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Visual yield measurement of seed potatoes works

09-02-2022 | |
Harvesting of seed potatoes in the Netherlands (Noordoostpolder). - Photo: Henk Riswick
Harvesting of seed potatoes in the Netherlands (Noordoostpolder). - Photo: Henk Riswick

Automated site-specific visual yield measurement of seed potatoes works. This is evident after completion of a three-year trial in the Netherlands.

Seed potato grower Henk Geerligs in Anna Paulowna (the Netherlands) is excited about the possibilities of visual yield measurement on his potato harvester. The most recent version of the detection system was tested at his farm during harvest last year. Researchers at Wageningen University & Research are still busy processing all the data, but as far as Geerligs is concerned the results show that the prototype has a lot of potential.

Revenue model

Geerligs says he already sees a revenue model. “Let’s suppose such a system comes onto the market for, say, € 20,000. If I can optimise my cultivation with it, I will have earned that investment back in a few years.” He calculates: “One daughter tuber extra per meter of potato ridge, gives me € 250 per hectare. However, at the moment I don’t know what cultivation decisions I have to make to get those extra tubers. By doing simple practical trials with planting distance, fertilisation and seed treatment and then registering the yield during harvesting, I hope to find out,” says Geerligs.

However perfect and site-specific yield measurement may be, it is not possible to immediately attach a revenue model in the sense of costs and direct benefits.

Looking at instead of weighing

At seed potato farms in Anna Paulowna and Wieringerwerf, research into visual yield measurement of potato yields ran in 2019, 2020 and 2021. “Visual” means acutally looking at how many potatoes are being harvested by the machine, instead of weighing them. And this is then done site-specifically, so that ultimately it is known exactly how many potatoes have grown at which location in the field. The latter is important to know which of Geerligs’ cultivation decisions produce extra tubers and which do not.

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Koen van Boheemen, precision farming expert of  Wageningen University & Research:
Koen van Boheemen, precision farming expert of Wageningen University & Research: "If you mount a device like this onto your harvester, you don't immediately start making more money. But it does give a precise indication of the effect of the variations you apply to your crop." - Photo: Jan Willem Schouten

Crop optimisation

The recent completion of the trials are certainly a step forward when it comes to cultivation optimisation. The objective of the project was to develop a system for very accurate determination of the net yield, tare and size distribution of harvested potatoes, more specifically seed potatoes. By now, there is a well-functioning prototype. Now, in the first months of 2022, the research project group is going to look at what steps to take next. Koen van Boheemen: “Maybe there will be a follow-up project. In any case, we want it to be put into practice and not remain on the shelf. It is not self-evident that a machine builder can immediately get to work with commercial kits. What we do know is that the visual yield determination on the DeWulf harvester from Geerligs works reliably. But that is just one machine. We need to know how it performs on other harvesters before we move towards commercialisation.”

The fact that visual yield measurement appears to be a promising technique for perfecting the cultivation of seed potatoes does not really come as a surprise, by the way. Van Boheemen already concluded after the first field experiments this technology is possible and has potential. Now, after harvest 2021, he is even more convinced. “We have now run the data from Henk Geerligs and we are tremendously close to the truth.”

Each tuber is recognized

The most important component in this project is the 3D camera hanging above the reading belt of the potato harvester, which recognises each tuber individually and can reliably measure its size. In this way, data is collected regarding the net yield, the number of tubers and size of the harvested potatoes. With this data, growers not only receive information about the harvested potatoes in general, but via the GPS on the harvester also about where exactly they were grown. This creates a yield map of the field with a grid of 1.5 x 1.5 meters for a two-row harvester, or 3 x 3 meters for a four-row harvester.

Compared to weighing with load cells, visual yield measurement has advantages. For instance, the camera distinguishes potatoes from tare, which can expecialliy be of great advantage of clay soils. Moreover, with visual yield measurement you get a clear picture of the grading. This is particularly important for seed potatoes, since the exact number of tubers in the various sizes is more important than the absolute yield in kilograms. Precision farming technologies for seed potatoes are primarily aimed at getting as many kilos as possible in the more expensive seed potato sizes.

Yield measurement with weighing cells on the harvester does give an immediate indication of how many tons of potatoes go over the harvester. In situations where the soil tare percentage is fairly constant – on sandy soils it is virtually non-existent – site-specific weighing gives a good idea of the yield variation in a field. With visual yield measurement, the kilogram yield must be calculated afterwards. Although this could also be done in real time.

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Tholhuijsen
Leo Tholhuijsen Arable writer
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