Backyard Aquaponics
A place to discuss aquaponics

I know a few folk use sea salt and have seen use of bicarbonate of soda here too.

Isn't salt harmful to plants?

Is there something obvious I've missed all these years.

Small amounts of salt don't harm plants and some plants are more tolerant of salt than others. Unfortunately I don't have the info on me but it's not too hard to find tables of salt tollerance in vegetables with their parts per million of salt that they can survive.

If you use an Electical conductivity meter you can make sure that the overall salt concentration is not so high (EC) as to dehydate the plants via osmosis. Hydroponic sites usually have a table of EC or TDS for various plant preferences.

This is where I was running into problems Johnnie, and I just got them mixed up again... For fish you have a recommended parts per million of salt to remain nice and healthy, but then for plants it is the electrical conductivity...

Anyone know how to compare the two EC to PPM???

Eb will try and hook up with a conversion table.

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The thing with an EC meter , is that it can't tll you how much of each nutrient is in there, or even give you an accurate figure for ppm or TDS only an estimate. There is a table to convert this into a ppm measurement or TDS. (But different companies use different conversion factors as some ions conduct different to others!)

There is really No way to convert EC or CF into ppm. Its only an estimate as it depends on the nutrient balance within the water.

I rather tended to use a meter to keep the EC or CF within the range.

http://www.lenntech.com/unit-conversion ... engels.htm

I used to make up an "organic" hydroponic solution using various animal manures, a little wood ash and dilute until I was in the correct EC range. Then I would adjust pH to that in the range favoured by the plant using a little very dil phosphoric acid or nitric acid or very dilute potassium hydroxide... and avoiding large fluctuations. Double checking the EC range.

http://www.firstrays.com/tds_and_ec.htm

I used to try and keep the pH range between 5.4 and 6.8.

I used to try and keep the EC at arond 0.8 - 3.0 milliSiemens per cm

or 8 - 30 cF (cF = EC x 10)

Plant to have different EC requirements as some ar more tolerant to Osmotic pressure than others.

Here are tables of recommended ranges for various fruits, veggies and herbs.

http://www.gthydro.com/plantguide.html


http://members.mailaka.net/norm34/veg2.html

Hope this stuff helps.

(I wish I had a pH meter and an EC meter these days!)

Johhnie, I actually tried to explain this in an earlier post. Ec can only trully be converted in to PPM if there is only one known dissolved salt. Its quite a common measuremnt in industry. PH and EC meters usually retail at around the $100 mark. Worthwhile if you are into taking measurements like me Be sure to regularly check the PH meter against a known buffer (usually included) and follow the care instructions for the electrode.

I think that is what I was trying to say Steve!

(Quick reply window didn't seem to work .. Doh!)

I know Johnnie, just agreeing with you

Just on the salt topic,

bi-carb and sea salt are tolerated in small quantities (as EB stated) by most plants. Primarily it is the sodium ion that casues the issues.

Many other salts are tolerated in higher quantities and are often applied to soils to rectify macro nutrient deficiencies. Some of them also modify the GH (general hardness) and /or KH (carbonate hardness) of the water.

For example,
epsom salts (magnesium sulphate) can be added to rectify magnesium deficiency and add sulpher. The magnesium also adds to the general hardness of the water.

Calcium chloride, like table salt but with the calcium ion substitued for sodium. plants can tolerate much higher levels of this due to it not containing sodium, the calcium goes into the calcium pool for theplants to take up and the chloride ion is helpful in protecting fish from nitrite poisoning (can happen in the cooler months as the bacteria resposible for nitrite coversion is the first to slow down and the more fragile) It will also add to the general hardness of the water.

Oh, Muz i remember you being dubious about the "damp-rid" CaCl.........i have used almost 1Kg of it between my indoor and outdoor tanks (during the cycling) Fish never complained (might be because they cant talk, but you get my meaning )

If any one would like more info on GH and KH i can post some info under the "useful inforation" topic, just let me know.

Steve

OK. Case Scenario. Mums wee pond. Roughly 1 kilo goldfish in it.

GH 600 ppm plus. pH 6.2. 200 litres.

Needs to swing up to 6.8-7.0 and remain there without killing the fish so I can put some scoria and veggies on the banks.

Any idea what your KH is? and what your grid water GH & KH is?

Let me know and i could probably give you very close figures

Steve

Grid water Gh is 50 ppm pH 7.

Can't get KH but suspecting most of hardness is calcium carbonate from overzealous liming of lawn.

AA, will get onto it tonight, but pH of 6.2 with most of the 600ppm being calcium carbonate hence also KH doesn't seem right. PH should be much higher

steve

160 ppm nitrate. Only tests I had.