water PH

[papheteer]

My tap water has a ph of 7.7. I use both nitrate and ammonia based fertilizers at very low dosage, about 1/8tsp per gallon and it doesnt really change the ph of the water. I guess my question is: is ph of 7.7 ok for irrigation water or is it best to use phosphoric acid and bring it down to 6-6.5? Thanks!!

 

[ALToronto]

Our tap water is well buffered, so a small amount of fertilizer will not affect it. If you used RO water, you would see a very different result.

I use citric acid - dissolve 5 tsp of crystals in a cup of water, put the solution in a squeeze bottle and figure out how much to add to your watering container each time. Phosphoric acid will add phosphate to your water and will affect the nutrient balance.

 

[papheteer]

Al, what type of water do you use then? How and what do you feed? And what do you adjust the ph to? Thanks a lot!

 

[Stone]

7.7 is slightly alkaline. With that water you can afford to use a nitrate to ammonium ratio of about 80/20 or something like that and you shouldn't see great (or fast) pH changes in your P/mix. If you want to use higher nitrate, then you may need to use acid in your water. I use sulphuric but its really dangerous. :evil: I think a pH of 5.5 to 6 is good but I grew nice plants for years with pH of 9 and no nitrate. With all the lime in that water, pH of the mix still stabilised to around 6 with the ammonium and Urea.

 

[ALToronto]

Are you growing only slippers or other orchids as well? Paphs won't mind a higher pH, phrags probably will. Phals and catts do better just below 7, and masdies need to be below 6.

I was not getting good growth with tap and even jug-filtered water. These ion exchange filters took water from 140 ppm to 117, so they didn't work nearly as well as advertised. So I put in an under-counter RO system (cost me $160 for 5-stage, faucet included), and now I have 10 ppm water. At this level of purity, a little fertilizer takes the pH from 7.6 to just under 7, so I no longer have to adjust pH. Until recently, I adjusted it for my living wall, as it's still leaching excessive calcium. By now unadjusted pH of runoff water is at 6.4, so I have stopped.

I've been following Rick's advice to feed very, very little every time. For potted plants, I alternate between K-Lite and Neptune's Harvest, keeping both to 20 ppm N. For the living wall, I use a tiny amount of ammonia / urea based fertilizer with Epsom Salts, and once in a while I use K-Lite or NH.

 

[papheteer]

7.7 is slightly alkaline. With that water you can afford to use a nitrate to ammonium ratio of about 80/20 or something like that and you shouldn't see great (or fast) pH changes in your P/mix. If you want to use higher nitrate, then you may need to use acid in your water. I use sulphuric but its really dangerous. :evil: I think a pH of 5.5 to 6 is good but I grew nice plants for years with pH of 9 and no nitrate. With all the lime in that water, pH of the mix still stabilised to around 6 with the ammonium and Urea.

Stone, thanks! Did you mean 80/20 ammonium to nitrate?

 

[papheteer]

Are you growing only slippers or other orchids as well? Paphs won't mind a higher pH, phrags probably will. Phals and catts do better just below 7, and masdies need to be below 6.

I was not getting good growth with tap and even jug-filtered water. These ion exchange filters took water from 140 ppm to 117, so they didn't work nearly as well as advertised. So I put in an under-counter RO system (cost me $160 for 5-stage, faucet included), and now I have 10 ppm water. At this level of purity, a little fertilizer takes the pH from 7.6 to just under 7, so I no longer have to adjust pH. Until recently, I adjusted it for my living wall, as it's still leaching excessive calcium. By now unadjusted pH of runoff water is at 6.4, so I have stopped.

I've been following Rick's advice to feed very, very little every time. For potted plants, I alternate between K-Lite and Neptune's Harvest, keeping both to 20 ppm N. For the living wall, I use a tiny amount of ammonia / urea based fertilizer with Epsom Salts, and once in a while I use K-Lite or NH.

I grow mainly slipper, Al. I tried using RO water with about 15-25% tap. It was too much work and I find that I get better growth with straight tap.
I have been wanting to try Neptune's Harvest. Are you using the Kelp/Fish blend? Or the fish only? Also where do you buy it in Toronto? Thanks@

 

[ALToronto]

I bought the fish/seaweed NH at Humber Nurseries, Hwy 50 @ Hwy 7. It's close to my work. In Toronto, you can buy it at Fiesta Farms, 200 Christie St., a little west of downtown.

 

[Stone]

Stone, thanks! Did you mean 80/20 ammonium to nitrate?

NO, other way round.

 

[papheteer]

I bought the fish/seaweed NH at Humber Nurseries, Hwy 50 @ Hwy 7. It's close to my work. In Toronto, you can buy it at Fiesta Farms, 200 Christie St., a little west of downtown.

Thank you Al. The downtown location is a lot closer to me. I will give it a try! Heard good things about it. How does it smell though? Offensive?

 

[papheteer]

NO, other way round.

Thank you!

 

[Rick]

What is the conductivity, alkalinity, and hardness?

pH is a very transitory value, and in low TDS waters the pH is highly influenced by gas balance. So you could sneeze on the water and drop the pH if it has very low buffer content.

 

[ALToronto]

It smells, but not for long. I use it at 20 ppm N (1/4 tsp per litre), which is a lot less than label recommendations. You have to keep it in the fridge and never leave leftovers for another day - or you'll learn the true meaning of "offensive smell". I alternate it with K-Lite.

 

[papheteer]

What is the conductivity, alkalinity, and hardness?

pH is a very transitory value, and in low TDS waters the pH is highly influenced by gas balance. So you could sneeze on the water and drop the pH if it has very low buffer content.

Rick, here's our water analysis:

http://www1.toronto.ca/staticfiles/...D/DrinkingWaterAnalysisSummary_2012_FINAL.pdf

 

[Rick]

Rick, here's our water analysis:

http://www1.toronto.ca/staticfiles/...D/DrinkingWaterAnalysisSummary_2012_FINAL.pdf

With a dash of N and P this water would be good to go with out using any comprehensive fert!

just a dash of ammonium nitrate and a drip of phosphoric acid:wink:

A kelp extract on top of the tap water by itself would probably do it.

 

[papheteer]

That's really good to know. I really hate collecting RO water. I don't like wasting water. For the kelp, is it ok to use it every watering? And at what rate should i use it? Thanks a lot.

 

[papheteer]

When using phosphoric acid, what ph should I shoot for? About 3 drops per gallon brings straight tap water to ph of 7.

 

[Rick]

That's really good to know. I really hate collecting RO water. I don't like wasting water. For the kelp, is it ok to use it every watering? And at what rate should i use it? Thanks a lot.

I'd shoot for a total N of about 2-5 ppm if you are considering using it for daily watering. So need to know the NPK of your particlular Kelp mix (that may have some inorganic fert added for a boost) to figure out how much per gallon to use.

If you are watering primarily to organic media that pH is fine. That water is similar to middle TN tap water, and plenty of folks are getting great growth using it as a base. (I still think Ideal would be a 50% dilution with rain or RO water).

Do you have a big barrel to play with?

 

[Rick]

When using phosphoric acid, what ph should I shoot for? About 3 drops per gallon brings straight tap water to ph of 7.

7 is fine.

What is the normality (or molarity) or your acid? Drops is a pretty meaningless unit without either knowing the stock concentration or the final P concentration in your irrigation water. You probably should try to hold final P to 1-5 ppm.

There's probably a good aquarium test kit available for that. I use Hach tests at work and the P test is a simple powder pillow with an indicator that turns shades of blue based on concentration.

 

[papheteer]

I'd shoot for a total N of about 2-5 ppm if you are considering using it for daily watering. So need to know the NPK of your particlular Kelp mix (that may have some inorganic fert added for a boost) to figure out how much per gallon to use.

If you are watering primarily to organic media that pH is fine. That water is similar to middle TN tap water, and plenty of folks are getting great growth using it as a base. (I still think Ideal would be a 50% dilution with rain or RO water).

Do you have a big barrel to play with?

Unfortunately I live in a condo so no big barrel. I mix my fertilizer solution in a 1 gallon container.