Awesome reply. I agree, remote sensing via satellite or even drone maybe. Can you explain how the field sensors for detecting soil NPK worked? What were they actually measuring?

I want to chime in as an agronomist with industry and academic experience in precision Ag. I currently work on irrigated vegetable farms in the southeast, but with familiarity of dry cropped grain production in the mid-west.

Most of our calories and fibers (corn, wheat, soybeans, cotton), especially those fed to livestock, are grown in dry cropped areas of the southeast and mid-west United States. That means that the majority of acreage is not irrigated and uses rainfall. The impact of soil moisture meters (tensiometers, etc.) for decision making in industrial scale production will be limited to irrigated operations.

As for nutrient analysis, the cost of fertilizing isn't in testing the soil. Most state labs do this for free. It is the cost of the fertilizer itself. The idea of testing in the field is novel and potentially time saving, but I imagine they mean some sort of electrical conductivity or total dissolved solids meter as a proxy for total nutrients. As far I know there is no economically viable way to analyze particular soil nutrients via a remotely operated field sensor. Shit would be pretty expensive, as is stated in the article itself:

"It may actually be cheaper to have people do the extra work than have sensors and sensor-based irrigation and fertilization."

You are still going to need somebody to mix fertilizers into solution for fertigation as with some vegetable operations. If it is dry cropped, someone is still going to drive the tractor to spread/spray the fertilizer.

I DO see drones and remote sensing helping tremendously with pest scouting and precision pesticide applications which would save money and time, and help to avoid resistance issues. Also, remote sensing for plant health can help optimize timing and amount of nitrogen applications in season, ESPECIALLY in big dry cropped acreages of crops such as wheat, even if the actual nutrient application is made by tractor.

edited: to clarify between remote sensing of nutrients in the soil vs in plant tissue