Optimise your yield
Potato trials are notoriously difficult to conduct, and results often vary considerably from year to year — depending on weather, variety, infection pressure and location. It is therefore difficult to draw general conclusions from a single trial.
To make a more robust statement about the relationship between blight attack and yield loss, researchers from the Department of Agroecology, Aarhus University, pooled data across 18 trials including all treatments and replicates. The graph below shows what this combined dataset reveals: there is a clear and consistent relationship between disease level measured as AUDPC (area under the disease curve) up to one month before harvest and the final starch yield (hkg/ha).
The higher the disease level — the lower the yield. And the curve is steep at the start: even relatively low levels of attack cost measurable yield. This underlines that effective and timely control pays off — not only to avoid major losses, but also to protect the full yield potential.
Source: Bent J. Nielsen & Niels Holst, Department of Agroecology, Aarhus University, Potato Workshop December 2017.
Based on the 18 trials, it is possible to calculate a theoretical curve showing the expected starch yield as a function of blight attack level in late August. The curve provides a concrete answer to what even a moderate attack level actually costs in monetary terms per hectare.
With a current starch price of 0.70 EUR/kg starch, the relationship becomes clear: even a relatively modest attack of 5% blight can reduce the yield by up to 7 hkg starch per hectare — equivalent to a loss of just under 489 EUR/ha. This underlines that precise and timely treatment is not just about avoiding the major attacks — every percentage point of blight prevented pays off directly on the bottom line.
Source: Bent J. Nielsen & Niels Holst, Department of Agroecology, Aarhus University, Potato Workshop December 2017. Starch price: 0.70 EUR/kg starch.
Key figures from the trials
- Each week blight can be delayed gives an additional yield of approx. 5 hkg starch per hectare — equivalent to 349 EUR/ha at a starch price of 0.70 EUR/kg.
- In late August the relationship is direct: for each percentage point of potato blight, a corresponding 1% loss in starch yield occurs.
What can a Danfoil sprayer do for your bottom line?
As the trials below show, Danfoil’s air-assisted technology can typically delay blight attack by one week and reduce attack level at the end of August by 5–10 percentage points compared to conventional spraying. Converted to monetary terms this equals:
- One week delay of attack: ~349 EUR/ha
- 5–10% less blight in late August: ~489 – 977 EUR/ha
For a farm with 100 ha of potatoes this means a potential extra yield of 34,900 – 97,700 EUR per year — not by using more active substance, but solely by utilising it better with Danfoil’s application technology.
Switching from conventional to Danfoil air-assisted spraying pays for itself quickly.
Late blight can be treated more effectively with air assistance
When controlling late blight, timely and preventive treatment is crucial to protect the leaves before infestation develops. Effective spraying is therefore about getting the crop protection evenly distributed on the leaves throughout the crop so that each treatment is optimally utilized. Air assistance can improve leaf coverage, even at lower water volumes, because the airflow causes the leaves to move during spraying, so that leaves that are otherwise covered by other leaves are also hit by the spray. With conventional spraying, leaves that are covered during treatment can later be exposed when the crop moves in the wind, leaving them unprotected. In the National Trials 2025, air spraying at 50 l/ha is compared with hydraulic spraying at 250 l/ha, where there is a clear difference in the development of mold.
Development of late blight in 2025
50% dose
100% dose
Important: The experiment documents a statistically significant reduction in mold infestation with air spraying – and shows that air assistance provides a more effective treatment in potatoes.
The trials show that air-assist consistently reduces the development of late blight compared to conventional spraying. At full dose, only 2% mold was seen with air-assisted spraying compared to 6% with hydraulic spraying, corresponding to approximately 65% lower residual infestation, and the same trend is seen at reduced dose. The results document that air-assist provides more effect per liter of spray liquid and thus a stronger and more robust protection throughout the season.
| Spraying technique | Dosage | Leaf mold, % | Starch, % | hkg tubers | hkg starch | DKK/ha |
|---|---|---|---|---|---|---|
| 1. Untreated | 97 | 20,6 | 453 | -42 | -21.944 | |
| 2. Hydraulic sprayer | 100% | 6 | 22,7 | 146 | 136 | 70.512 |
| 3. Hydraulic sprayer | 50% | 62 | 22,0 | 113 | -11 | -5.720 |
| 4. Air Sprayer | 100% | 2 | 23,1 | 152 | 4 | 2.184 |
| 5. Air Sprayer | 50% | 40 | 22,5 | 124 | -6 | -2.964 |
Important: The report also mentions a trend toward higher yield.
Conclusion: The trial shows that better mold control can also be seen in the harvest yield. At full dosage, 152 hkg of tubers per hectare were harvested with an air sprayer compared to 146 hkg with a conventional sprayer, with a slightly higher starch content. This corresponds to an additional yield of approximately 4 hkg per hectare, which in the trial yields around DKK 2,000 extra per hectare (≈ 270 € per hectare). In short: better coverage means that a larger proportion of your treatments end up as more yield and better economics on the bottom line.
Development of late blight in 2022
50% dose
100% dose
Conclusion (2022): Both trials show the same picture: air assistance consistently results in lower mold than conventional hydraulic spraying – both at 50% dose and 100% dose. It is particularly worth noting that a 50% dose with air can in practice be lower than a 100% dose with conventional technology. In other words: you get more effect per treatment, stronger protection, and a setup that can help you achieve your goal with less input.
| Spraying technique | hkg tubers per ha | hkg starch per ha |
|---|---|---|
| Hydraulic sprayer 100% | 592,5 | 123,2 |
| Hydraulic sprayer 50% | -45,8 | -10,4 |
| Air Sprayer 100% | 3,3 | 0,7 |
| Air Sprayer 50% | -23,4 | -1,5 |
Conclusion: When you combine air assistance with a more targeted application, you can, in practice, achieve results that are close to what you would normally expect from a 100% dose with conventional spraying—even at a reduced dose. That is precisely the kind of robustness that delivers value in the field: more “punch” per liter, greater coverage reliability, and the ability to maintain performance levels when you want to optimize consumption, logistics, and capacity.
More impact from crop protection
More value per hectare
More profit per hectare
What does this mean in practice?
By switching to aerial spraying, you can reduce environmental impact, get more out of crop protection and increase yields per hectare. Lower water volume also means higher capacity and fewer fillings, contributing to a more efficient operation and a better bottom line economy.
Glyphosate for desiccation of grass seed crops — Danfoil utilises the active substance more effectively
Grass seed growers have long experienced that glyphosate for desiccation works better with air-assisted sprayers. In autumn 2021, VKST Planteavl — with support from Søgaard Fonden and in collaboration with farmer Lars Andersen, Haslev — conducted two independent field trials to investigate this systematically. The trials compared four spray techniques in red fescue and tall fescue respectively. The results confirm practical experience and document that the Danfoil air sprayer delivers significantly better desiccation — and opens the possibility of saving up to 50% glyphosate compared to conventional spraying.
Best in test
Half dose — same effect
Low water volume — high capacity
Trial conclusion: “It is possible to save glyphosate when desiccating red fescue with an air sprayer. 360 g/ha with Danfoil delivers the same desiccation effect as 720 g/ha with conventional technology.” — Christian Rabølle, machinery consultant, VKST Planteavl. Magasinet Mark, February 2022.
About the trial
The trials had eight treatments with four replicates, and covered doses of 360 and 720 g glyphosate per ha — well below normal practice of 1,080–1,440 g/ha (3–4 litres of 360 g/l product) — specifically to make differences in spray technique visible. Danfoil operated at 40 l/ha and 15 mbar air pressure. The conventional treatments used 120–240 l/ha. Desiccation was assessed manually and by NDVI reflectance measurement three and seven weeks after treatment. The trials were also overflown with a drone, where the effect of the Danfoil treatment was already clearly visible three weeks after spraying.
In red fescue — the most difficult species to cover, with thin round leaves — the difference was most pronounced. Danfoil with low dose (360 g/ha) was statistically significantly above all conventional treatments with low dose, and on a par with conventional treatments at full dose. Twin air assistance (Hardi LD02) showed no statistically significant difference from conventional spraying — it is Danfoil’s specific application technique that makes the difference.
What does this mean in practice?
With a Danfoil air sprayer you can desiccate grass seed crops with half as much glyphosate and still achieve effective desiccation. Combined with a water volume of only 40 l/ha, you get a spray capacity that is hard to match with conventional technology. For larger grass seed producers, the investment in a Danfoil air sprayer can quickly pay for itself through reduced chemical costs, lower water volume and higher daily capacity.
Source: VKST Planteavl, machinery consultant Christian Rabølle. Trials conducted in autumn 2021 with support from Søgaard Fonden. Published in Magasinet Mark, February 2022.
Scientific documentation: lower water volume significantly increases efficacy
The Danish field trials are supported by independent international research. A field study from North Dakota State University (Ramsdale, Messersmith & Nalewaja, Weed Technology 2003) systematically documented what happens when water volume is reduced from 190 to 23 l/ha in glyphosate treatment: efficacy almost doubles, and doses can be reduced by at least one third and still achieve the same effect. The graph below is reconstructed from the regression equations in the trial and shows control rate (%) as a function of glyphosate dose at four water volumes.
Trial conclusion: Applying 23–47 l/ha (Danfoil) almost doubles efficacy compared to 190 l/ha at the same dose. Alternatively, the glyphosate dose can be reduced by at least ⅓ and achieve the same level of control. This applies regardless of nozzle choice and is confirmed across four trial species and three years.
Source: Ramsdale BK, Messersmith CG, Nalewaja JD. “Spray Volume, Formulation, Ammonium Sulfate, and Nozzle Effects on Glyphosate Efficacy.” Weed Technology 17(3):589–598. 2003.
Spray capacity – low water volume delivers massive gains
Timeliness is one of the most important factors for achieving good efficacy in crop protection. But weather is often a constraint: windy conditions significantly reduce the number of possible spraying hours, particularly during busy periods such as spring and autumn. A model calculation conducted by Aarhus University in collaboration with Danfoil documents that the single most effective way to increase spray capacity is to reduce the water volume — exactly what the Danfoil air sprayer is designed for.
+55% capacity
−26% costs
+77% capacity
Model calculation: effect of four parameters on capacity and economy
The calculation was performed on a specific larger farm with 1,562 ha (640 ha potatoes, 135 ha grass seed, 787 ha cash crops). The baseline is a conventional sprayer with a 4,000 l tank, 36 m boom, 200 l/ha and 8 km/h. The table shows the percentage change for each measure.
| Comparison scenarios | ★ Danfoil scenarios | |||
|---|---|---|---|---|
| Parameter | Larger tank 4,000 → 12,000 l |
Higher speed 8 → 14 km/h |
Low water volume 200 → 50 l/ha |
Tank + low water combined |
| Spray capacity | +47% | +11% | +55% | +77% |
| CO₂ emissions | +18% | — | −29% | +2% |
| Road transport time | −56% | 0 | −62% | −76% |
| Total costs incl. depreciation |
−6% | −9% | −26% | −10% |
| Total time consumption | −32% | −10% | −36% | −44% |
| Investment in new sprayer 1) | +208% | 0 | +130% | +260% |
1) Percentage increase in sprayer acquisition cost compared to baseline (4,000 l / conventional). Green = improvement, yellow = higher investment.
Konklusion: Reducing water volume from 200 to 50 l/ha increases capacity by 55% and reduces total operating costs by 26%. This is precisely the water volume a Danfoil air sprayer works with — and the gain is achieved without compromising treatment efficacy.
Source: SEGES Innovation & Aarhus University. “Maximum effect and minimal drift with air sprayers”, version 2, November 2024. Model calculation conducted by Aarhus University, Department of Electrical and Computer Engineering.
Fungicide application in wheat – more crop yield with 5× less water
In 2013, Danfoil participated in the National Trials (Series 090891313) with the aim of highlighting the effect of fungicide spraying with low water volume using the Danfoil sprayer compared to conventional spraying technique. The trial was conducted in wheat, variety Hereford, and the fungicide Bell (0.3 l/ha) was applied twice – at growth stages 39 and 55–61. Both technologies used identical dosage and timing; only water volume and sprayer type varied. The trial was conducted with a 24-meter Danfoil trailed sprayer and a conventional 24-meter trailed sprayer.
The yield measurement shows a clear conclusion: The Danfoil sprayer achieved an additional yield of 4.7 hkg/ha with only 40 l/ha of water – compared to 3.3 hkg/ha with a conventional sprayer at 200 l/ha. This corresponds to a 42% higher additional yield with Danfoil, even though the water amount is five times lower.
+4.7 hkg/ha
+1.4 hkg more than conventional
5× lower water volume
Effect of different water volumes with different spraying techniques
Source: Field Trials 2013, Series 090891313. Wheat, variety Hereford. Bell 0.3 l/ha at growth stage 39 and 55–61. Harvested August 26, 2013.
| Sprayer type | Water volume | Yield (hkg/ha) | Additional yield (hkg/ha) |
|---|---|---|---|
| Untreated | — | 83,7 | — |
| Conventional sprayer | 200 l/ha | 87,0 | +3,3 |
| Conventional sprayer | 150 l/ha | 86,8 | +3,1 |
| Danfoil air-assisted sprayer | 40 l/ha | 88,4 | +4,7 |
Konklusion: "With a Danfoil sprayer, it is possible to achieve a higher effect with 40 l/ha in the form of an additional yield of 1.4 hkg, compared to a conventional sprayer with 200 l/ha. Therefore, the water volume has no impact on fungal disease control when comparing Danfoil's spraying technology with the conventional."
Source: Field Trials 2013, Series 090891313. Danish Agricultural Advisory Service. Test crop: wheat, variety Hereford. Sprayed June 4 and June 17, 2013. Harvested August 26, 2013.
Spraying technique in potatoes – Danfoil ensures best coverage in the middle of the top
In July 2007, the Danish Agricultural Advisory Service, National Centre, conducted a FarmTest (no. 84) with the aim of highlighting which spraying techniques ensure the best and most uniform deposition at the top and middle of potato tops. Uniform coverage of all leaves is crucial for effective control of potato blight, as the agents predominantly have contact action. Three sprayer types were included in the study: a traditional field sprayer (Hardi) with four nozzle types, an air-assisted Hardi TWIN, and a Danfoil ConCorde air-assisted sprayer.
The deposition was measured using the tracer sodium fluorescein washed off from leaves taken from the top and middle of the potato top. The results are converted to µl/m² leaf area normalized to 1 liter of substance per ha, so the three sprayer types' very different water volumes (50–200 l/ha) can be directly compared.
Greatest deposition in the middle of the top
50 l/ha
Good coverage at the top and middle
Deposition on potato canopy – 1 liter applied per ha
Source: FarmTest no. 84, 2007. Measured at 2–3 m/s wind, average of six measurements per treatment. Tracer deposition normalized to 1 l/ha for direct comparison across water volumes.
Summary of results
| Sprayer type | Water volume | Deposition at the top | Deposition in the middle |
|---|---|---|---|
| Traditional sprayer (flat fan nozzle) | 200 l/ha | Moderate | Low |
| Traditional sprayer (twin flat fan air induction nozzle) | 200 l/ha | Good | Low |
| Hardi TWIN air assistance | 120 l/ha | Good | Moderate |
| Danfoil air-assisted sprayer | 50 l/ha | Good | Best |
Konklusion: Air assistance and air-assisted sprayer provide increased deposition at the top of the potato canopy compared to traditional sprayer. The Danfoil sprayer provides significantly the highest deposition in the middle of the potato canopy – achieving this with only 50 l/ha compared to 200 l/ha for a conventional field sprayer. No increased deposition is observed by increasing the water volume beyond 50 l/ha for Danfoil, 120 l/ha for Hardi TWIN, or 200 l/ha for conventional sprayer.
Bemærk: There is great variation in the measurements in the trial, and it is not possible to distinguish the techniques with statistical certainty. However, the results consistently point in the same direction.
Source: FarmTest no. 84, 2007. "Spraying Technique in Potatoes." Niels Enggaard Klausen & Hans Henrik Pedersen, Danish Agricultural Advisory Service, National Centre, Crop Production / AgroTech. ISSN: 1601-6777.
Desiccation of potatoes – dramatic difference on the lower leaves
Trials from the State Plant Breeding Institute, Flakkebjerg (Ole Permin, 1991), document the desiccation effect of Reglone (diquat) in potatoes with Danfoil air-assisted sprayer (30 l/ha) compared to hydraulic sprayer (270 l/ha). Desiccation is measured in percent coverage distributed over four plant zones: lower and upper leaves as well as lower and upper stems. Effective desiccation of the lower parts of the plant is crucial to stop potato blight and reduce the risk of tuber infection.
Danfoil achieves statistically significantly better desiccation on the lower parts of the plant – and this with only one-ninth of the water volume.
83% vs. 22%
30 vs. 270 l/ha
Good coverage everywhere
Desiccation of potatoes – % coverage per plant zone
Konklusion: Danfoil air-assisted sprayer with 30 l/ha achieves significantly better desiccation of potatoes than hydraulic sprayer with 270 l/ha – especially on the lower leaves and stems, which are hardest to reach with conventional spraying technique. The lower water volume and air assistance ensure effective penetration into the crop.
Source: Ole Permin, State Plant Research, Flakkebjerg. Published: 8th Danish Plant Protection Conference 1991. Values read from diagram in source material.
Deposition in winter wheat – Danfoil utilizes the active ingredient better
Trials with winter wheat at stage 10 (ear protection) compare deposition of active ingredient on four successive leaves with traditional flat fan nozzle (nozzle no. 14, 150 l/ha, 3 bar) and Danfoil air-assisted sprayer (30 l/ha, 35 cm VS air pressure). Deposition is measured as µg active ingredient per leaf. Danfoil deposits about 75% of the sprayed amount directly on the plants compared to about 50% for traditional sprayer – thus achieving better coverage on all leaves with only one-fifth of the water volume.
75% vs. 50%
7.0 vs. 4.0 µg
30 vs. 150 l/ha
Deposition of active ingredient per leaf – winter wheat stage 10
Traditional nozzle: ~50% deposition on plants — the rest falls on the soil surface.
Danfoil: ~75% deposition on plants — significantly lower loss to soil.
Konklusion: Danfoil deposits approximately 75% of the active ingredient directly on the plants compared to about 50% with a traditional flat fan nozzle. With five times lower water volume (30 vs. 150 l/ha), better protection is achieved on all leaves – and with significantly reduced loss to the soil.
Source: Danfoil information folder. Deposition trials, winter wheat stage 10. Trad. flat fan nozzle no. 14 (150 l/ha, 3 bar) vs. Danfoil (30 l/ha, 35 cm VS). Values read from diagram in source material.
Powdery mildew in spring barley 1989 – Danfoil achieves better effect with reduced dose
In 1989, the State Plant Research conducted a trial with the control of powdery mildew (Blumeria graminis) in spring barley using the fungicide Tilt Top (propiconazole + fenpropimorph) in three dose levels: 0.60 l/ha, 0.30 l/ha, and 0.15 l/ha. Three sprayer types were included in the trial: Hardi hydraulic, Hardi Twin, and Danfoil air-assisted sprayer. Powdery mildew coverage (%) was recorded five times during the season from early June to mid-July. The trial is published in the 8th Danish Plant Protection Conference 1991.
The diagram below shows the progression for the lowest dose (0.15 l/ha), where the difference is statistically significant (LSD = 3.8) at the final recording on July 13.
Statistically significant
Dose reduction possible
Consistently better
Powdery mildew coverage (%) over the season – Tilt Top 0.15 l/ha
Konklusion: Danfoil provides statistically significant better powdery mildew control at the lowest dose (0.15 l/ha) compared to the hydraulic sprayer (LSD = 3.8). The results suggest that the dose can be halved with Danfoil without compromising control effectiveness – an important advantage for economy and environment.
Source: Experiment A, 1989. Tilt Top (propiconazole + fenpropimorph). State Plant Research. Published: 8th Danish Plant Protection Conference 1991. LSD value (July 13) = 3.8. Values read from diagram in source material.
Sugar beets – Danfoil provides up to 7× more droplets on the lower leaf surface
Experiment with deposition in sugar beets compares droplet deposition on the upper and lower leaf surfaces with hydraulic sprayer (nozzle 4110-14, 180 l/ha) and Danfoil air-assisted sprayer (40 l/ha). Deposition is measured as the number of droplets per cm² and average droplet size (mm) on the upper leaf surface and lower leaf surface, respectively.
Danfoil provides significantly better coverage on both sides – especially on the lower leaf surface, which is crucial for controlling aphids and fungi that thrive in the shelter of the lower leaf surface.
2.7× more droplets
6.7× more droplets
Finer droplets
Droplet deposition in sugar beets – droplets per cm²
| Droplet size | Hydraulic (4110-14) | Danfoil |
|---|---|---|
| Upper leaf surface – avg. diameter | 0,40 mm | 0,15 mm |
| Lower leaf surface – avg. diameter | 0,10 mm | 0,10 mm |
Konklusion: In sugar beets, the Danfoil air-assisted sprayer delivers 2.7 times more droplets on the upper leaf surface and 6.7 times more droplets on the lower leaf surface compared to a hydraulic sprayer – achieving this with 40 l/ha versus 180 l/ha. The significantly increased coverage of the lower leaf surface is particularly important for the control of aphids and fungal diseases.
Source: Danfoil information folder. Deposition trials in sugar beets. Hydraulic sprayer (nozzle 4110-14, 180 l/ha) vs. Danfoil (40 l/ha).