Are hydroponic vegetables really organic, healthy, and safe?

In recent years, LED plant factories and hydroponic vegetables have frequently been covered in the media. But from the perspective of agriculture and food safety, the author would like to offer some views on this. These views may be misconstrued by vendors or media reports for ordinary consumers. However, by visiting and consulting agricultural experts, one can learn what is right and what is wrong.

First, let us understand what a plant factory is.

What is a plant factory?

It is defined as the artificial control of a plant's growing environment: such as the required light, the growing environment, the humidity during growth, the carbon dioxide concentration during growth, and controllable nutrients and water, among others, so that the crops grown can be free from external environmental constraints and natural influences, and can achieve the goal of planned mass production of crops.

What is an LED plant factory?

Plant factories can be divided into two types: one is fully indoor cultivation with no light at all, and the other is supplemental-light cultivation using sunlight. Both types of plant factories need to use existing artificial light sources to supplement and adjust the light source requirements during plant cultivation, and the light conversion energy required for plant growth. An LED plant factory refers to one whose artificial light source uses LED lamps to replace traditional high-pressure sodium lamps.

What are hydroponic vegetables?

If one carefully looks up the definition of hydroponic vegetables, one will find that there is more than one definition, and there are also several cultivation methods. The author will only explain the one commonly used in plant factories at present: liquid hydroponics - using soluble chemical fertilizers blended into a nutrient solution to provide the nutrients needed for plant growth, and providing sufficient oxygen during the growing process. It is also a type of nutrient solution cultivation.

Among the many reports and myths, the author considers several items misleading or possibly fraudulent, and offers explanations for consumers' reference.

1. No chemical fertilizers?

If a company dares to promote its vegetable products to you as not using chemical fertilizers, and you cannot accept vegetables grown with chemical fertilizers, or you want to buy organic vegetables, then please think twice. Hydroponic vegetables must use chemical fertilizers for the plants to survive and grow, and ultimately to become products with commercial value.

Likewise, if a company tells you that they only use terms such as pure natural organic fertilizer or microbial enzymes to grow hydroponic vegetables, you should likewise think twice, because purely organic fertilizer cannot achieve the purpose of hydroponic cultivation.

The reason the author makes this judgment: the essential nutrient elements required by plants number 16 in total, including carbon (C), hydrogen (H), oxygen (O), nitrogen (N), phosphorus (P), potassium (K), sulfur (S), calcium (Ca), magnesium (Mg), iron (Fe), manganese (Mn), copper (Cu), zinc (Zn), boron (B), molybdenum (Mo), and chlorine (Cl), among which carbon, hydrogen, and oxygen mainly come from air and water, while the other 13 nutrient elements mostly come from soil.

Crop roots can generally absorb gaseous, ionic, and molecular nutrients. Gaseous nutrients include carbon dioxide, oxygen, and water vapor. Ionic nutrients can be divided into two types, cations and anions. Cationic nutrients include: NH4+, K+, Ca2+, Mg2+, Fe2+, Mn2+, Cu2+, Zn2+, etc.; anionic nutrients include: NO3-, H2PO4-, HPO42-, SO42-, H2BO4-, B4O72-, Cl-, etc.

Crop roots can also absorb a small amount of molecular organic nutrients, such as urea, amino acids, sugars, phospholipids, auxins, vitamins, and antibiotics, etc. (Taiwan Agricultural Encyclopedia). But these small amounts of molecular forms are not enough to supply all the plant's nutrients.

Therefore: hydroponic vegetables must have chemical fertilizers added. And they are absolutely not organic vegetables.

2. Low nitrate?

If a company or vendor presents a test report showing nitrate below 1000ppm, the author would advise you to refuse to buy. Currently, those in the trade all claim that as long as the lighting time is increased before harvest, nitrate can be reduced, so that consumers can eat vegetables with very low nitrate. But the author points out a fact: increasing the lighting time increases the cultivation cost of the vegetables.

Taking LED-grown hydroponic vegetables as an example, electricity accounts for 30~40% of their production cost. If the lighting time is further increased, their production cost would far exceed the selling price, so this special treatment is only done when submitting samples for testing. Moreover, the effect of increasing lighting time on reducing nitrate is not good. It was once tried with 24 hours of extra lighting, and the nitrate content did not decrease significantly, still remaining at the level of 2000ppm.

3. High nutritional value?

The author once heard management of a certain hydroponics company publicly claim that the nutritional content of its hydroponic vegetables was ten times higher than that of traditional soil-grown vegetables. At that moment, the author almost sprayed the bubble milk tea in their mouth all over their face. Because it was just too ridiculous. The nutrients in hydroponic vegetables are all artificially added, and there are only about a specific dozen or so chemical components, and they cannot provide special nutrients such as organic acids, humic acids, amino acids, phospholipids, auxins, and vitamins.

Not to mention that there are still many components in soil unknown to scientists. At the same time, looking through previous research reports, one can find that the nutritional content of soil-grown vegetables is higher than that of hydroponic vegetables. One can even buy the two kinds of vegetables oneself and send them for testing, and it can be confirmed that it is a fact that soil-grown vegetables have higher nutritional content.

Conclusion:

Hydroponics is a selective method of agricultural production. In the past, the government also actively promoted it. But in fact, hydroponics still has many areas in need of improvement technically.

The first is the accuracy of nitrate content; the second is how to regulate crop physiology when applied to crops other than leafy vegetables, such as how to make muskmelon sweeter, and how to make cabbage head, etc.; the third is that hydroponic vegetables look clean in appearance, but their total bacterial count is not lower than that of field production. In the high-humidity environment during planting and harvesting, hydroponic vegetables' bacteria multiply rapidly.

Fourth, because of the high labor input and high energy input of hydroponics, in exchange for limited vegetable production capacity, these input costs are all passed on to consumers. Yet hydroponics is neither organic nor high-quality, and its nutritional value is not higher either. A slightly bland taste is a matter of personal preference. For such a product, why still pay a high price to buy it!?

The author thinks it would be better to take this extra expense and use it to support the small farmers in Taiwan, China who truly grow good products!