This case study focuses on improving onion quantity and quality throughout the onion supply chain of the Netherlands.

Over the last few years onion growers have been affected by serious quality issues, which is a growing concern for the whole supply chain. Approximately 85% of the Dutch produce is exported and this market expects optimal product quality, grown in a sustainable way.

'Read more' for further details on the case study, updates from the field trials, and the summary field trial leaflet on Onion neck rot:

Contact: Harm Brinks; This email address is being protected from spambots. You need JavaScript enabled to view it.

Location: Most of the onions are grown in the South West and centre of The Netherlands, although many stakeholders work nationwide
Main land use: arable and horticulture production
Stakeholders: growers, seed companies, packers, exporters, suppliers of fertilisers and pesticides, Onion Innovation Centre, extension service, experimental station and research
•    Key issues:
o    New sustainable crop management strategies are necessary to control the soil born fungi: Fusarium oxysporum, Sclerotium cepivorum and Ditylenchus dipsaci
o    Techniques to control air borne fungi (especially Botrytis spp.) during the growing season (Decision Support Systems) and intelligent storage strategies
o    Optimize nitrogen fertiliser strategies to avoid adverse effects on crop quality and reduce loss of nitrogen to the environment
o    Waste management, management of (infected) waste product that is generated during harvest, storage and handling

VALERIE themes covered:
1. Crop rotation, soil cover management and integrated pest management ►
3. The management of agricultural soils as integrated agro-ecological systems ►
5. Integrated supply chain services and tools, innovative farm management ►

Case study updates:
• A kickoff meeting with stakeholders was held in September 2014.  Issues were discussed and captured in a ‘structured vocabulary’ (an inventory of related terms linked together into a hierarchical structure).

• A second stakeholder meeting was held in mid-January 2015 with onion case study farmers, buyers, packers and traders/exporters. VALERIE was able to uniquely bring together members of the supply chain to exchange knowledge as well as solutions to problems. Priority for 2015 and a promising topic for the field trials, is the integrated control of the "multi factor" problem of Botrytis aclada (related to crop protection in the field, fertiliser strategies, storage strategies & product handling in the value chain).

• A stakeholder meeting will take place in winter 2015/2016 where the first results from ask-Valerie will be presented.

Field trials:
• Issue to be addressed in the field trials:
o    The effect of variety & harvest method has on Botrytis spp. during onion storage

• Stakeholders have participated in discussions developing the experimental design of the field trials. The experiment is located at the experimental station Rusthoeve, home to the UiKC (Onion Innovation Centre) in the South West of The Netherlands. The trial aims are:
o    To test the effect of variety and harvest method on the infestation of onions with Botrytis spp, causing rot during storage

• The trial started in spring 2015.

• On 27th of August 2015 the national ‘onion-day’ took place at the Onion Innovation Centre, station for applied research in Colijnsplaat, The Netherlands. The event was organised by UiKC and DLV Plant (now Delphy). Despite the heavy rain, about 2000 visitors comprising farmers and other representatives from the whole onion value chain attended. During the event, groups of farmers were taken on a guided tour of the VALERIE field trial, which was located at the site.


Field experiment - preventing neck rot infection:

• In The Netherlands it is normal practice to ‘top’ onions by chopping the leaves shortly before harvest. After harvest, the onions have a short drying period in the field before they are removed and stored. Scientific and grey literature, reviewed as part of the VALERIE project, indicated that leaf chopping is a potential infection route for the neck rot fungus; not chopping can have a positive effect with lower neck rot infestation rates. The VALERIE field experiment was set up to investigate this finding.

• Detailed objective:
o    To test the effect of leaf destruction methods on the neck rot infection rate in onion bulbs

Neck rot


• Field experiment details:
o    Two onion varieties; Delta Gigant and SV3557
o    Four treatments; standard practice, no leaf chopping, short leaf chopping; extra water after chopping
o    Four replicates of each treatment:
o    Nitrogen applied at the commercial rate of 146 kg N/ha

• The results from the 2016 field experiment indicated that there was no neck rot in the bulbs. This was typical for The Netherlands in 2016, due to extremely hot and dry weather and field conditions at harvest in September 2016.

Field trial


• In the subsequent case study meeting, it was decided to repeat the field experiment in 2017 using the same lay out and experimental design as in 2016.

• The field trial was featured in guided tours at the Dutch national 'onion-day' event, in both 2016 and 2017.


• The summary (including results) field trial leaflet, 'The use of leaf treatment on the infection rate of neck rot in Onions in The Netherlands' (English version) can be downloaded here