Research partnership explores growing onions with aeroponics

What are the current issues with growing onions? 

Onions are a staple crop in the UK and around the world, with over 100M tonnes produced each year. There are three key challenges with growing onions in the UK and globally: disease, seasonality, and storage. 

Onions can only be grown over the spring and summer months, since light levels are important to their development. They are sown outdoors around March and typically begin to bulb after the summer solstice. So with conventional methods, you are limited to one crop per year - but of course the demand for onions remains all year round. This means that often onions are imported from as far away as New Zealand, resulting in high food miles, a larger carbon footprint, and increased costs. To extend the UK season, onions are kept in cold stores and can be held for up to 10 months. This demands a huge amount of energy and often the quality of the onions can suffer, leading to further waste when onions are sorted.

Another issue with growing is the prominence of soil-borne diseases. Fusarium, a type of rot, can cause losses of up to 40% in the UK. This not only results in food waste, but waste of growing resources and profit losses for the grower. 

How could controlled environment agriculture (CEA) help? 

By growing onions from seed to bulb in a controlled indoor environment, there is the potential to quadruple the number of crops in a year in the UK. In trials conducted at the University of Essex, Professor Tracy Lawson and the team are aiming to reduce the overall carbon footprint of growing, remove the need for storage, increase the speed of growth and grow a consistent quality product. 

Onions are being grown in an indoor environment, using LettUs Grow’s aeroponic irrigation systems. In an aeroponic system, onions are growing without soil. Instead, roots are suspended in air and nutrients are delivered through a mist that is generated using ultrasonic technology. This method boosts access to oxygen, which promotes root zone strength and growth, but crucially the lack of soil here reduces the risk of soil-borne disease in the early and vulnerable stages of growth. 

The academic team has been recording crop growth, climate parameters and energy consumption data - and so far, the results are promising. Jonathan Bell, Operations Manager at Stourgarden, said, “we have successfully grown onions to a stage where the first signs of bulbing can be seen. The aim of the project is to investigate how CEA can play a part in the supply of onions to UK consumers. To wholly replace traditional field production is not the aim, but there is a role for CEA to play in improving current growing and supply.”  

Nick Green, Head of Commercial at LettUs Grow, said, “it’s really exciting to see our innovative aeroponic technology support traditional growing methods. This is an excellent example of how partnerships across agricultural sectors can benefit sustainable food production in the UK and we’re so proud to be working with the industry and research experts at both Stourgarden and the University of Essex.” 

This project is jointly funded by Stourgarden, Innovate UK and Biotechnology & Biological Sciences Research Council in a partnership between University of Essex and Stourgarden. You can read the original partnership announcement here.  

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