Precision FarmingIncrease prof­itability while reducing nitrogen use

The goals of the trial were to opti­mise NUE, improve appli­ca­tion timing, under­stand the appli­ca­tion of the John Deere HarvestLab sensing tech­nology and increase prof­itability. But why is opti­mising nitrogen use so impor­tant? “Nitrogen fertil­i­sa­tion accounts for 20-40% of crop produc­tion costs,” explains Dr David Purdy, Terri­tory Busi­ness Manager at John Deere UK. “If there is too much nitrogen left in the soil, it might lead to lodging and harvesting prob­lems, as well as losses in soil carbon due to the rela­tion­ship between carbon and nitrogen. Further­more, excess nitrogen can leach through the soil profile to the envi­ron­ment in different forms, for example, as nitrous oxide (N₂O) or nitrates, which can be harmful.” Finally, farmers might be pros­e­cuted for envi­ron­mental pollu­tion in some circum­stances.

Team and method

NUE measures how well a crop uses nitrogen. It compares how much nitrogen the plant takes up (the output) to how much nitrogen was avail­able to it (the input – what was already in the soil or applied through fertiliser). 

With help from Carl Pitelen, Inno­va­tions Manager at the John Deere dealer Ben Burgess, Norfolk farmer James Goodley began setting up the first test site during the 2022/23 growing season. The trial is now in its third year, with two further fields selected during the 2024/25 season. The first field, called ‘Tivans’ was ploughed and drilled with a power harrow, while the second field, called ‘Foot­path’ was direct drilled without tillage. Both fields have sandy loam soil and were sown with wheat.

---

---

The FINE exper­i­mental design was devel­oped by Clive Blacker and Joe Walters, both from the project partner Data­Baler. “The project is supported by Inno­vate UK,” says David. “When applying nitrogen, they look at the crop growth stage and soil condi­tions, with a special focus on soil mois­ture. Inte­grating this approach into the field trials has been very helpful for us.”

Impor­tantly, each of the treat­ments was repli­cated and randomised three times. Data to esti­mate the NUE was mainly gath­ered by drone flights, the John Deere HarvestLab near infra-red (NIR)sensor mounted to the combine, a Soil Plant Analysis Devel­op­ment (SPAD) measuring device and soil samples, as well as manual measure­ments like plant counts.

The results

For the analysis, nitrogen input and output data were uploaded into the Agronomy Analyser. This is a tool that allows geo-fenced plots to be created in a way that all inputs and outputs are precisely collected, avoiding the need for specialist trials equip­ment like a plot combine. This soft­ware tool was devel­oped by John Deere and is used locally by Ben Burgess while lever­aging the existing tech­nology and machinery avail­able on the farm.

The average yield of the ‘Foot­path’ field (7.43t/ha), which was not tilled, was about 6% higher than the culti­vated ‘Tivans’ field (7.02t/ha) despite the 207kg/ha fertiliser appli­ca­tion to ‘Foot­path’ being almost 11% lower than to the 232kg/ha applied to ‘Tivans’. At the same time, the measured nitrogen supply from the soil was 56kg/ha for ‘Tivans’ compared to 71kg/ha for ‘Foot­path’.

Looking at the yields of the different trial set-ups, unsur­pris­ingly, the yields were lowest in the zero-nitrogen fertiliser plots, deliv­ering 4.70t/ha in ‘Tivans’ and 4.93t/ha in ‘Foot­path’. In both fields the FINE treat­ment, with specific nitrogen appli­ca­tion timing, deliv­ered the highest yields (7.93t/ha in ‘Tivans’ and 8.67t/ha in ‘Foot­path’).

The second highest yields occurred in the 220kg/ha N-treat­ment plots (7.65t/ha in ‘Tivans’ and 8.08t/ha in ‘Foot­path’). In the plots which received both 160kg/ha N and the micronu­trient package, there were higher yields in both fields (7.47t/ha vs. 7.72t/ha for ‘Tivans’ and 7.58t/ha vs. 8.01t/ha for ‘Foot­path’). When it comes to crude protein content, it increased with the amount of nitrogen applied in both fields, as well as with the micronu­trient package. However, in the FINE plot, it was slightly higher in the ‘Tivans’ field than in the ‘Foot­path’ field.

The crude protein content was lowest at the zero nitrogen control trails with only 9.5% in the ‘Tivans’ as well as in the ‘Foot­path’ field. This highest crude protein content with over 12% was measured under the high nitrogen fertil­i­sa­tion regimes at 220kg/ha respec­tively the FINE treat­ment. The results were similar in both fields. A medium crude protein content of around 10.5% was measured at the 160kg/ha N treat­ment vari­ants. Also in this setting results were very similar in both fields.

---

---

The economic perspec­tive

However, what really counts for the farmer is the net profit. “We are looking for an economic optimum,” explains Carl. The wheat price was at £160/t (€182/t) and the nitrogen cost at £360/t (€410/t). To get an idea of the appli­ca­tion which delivers the best economic outcome, the margin over nitrogen costs is calcu­lated, comprising the revenue from grain sales minus the cost of the nitrogen fertiliser. Here, the 160kg/ha N plus micronu­tri­ents package and the FINE appli­ca­tion in the ‘Foot­path’ field stood out.

---

---

Nitrogen effi­ciency (NUE)

To build confi­dence in the accu­racy of John Deere’s tech­nology, measure­ments from an on-board as well as a stationary turn table HarvestLab NIR-sensor were compared with lab results obtained from industry-stan­dard devices “We have run linear regres­sion analysis on the data and found strong corre­la­tions between HarvestLab read­ings and lab results, showing that HarvestLab delivers reli­able, real-time protein measure­ment,” says David. “This makes it a valu­able tool for preci­sion nitrogen manage­ment as well as for the segre­ga­tion of milling wheat loads, which can earn the farmer a premium of £20–£50/t,” he explains.

---

---

But coming back to effi­ciency; as expected, the highest NUE at over 100% was observed in the plots which didn’t receive any fertiliser, because addi­tional soil nitrogen is mobilised during the growing season. However, this method also delivers the lowest economic results and removes nitrogen from the field, thus depleting the soil nitrogen stock in the long run. As with the economic assess­ment, the plots with 160kg/ha of nitrogen plus micronu­tri­ents proved to be partic­u­larly effi­cient in util­ising the nitrogen provided. A possible expla­na­tion is the role of molyb­denum for nitrogen manage­ment in the plant. A similar NUE can be achieved by the FINE set-up.

“Obvi­ously, not applying nitrogen does not make sense for the farmer, but if we use nitrogen intel­li­gently, as our calcu­la­tions show, farmers can achieve consid­er­ably higher profit margins,” says David.