What precision agriculture hides

Precision agriculture will often improve production efficiency and deliver profit. However, there is a crucial hidden assumption that underpins the benefits.

Huge mechanical arms spread out across a field. A young man in a check shirt and felt hat peers at a computer screen perched on the bonnet of his truck. His finger hovers over a colourful image of his paddock and then touches the screen.

One of the monster arms lurches into life. It inches forward and releases an intermittent spray of water and fertilizer mixed in exactly the right proportions. The droplets fall onto green and perky shoots of winter wheat below.

The map is generated from data on last years crop yield and this year’s weather. These numbers guide the release from the booms as they complete their circuit. Just the right amount of water and nutrient ensures the plants grow at a rate to deliver the optimum yield in the best time. Later in the year a harvester guided to the inch by satellites will follow tracks so closely that only the soil under the wheels will be compacted.

This is precision agriculture — the application of technology to the challenge of growing crops. And it works. Each plant receives what it needs just when it needs it. Crops are tended as much as grown.

Yields are high and consistent across both the field and the property so that after each harvest many tonnes of grain exit the farm gate.

The farmer marshals the guts and reckless abandon of youth to cope with the risk in this hi-tech operation. The maverick spirit comes from his great grandfather who carved the property out of the bush a century ago. Today the bank has funded the infrastructure happily letting the youngster wear the financial exposure. The loan is secured against the value of the land.

This is usually billed as a story of progress. Capital is mobilized to create and deliver goods to market. An entrepreneur is rewarded for his courage and a long supply of inputs and support services feed off the economic flows. This is what most of us understand by success.

What could possibly go wrong?

Well, there is a crucial hidden assumption in this production model. The farmer, the bankers, and the tech designers all believe that the precision agriculture system is in a steady state. So long as inputs match outputs production is stable. Precision simply evens out and optimizes the zero sum game.

All the players expect that the soil will behave as a medium in which the plants grow. It will sit there and accept crop after crop that will be sustained by the nutrients raining down from the slow moving booms.

Chances are that the white-collar players did not even think about soil. The farmer gave them details of his pre-boom crop yields and that was enough.

The reality is that the soil is a player too.

Soil holds the nutrients and exchanges them with the plant roots. Its physical structure, carbon content, and biological composition combine to determine how well nutrients reach the plant. And none of these properties are fixed. The efficiency of this critical transfer depends on properties that can change over time.

All soils show a measurable and ongoing change when vegetation is cleared for agriculture. Initially changes can be acute which is why soils under tropical forest only produce crops for a handful of seasons once the trees are felled. Other soils can deliver crop yield for generations and appear to retain the properties that matter. But most soils show a steady decline in how well they hold and exchange nutrients and moisture.

What precision agriculture does is mask these changes. It tends to treat soil as a medium, a bucket to hold the nutrients and the plant, because the inputs are what matter. Even if soil loses some of its innate productivity this can easily be compensated by more inputs from the booms.

It is easy to admire engineering solutions. They are often extraordinary. They have taken mankind to places and wealth our ancestors could never imagine. Precision agriculture looks like another in this line of life changing technologies and it will have a place.

What the farmer and his backers need to know is that a zero sum game carries more risk than just having enough cash flow to make loan repayments. If the process degrades the soil, even a little, then future yield cannot be guaranteed by nutrient inputs.

And when the FAO admits that 40% of soils under agriculture are degraded there is a good chance that those under the booms are too.

Farming has always been much more than throwing a few chemicals onto the dirt. The soil is alive, quite literally, and must stay healthy to perform the functions demanded of it. And healthy soil requires more than the nutrients fed into it.

Precision in nutrient delivery makes this easy to forget.



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