5 Reasons to Say Goodbye to Conventional Spraying Practices

October 15, 2020

Herbicides, insecticides, fungicides and fertilizer — many inputs are applied through the sprayer. 

But spraying these chemicals and fertilizer the conventional way can end up costing farmers a lot of money, whether it’s wasted resources, ineffective pest control, or even damage to the crop. The more often you make a pass without precision ag technologies on the sprayer, the more likely you’re making costly errors. 

We spoke with Scott Shearer, Professor and Chair of the Agricultural Engineering Department at The Ohio State University, and Joe Luck, Associate Professor and Precision Agriculture Engineer at the University of Nebraska-Lincoln, about why farmers should adopt precision ag for their spraying practices and the benefits you’ll reap in doing so.

1. You want to reduce your chemical and fertilizer bills.

One of the most common issues Shearer and Luck see with conventional spraying is overapplication. 

This happens when the sprayer goes over an area it has already sprayed, resulting in overlaps, or it sprays parts of the field that don’t need application. 

Growers can use automatic section control to solve this problem, which works by turning off sections of the boom or even individual nozzles when it reaches a boundary or a part of the field already sprayed.

For a lot of farmers, it can provide a great return on investment (ROI) quickly.

Ohio State research has shown that farmers can see excess application rates of 12-17%, so Shearer suggests taking 10-15% of your chemical bill and seeing if the savings from that would be greater than the investment in section control. For most farmers he’s worked with, the payback period has been as little as 1 year to 18 months. “That was a pretty common number we see all the time,” Shearer says.

Luck has also seen growers achieve significant savings from investing in section control. For one farmer in Kentucky he worked with, the $3,000 investment produced $5,000 in savings the first year.

To reduce input costs even further, you can explore using variable-rate (VRT) or sensor-based technologies.

Fields don’t have uniform yield potential or even soil types, so for nitrogen application, Shearer says it makes sense to adopt VRT to adjust the rate across the field. Luck adds that since pre-emergence herbicides can require different rates based on soil type, you could variable-rate your herbicide application in fields with variable soils.

Trimble’s WeedSeeker2 and GreenSeeker take these savings a step further. Using optical sensors to identify weeds or nitrogen variability in the crop, respectively, they help ensure applications are as precise as possible. 

2. You don’t have perfectly square-shaped fields.

Most growers can expect to see a good ROI from automatic section control because they have irregularly shaped fields. 

“If you have perfectly square fields, your savings are not going to be that great,” Luck says.

“It could be 2-3%. That’s some of the minimum savings we saw [from spraying data collected from growers in Kentucky].”

But as the field boundaries and obstacles get more complex — such as point rows, angled headlands, or grass waterways that cut through the field — the savings can go up substantially, he says. In the data out of Kentucky, some fields saw savings as high as 30%.

Automatic section control isn’t the only sprayer technology beneficial for odd-shaped fields. Luck says most farmers don’t realize how much they turn in their fields, and when they turn, the sprayer isn’t applying a consistent rate across the boom.

Why does this happen? Because the inside of the boom isn’t traveling the same distance as the outside, Shearer explains. 

“It’s the same elapsed time to cover that inside arc as the outside arc,” he says. “The spray boom on the outside has to go at a much higher velocity to make that turn.”

With booms only getting wider, Shearer adds the inside of the turn may have 3-4 times the target application rate, while the outside may be as low as 25-30%.

The precision ag solution to this issue is turn compensation technologies, which use pulse width modulation in the nozzles to adjust the application rate during turns.

3. You’ve experienced crop damage from your spraying.

Another reason sprayer overapplication is so costly is that it can have serious consequences to your yield. 

Soybean injury from herbicide and wheat lodged from excess nitrogen are two common yield-reducing effects Shearer has seen with overapplication.

But it’s not just cash crops. Shearer has seen growers accidentally spray out their grass waterways, which means they either need to reseed them — an additional expense — or risk soil erosion. 

While automatic section control can prevent overapplication and spraying outside of the fields, application speed may contribute to these problems. Shearer says that anytime you decelerate in the field, pressure increases in the system, resulting in a higher spray rate. It’s another instance where pulse width modulation nozzles could pay off because they’ll keep the rate consistent.

But if crop damage occurs because of application drift, you should consider boom height control, which automatically raises and lowers the boom based on the crop’s height.

“The higher the boom unnecessarily gets from the target, that’s just more drift potential,” says Luck. 

Shearer adds that boom height control makes a lot of sense for farmers with elevation differences, especially as the width in equipment increases.

4. You’re not getting effective pest control. 

Sometimes the problems you see from spraying are the result of underapplication. 

If you’re experiencing inadequate weed, insect or disease control, it could be a sign that your sprayer boom is too low, resulting in insufficient application coverage.

“With a flat-fan nozzle, we depend on a 50% overlap,” Shearer says. “If that spraying boom is too close to the crop, you could be getting ineffective control because you’re getting striping in that crop. In other words, we didn’t have the ability for those nozzles to make that flat-fan pattern overlap before they hit the top of the crop canopy.”

But it might be due to your application speed. Acceleration causes the pressure to drop, Shearer says, so if you see insufficient pest control in areas where you typically speed up, then pulse width modulation nozzles would likely be a good investment.

5. You already have the components to be more precise with your spraying.

If you have some level of precision ag, chances are there’s an opportunity to make some of these technologies a reality for minimal investment.

Shearer worked with about half a dozen farmers in Ohio on adopting section control, and most farmers were only missing a component or two — an investment of around $500.

“In many cases, it was getting the farmers to export boundaries from their farm management information systems and upload them to the controller,” he says. 

The payoff for investing in those extra components was well worth it.

“I don’t think there’s any question about it. Farmers on all scales are going to benefit from it,” says Shearer. 

“If I walk onto a farm and I don’t see [automatic section control], that’s one of the first things in terms of technological investments I begin talking to the farmer about, because I know they’re going to be better off with that technology than without.”

If you’re interested in adopting some of these technologies or wondering how you can take your precision ag implementation a step further, we can help. Contact your local Trimble Ag Reseller today.