Quality fertilizer application is critical every year, but the spotlight is intense on this field-pass given current input costs. No matter the application system used, factors such as weather, humidity, and field conditions can make quality applications difficult to achieve. However, accurate and precise application can be attained by regularly testing for calibration and uniformity, and machine maintenance.

Accurate applications are achieved through routine calibration testing. It’s recommended that calibrations are checked bi-annually at a minimum. This process only takes a few minutes, and any rate-controlled system likely has a wizard that walks you through these steps. Perform rate calibrations anytime application components are swapped out during repairs. When performing a static test, target <5% error but keep in mind that most systems will have a degree of error depending on the amount of overlap in a respective field. For dry fertilizer systems, ensure the operator is the person measuring the density of the product during calibration. Density has a huge influence on the calibration and on ability of the machine to stay on rate when it gets to the field. On self-propelled machines, if the density measurement is off by 1 lb/ft3, each load of fertilizer applied will be off by about 300 pounds. Another consideration is that density should be measured at every tender load as this measurement can change from morning to afternoon with changes in humidity and temperature.

Precise applications can be attained by testing for uniformity. Blends of fertilizers can be challenging to apply uniformly due to differing material properties in the components to make up these blends. For example, urea has an average density of 48 lb/ft3, while potash is usually around 70lb/ft3. In other words, we are throwing a golf ball and ping-pong ball simultaneously and expecting them to land in the same area of the field. Machines must be set up properly, and uniformity tests should be performed multiple times throughout the growing season to prevent “streaking” of crops with misapplied areas. 

Always perform a pan test on spinner spreader machines to check uniformity for each type of fertilizer applied. It’s important to pan test a single swath but also check an “S” or triple-pass pattern to see if there is too much overlap. Bag testing should be done to check for uniformity on air-boom machines and can double as the rate calibration procedure, as well. Be wary of buildup in waterfall outlets and dog boxes that could lead to potential clogs during operation. Sprayers should be checked at each nozzle for the target GPM to ensure uniformity. Be sure to check for proper orifice sizes that enable you to hit the target gallons per acre at operating speed. 

A well-maintained machine is at an advantage during the hustle of late spring and early summer. Fertilizer is naturally corrosive on mild steel, and no time of the year reveals this more than the hot, humid months of May and June. Take the time to thoroughly wash fertilizer applicators at the end of every day when possible. Even slight amounts of buildup can alter the way a machine was engineered to apply and cause in-field issues. Consider installing preventative maintenance measures to avoid downtime. Some examples of these are Denso tape (a petroleum-based wrap to protect hydraulic fittings), fluid film (a heavy-duty rust inhibitor), and lubricants maintained at the manufacturer’s specifications. This will help keep components functioning properly when you need them the most. 

While many portions of the fertilizer pass have the potential to go wrong, a little attention to detail can go a long way. It is better to spend an extra 30 minutes before a big job to thoroughly inspect and calibrate your machine than to realize post-application that major problems occurred. GreenPoint Ag’s Ag Technology Team is here to help with your fertilizer application systems. Reach out to your local Co-op for help on your machines, resources, and in-field support.