PHOTO: PROAGRICA / FUTURE FARMING


PHOTO JAN WILLEM SCHOUTEN


GLOBAL VIEW ▶▶▶ A geographical perspective BY MATT MCINTOSH A


ccording to re- searchers at the University of Guelph apprehension is often warranted


when it comes to variable rate application and yield mapping. Neither technology offers a true understanding of why yields and fertiliser de- mands vary in the first place. John Sulik, geogra- pher by trade and assistant professor of precision agriculture, says a wide range of bio- logical data is needed to make precision agricul- ture actually pay for farmers. More specifically, he says knowledge of an area’s unique geogra- phy and other biophysical factors are critical for farmers to make more accurate in-season decisions, hopefully improving economic and environmental efficiency in the process.


Precision mapping answers what, not why


While yield mapping and field prescription maps can be useful, Mr Sulik says they fail to re- veal a lot of important agronomic information that producers require. By measuring other


“Anyone can make a map but they may not be able to tell you anything about the agronomy,” says John Sulik.


plant and soil characteristics through “biophysi- cal remote sensing” and comparing that data to yield and prescription maps, farmers can better evaluate whether the information presented by precision-ag technologies is worth acting on. An example: if a map showing nitrogen levels indicates the need for more fertiliser in a given area, but fails to show why that nitrogen is needed – such as a lack of in-soil availability as a result of ongoing water stress issues – then such agronomic information is not useful. In- deed, acting on it may be economically and en- vironmentally detrimental. Data, he says, needs to be used differently in different conditions.


Flat payoff function The problem is that variable rate fertiliser ap- plication works as a “flat payoff function” where the level of fertiliser applied can vary, yet generate the same yield profitability – soil type is a particularly significant factor here. Applying 60 kg of nitrogen per hectare might bring the same returns as applying 120 kg, though with a considerably reduced cost. Something not communicated in standard nu- trient maps. “At some point there’s no benefit to applying more,” he continues. “Variable rate doesn’t always pay off. We want to know when it does and how we can act on it.”


How many terminals does one farmer need?


BY KOEN VAN BOHEEMEN R 46


ecently I visited one of the NPPL preci- sion agriculture (PA) project partici- pants to discuss the PA applications


he was going to apply during the 2019 grow- ing season. The participant had requested quotations for different systems per PA appli- cation. It struck me that each quotation con- tained a terminal, which was said to be re- quired to make the application work. Though I knew the SBG/Raven GPS autosteer terminals


on the farm do not support ISOBUS, buying a separate terminal for each application did not feel right.


One cable could be all you need We discussed the new tractor the participant had just bought. Built in 2018, surely this trac- tor must be ISOBUS compatible. A call to the local dealer uncovered that there were already two ISOBUS tractors on the farm. All we had to do was get the RTK-corrected GPS location from the SBG/Raven autosteer terminal to the integrated ISOBUS terminals. We quickly found


▶ FUTURE FARMING | 22 February 2019


that a simple cable was all that was needed to make this happen. Unfortunately, not all ISO- BUS terminals support variable rate applica- tions, so our next step is to find out if the ISO- BUS terminals integrated in the two tractors on the farm do.


Why more than one terminal? I understand that each manufacturer prefers to use his terminal for a PA application. Hav- ing designed and tested the terminal, the company can be sure the system works. How- ever, this also increases the investment


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