KNOW YOUR H20

Does the source of water for your plants really make much difference to their performance?

Sure does.

Town water, rainwater or bore. Doesn’t matter, they can all have an impact on plant performance, and sometimes not for the good.

Bore Water

The biggest potential for ‘not good’ generally lies with bore water.

There are some things you can be fairly sure of with bore water.

One is that it will have a high mineral content that may not be beneficial to your plants.

As water percolates through the various strata from the surface to the underground aquifer that the bore taps into it will dissolve minerals on it’s way through.

Mineral concentrations in the bore water will also tend to increase during periods of drought when aquifer levels are not being re-charged. Exactly when you need your bore most. Oh, the irony!

On our own property the bore water is extremely high in manganese and chloride.

The chloride level, in our particular case, is problematical. And dealing with it an expensive exercise. But not doing it renders the bore un-useable for plant irrigation.

Which brings me to the main point I want to make.

Putting a bore down is not cheap and there is always the possibility you will ‘come up dry’.

If you are considering putting a bore down (aside from all the requirements to be met and logistics involved), two points:

1. In Queensland, check the State Governments ‘Queensland Globe Registered Bores Map’ to see what bores are in your area and the kind of flows they generate.

   But be aware, just because they might be close geographically to you that doesn’t necessarily mean they are utilising the exact same aquifer your bore would be.

   And more than one bore tapping into an aquifer potentially means competition for a resource.

2. Make sure your budget allows for not just the drilling of the bore but the probable (should that be inevitable?) costs of amending the bore water to make it suitable for your plants. And there is a good chance that will run into thousands.

   And sometimes the amending creates it’s own issues, such as with reverse osmosis (which purifies water) where there can be as much if not more water produced as potentially un-recyclable waste water as there is pure water. There are of course other ways of dealing with this issue. It might be easier and cheaper (highly subjective term that!), for instance, to have a set-up that blends the rain and bore water together to dilute the mineral content of the bore water to acceptable levels.

   Nb. Only full analysis of your bore water will tell you where you stand on this. Unfortunately you can’t do that until after your bore has been drilled!

Rainwater

Why is it when it rains the plant response seems to be better than when you use the garden hose on your plants?

Some of you will say it’s because of the nitrogen in rainwater.

And you would be right.

Nitrogen (N) is an essential nutrient which plants use, in particular, to make chlorophyll, the green pigment used to help convert light energy into chemical energy within the plant (a process called photosynthesis).

The atmosphere is nearly 80% N and rain droplets pick-up plant available forms of N as they fall to the ground, especially in thunderstorms which ‘super charge’ this process.

But the amount of N input annually this way can be variable.

A study undertaken in Hawaii back in the fifties showed that rainfall variances at different locations led to significantly different total N inputs annually.

Potentially there are other factors at play here too.

At the end of the day I am a landscape designer, not a botanist, so there are sometimes statements made I can’t definitively say are right or wrong but this was written by someone more specifically qualified to make the statement than I and it was that although plants take up the bulk of their water through their roots, leaf uptake after rain is what really drives plant responses (not N) as this optimizes the conditions for plant tissue expansion and that the contribution from N is only minor.

It makes you think, though, that if this is the case, with the N contribution only being minor, plant response should be equal irrespective of whether the water source is tap or rain.

My personal assessment is N still plays a significant part, but would love some feedback from anyone qualified to provide some clarification on this.

Town water

Probably fair to say that we don’t give too much thought to what comes out of our taps.

We cook, clean and bathe with it and we also water our plants with it. Without a care in the world.

But both the chlorine which is designed to kill microbes and the flouride (used to prevent tooth decay) in town water can be harmful to plants.

In the case of town water in South-East Queensland I would suggest to you one of these is very unlikely to be an issue and one might or might not be depending on what plants we are talking about.

Read more about this in our blog:

'Is town water killing my plants?'

What to make of all this?

The conclusion’s I have personally come to are:

• Rainwater is best overall

• Town water is probably not quite as bad for plants as some people make out

• Bore water should only be used if it has been amended (as required) to avoid any adverse affect on your plants, but it is good news where you have no access to or don’t want to use town water and the water levels in the rainwater storage tanks are only heading one direction during a prolonged dry spell and that would be down!