Professor David Jimenez Arias Plant Physiologist in the Canary Islands

Dr. Arias is a plant physiologist doing research on agriculture in the Canary Islands. The Canary Islands is in the Atlantic Ocean. It is a chain of 8 islands, approximately 1000 miles from the Spanish Mainland. Its economy is mainly tourism based. The Canary Islands operates more than 500 desalination plants. These plants produce large amounts of waste salt. As a means of using the salt waste, Dr. Arias has been doing experiments using the waste brine as a plant material in hydroponic green houses as it naturally contains minerals that farmers would otherwise have to import. Here is the interview we conducted

Why do you use salt brine in agriculture?

In my opinion, brine is a way to save money by using hydroponics. I think the brine can be used in tourist facilities and hydroponic farms, but the pilot plant is very important because one of the problems with working with salt can be the shelf life of the crops. We need to test them to use them in the local or export market.

Your experiments with brine mixed with certain fertilizers - after the brine is used once in solution. Can it be reworked into other experiments or does it pose another disposal problem?

The idea is to work in a truly circular system. At the beginning there is the idea of working with plants that have a certain tolerance to salinity. These plants will remove some of the Na and Cl from the solution and then use this solution for a new plant with a lower tolerance to salinity. In our first manuscript we talk about using the surplus  solution from the tomato hydroponics to irrigate the hotel grass. The main problem here is the need for a good evaporation system to provide  enough water to dilute the rejected brine.

The world is suffering from a shortage of food following the Ukraine War do you see your efforts as having

An impact beyond the Canary Islands as a means of increasing vegetable production?

In my opinion, hydroponics is one of the best ways to increase production because we do not need agricultural soil, we can build a hydroponic farm on the roof or in abandoned buildings, we have enough space for it in our cities. Brine can be used to increase the exploitation revenues and shorten the payback time of the installations. With the right research, the incomes can be higher and make the use more sustainable.

What is the biggest challenge in using Brine?

In my opinion, the evaporator system is the bigger challenge. Most of the work is focused on evaporating seawater, but not so much on using rejected brine. We have some commercial systems that are interesting to use here, but we need a pilot plant to demonstrate the possibilities of discarded brine.

Can brine be used in higher value crops than tomatoes such as cannabis or cacao? 

I think we can use the brine for other crops, but we need to test it in the system before it can be used on a large scale. Cocoa, for example, has a low tolerance to chlorine, which is a problem for this system. Cannabis can be interesting because it is worth noting how stress affects secondary metabolites such as cannabinoids. Studying how different stressors can change the amount of these compounds I think can be very important for the pharmaceutical industry. Another interesting area (my actual research area) is the application of bio stimulants. I have been working on an agent that can increase salt tolerance since 2010, and we can try to improve the response of plants with this kind of treatments.

As a plant Physiologist what direction would you see vegetable growing go? In the direction

Of hot houses and hydroponics or traditional field agriculture?

This is an interesting question. I am a proponent of hydroponic culture because it optimises water and fertiliser use and reduces the use of pesticides. From a plant physiological point of view, I think it is the best way to ensure proper plant nutrition and achieve better crop yields. For example, with a modern controlled hydroponic system like NFT, where the solution is circulated, one can achieve crop yields averaging 2.74 kg/plant. This can achieve a higher productivity of 161.8 ± 6.6 tonnes per hectare compared to 10.07 ± 0.4 tonnes in soil. I am not sure we need to change the whole agricultural system, but perhaps we can use hydroponics in cities to promote self-sufficiency among the population.

What are the principal lessons that have been learned from your experiments on the Canary island that are useful To places like Hawaii or any other island area?.

The most important lesson is that we have to think we are islands, with a limited space and a high population density. Waste management is one of the biggest problems that islands have to face. The circular economy is a necessity for us. I think we have to study all the waste we produce and try to transform it into new economic activities.