Here's a practical checklist for sizing GPS-aided manure application equipment.

When Jeff Fields bought global positioning system (GPS) equipment to record manure injection data and vary his application rate within fields, he spent $1,700.

Fields considers that a reasonable cost on a package deal, which probably falls in the middle of the current cost spectrum. Basic GPS-based tracking and recordkeeping packages can be constructed for as little as $1,200.

The most common uses of GPS-based technology for manure application are to help with fertility setbacks from streams, field borders, tile inlets, wells and sinkholes. It also helps record application patterns and the basic data needed to avoid ecologic liability.

Fields demands more of the equipment he purchased, however. As manager of farm operations at Purdue University's Animal Science Research & Education Center, his crews inject about 3 million gallons of slurry, mostly from the university dairy, into crop ground each year.

This fall, Fields will begin to use three rates of manure slurry application, depending on his soil tests for phosphorus and potassium. He'll vary the three rates within fields according to pre-tested grids, writing the prescription for each field on his desktop computer, then downloading it to a portable computer.

Fields' three-piece package included a Hewlett-Packard iPAQ 2110 handheld computer, a plug-in GPS receiver accurate to within 15 ft., and a protective box called an “OtterBox.”

He added these to existing university equipment to accomplish variable-rate application. Fields combined the GPS-based equipment with Farmworks software, a Balzer tanker with a Rite-Rate application controller, and a Raven 660 electronic spray controller.

When Purdue scientists began experimenting with variable-rate manure application in the mid-1990s, the equipment was more complex, harder to tie together, and cost perhaps $15,000, says Stephen Hawkins, a Purdue agronomist now in administration. Today, it's much easier and less expensive to build a GPS-based system, whether for recordkeeping or true variable-rate application.

The basic requirements

To achieve the more basic purposes of GPS-based tracking and fertility setbacks, a manure applicator could build a system with three components:

  • A GPS receiver with a receiver card to plug into the pocket computer. Wide-Area Augmentation Signal (WAAS) is an adequate correction signal.

  • A pocket computer such as Hewlett-Packard's iPAQ 2110.

  • Software such as Farmworks Farm Site and Farm Site Mate or SST Summit with SST Stratus.

This combination could be used manually or connected to electronic controllers, Hawkins says. Its records could show the equipment paths in each field and a report with details about the application, such as applicator name, application rate, manure content and weather.

Here's an example of such a system from SST Marketing Director Dana Waits:

  • SST Summit/Stratus software — $600
  • iPAQ 2110 — $320
  • Emtac Trine Bluetooth GPS — $295

Total cost — $1,215.

First things first

Purchasing equipment isn't the place to begin, however, Hawkins says. First, decide what tasks you want the equipment to perform. That will determine the equipment and the capabilities needed.

For example, if high accuracy is desired, you'll need to move up from a GPS receiver with WAAS to something utilizing more accurate correction signals, such as RTK or Omnistar, explains Keith Morris, a Louisiana State University agricultural engineer.

Adding a moisture- and dust-proof cover to your handheld computer is probably a good investment since electronics don't mix well with nature's elements.

A manure applicator who wants to use true variable-rate application or high-accuracy mapping with manure products will need more equipment, Morris says. That includes a flow meter and gate valve to interface with a controller and allow your handheld computer to control and log the flow rate. Moreover, to really log “as-applied” rates, you'll need flow meters on the main line and closer to the nozzles or at each nozzle.

You'll also need a device that accurately measures ground speed. However, high accuracy is probably futile because manure products vary so much, even as they exit the same tank, Morris adds.

Regardless of how much accuracy you want or need in your manure applications, the plug-and-play nature of today's electronics has made things simpler and automation of tasks much easier. GPS-based control and logging of manure application is now practical for most applicators.

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