Wayne McCray says his yield monitor has made him a better manager. It's helped him improve weed control and variety and hybrid selection. And in one field, yield comparisons convinced him to tile a wet spot.

The result: higher corn and soybean yields.

McCray is one of the early adopters of this six-year-old technology. He and a number of other growers and consultants now have several years of data, and most report a positive payback.

McCray, from Compton, IL, has been monitoring yields since 1993. Since then, he has seen slow yield gains in both crops. Last fall he got another benefit: a 1998 contract to produce specialty corn and soybeans at very respectable premiums.

"Back in 1993, I had average yields and average weed control for this area - neither real good nor real bad," says McCray.

He typically plants four to five corn hybrids and three soybean varieties. But after getting his yield monitor, he began splitting his 12-row planter - six rows with one hybrid or variety and six rows with another. That gave him side-by-side comparison strips across the field. Since he has a six-row combine, it was easy to check yields on each hybrid or variety.

"Each year since getting the monitor I have replaced my lowest-yielding corn hybrid and soybean variety with the top yielding corn hybrid and soybean variety in University of Illinois trials," says McCray. "That seemed a good way to bring up my average."

Once McCray started monitoring yields, he saw the full impact of weeds.

"Weeds are yield killers," he declares. "At one time I would have settled for a little grass and some broadleaves, but today my goal is 100% weed control."

The yield monitor also has spotlighted the damage that wet spots can do to yields.

"We have a wet area that I had farmed around for years - and my father before me - because it didn't seem all that large. But the monitor showed me that the yield impact of a wet spot can extend well beyond its borders. It convinced me to finally put in a tile."

McCray says his yields are now relatively higher - compared to the area average - than a few years ago.

And it seems that the improvement is noticeable to others. Last fall, a seed company representative who had been observing McCray's fields was impressed with his crops and weed control. As a result, he offered McCray contracts to grow specialty corn and beans for premium prices.

"I never thought I would see the day when somebody was that impressed with my crops," says McCray.

Several years of yield-monitor data are essential, says independent crop consultant Paul Gordon, Bentonville, IN. He has several clients who have had yield monitors for the past three harvests.

"The biggest lesson that we've learned is that each year is unique in regard to temperature and moisture and their effects on yield. So we need multiyear data to get the big picture," Gordon points out.

"We need to build a history for each field, and we can't expect a payback every year. That's sometimes difficult for a farmer to accept."

Nevertheless, Gordon notes, some things become obvious faster than others.

"We've seen how much herbicide damage can cut yields. The yield monitor has documented yield losses of 10-15 bu/acre due to herbicide damage, either from carryover or from the susceptibility of a particular hybrid to a particular herbicide."

Rob Meyer, division manager with Crop Quest, Inc., St. John, KS, also has used a yield monitor to confirm herbicide damage.

"We knew from scouting that damage had occurred," points out Meyer. "The yield monitor quantified the damage, and that information was used as a basis for settlement."

Build at least a five-year data base on a field before making major changes. That's what Kirk Wesley of Key Agricultural Services, Macomb, IL, recommends to yield-monitoring farmers.

"However, one of the first things we can do with yield monitor data is to get a better reading of soil types," says Wesley.

"Most soil-type maps are generalized. As we begin overlaying yield maps on soil maps - along with using our soil sampling results - we can better-define where a soil type actually begins and ends."

That helps Wesley better-determine the relationship of soil type to yield.

"We can fine-tune our soil maps, and as we do this fine-tuning we can begin to reduce inputs in the proven low-yielding areas," he adds.