Utilization of Variable Rate Controllers for On-Farm Fertilizer Research with Small Scale Equipment.

Greater adoption of variable rate application of nutrients has led to increased questions on how to adapt current nutrient guidelines to “on the go” control of crop nutrients. One of the main questions in growers’ minds is whether nutrient applications should vary based on soil types. In order to do this type of research large commercial fertilizer applicators have been used. The disadvantage to the use of commercial applicator use is that plots need to be large because of limitations on minimum application widths and the lack of statistically sound design for the treatments. Our objective was to evaluate small scale research plot fertilizer application equipment equipped with commercially available precision fertilizer controllers for use in establishing larger more complex strip trial designs and to assess how quickly a constant application rate can be achieved when changing on the go without stopping between plots. A Raven Viper Pro (Raven Industries Sioux Falls, SD) controller was adapted for use with small scale research plot equipment. The fertilizer control unit was equipped with a GPS receiver with real time kinematic (RTK) signal correction to increase the precision and reduce the need for flagging large field areas to mark applicator passes. A dry fertilizer applicator and a corn planter were set for variable rate application of two and three product application, respectively. These pieces of equipment were able to apply broadcast nitrogen and starter fertilizer, respectively, using a prescription map. Two field trials were designed to assess the capabilities of the two pieces of equipment. The first field study was a nitrogen rate study with 8 treatments replicated 16 times set up like a traditional strip trial study with the fertilizer rates varied along the length of the strip. The second study evaluated the used of planter banded fertilizer with and without the application of broadcast P. Trials will be evaluated to determine how quickly rates can be modified on the go and the evenness of application using real time data collected at application and collected in the field during the growing season.