Growing organic onions can be challenging. Manual weeding can take hours and still leave growers struggling to stay ahead of weed pressure. The result is often fewer marketable onions and lower overall yield.
That is exactly why more onion growers are turning to FarmDroid. Our solar-powered field robot combines 8 mm ultra-precise seeding with fully automated mechanical weeding in one system. Today, FarmDroid operates on around 600 hectares of onions worldwide.
Germany is seeing a rapid increase in FarmDroid adoption, especially among organic growers and producers aiming to reduce labor inputs. In Northern Germany, robots are commonly configured with row spacings of 22.5, 25, 30, 40, 45 and 50 cm, depending on farmer’s needs. Kevin Mischker, from one of our German partners Solar-Energie Andresen GmbH, reports that growers in his region are often experiencing higher yields when using FarmDroid cultivation methods.
So, what makes FarmDroid especially suited for onion production?
Group seeding onions
One of the most impactful innovations in onions is group seeding. Instead of placing single seeds, FarmDroid places several seeds in one precise spot, forming a compact onion cluster. The purpose of group seeding is not primarily to increase yield per hectare. It is to enable efficient and precise in-row mechanical weeding. By clearly defining each cluster position during sowing, the robot can later weed both between rows and between the plants in-row. This increases weeding efficiency compared to systems that only weed between rows.
Getting started with group seeding requires some consideration and setup, but once the robot is configured, it handles both seeding and weeding with consistent precision.
Defining the right cluster setup for seeding onion clusters
Before starting to seed onion clusters, growers must define number of seeds per cluster as well as the distance between clusters. These two parameters will then play a role in determining the correct seed disc for FarmDroid.
Cluster size
Choosing the right number of seeds per cluster is a balancing act. Too few seeds naturally reduce yield potential and could potentially produce onions that are too big. However, too many seeds can result in smaller onions that are harder to market.
Field experience in Northern Germany shows that 7 to 9 seeds per cluster delivers strong results, with many growers leaning toward 9 seeds per group. This setup has often been linked to higher yields in FarmDroid-based systems.
It’s important to note that clusters will not always contain exactly the same number of seeds due to many variations in seed sizes and thousand-kernel weight (TKW), which affect how seeds pass through the seed disc. The goal is not identical clusters, but a stable and reliable average. This is why seed testing and proper disc calibration are essential.
When choosing cluster size, it is essential to match the desired plant density. Plant density influences crop development, disease pressure and final yield.
Cluster-to-cluster distance
When seeding onions in clusters, we typically recommend group-to-group distance in onions to be between 15 and 25 cm. This allows the robot enough space to mechanically weed between each group without compromising density.
Spacing beyond 25 cm increases the number of seeds needed per cluster to get beyond 10 seeds. Going below 15 cm slows the robot down and reduces its capacity. The best practice is typically between 16 and 18 cm. This spacing allows efficient in-row mechanical weeding while maintaining optimal density.
In 2025, the average spacing between onion clusters in Northern Germany was 182 mm, with an average of 8 seeds per cluster. The image below shows the practical field result of a disc calibrated to achieve an average of 9 onion seeds per cluster with a 16 cm cluster-to-cluster distance.
Choosing the right seed disc
After the cluster size and cluster-to-cluster distance have been determined, the next step is choosing the correct seed disc type for the crop. The seed disc is never standard, especially for onion crops. It is always adapted specifically to:
− Thousand-kernel weight (TKW)
− Onion variety
− Desired seeding cluster size
− Desired cluster-to-cluster distance
These factors will change the number of holes in the disc, as well as their diameter and thickness. Because there are many factors that play a role in the decision, we provide an easy process to find the right seed disc type, so our growers are never in doubt:
- The grower sends seed samples to FarmDroid.
- We at FarmDroid test and identify the optimal seed disc type for the specific seeds sent to us.
- The grower receives tailored recommendations for disc type and robot settings.
Weeding mechanically even before emergence
Once seeding is completed, FarmDroid can begin mechanical weeding immediately between the rows, without waiting for the crop to emerge. Later, in-row mechanical weeding can be applied to weed between the plants.
Because the robot knows the exact GPS position of every seed it has sown, it can work close to the crop without causing damage and without relying on camera systems to identify weeds.
By enabling early and repeated mechanical weed control, FarmDroid helps maintain low weed pressure during the initial growth stages, when onions are most sensitive, and can reduce the reliance on manual hand weeding.
Preventing soil crusting and supporting root growth
Onions are sensitive to soil crusting. During emergence, the seedlings are thin and do not generate enough force to break through a hardened soil surface. The crusted soil also reduces water and oxygen transfer to the roots. This usually means lost plants, uneven or delayed growth.
By mechanically weeding and loosening the soil surface in the process, FarmDroid helps prevent crust formation. This improves water uptake and increases oxygen availability in the root zone, supporting stronger early root development.
With a total weight of around 1000 kg, FarmDroid also minimizes soil compaction compared to conventional tractor-based systems.
Typical FarmDroid configurations for onions
Across our onion growers, we see the following two FarmDroid robot configurations being used the most:
- Passive Front Wheel, 8 rows, 25-50 cm row spacing, 300 cm working width, 160 cm wheel spacing
This FarmDroid configuration is commonly used by many organic growers. Our partner Solar-Energie Andresen has seen strong results with this setup, and several new customers have followed their recommendation when choosing their configuration.
It is not a traditional onion bed system, but the wider layout allows improved airflow through the field, which can help prevent fungus.
- Active Front Wheel, 7 rows, 25 cm row spacing, 200 cm working width, 200 cm wheel spacing
This FarmDroid configuration is based on how conventional onion growers usually set up their bed systems, which are also adapted by some organic growers. The bed setup allows traditional harvesting equipment to be used easily.
With FarmDroid, row spacing and seed distance can be adapted to match almost any field setup. Use our online FarmDroid Configurator to design a FarmDroid that fits your specific bed system and row spacing with almost any cluster-to-cluster distance you want.
Acknowledgements
Thanks to Kevin Mischker from Solar-Energie Andresen GmbH for collaborating with us on this article and sharing insights on growing onions with FarmDroid in Northern Germany.