Geo-referencing lime application can grow farm profits

Jeff Mayfield, agronomist at Ag Service Inc. near Hillsboro, often finds that when the company begins a new farm technology, other new and better ways of doing things soon follow.

?It just keeps snowballing,? he said.

That?s the way it is with the satellite geo-referencing and computer precision the company is using for applying lime to area farm fields. Mayfield said it appears the practice will lead to more precise applications according to point of need for seed, fertilizer and maybe even pesticides.

It already makes those other practices perform better where applied by pinpoint correction of soil acid/base balance.

The company can already hand a card, developed from the liming computer program, to a farmer who used the technology to plug into the GPS computers on his newer tractor or planter to regulate changing rates of seeding.

For example, Mayfield said, if the farmer is planting corn, he may want to put less seed on upland parts of the field that grow corn poorly, but more seed in a part with rich loamy soil where corn grows well.

The method

To understand all of this, it probably helps to know something about the method of the liming, and how it helps. Even though Ag Service has had the service for three years, Mayfield said it probably is still unique in this area.

Now, that doesn?t mean a producer should entirely throw out the way things have been done in the past, Mayfield said. The old method of going across a field on a four-wheeler, or walking to take soil core samples and mixing them to send in for testing to determine average pH across the field still has value, he said.

But the new method delivers precision with ?extremely? greater productivity, he said.

It may not cost less to lime because delivery puts more lime in spots where it?s needed, and less lime in spots where it isn?t. But the greater benefit is created by higher crop yields and better use of other chemicals that need the proper pH balance to perform correctly.

The process performs so well, Mayfield said, that farmers often find the phosphorus they have applied for years slowly becomes available to boost crops. It also may mean that less phosphorus is washed off, he said, which often is a concern to environmentalists.

The pH factor

The pH number is a logarithmic value related to the balance of hydrogen and hydroxide (acid?base balance). A pH of 7.0 is about neutral, while numbers lower are acidic and numbers higher are basic.

According to Ag Service data, pH over several thousand acres in this area has varied from 5.0 to 7.5 with an average of 6.2. In many cases, the areas of fields with lower pH ?acidic? soils ?are the better quality soils with historically higher yield potential, but are now dramatically underperforming,? Mayfield said.

He said the crop that needs liming the most is alfalfa.

?Alfalfa wants pH right at 7.0,? Mayfield said. ?It hates a lower pH.?

Soybeans come in at No. 2, then corn and milo at about the same need, and then wheat.

?Wheat has been more tolerant of conditions for us,? Mayfield said. ?We have wheat fields down around 5.0 that still produce.?

The process

Mayfield said Ag Service begins its liming service with a high-density, geo-referenced soil survey test machine pulled behind a tractor at 4 mph.

The device has paired coulters in the ground, and sends an electrical current between them. This determines the heaviness of the soil. Less lime may be required on the more sandy soil, and additional lime on the clay soil?both within the same field and typical of this area, he said.

In the same operation, a probe collects cores of soil that passes by a sensor to determine the pH level. This operation is performed every 10 seconds while running in the field.

At the same time, Mayfield said the GPS system is mapping the elevation with such precision that it could be used later for the construction of terraces, waterways and drainages. A computer-generated map from the operation would show land contours, and it also produces a colored map that pinpoints lime needs.

In the next phase of the Ag Service operation, a lime-gator variable-rate applicator machine uses the resulting computer card to apply a slurry of 92 percent lime solution applied at 50 percent mix with 50 percent water, Mayfield said.

The lime-gator puts the lime?a calcium mix that raises pH?precisely where it is needed in the field to increase the 5.0 pH readings on that good soil to the upper 6?s. And, Mayfield pointed out, it doesn?t apply it where it isn?t needed.

The new procedure is a departure from the old application of lime that lacked precision in applying the substance dry and evenly across a field, with part of it often blowing away in the wind, he said.

The current process is a real ?gateway to variable rate application? for fertilizers, seed, pesticides or other chemicals, Mayfield said.

Already, the program can be used in combination with data obtained from yield monitors in combines with four or five years of information to greatly increase the amount of useful data available to the producer.

For farmers, it means significant dollars in productivity, plus environmental savings.

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