Future-proof lettuce cultivation: a shift towards hydroponics

Published on 20/07/2021

Cultivators continually conduct research and monitor developments in the industry. In the past weeks, we, as a group of students. Wageningen University conducted research on the range of lettuce under the supervision of Cultivators. For this research, we conducted interviews with stakeholders in the lettuce industry. They included growers, builders of hydroponic lettuce systems, financial institutions, retailers, and processors. Below, you will find a summary of our findings from the report.

Currently, the Netherlands is the world’s second-largest agricultural exporter by value. The Dutch agriculture industry must stay ahead because it has limited space for expansion in the Netherlands. This makes it a priority for them. Multiple crops, namely tomatoes, cucumbers, and peppers, have transitioned from soil-grown to hydroponic production. Lettuce is expected to be the next crop to follow.

Technological advancements

Several hydroponic systems have been developed. So far, two are currently economically feasible on an industrial scale: the Nutrient Film Technique (NFT) & Deep Flow Technique (DFT). What we see is that it is based on the desired crop variety, location, and initial investments. Allowing growers s choice of the most fitting cultivation system and level of automation.Thus, continuous development in this relatively young industry, no two hydroponic systems seem to be the same. As technologies improve and knowledge increases, systems become more standardised and eventually cheaper.

Figures 1 and 2 schematically represent the two systems below, which exist in multiple variations. For example, we have identified vertical farming systems, fully automated NFT systems, high-density deep-flow systems, as well as NFT moving gutter systems and static NFT systems. Each of these systems suits the production of specific crops, ranging from baby and teen leaf to small and large heads.

Figure 1. Schematic representation of a NFT system; [P] water pump, [N] nutrient solution (Geilfus, 2019). 

Figure 2. Schematic representation of a deep flow system; [N] nutrient solution, [A] air pump (Geilfus, 2019).

NFT uses gullies that are spaced automatically to optimise irradiation at each plant stage. A nutrient mix flows constantly through the gullies, passing past the plant roots. This continuous flow of nutrients creates optimal growing conditions. Using multiple gullies allows for different nutrient mixes tailored to each crop’s growth stage.

DFT is a robust yet straightforward approach for a hydroponic system to grow crops. A DFT system consists of a pool with floaters. These floaters contain plants that have their roots in a pool filled with a nutrient-rich mix. Differentiation of nutrient mixes is less interesting as new and old plants share the same pool. Because the floats have a fixed plant density, they utilize the growing area less efficiently for lettuce heads or teenleaf production.

Vertical farming is not a system in itself, but rather an implementation of other hydroponic systems, such as NFT, stacked vertically. It has the advantage of being very space-efficient, but it cannot utilise the sun for lighting. Because of this, a vertical farm always requires artificial lighting, which increases its energy demand. Currently, this energy cost makes it unviable compared to regular hydroponic implementations. However, during the early stages of plant growth, we find it interesting because a higher plant density exists, and the high level of environmental control results in more uniform crops.

The production of baby and teen leaf is primarily for pre-packed lettuce and salad mixes. It is harvested and packed on-site at the grower’s location, potentially changing the current supply chain.  Harvesting, cleaning, cutting, and packing full lettuce heads at a processing company might no longer be necessary.

The future will reveal what the lettuce supply chain will look like, but changes are expected to benefit high-quality, locally produced food.

Future expectations

The consensus indicates that hydroponic cultivation of lettuce will increase in the future. Based on retail demands year-round delivery of locally produced products. Currently, most retail production still occurs in soil, often in southern Europe.It is unlikely that new open soil growers will enter the market for lettuce. However, conventional production is not likely to disappear completely, since popular varieties such as Iceberg and romaine lettuce can be difficult to grow hydroponically due to their crop morphology. Additionally, hydroponic lettuce must compete on price with conventionally produced lettuce from Spain and Italy.

Additionally, we observe that the introduction of new crop varieties and highly automated production systems may affect the lettuce supply chain. In the latest supply chain, production will not only be local to the market, but also packaging and processing may take place on-site at the grower’s location. We will grow products hydroponically and locally, then pack and process them as close to the customer as possible. Shoppers will see this approach reflected on the retail shelves of the future.

Although growing lettuce using a hydroponic system brings major sustainability benefits such as reduced water requirements, reduced pesticide usage and fewer food miles. Based on the prerequisites set by the EU,  growing crops hydroponically is not deemed biological or organic. Guidelines state that “organic” growing must occur in open soil, and this is not the case for hydroponics. A separate quality mark, such as “hydroponically cultivated”, is unlikely to be successful, but it is possible to use the “On the way to PlanetProof” quality mark to indicate sustainability.

Conclusion

We believe hydroponic systems will continue to evolve, and the supply chain will adapt to the new possibilities this innovation brings. Many more crops are likely to shift toward hydroponic cultivation.

In the future, fewer workers will be required for crop cultivation, but those who are needed must have higher levels of education. System support and human capital may become limiting factors in the large-scale adoption of hydroponic cultivation.

Not only is there a need for interest from growers and investors, but we also require a new generation that is excited about this wonderful development.

ACT Team: Anthony Vermue, Bart Jansen, Cas van de Voort, Daan van Munnen, Elbert Niemeijer, Harold Weekamp and Lorenzo Nielen

Note by Cultivators:

Cultivators continuously conducts and supports research and development in the industry. In this case, we are a partner of Wageningen University ACT project program supporting students in the development of their consultancy and research skills. The article is the result of the research and reflects the insights of the consultancy team.

Reference:
Geilfus, C. M. (2019). Hydroponic Systems in Horticulture. In Controlled Environment Horticulture (pp. 35-40). Springer, Cham.