Fiber optic cables reveal a serious problem at the heart of modern farming

Thousands of years ago, beasts of burden helped make humanity what it is today. When farmers first started putting down roots, they’d plant and tend their crops by hand. With the power of oxen, they could drag plows across their fields before sowing, which boosted soil fertility and eliminated weeds. Today, that job has been made even easier by giant machines that rake the landscape.

Millennia of tilling, though, has come at a cost. While plowing releases nutrients in the short term...