This article forms part of a series concerning the development of methods of compost tea application via the keyline plow which are being published on taranakifarm.com

Part 1 : Introduction
Part 2 : Designing the Keyline plow frame extension.
Part 3 : 1:1 Scale Wooden Model
Part 4 : Re-Inventing the Herbicide Tank
Part 5 : Farm Like a Gardener
Part 6 : The Final Prototype

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.

Next, I’ll be rigging the shank application boots and ground spray unit. Stay tuned…

Part 5 : Farm Like a Gardener