April 11, 2013

Cooler temperatures this March have resulted in planting dates being pushed back across much of the state in comparison to 2012. Many producers who are ready to get into the field should consider using this time to double check their application equipment, especially those who use precision agriculture technologies. Examples include simple rate controllers that compensate for ground speed variation, automatic section control systems which reduce overlap, or variable-rate application systems. Whether you’re spreading, planting, or spraying, pre-season updates and calibration of your application equipment will help to minimize errors.

Global positioning systems (GPS) are an essential component for almost every piece of precision technology that we use in the field today. It’s important that your GPS receiver’s firmware (software that controls the receiver) is up to date. Many manufacturers will usually let you know when an update is available; however, it’s always a good idea to check the version that’s currently installed on your GPS unit to make sure it’s current.

Updating firmware on many GPS systems is often as easy as downloading the firmware file to a USB drive and then uploading it to your receiver. Another component that may be common to application equipment is a ground speed radar (GSR). The main function of the GSR is typically to inform the rate controller so it can adjust for any changes in ground speed. Yearly calibration is recommended (check the manufacturer specifications). It’s also important to ensure that the GSR is mounted securely to the vehicle frame so that there’s no movement during field application.

Measurement of offsets from the GPS antennae to any equipment is another important procedure during equipment setup. For example, sprayers with automatic section control require a measurement from the GPS antenna to the boom centerline. This ensures that boom sections are turned off when they (not the GPS antennae) pass over previously sprayed areas. Similar measurements are necessary for planters and spreaders to minimize skips and overlaps at the end of the passes.

Calibration of these systems is also critical for proper performance. Distribution tests should be performed for spinner spreaders to ensure that a proper pattern is being achieved, keeping in mind that different products may require their own calibration and swath settings because of density and particle sizes. For sprayers, verify that nozzles are within 5% of the manufacturer’s flow rate at a given pressure. If possible, perform a flow meter calibration to confirm that actual output doesn’t differ from the spray rate controller flow value. Seed drop tests can help evaluate the planter’s ability to maintain proper seed populations.

When calibrating any of the systems mentioned above, it’s important to remember that application errors will typically be less at the settings (speed and target rate, for example) chosen for the calibration. It’s a good idea to select those calibration settings close to values that you will try to use out in the field. Performing additional checks at higher or lower settings may help you evaluate the potential for error when you deviate from your typical field operating ranges.

While technology has come a long way over the past few years, it won’t solve all of our application problems; proper maintenance and management is still a must for minimizing your field errors.

Joe Luck
Extension Precision Agricultural Engineer