming that the disturbace to the subsoil would not be damaging in some way …)

    Best of Luck
    Rob Davidson

  5. Just purchasing a 3 tine plough, looking to kit it out for small farms around Perth and further south as a useful service to trade for the Permie association. I was also considering the keyline in deep sand issue, to me it would be ideal if I can mix a compost tea, bentonite slurry and inject that as we go along. Would be a good way of holding moisture and nutrients in otherwise very sandy dry soil. Anyone had any experiences or have any suggestions, obviously bentonite clay slurry would be a lot more prone to blocking than compost tea so a more rough/block proof kit would be required

  6. This is a fantastic idea, i love it. However, I’m thinking that maybe you could put a bigger tank on a trailer and tow that behind the plow. So it would be tractor- plow- trailer with big tank on it. you could put the manifold and the pump all on the trailer. What you think?

  7. I’ve heard that forcing the tea through small orifices will kill many of the microorganisms. Also that an impeller pump is kinder to the microorganisms than a diaphragm pump.

  8. Thanks a MIL for sharing this Ben – it’s exactly what I’m wanting to upscale my current ripper / tanker too – love the combo of the boom sprayer together with tine drizzler’s!

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