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When University of Wisconsin Extension Service engineering and new technology specialist Brian Luck spoke at the Calumet County Forage Council's annual forage day, he quickly learned that most of the attendees either did not use or were not too familiar with the products he was describing.

Luck's message for the day was that those products, which are designed for precision agriculture practices, are suitable for much of the terrain and many of the field shapes in Wisconsin. But based on his experiences, including in other states, he has noticed that use of those management tools is not a widespread practice in Wisconsin.

Field Variations

As a starting point, Luck suggested that many Wisconsin farmers could benefit from variable rate inputs to major crops such as corn and soybeans based on the soil types and existing residual nutrient availability within fields. Only a field that is perfectly square and without any crop growing variations would not benefit from one or more precision agriculture practices or variable rate inputs, he suggested.

'Having a computer in a tractor will not provide 300 bushel per acre corn yields,' Luck observed. But computer guided crop inputs are very likely to improve returns, he promised.

As an example, Luck cited his monitoring of a 120-acre field owned by Dunn County in which soil samples were taken for each acre with the help of students at the Chippewa Valley technical college. The 120 sample tests suggested the application of anywhere from no to 15 tons of lime per acre, he reported.

With the help of variable rate application equipment, many parts of the field received five to six tons of lime but many others received far less, Luck noted. He said another choice could have an application of three tons of lime on every acre but that the variable rate approach put the per acre average at 1.57 tons, saving $4,463 compared to putting three tons on every acre.

Row unit shutoffs

Row unit shutoffs on planters would be appropriate on many Wisconsin fields because not many have a pure rectangular shape, Luck observed. Not having that technology can easily result in overplanting, which does not contribute to higher yield.

Luck estimated a 2.4 percent waste of corn seed due to overplanting. For a 100-acre field, that would be the equivalent of wasting one bag of seed, he said.

A similar point applies with overlaps and skips during other field activities such as tilling and spraying, Luck pointed out. He noted that this occurs during turns and can amount to five extra trips for only a one-foot overlap when tilling an 80-acre field.

Equipment offerings

To address such shortfalls in precision agriculture, Luck advises starting with tablets or smartphones to map field boundaries that would guide field activities later, particularly for custom operators. He said the global positioning system (GPS) accuracy built in to those devices is 10 feet while an external GPS (cost of $50 to $200) improves the accuracy to 3.28 feet.

While Luck likes the AgLeader commercial app which is available for that purpose, he also listed Trimble, SST Sirrus, and AgDNA as other choices. He mentioned a price range of $150 to $1,600 for those tablets and suggested an update every two years.

Luck mentioned the real time kinetic (RTK) satellite-based positioning systems as being a good choice for a cost of about $1,000. He explained that this will enable a linkage of soil sampling locations with subsequent management practices pertaining to organic matter in the soil, the soil pH and residual phosphorus and potassium.

Updating of equipment

Auto steering on tractors and other powered units allows an operator to concentrate on other tasks such as monitoring the performance of attached equipment rather than having to control the travel path of the vehicle, Luck pointed out. He said it is possible to retrofit existing equipment to auto steering.

Yield monitors on grain combines identify differences within fields but doing so is worth the effort only if the data is used in subsequent management, Luck emphasized. Just as important is saving of that data on the computer cloud (Internet storage) or in backup format or to have one's crop consultant keep it.

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