Deficiency issues with plants in large planters - very hard water possibly the cause?

Hi Folks,

I'm hoping the hive mind can help me out.

A few years ago I made some large planters for the patio out of 55gal plastic drums.  These planters get topped up with good compost from our deep litter chicken system each winter, and this year they also got a bag each of commercial potting mix. I currently have a mix of strawberries, pumpkin, blackcurrant and geraniums in these. They work nicely BUT I'm having issues with nutrients.  

I water with the supply from our borehole, which comes from a chalk aquifer. The water is very hard. Well over 450pmm calcium carbonate. I have notice that where there is evaporation from exposed soil surfaces, a white crust is appearing. I presume that I am getting some precipitation of calcium carbonate.

I've noticed that some plants tend to grow with yellowing leaves, with green veins - my google-fu suggest that this is to do with an iron deficiency, and that high pH/hard water is likely an aggravating factor.  Now that I have noticed it in these pots I can see it much more mildly in other berry bushes planted directly in the ground elsewhere on the property.

Any thoughts for how I can fix this?

I would have presumed that adding good compost would have balanced most issues, but apparently not.  I have thought about adding an iron supplement directly, but if I continue watering with high alkalinity water, the balance will continue to be unfavourable to iron uptake.

Michael Cox wrote:I water with the supply from our borehole, which comes from a chalk aquifer. The water is very hard. Well over 450pmm calcium carbonate. I have notice that where there is evaporation from exposed soil surfaces, a white crust is appearing. I presume that I am getting some precipitation of calcium carbonate.

I believe you answered your own question with this statement.  Could the problem be to much calcium?

Anne Miller wrote:

I believe you answered your own question with this statement.  Could the problem be to much calcium?

Almost certainly. But what is the solution?

My water supply is what it is. What can I do to help?

I have the same problem since my well-water is filtered through tons of limestone rock.

What I do is mix 1 part vinegar with 4 parts water.

Other acid can be used in place of the vinegar such as lemon juice though I use vinegar because it is the cheapest.

The calcium is having an alkalizing effect on the soil, raising the pH into a range that is problematic for some of your plants. Watering with acidic water like Anne suggested will remedy this, but results likely won't be immediate. Granular food grade citric acid will work too and is readily available online. pH test strips will help guide you to making acidic water that isn't too acidic. My suggestion is to aim for something more acid such as a pH of 5.0 to rapidly help bring the soil pH down, then a less acidic solution for maintenance, such as a pH of 6.0 or so. pH test strips aren't exact and only give a ballpark reading, but it works and is what I use to make acidic water when watering my blueberries as my well water is alkaline similar to yours.

If I have this right, people add sulfur to the soil to acidify for e.g. blueberries. It takes a year or so because it's causing the microbiota to do the work rather than just causing a chemical reaction, like adding acid. I don't know enough to recommend it, but it might be worth some research.

Adding sulfur is a good way to lower the PH, especially if a person knows what the PH is.

The problem with having a chalk aquifer is that every time the garden is watered, more calcium carbonate is added.

I guess if a person knows their PH then a little sulphur could be added every time the garden is watered.  Would this work?  I have no idea since I have not tried this.

Are your rainfall levels reliable enough that you could capture barrels of rainwater for watering the planters? You might still have to add the acid to get the plants happy in the short term, but I know when I was having difficulty with my blueberries, that was one of the recommendations I read. (We are also on a deep well, but I don't think we're as high in calcium as you are dealing with.)

Another possibility once at more of a "maintenance" position would be to find an acid mulch to top the barrels with - pine needles would be the obvious in my area, but I don't know the UK options.

Christopher Weeks wrote:If I have this right, people add sulfur to the soil to acidify for e.g. blueberries. It takes a year or so because it's causing the microbiota to do the work rather than just causing a chemical reaction, like adding acid. I don't know enough to recommend it, but it might be worth some research.

This is correct. Adding elemental sulphur to a soil will lower a soils pH, but there are a few variables at play. One is the type of soil, another is the soil moisture consistency, and third is, as mentioned above, if alkaline water is continuously being added to the soil it will essentially negate the acidifying effects. It's soil microbial life that takes the sulphur and makes sulphuric acid which lowers the pH, but the microbial life needs moisture to do this and dry or drought conditions retards this process. Also, soil microbial life is much more active in warmer temperatures than during winter, so depending on how long ones warm season is, is another variable as to how fast this process takes place. If a soil has a pH that is near neutral, or 7, and needs to go to a pH of 6 for example, that will happen faster than a soil starting pH of 8.0 say, and the target is a range around 5.5. That will take longer. Suplhur works, but in many cases it happens at a snails pace and can take multiple seasons to see the visible results in happy plants thriving in their preferred soil pH range.

Jay Angler wrote:Are your rainfall levels reliable enough that you could capture barrels of rainwater for watering the planters? You might still have to add the acid to get the plants happy in the short term, but I know when I was having difficulty with my blueberries, that was one of the recommendations I read. (We are also on a deep well, but I don't think we're as high in calcium as you are dealing with.)

Another possibility once at more of a "maintenance" position would be to find an acid mulch to top the barrels with - pine needles would be the obvious in my area, but I don't know the UK options.

Sadly rainwater is not an option here. We live in an ancient listed building, and can’t alter the guttering/drains in anyway that might be visible. Big roof area, but can’t make use of it. It is an ongoing annoyance.

Re: acidic water.

I’ve been using concentrated hydrochloric to reduce the alkalinity in our above ground swimming pool. It seems to take a huge amount to bring it down to “ok” range of around 100ppm.

I think I used 2 litres of conc HCl for 3 cubic meter pool.

I would probably need to use a total of around 3 litres to reduce the alkalinity to zero, and make the water slightly acidic.

Any issues using appropriately diluted HCl to reduce the pH for a few heavy waterings? I suspect there is a lot of carbonate trapped in the soil from previous waterings, for any excess acid to react with.

Michael Cox wrote:Re: acidic water.

I’ve been using concentrated hydrochloric to reduce the alkalinity in our above ground swimming pool. It seems to take a huge amount to bring it down to “ok” range of around 100ppm.

The way I interpret what you wrote is that you're somehow measuring total dissolved solids (TDS) in the water before and after using HCl. It is my understanding that while TDS and pH are interrelated, one does not accurately reflect a measurement of the other. Acidic water can still have high ppm, as can alkaline water also. Distilled water with a ppm of 0 TDS can be very acidic, neutral or alkaline. Using ppm as a marker to determine pH of a solution won't yield accuracy. pH test strips or a pH meter are the better ways to accurately determine a liquids pH.

Any issues using appropriately diluted HCl to reduce the pH for a few heavy waterings? I suspect there is a lot of carbonate trapped in the soil from previous waterings, for any excess acid to react with

Appropriately diluted, no I don't see any. The only issues that may arise is if the solution becomes way to acidic and it begins to kill soil microbial life and damage or kill plant tissue like roots, otherwise it will work. Keep in mind the chlorine molecule that will be there leftover after the acid does it's work, as it is possible that chlorine may begin to build up in the soil.

James Freyr wrote:

Michael Cox wrote:Re: acidic water.

I’ve been using concentrated hydrochloric to reduce the alkalinity in our above ground swimming pool. It seems to take a huge amount to bring it down to “ok” range of around 100ppm.

The way I interpret what you wrote is that you're somehow measuring total dissolved solids (TDS) in the water before and after using HCl. It is my understanding that while TDS and pH are interrelated, one does not accurately reflect a measurement of the other. Acidic water can still have high ppm, as can alkaline water also. Distilled water with a ppm of 0 TDS can be very acidic, neutral or alkaline. Using ppm as a marker to determine pH of a solution won't yield accuracy. pH test strips or a pH meter are the better ways to accurately determine a liquids pH.

Any issues using appropriately diluted HCl to reduce the pH for a few heavy waterings? I suspect there is a lot of carbonate trapped in the soil from previous waterings, for any excess acid to react with

Appropriately diluted, no I don't see any. The only issues that may arise is if the solution becomes way to acidic and it begins to kill soil microbial life and damage or kill plant tissue like roots, otherwise it will work. Keep in mind the chlorine molecule that will be there leftover after the acid does it's work, as it is possible that chlorine may begin to build up in the soil.

Correct - Total Alkalinity measures resistance to changes in pH. You can add a bunch of acid to water with high TA, and the pH will initially fall but will drift up again over 24 hours or so. You can keep adding acid in batches, with little net change to the pH, with the TA is being used up.

This is why you have to fix the TA in pools, before you can get the pH stable in the correct range. In practice the TA is carbonate ions, that are chemically broken down to CO2 and water by the acid. The CO2 is slightly acidic itself, but evaporate over a few days, which is why the pH rises again.

My understanding of alkalinity in general has come from my learning how to manage our new pool though, not from plants and gardening. But it has hammered home how stupidly hard our water actually is.

My thinking is that I could fill a water butt near where I need to do my watering. Dose it with acid, and let it breathe for 48 hours to evaporate off the produced CO2, before using it for watering. Even if the water is still slightly acid, there is so much calcium carbonate in the soil of the pots already that it will react to neutralise some of it.

Water Quality: pH and Alkalinity
Recently, some growers have expressed concern about the "high pH" of their irrigation water and its potential adverse effects on plants. The purpose of this article is to allay some of these concerns by pointing out the difference between "high pH" and "high alkalinity".

Alkalinity and pH are two important factors in determining the suitability of water for irrigating plants. pH is a measure of the concentration of hydrogen ions (H+) in water or other liquids. In general, water for irrigation should have a pH b etween 5.0 and 7.0. Water with pH below 7.0 is termed "acidic" and water with pH above 7.0 is termed "basic"; pH 7.0 is "neutral". Sometimes the term "alkaline" is used instead of "basic" and often "alkaline" is confused with "alkalinity". Alkalinity is a measure of the water's ability to neutralize acidity. An alkalinity test measures the level of bicarbonates, carbonates, and hydroxides in water and test results are generally expressed as "ppm of calcium carbonate (CaCO3)". The desirable range f or irrigation water is 0 to 100 ppm calcium carbonate. Levels between 30 and 60 ppm are considered optimum for most plants.

Irrigation water tests should always include both pH and alkalinity tests. A pH test by itself is not an indication of alkalinity. Water with high alkalinity (i.e., high levels of bicarbonates or carbonates) always has a pH value ÷7 or above, but water with high pH doesn't always have high alkalinity. This is important because high alkalinity exerts the most significant effects on growing medium fertility and plant nutrition.

Water quality, pH and Alkalinity

I've bolded the key bit there. "Levels between 30 and 60ppm are considered optimum" - we are at around 450ppm!!!

High pH, high alkalinity water
High pH and high alkalinity water (150+ ppm CaCO3) has the greatest effect on species that require low growing medium pH and are prone to iron chlorosis. Some important greenhouse crops sharing these two characteristics include petunia, calibrachoa, scaveola, bacopa and snapdragon. Irrigating with high alkalinity water tends to increase the growing medium pH because of the liming effect caused by the carbonates and bicarbonates (sources of alkalinity) in the water.

Corrective actions are meant to lower the growing medium pH by using acidic fertilizers, avoiding overliming and in some cases by water acidification. Also, application of an iron chelate fertilizer solution to prevent or correct iron chlorosis is a very effective action.

These corrective actions are meant for the very small group of species listed above. No action would be needed for most greenhouse crops because they are not susceptible to iron chlorosis. In fact, irrigating with this water might help prevent iron and manganese toxicity on marigolds and geraniums and provide supplemental Ca and Mg to crops with a special need for these elements.

More on alkalinity

So it looks like both iron chelate fertiliser AND water acidification are viable options. Given that I have directly observed the chlorosis, it seems like I am on track with my suppositions. Now to work out what an application of iron chelate fertiliser might look like in practice.

Anne Miller wrote:
I guess if a person knows their PH then a little sulphur could be added every time the garden is watered.  Would this work?  I have no idea since I have not tried this.

The sulfur itself isn't acidic, it is made inso acid by the microbiome in the soil over time, so you add a bunch of it once and then it only gradually works. I did it because my garden soil was horribly alkaline (it fizzed impressively when I dribbled a little vinegar on it). I can't really tell if the sulfur has made the difference, or the the soil is just improving as I add mulch and compost and/or cow dung every year.

Hi, Michael, how are your container plants doing? Any improvement after adding chelate Fe?