Imagine a veggie patch at the beginning of spring. The soil is turned, watered, and ready for planting. This dark, lumpy bed is a bank account. For the purpose of this experiment the dollars and cents will be organic matter and nutrients.

In this soil account you can deposit compost and fertiliser. And lucky you! Before you begin gardening you receive interest payments from the compost you deposited last season and the old plants left in the ground. These organics have been feeding the soil ecosystem, the branch of the bank in control of calculating and providing interest payments. The soil ecosystem—a thriving underground city with billions of inhabitants—is what makes nutrients available for plants to absorb and helps protect plants from disease. The more you deposit and the higher the balance, the higher the interest payments (up to a point).

It is important to refrain from over depositing. The mentality that some is good therefore more is better does not work here, as soil accounts are a bit leaky – sandy accounts more so than clay. Depositing too much at once often means losses via leaching out the bottom or run-off from the surface.

A wonderful feature of soil accounts is that they rarely start off empty. However, all soil accounts are not created equal and each has a different starting balance.

Deep, fertile soils on arable land are fat bank accounts while shallow, rocky soils have a lean balance. A well cared for soil stays in the black while overworked soils have an overdraft and are regularly in the red.  The rich, black, cracking clays of the Darling Downs in southern Queensland are the soil equivalent of a railroad tycoon’s Swiss bank account. These soils are so wealthy it is not inconceivable that markets would open up to trade this precious commodity.

But back to the veggie garden. Your account has a modest balance. You deposit compost and fertiliser, plant seeds, you water and let the magic begin. The deposits create a frenzy of activity, generating interest payments in the form of available nutrients for the veggies. The veggies grow making automatic withdrawals as they absorb nutrients. This is great for your veggies but not so great for your account. Your bank balance declines as the plants suck up nutrients like a six-year-old drinking a chocolate milkshake. Going into the red will incur bank fees and, if not rectified, the soil bank will repossess your veggies.  So you deposit some more fertiliser or compost, making sure there’s enough nutrient dollars to feed both your plants and the soil microbes.

The veggies grow and ripen, a colourful, tasty testament to your accounting skills. You harvest and cook up a stir fry, leaving the soil account slightly in the black. Should you choose to plant winter veggies you need to deposit again because the soil bank is unlikely to loan you cash for another season.

You eat the delicious dinner, your body absorbs some of the deposits, and the rest is flushed down the toilet a day or so later.

At this point let’s stop to consider what’s been flushed away. Those nutrients ($) we added to the soil, the plants absorbed and then ate, are on loan. Nutrients should cycle through various life forms, from soil to plant to animal and back to the soil again.

However, today’s nutrient system is rather linear. Elements are extracted from the ground, used to grow crops, then wasted at various stages throughout production and transport. We absorb some in the form of food, then flush the rest out the sea. Water bodies are like a foreign nation—they don’t want our currency.

The soil is a dynamic being. As stewards of the soil we can act like the taxman or the State—taking excess nutrients and redistributing them to the needy. We can be the Robin Hood of soil.

Just because a soil has a small account balance now doesn’t mean it has to stay that way. We can be a bank, printing our own money – then unlike the banks, give it to the needy. Through recycling and reusing nutrient ‘wastes’ such as animal manures, food wastes, green waste and biosolids, we can deposit healthy amounts into our soils.

How do you think the global soil account is looking?

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Authors note: I understand this simple thought experiment is just that – simple. There are many aspects not addressed such as contamination, toxins, translocation, land use change etc.