If you're not making money with precision agriculture technology, don't blame the tools! That was the message presented to crop consultants attending the recent National Alliance of Independent Crop Consultants "Focus on Precision" conference. In a review of what works and what doesn't, three agronomists discussed how their use of precision technology has evolved to better serve their customers' interests.

Matt Duncan, Key Agricultural Services (KAS), Macomb, Ill., started out by getting some myths out of the way. "If you got into precision agriculture for cost control, you got in it for the wrong reason, and you probably know that today," he said. "Precision technologies won't reduce fertilizer costs, and they won't make soil test levels uniform across a field. However, they will likely increase yields, and depending on the field, they may save the operator money. They will improve fertilizer placement and application efficiency, and that should improve profitability."

In fact, he added, one of the advantages of soil-specific field management (SSFM) and variable rate technologies (VRT) tends to result in increased fertilizer use. He points to ag retailers who use his company's mapping services to in turn service their own clients. When they asked if site-specific management was hurting their fertilizer sales, Duncan ran the numbers based on yield averages and what was actually being applied under their conventional program versus what should have gone out to meet university recommendations.

"They were actually applying less than they should have by about 25 percent to keep the customer happy when it was hurting the retailer short term and the customer in the long term," said Duncan. "Agronomically it was completely valid to justify the added 25 percent, but with site-specific variable rate, the increase is easier to defend."

Variable Rate Applicaton
That myth of lower fertilizer sales with variable rate application can reduce management enthusiasm for investing in precision. Busting the myth is easy for Kevin Jeurissen, precision ag coordinator, Crystal Valley Cooperative, Madelia, Minn. He points to one location where he has done the math.

"The average spread of P and K with VRT is 321 pounds per acre," said Jeurissen. "Conventional acres average 50 to 75 pounds less per acre."

Jeurissen's management is hardly going to complain with more than half a million acres spread across nine locations in the precision program. Customers don't complain either, he said, as their application rates go up with SSFM.

"The customer is always concerned about dollars and cents," he said, "but you have to walk them through the math of removal of nutrients, what the application recommendation is and why. Once they understand the what and the why and they see they are getting more and more yield per acre, they stay with the program."

When Centrol Crop Consulting of Twin Valley, Minn., first got involved in precision technologies in the early 1990s, grid sampling drove the business, recalled Kevin Hollands. Even without data to justify it, the concept appealed to sugar beet growers, and the business took off like a rocket. Initial sampling set the stage.

"Some of our fields had areas with N levels of 200+ pounds total in the top 4 feet when our beet growers were shooting for 130," said Hollands. "Initially growers wondered why they weren't seeing positive results in sugar yield from their variable rate fertilizer. The grids showed it was because the N was already too high in many places. At that point in time, we were saving money in nitrogen fertilizer! Taking from the rich and giving it to the poor, instead of one uniform rate across the field!"

As fertilizer rates were varied according to grid test results, sugar yields became more uniform. When American Crystal, the local sugar beet processing co-op, compared SSFM with conventional management, they found a $45 per acre benefit. Everyone wanted on board at that point, noted Hollands. By the late 1990s, the crop consultant firm began to switch grid sampling to zone sampling based on topography. Since then, the firm has moved on to using aerial images supplied by American Crystal and other companies to define zones.

"Zone sampling gave us the data we needed to make better decisions, was less intensive, less costly and more fruitful for growers," said Hollands.

Soil Tests And Soil Maps
KAS started out in the early 1990s relying on soil tests and soil maps and making applications to meet yield goals based on university recommendations. In the late 1990s, they began bringing in yield data to compare with soil test results. By breaking a field into 2.5-acre grids for soil sampling and then further breaking that down into 3- to 4-acre yield grids, it was possible to correlate yield more accurately to soil test results.

"We found that the highest yields often came from the lowest soil test areas, and the lowest yields were from the highest testing areas," Duncan said. "Using whole field yield goals and just grid tests, we were pulling more out of the low test areas than we were putting on and pulling less off the high test areas than we were applying."

Today, KAS utilizes 2.5-acre grid soil testing and cation exchange capacity to evaluate potassium building rates and a yield map based on the two years prior to the latest crop. Fertilizer recommendations are adjusted by what was actually removed from the field. One of the advantages of this method is that it eliminates pressure to create fall application maps based on the just harvested crop.

Instead, the firm can take time to ensure data is cleaned up and properly evaluated before it is used.

Soil types are only used for rating performance potential and long-term trends. That is not to say that soil types have no value. "If soil type is the only difference in a 30 percent yield drop between fields, it tells you to look at management," said Duncan. "The lower yielding fields may be close to the buildings and are being planted first for that reason, when they need to be planted later due to their soil type. The fun thing about being a consultant is using the data to find inconsistencies and figuring out how they can be made more consistent."

The Yield Proves It
The proof of the program is in the yield results. Of 7,500 acres in the KAS program for more than five years, 91 percent of the fields had a yield increase over that five-year period. Average corn yields across the 7,500 acres went from 142 bushels per acre to 162 bushels. This was a 14 percent increase, compared to a 9 percent increase in the state average over that same time period. Individual growers had fields with increases as high as 40 percent, where inconsistencies had pointed out the need for management changes aside from fertilizer applications. The data also pointed out other opportunities to customers.

"The data clearly showed that marginal soils could make as many bushels per acre as the best ground," said Duncan. "As a result, we now have clients who go after marginal ground when it comes up for sale. They know they can make as much off of it as they can off the best ground, yet price and taxes are all lower."