[plant factory]Hydroponics and root vegetables are a worst-case scenario… Explanation of the reasons

Hello everyone! I’m Shohei.

Plant factories are mainly used for growing leafy vegetables, right?
Growing root vegetables is not common. You don’t see factory-produced radishes or carrots at all in supermarkets.
There’s a reason for this, but in the first place, the types of vegetables that can be grown in plant factories are quite limited.
Root vegetables are considered quite difficult to grow in plant factories. This is because the growth characteristics of root vegetables and the cultivation equipment in plant factories are not compatible.

This time, I will explain the technical possibilities of growing root vegetables in plant factories and the challenges that need to be overcome.
If you’re wondering, “Why are plant factories only used to grow leafy vegetables in the first place?”, you can also refer to the following article.

Characteristics of root vegetables and challenges in plant factory cultivation

Root vegetables are a general term for vegetables that have edible roots that grow large in the soil, such as carrots, radishes, and burdock.
Root vegetables are taprooted, characterized by forming thick roots that grow straight down deep into the ground.
To support this root growth, a soft growing medium with sufficient depth and width is required.
However, panel-type equipment, which is common in hydroponics, the mainstream cultivation method in plant factories, is suitable for growing leafy vegetables, but it is difficult to secure the depth and width necessary for the root elongation of root vegetables.
In addition, one of the challenges is that oxygen supply to the roots tends to be insufficient when the root zone is filled with liquid.

Cultivation techniques in plant factories suitable for root vegetables

If you are going to grow root vegetables in a plant factory, two techniques, Nutrient solution soil cultivation and mist hydroponics, are promising.

Nutrient solution soil cultivation is a method in which soil with sufficient depth for root growth is placed in a container such as a planter, and Nutrient solution is supplied by a drip tube or the like. It can be said that this method is optimal for the natural growth of root vegetables because the roots can grow taprooted in the soil.
Mist hydroponics is a type of hydroponics in which plants are grown without soil by spraying a mist of Nutrient solution directly onto the roots. The mist particle size is as small as tens of μm, so it is characterized by being able to sufficiently supply oxygen to the roots along with water and nutrients, and it can be said that this is a new option for root vegetable cultivation.

With these methods, it is possible to secure the growing medium space and oxygen supply necessary for root vegetables, while also sufficiently supplying the nutrients necessary for hypertrophy growth by managing the Nutrient solution.

Challenges in profitability of root vegetable cultivation in plant factories

Although it is possible to grow root vegetables in plant factories using Nutrient solution soil cultivation or mist hydroponics, there are major challenges in terms of profitability.
Root vegetables have a longer growth period than leafy vegetables and a lower turnover rate. In plant factories, production volume per unit period, i.e., turnover rate, is directly related to profits, so growing root vegetables is disadvantageous in this regard.
While lettuce and other leafy vegetables can be harvested in about 30 to 40 days, carrots take about 70 to 120 days from sowing to harvesting, highlighting the difference.

Plant factories have limited types of vegetables they can grow due to cultivation technology and economic factors. For example, grains are also quite difficult. Please refer to the following article if you like.

Future prospects of root vegetable cultivation in plant factories

At present, root vegetables are not chosen in conventional hydroponic equipment.
To realize root vegetable cultivation in plant factories, it is essential to develop cultivation equipment specialized for the growth characteristics of root vegetables.
If cultivation equipment specialized for root vegetables is developed in the future and a sales strategy for high-value-added root vegetable products is established, there is a possibility that root vegetable cultivation in plant factories will become a reality.
However, even in that case, considering competition with other high-priced crops, the possibility of root vegetables being chosen may not be very high. Many technical and managerial hurdles need to be overcome for root vegetable cultivation in plant factories to become mainstream.

Summary

Root vegetable cultivation in plant factories is currently a challenge due to the large gap between the growth characteristics of root vegetables and the current plant factory equipment and business models.
Traditional hydroponic equipment is not suitable for taprooted root vegetables that grow large, and it is necessary to introduce new cultivation techniques such as Nutrient solution soil cultivation and mist hydroponics.

Root vegetable cultivation in plant factories still faces many technological and managerial challenges.
For the time being, it may be realistic for plant factories to focus on the stable supply of leafy vegetables, while root vegetables are grown in fields and greenhouses.
However, if groundbreaking cultivation techniques specialized for root vegetables are developed in the future and a sales strategy for high-value-added root vegetable products is established, there is a possibility that the situation will change.

What are the advantages of growing vegetables in plant factories?

The advantages of growing vegetables in plant factories include year-round stable production, stable quality, pesticide-free cultivation, labor saving and automation. They are particularly suitable for growing leafy vegetables.

What are the types of plant factories?

There are two types of plant factories: solar-powered and fully artificial light. Solar-powered factories use sunlight as the primary light source and supplement it with artificial light as needed. Fully artificial light factories use only artificial light without sunlight. In addition, there are plant factories specifically for seedling cultivation.

What vegetables are grown in plant factories?

Currently, the main crops grown in plant factories are leafy vegetables. Lettuce, salad greens, baby leaf, spinach, and komatsuna are typical examples. Tomatoes and strawberries are also grown in fruit vegetables. On the other hand, root vegetables such as carrots are currently considered difficult to grow in plant factories.