You might be surprised to hear it, but some people use seawater as a… fertilizer. I know you might think that’s crazy, because seawater contains a lot of salt (sodium chloride). Well, that’s true. But that’s not the only ingredient!
Seawater chemical composition. What elements and minerals are there in the seawater?
Sea water contains many different elements. In fact, most of the naturally occurring elements on earth are present in seawater. Some even say all 94 of them, although some are in extremely small amounts.
List of elements with atomic weight and ppm in sea water
Argentum (silver) Ag
Stannum (tin) Sn
Ferrum (Iron) Fe
Aurum (gold) Au
Not only that, but it also contains lot of different isotopes of certain elements, which makes it an extremely rich source of the ultra trace minerals. These minerals are beneficial to not only your plants, but also their animal and human consumers. Areas in South East Asia that were hit by the tsunami in 2004 produced bumper crops for 2 years, as soil was reminerilized with elements that had leached out from the soil to the sea.
Seawater and sea salt prevent cancer
Did you know that chemical composition of the sea water remains pretty much constant over millennia? Because of that stability, sea plants and animals have been living in the same environment they evolved in.
Compared to soil, this constant balance is a great advantage. Soil is often is deficient in some nutrients. In other cases the concentration of certain trace elements could be too high- sometimes even to the point of toxicity. The stable and constant environment of the oceans provide sea life with almost complete immunity to cancer.
Recently, this chemical composition has been changing due to issues such as ocean acidification, nuclear leakage and fallouts. Local sources of pollution are also causing significant change in seawater chemistry and biology.
Seawater, selenium, iodine, and the prevention of thyroid diseases
Seawater contains both selenium and iodine, two uncommon minerals. As both iodine and selenium join water in the evaporation process , areas close to the sea get some of the iodine and selenium through rainfall. That will significantly decrease the chance that members of the local population are going to be deficient in iodine or selenium. Because deficiencies of either of these are strongly correlated to thyroid diseases such as goiters, this proximity greatly reduces incidences in the local population of hypothyroid or Hashimoto disease.
Seawater – the biggest compost tea ever…
The naturally occurring elements on earth, discussed above, are not the only interesting components of the ocean. Seawater also has a lot of microbes that can inoculate your soil.
Sea water and sea salts stimulate plant health by providing some trace nutrients that are usually lacking in the soil. The more water soluble a given nutrient is, the more likely it is that it will leach out of the soil, making it unavailable to the plants. Where do these nutrients end up? In the ocean!
Rose fertilized with seawater
On an anecdotal note, I fertilized my rose plant with sea water and some interesting things happened. First of all, my rose plant started to produce more flowering buds. It usually has only one flower, but a week or two after fertilization with sea water it already had 5 flower buds. In addition to this, the color of new flowers changed. Before seawater fertilization they had a pinkish color; after fertilization it became more red and intense.
The flowering buds were not the only parts of the plant affected by the new fertilization treatment. The new leaf growths became perfect, more shiny– an indication that photosynthesis is getting more efficient and leafs are producing lipids (that create protective layer from air borne fungi disease). They had that photoshopped look you only get on the pictures in magazines.
The best part though is that all this happened in the middle of the winter in dark and cloudy England. What would happened to that plant if it was in the middle of sunny summer? We’ll never know as second application of seawater I did around 6 weeks after the first one was detrimental to rose’s health and well being.
Unfortunately I was not able to take Brix reading as the plant was too small to sacrifice a significant part of plant that is required to take a Brix reading using my favorite juicer (omega 8006). I was not able to squeeze out the juice manual, using garlic press, mortar, pest and pantyhose.
Fertilizing poor, acidic, sandy soil with different types of salts, including sea salt
I asked my friend Jacek Kobus, who breeds Akhal-Tekes horses in Europe to do an experiment. He kindly agreed:
3 plots of poor, sandy, acidic soil were used.
Soil test results in ppm or in kg/ha, in brackets notes from the soil lab
- pH 4,09 (very acidic, liming required)
- P2O5; 270 kg/hg (low)
- K2 O; 60 kg/ha (very low)
- Mg 30kg (very low)
- iron 825 ppm (low) [It’s actually extremely high level -W.M.]
- boron 0,42 ppm (low)
- manganese 61 ppm (average)
- copper 3ppm (average)
- zinc 3ppm (average)
As you can read it’s a very, very poor soil.
On March 23rd each 10m x10m (33 feet x 33 feet) plot 2 kg (approximately 4.4 pounds) of salt was spread. That would be equivalent of 200 kg/ha (200 lbs/acre). Different salts used on the plots:
- Sea salt (brand O’Sole)
- Rock salt (from Kłodawa salt mine in Poland)
- Refined salt (99,9% NaCl) with added iodine
After few months the results were inconclusive or not very positive for the sea salt as fertilizer.
Results of experiment with sea salt fertilization
The only plant that grown in the plots during the harvesting time (20th of July) was sheep fescue (Festuca ovina). Jacek checked the Brix of overripe grass (he was not able to extract the juice from sheep fescue using manual method, ordering a juicer took some time).
He checked Brix reading of grasses from different plots:
- Sea salt fertilized: 6,5-7,5
- Refined, iodise salt: 8,5 – 9,5
- Rock Salt: unfortunately Bulgarian, manual juicer broke down during extraction of the juice from this high silica, woody grass of low nutritional value.
- Although there was no controlled plot, but Brix of grass and oats grown on a pasture fertilized with horse manure was 8,5. Brix of herbs (clover, sorrel, dandelion, plantain…) grown on pasture (that’s being fertilized) was 3,5 – 4,5. That’s not very good especially for clover, as it indicates that it doesn’t have good conditions for growth. Jacek has already taken some measure to improve the pasture. In the autumn a truck of marble rock dust will be spread and probably around 25 tones of either basalt rock dust or granite rock dust.
Jacek thinks that higher Brix of refine salt might not mean anything significant because it might be caused by some random difference within soil condition.
Dose of sea salt or sea water as fertilizer
Dr. Maynard Murray, who was a pioneer of using sea salt (or as he calls it sea solids) and sea water used from few hundreds up to 3500 pounds per acre (3,5 tones per hectare) of sea solids. I guess that on this sandy soil that amount would be just washed out quickly. I recommend using 1/10 of that. That is 35g per 1m2 (1 oz per 10 square feet). If you want to use seawater you should use 1 litre (32oz) per 1 m2. Do not apply more than once a year (two times per year if you live in tropical climate with heavy rainfalls).
If you want to spray your plants as foliar feed dilute seawater with rainwater 1/20.
I’ve personally used seawater and sea salt as fertilizer many times. My mixed results are below:
- A little goes a long way
- If a bit is good, more is not better as you can kill or harm your plants easily
- It’s useful to make average or good soil even better
- It doesn’t show it’s benefits on poor, acidic, sandy soil
- Sea water seems to enhance the growth and health of plants.
- It seems to stimulate flowers and fruit production
On sandy soil it seems better to invest in lime, dolomite, phosphate, rock dust, micronutrients and biochar. Sea salt should be treated as a source of ultra trace elements or sodium, not a magic bullet that will solve all your soil fertility problems.
I would like to know your experience with using sea salt or sea water as a fertilizer. Please write a comment bellow.