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Switching The Ratios

The key to Elaine Ingham’s approach to enhancing soil fertility lies in adjusting the ratio of fungi to bacteria.

For grasses, vegetables and brassicas, the optimal fungi to bacteria (F:B) ratio is 0.75:1, compared to 1:1 for row crops, and anywhere from 5:1 to 1,000:1 for old-growth forests, he said. Weeds, as hardier pioneer species, typically thrive under a low fungi:bacteria ratio of 0.1:1.

“That’s why when you clear cut old-growth forest and rip up the fungi and microbial life that’s in the soil, your best production is in the first five years. That’s because the fungi-to-bacteria ratio, even though it is declining, is more in line with what you’re trying to grow,” he said.

To get more fungi in the soil, the first step is making the kind of compost in which fungi can establish and thrive. This is done by mixing 25 per cent high-nitrogen materials, such as raw manures, 30 per cent green plants, and 45 per cent woody materials in a pile, keeping it moist, monitoring the temperature with a probe, and turning it often to let air in and prevent it from exceeding 70C.

FERTILE BLEND

Then, a portion of the compost containing a “starter” dose of the desired microbes is put into a mesh bag in a vat of water along with “fungi food” such as hydrolyzed fish oil, soluble kelp and brewed into “tea.”

Since the goal is to multiply beneficial organisms under aerobic conditions, some type of aeration device is needed to bubble sufficient air into the mix, much like in a fish tank. The vat must be thoroughly cleaned after each batch, otherwise unwanted anaerobic bugs may spoil successive batches.

To boost bacteria, a bacteria-friendly compost is used, and fish emulsion and sugars added to the vat. But close attention to the process is critical, because bad compost makes bad tea, and may do more harm than good, he warned.

Where soil biology is weak, up to six treatments of 20 gallons of compost tea per acre per year are applied with a sprayer. Once health has been returned to the field or pasture, the number of applications can be cut back to three.

Although Vulcan, Albertabased Soil Foodweb Lab offers a range of soil-and compost-testing services, George said that for most farmers, gaining a good enough understanding of soil ecology to maintain their own soil fertility is easily within reach.

WITHIN REACH

Some special tools, such as a binocular microscope, however, come in handy for identifying soil bugs and estimating their populations under the system.

A Brix meter, or sucrose refractometer, which costs about $100 at local supply outlets, is also useful for measuring the effects of compost tea applications on crop and forage health, he added. To use the device, a drop of plant juice is squeezed out and dropped onto a mirror and held up to the light.

Low Brix, or sugar levels, indicate sick plants. A reading of seven means the plant is susceptible to disease, mould, fungus and insects, while 11 to 13 indicates a healthy vigorous plant that can outcompete weeds.

Over 14, and its high sugar content makes it unpalatable to insect pests, he added. [email protected]

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