Machines that recognize weeds and target them — and only them — with herbicide, keeping the nearby crops safe from harm. Tractors that plow fields in perfectly straight lines with far more precision than a human could ever manage.

And coming next year, tractors that drive themselves, leaving the farmer free to do other work.

“Ag technology in the last five years has not doubled, it’s tripled,” said Kyle Allen, co-owner of Gateway Precision Ag. Located just south of Hawk Point, Missouri, in Lincoln County, the company repairs and refurbishes farm equipment, often retrofitting older machines with the newest technologies.

“If you told me five years ago that we would be spraying from drones, I’d say you were crazy,” he said.

Shannon and Jessica Claborn, who also live in Hawk Point, own the drone-spraying company Prairie View Ag Drone with Melanie Miller.

Miller is also the pilot of their 6-foot drone, which they use to spray herbicide and fungicide on area farms.

The drone can do everything a crop duster or helicopter can do, Shannon Claborn said. While planes and helicopters can cover a much larger area much faster, the drone is better for smaller fields, he said.

In addition, crop dusters and helicopters drop their chemicals with less precision. They have to fly higher than drones, too, which means the chemicals can drift into neighboring farms or yards, and they can’t fly as close to a stand of trees. When they encounter power lines, they have to fly over them, which leads to an uneven disbursement of the chemicals.

On the other hand, drones have a much smaller reservoir; the drone Miller flies has a five-gallon tank, she said. That’s good for covering a little more than two acres before she has to fly it back to refill the tank and change the battery.

Then, the drone automatically flies back to the exact spot where it had left off and begins spraying again from there.

That ability to know precisely where a machine has been and where it needs to go comes from the technology that has been the most revolutionary in agriculture. GPS — Global Positioning System — has been available to farmers for 15 years.

The same technology that shows your cell phone where to find the nearest gas station also tells farm implements precisely where to plant the next seed.

The advantages are obvious. Farmers can save money by not overseeding their fields and not spraying too much — or too little — fertilizer, fungicide or herbicide.

“Chemical prices are our highest cost,” said Chris Otten, who grows soy, wheat and corn on 1,400 acres he owns with his family near Fayetteville, Illinois.

“We were probably using 10 to 20 percent more chemicals than we had to” before they started using the GPS technology, he said.

That works out to a savings of $7,000 to $10,000 a year in chemicals and seed alone. Less chemicals also means less runoff, which helps the environment, Otten said.

GPS is the key technology behind Autosteer, a program that is now used by a large majority of farmers in the area. With Autosteer, a farmer only has to drive around the perimeter of his fields once. That action creates a map for the computer to follow.

The computer directs the farm vehicles to plant, spray and harvest in straight, evenly spaced rows that can begin and end at the exact edge of the field. When the vehicle gets to the end of the rows, it will stop planting, turn around (the farmer has to help with that part) and begin new rows as close as one inch or less to where they need to be.

Before Autosteer, farmers could line up the machines within “a couple of feet, if you were good,” Otten said.

One particular advantage to Autosteer and programs like it is that it gives the farmers more hours in which to work. Because they don’t have to see where they are going, they can even work at night.

That ability is invaluable to farmers like Adam Jones, who plants corn and soybeans and runs “a very small cattle herd” on 800 acres near Old Monroe, Missouri.

Jones has a day job; he is a commercial agriculture lender for CoBank. Only when he gets home from that job can he begin to work on his farm. Because he can still work the fields after the sun goes down, he can put in 16-hour days.

“I’m not exhausted, because I’m just sitting here pushing buttons. It’s like playing a video,” he said.

The extra hours spent farming in the dark were especially important this spring, which was unusually rainy. When farmers learned that rain was expected the next day, they got in as much planting as they could the night before, Otten said.

The permanent map that the computer draws of each field is a vital part of the technological advances that have been growing by quantum leaps and bounds.

With information fed to them by sensors on each of the machines, the maps give farmers a real-time look at every aspect of the farming cycle. The information even goes straight to their cell phones

Recently, Otten directed his machine to plant 28,000 corn seeds per acre on one particular field, but the monitor showed that he had planted 30,500 seeds. A quick look at the map on his phone showed exactly where the problem was, on part of three adjacent rows.

He couldn’t tell what the problem was by physically examining the machinery, so he videotaped it in action and examined the result frame by frame. That is how he discovered that three rows of his planter were planting two seeds at once instead of one. He fixed the problem overnight, and the next day the map confirmed that the rest of the planting was perfect.

The computer-generated maps also are used on the combines that harvest the crops. Sensors inside the combine relay real-time information on how much grain is being collected, down to each square foot of land.

Variations in the yield as depicted on the maps can show the farmer how much more fertilizer he needs to spread over certain parts of the field in the coming years, said Allen of Gateway Precision Ag.

The sensors also instantly test the amount of moisture in the grain, which can have a direct impact on how much money the farmers will make.

Corn should generally be harvested when it has no more than 15% moisture and soybeans at no more than 13%, according to a paper written for the Center for Agricultural Profitability at the University of Nebraska-Lincoln. Anything higher than that results in a lower price they will receive when they sell their harvest to a grain elevator.

If the yield monitor shows that the moisture is too high, the farmers may consider waiting to finish the harvest.

Shannon and Jessica Claborn, who co-own the drone company in Hawk Point, use a different type of high-tech map in another part of their business: satellite maps.

As part of their Prairie View Seed company, they consult with farmers to determine the amounts and types of fertilizer the farmers need to produce the best yield of crops over each portion of their fields.

The work begins with satellite photos, which they use to divide a field into a grid of 2½-acre units. Miller, who is also the drone pilot, takes several soil samples from each portion of the grid.

The samples are labeled and sent to a lab, which tests them for phosphorus, nitrogen, potash and other nutrients and minerals, as well as the all-important pH balance.

“If the pH isn’t right, the fertilizer won’t do anything,” Jessica Claborn said.

The Claborns plot the results of each lab test on the satellite-photo grid. Using their backgrounds in agronomy, they then make recommendations for how to address the needs of each section of the field.

One customer’s field, for instance, showed very high levels of phosphorus, but very low levels of potash. They told him he would not have to add any phosphorus for several years, but would have to add potash over the next few years to get those levels up to where they need to be.

The information saved the client money on phosphorus, and the addition of more potash should also boost his yield.

The computer-generated maps are also used in an increasingly important part of farming, variable-rate technology. This technology allows the farmer to plant seeds, spray water or spread fertilizer in different amounts as needed as he rides throughout the field.

In the not-too-long-ago old days, seeds would come out of the planter — or chemicals out of the sprayer — at one, unchanging rate. The farmer could only change the number of seeds he planted, or the liquid he sprayed, by driving the vehicle faster or slower.

Variable-rate technology allows the farmer to drive at any speed he needs, putting down seed or fertilizer depending on conditions of the soil that are plotted on the map.

If the soil is unproductive in one part of the field, the farmer will plant fewer seeds. But he will plant more where the computer shows the soil is better.

Variable-rate technology also makes accommodations for changes in the tractor’s speed. If the tractor or planter has to slow down, such as when it comes to a ditch, the computer automatically slows the rate of spraying in proportion to the change in speed. That way, the optimum number of seeds is planted across the whole field.

It all sounds helpful and invaluable, but some look at the technology and see a downside.

Jones, the Old Monroe part-time farmer whose 800 acres is relatively small, said, “Some of the technology scares me because I feel like it is going to put me out of a job because I can’t afford it. Only the bigger farms can afford it, so they will be able to outbid me because of their increased efficiency.”

Jones uses all the work-saving technology that he can, but not everyone is as enamored of the whole idea.

Otten, who has the farm near Fayetteville, Illinois, took a 96-year-old farmer neighbor for a ride to show him how the GPS worked. The neighbor was unimpressed.

“Why do you want to push all those buttons?” he said.