Like an instructor watching students graduate from high school, Gary Roberson wants to see cotton farmers move to the next level in precision farming.

After an introduction to yield monitoring, farmers need to take the next step and build economic maps.

“Economic maps help producers record how much it's costing them to produce a crop on a certain part of the field, comparing the yield and the returns,” says Roberson, a North Carolina State University agricultural engineer.

The goal is to hit a sort of agricultural balance, something Roberson calls optimum economic return.

“That term simply means you have the best combination of inputs and outputs,” Roberson says.

“If we shoot for the maximum yield, then we're going to be putting the maximum inputs on the field to get the maximum yield,” Roberson says. “But if we look at an economic analysis of what it's costing to get that maximum yield, then we might show we have actually lost money.”

By using economic maps, the grower can take the cotton crop from planting to the gin and back again.

“When farmers sell their cotton, they know what they get per pound and the yields,” Roberson explains. “They can create a return map and compare that to the input map they used to get those yields. This type of information is useful to help them make decisions about producing a crop in a certain field.”

For example, knowing the economic return from a field may lead a farmer to consider growing a different crop in the same field next season.

Another part of that economic map would contain soil sample information, which may mean several layers of data — inputs, lime, fertilizer, land plaster, tillage and labor costs. Cost of harvest, yields and selling price of the crop would complete the total economic picture.

In a strict sense, yield monitors help farmers determine where the so-called economic holes in the field are

As the cotton is being harvested in the picker, optical sensors connected to GPS coordinates tie the yield back to the place in the field where it's being harvested, Roberson says. From this information, the grower can see problem spots in the field, as well as where the top yields are coming from in the field. Perhaps a low-yielding area lacks the fertility to produce efficiently. Perhaps there's a weed problem at a certain point in the field. Whatever the situation, the yield monitor gives the producer an insider's view of what's actually taking place in the field.

Optimum economic return won't necessarily mean the maximum yield, Roberson points out.

As with any new technology, farmers have to look at it and be able to say that it will make him a more efficient producer than he was before, Roberson says. In tests with three yield monitors on the market, he found the accuracy within “reasonable expectations.” He has tested the Ag Leader, Microtrak and Agriplan yield monitors.

Farmers who use yield monitors should have the unit “far enough into the chute so as not to expose it to ambient light,” Roberson says. “The concerns we have with the sensors, because they are light sensors, are due to the fact that we have to be careful about cleaning them. In my opinion, nothing replaces cleaning to help insure the quality of the data.”

Roberson also recommends calibrating the yield monitor at least one time each season “at the very minimum. Calibrate more often if you have a couple of different varieties that have noticeable differences in boll size.”

Roberson believes the increasing number of North Carolina cotton growers using yield monitors testifies to the technology's usefulness. But he says the purchase of a yield monitor must be based on “whether it will make me a more efficient producer. If the farm is small and the numbers are not there, then it's just a gadget or a toy.

“If the grower is only interested in the total weight or yield, then the yield monitor is not the appropriate technology,” Roberson says. “For that grower, it would be a lot cheaper to measure yield over the scale.

“If he's interested in finding out where the variability is in the field, the cotton yield monitor is the way to go,” Roberson says.