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Corn+Soybean Digest

Staying on Track Pays Off

You might call precision-ag technology your guidance counselor.

By whatever name, precision guidance and auto-boom sprayer control are proving their value. A recent Ohio State University (OSU) study found that they saved eight acres' worth of overlapped spraying on a 100-acre field. This represents $3.39-5.84/acre in spray materials, fuel and labor, the study finds.

THE RESEARCH COMPARED a non-precision self-propelled spray machine without any GPS, using foam markers, to an RTK-guided system with auto-boom individually controlled sprayer nozzles. The latter systems are accurate to within 2 in.

The technologies' biggest savings are in spray materials, and when using a wider spray boom on irregularly shaped fields with obstructions like waterways. The study was led by Marvin Batte, OSU farm management professor and director, Center for Innovation-Based Enterprise.

The RTK with auto-boom paid for itself between 688 and 756 acres/year if sprayed twice a year, Batte found, depending upon auto-boom width.

The study assumes spray material costs of $20/acre, two spray applications annually, fuel at $3/gal., a $10/hour driver wage, 10-mph sprayer ground speed and a 7.5% overlap in the non-precision applicator. The RTK-based precision guidance system is assumed to have a 2-in. sprayer overlap for parallel swaths.

BASED ON THESE accuracy rates, a 100-acre field wasted two or three passes, depending upon sprayer boom width, Batte found; or about 8 acres of overlap.

In fields with waterways, the non-precision applicator overlap amounted to 13 acres' worth in a 100-acre field, Batte found. The extra travel required to spray around the waterways roughly doubles the travel difference between precision and non-precision systems.

Applicator driver error rates vary widely. A study (Ehsani et al., 2004) found the range of overlap was from 0.6% to 26% for custom applicators with a foam marker system in field conditions. Researchers also found that a driver with the average overlap below 5% also had many application skips, Batte reports.

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