Can anyone tell me if hard or soft water is better to use for effective weedkilling ?
If one is better than the other, Why?
Thanks MAT
16 Dec 2009 by Ken Barber Last edited 16 Dec 2009
Water that is hard contains calcium and magnesium compounds. Rain water is naturally soft - it does not contain any minerals, but as it seeps through the ground it can pick up minerals, such as calcium and magnesium compounds, from the soil and rocks it passes through. If rain water passes through soft rocks like chalk or limestone, it picks up these minerals. If it passes through hard rocks, such as granite or through peaty soils, it does not pick up these minerals and so remains soft.
As a result, hard water will have a higher pH (in the high 7's). This can effect the longevity of some pesticides. Have your water tested by a lab or a simple pH kit can identify the pH of your water and an acidifier can be added to your spray tank. You may only need something like 200 mls in 300 ltrs of water and there are a number of acidifiers on the market. Some supply companies will even test your water with a simple kit from the boot of their car! One pH test is all that's needed, because the pH of the water will remain fairly constant. I always add an acidifier to my tank!
KB
The true meaning of life is to plant trees, under who’s shade you do not expect to sit.
16 Dec 2009 by Mike
That was an interesting read to start the day, Ken.
All the best.
16 Dec 2009 by Bjarni Hannesson
A slight correction on the pH of soft water, Ken if you don't mind.
If you do have ultra pure water (e.g. rain water) that contains very little total dissolved salts (TDS) and thus very low electrical conductivity (EC lower than 0.5 dS/m or below 320 ppm TDS) the water will have a very low buffer against pH changes. This can lead to ultra pure water often having a very high pH (sometimes above pH 9, I have seen that my self), but it can fluctuate.
High pH can affect half-life of pesticides, especially insecticides, but doesn't affect herbicides as much. Still it can have an effect, so check with your distributor.
If you are going to make alterations to your spray, you should mix first, check the pH and then make adjustments with acidifiers.
I agree with Ken Barber, that you get your water tested, and I would also suggest a very good book on water and water quality called "Turfgrass and Landscape Irrigation Water Quality. Assessment and Management" (2009) by Duncan, Carrow and Huck.
Read through this and it will help you understand your water tests better and, more importantly, what to do with the information.
Check the following link for the book:
http://books.google.co.uk/books?id=dFN1K8k8FmcC&printsec=frontcover&dq=Turfgrass+and+Landscape+Irrigation+Water+Quality:+Assessment+and+Management&cd=1#v=onepage&q=&f=false
If you need to purchase a pH meter you have quite a few options, but here is a link to a simple one from spectrum technologies to get you started on your search.
http://www.specmeters.com/pH_Meters/SoilStik_pH_Meter.html
Hope this helps.
Bjarni
Hi Bjarni, It is obvious, your knowledge is far greater than mine and I will humbly stand to one side...... although you speak of a pH reading of 9, I wonder how many people out there can confer they have seen such a reading in their soil? Very few me thinks! I have little knowledge in this area and my opinion is based upon the average pH reading that 70% of the turf-grass manager will find here in the UK i.e. in the 7's. I bet that's probably opened a can of worms now..... Why do I make these stupid statements without technical data!!!!
The way I see it is that the average man in the street can relate to what I am saying and that if they try to get their pH around the 5 to 5.5 range they will have a better chance at improving the half life or longevity of most pesticides.
Merry Crimble everyone!
KB
The true meaning of life is to plant trees, under who’s shade you do not expect to sit.
16 Dec 2009 by Bjarni Hannesson
Hi Ken
I thought your input was very good. I probably should have mentioned that ultra pure water sources are not that common (apart from rain, which you have plenty of in the UK). I put this info in here for people who perhaps know (or think) that they have soft water and thus think that their water probably has a good pH level, they might have to check again.
I would think you are spot on when you say that most managers would find their water being in the 7's, despite lack of technical data, so I certainly won't be opening any cans of "whoop ass" on you ;)
And you are right that most pesticide will work best in slightly acidic spray solution (especially insecticide).
Cheers
Bjarni
ok ladies, handbags at the ready!! so as i asked initially! should i make my water softer by adding a water softener to my water inlet before mixing weedkill?
please keep it simple ladies, no more gibberish.
As rain falls through the atmosphere it absorbs small amounts of CO2 which turn it into a weak acid. Rainwater is not pure water it is in fact weak carbonic acid. Thus it's eroding effect on chalk and limestone rock.
And Matt. Why not try it over the next season and see what happens. I think we will all be interested to hear the results.
Chris
You will never see a statue in honour of a committee.
18 Dec 2009 by Bjarni Hannesson
Sorry Mat, my menstrual cramps have been excessively strong last coble of days, causing me to speak gibberish ;)
What me and Ken were trying to say is that hard water can mean few things and I have never seen any information saying that hard water causes problems with pesticides as long it isn't ridiculously hard (please correct me if I'm wrong). You are better of knowing what is in the water, cause there might be something there causing problems. That's why we recommended you getting you water tested at a laboratory.
Ken talked about that since you have hard water you are likely to have alkaline water (pH above 7). Alkaline water is known to cause problems with some pesticide, so that might be more of a problem to you. That's why he recommended acidifying your spray tank solution (even though that wasn't your original question).
However, some pesticides have buffers in them which correct your pH in the spray solution, so that's why you should mix your spray solution first and then check the pH and make alterations.
So to sum up: It's unlikely that softening the water will be of great benefit, but get your water tested, speak to an expert and then you will know the answer to your question. We simply don't know enough about your water at this point.
Back to gibberish (my cramps are kicking in;). Chris, you are correct that CO2 causes rain water to become a weak acid. Still rain water is generally in the "ultra pure" category (having very low TDS), but this will depend on how far from the sea and pollution you are and other factors.
Ultra pure water doesn't mean that your pH is high, it just means that it can be high given the low buffering capacity and thus possibility of fluctuation in pH. Ultra pure water can also change in pH (even as much as two pH points, hens the pH 9 level can be achieved) after being pumped into reservoir due to evaporation of carbonic acids (Duncan et. al, 2009).
The reason I mentioned this in this threat is just that I wanted to make sure that people reading this that have soft water of some kind (perhaps use rain water for irrigation), don't think that their water is "perfect". Check your water regularly cause it might be the reason for some of your problems.
Hope this helps
Bjarni
p.s. I still recommend reading that book, it's a good source of information on water.
bjarni, ya a star, thanks very much. and all the best with the camps ; )
18 Dec 2009 by GaryA Last edited 18 Dec 2009
If you do wnat to know more speak to Manda Sansom, Monsanto technical helpline as they have masses of data with regard the performance of Roundup ProBiactive and hard and soft water and how efficacy is affected.
Published contact details are 01223 849540.
technical.helpline.uk@monsanto.com
Gary
* edit to change date to data !
Be Just and Fear Not
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