Calibration questions

Hi guys, I have already asked this question on another thread but felt I had strayed to far away from the initial question. Basically i've got a couple of questions regarding trying to calibrate my knapsack sprayer to apply Mascot crossbar selective herbicide. I've got my calibration sheets from my pa 1,2 and 6 courses but I haven't had to do use them for so long I just need to be sure on my workings plus my maths is really poor!.

Also I have found a few conflicting figures that are throwing doubt into my workings. Anyway i'll show what i've done below. I'm using a red polijet nozzle with a spray width of 2 meters at 0.5 meters height. The link for the calibration data sheet for the nozzle is below.

http://www.agratech.co.uk/pdf-downloads/Polijet.pdf

O.k here are my workings so far using the red nozzle at 1.5 bars of pressure.

1. Operated the sprayer for one minute 3 times into a container and collected an average of 2.6 liters of water.

2. then to find out my litres per hectare I did 2600/(no divided symbol on my laptop!) 2.0 spray width divided by 10 to give me a spray volume of 130 litres per hectare.

3. So in order to up this without increasing the spray pressure for drift purposes I need to slow my walking pace so that I cover 100 meters in 180 seconds which gives me a walking speed of 2 kph.

4. Then I can assume that my sprayer output for 180 seconds would be 3 x 2.6 which is 7.8 litres.

5. I then repeat step 2 to give me a spray volume of 390 litres per hectare which is within the correct rates stated on the container.

here are a couple of questions I have.

1. On the polijet data sheet it states that the red nozzle at 1.5 bar of pressure at 2 kph will give an application rate of 510 L/ha??.

2. when I then go to calculate the dose rate 2.0 L/ha x 15 litres (my knapsack capacity) divided by 390 (my spray volume) I get a figure of 0.0769???.

On the container it says that 20ml of product needs to be applied in 10 litres of water to cover 100m2 so does that mean as long as my sprayer is calibrated at between 200 l/ha - 1000 l/ha I just need to add 30ml to my 15 liter tank?.

Sorry this is so long winded but all these conflicting figures are doing my head in!!, am I just being stupid and missing something?.

Michael

It does not matter if you are spot spraying or blanket spraying, using a knapsack or a boom sprayer, the calibration process is the same. Spot spraying is a little dangerous of over applying a control product. Best to blanket spray or do a large sweep of the nozzle rather than a quick spot to avoid over kill.

The manufacturers nozzle handbook is just for a guide. Polijet or Anvil Red Nozzles put down shed loads per Ha and you would be best to use an Anvil 1.2 Green. Why apply water when you do not need to. Aim for a spray volume of around 200 sqm only for most medium sprays.

You can have the best most expensive knapsack in the world but the effectivness of it depends upon the choice of nozzle and the operator working in harmony together and calibrating it. The process can take just a few minutes.

See this post were at the bottom you can print out or save for future use a calibration sheet. Knapsack Calibration Sheet or see the uploaded files.

Hope this helps. Basically once you know your knapsack output (volume per Ha) there is a simple formula you can use to work out how much product to put in a full tank thus:

Amount of concentrate to put into a full tank = Tank Capacity multiplied by the Dose Rate divided by the Spray Volume TC x DR / SV

Example - 15 (Litres) x 5 Lts (Per Ha) divided by 200 = 0.38 (litres) or 380 ml

You can check your figures of any calibration process by quickly working out how much water and chemical is required per SINGLE SQUARE METRE. Let's assume you have a 200 sqm lawn to treat -

How much Chemical per single square metre = Chemical Dose Rate per Hectare (Ha) divided by 10,000 (number of sqm in a Hectare) x 200 (area to be treated in square metres)

Chemical Example = 5 divided by 10,000 multiply by 200 - 0.10 (Litres) or 100ml

How much water per single square metre = Spray Volume per Hectare (Ha) divided by 10,000 (number of sqm in a Hectare) x 200 (area to be treated in square metres)

Water Example = 200 divided by 10,000 multiply by 200 = 4 Litres

So you need 100ml of product in 4 Litres of water to treat 200 sqm.

The critical bit to know with any calibration is the Spray Volume (mix of chemical and water) which for most products for lawn is within a range of 200 - 400 lits per Ha. Armed with this information, you can quickly look at any product label and use the formulas above to determine how much goes into a full tank and how much per each singel square metre or multiple of. You should also be able to know how many square metres on a good day your knapsack can cover.

Too much or too little will give inconsistent results.

Weed Free provide NPTC training and qualifications in the use of PA1, PA2A and PA6A. We are happy to help you get it right otherwise if gets a bit costly if mistakes are made. Email us

Replies

Geoff Norfolk August 29, 2011 at 9:20pm

Good grief....... you're making this sound incredibly complicated!!!! Not strictly correct way I know but if the area I was spraying was say 90m2, I'd just put 18ml in 9 litres of water and I invariably find that the whole lot is used with 2 sprays at rightangles to each other!!......... never had a problem.
Michael Bates August 29, 2011 at 9:39pm

??, i'm only going with the calibration method stated in the handbook that came with the courses, how did you calibrate your sprayer? or did you just use it?.
Dan Frazer Gardening August 29, 2011 at 10:20pm

What product are you spraying?
Michael Bates August 29, 2011 at 10:30pm

Dan, i'm using Mascot crossbar from rigby taylor.
Michael Bates August 30, 2011 at 1:10pm

Jez, your a total star!, the figurs on the polijet calibration sheet was what was confusing me but I also came to the same conclusion last night that the slight difference was due to my pressure being slightly low, it's quite difficult to maintain a steady 1.5 bar on my sprayer.

Totally agree about the spray volume and i'll probably do what you suggested, the only reason i went for about 400 l/ha was I was always told to go roughly in middle of the spray volume. Thanks allot for your help, hope you get a better nights sleep later!!!.
John Baker August 19, 2012 at 11:42pm

For spot spraying, surely, you time how long it takes to dispense a reasonably measurable quantity, then 'divide' to find out how long a burst you need to apply to your spot to deliver the desired quantity of the pesticide.
PRO

Brian www.mibservices.co.uk August 20, 2012 at 7:14pm

Calibration doesnt come into spot spraying. Only chemical / water ratio mix calculations. Only decision really is if you need to spray a course or fine spray depending on what your needing to spot spray.
PRO

Mike Seaton August 21, 2012 at 5:28pm

Michael

It does not matter if you are spot spraying or blanket spraying, using a knapsack or a boom sprayer, the calibration process is the same. Spot spraying is a little dangerous of over applying a control product. Best to blanket spray or do a large sweep of the nozzle rather than a quick spot to avoid over kill.

The manufacturers nozzle handbook is just for a guide. Polijet or Anvil Red Nozzles put down shed loads per Ha and you would be best to use an Anvil 1.2 Green. Why apply water when you do not need to. Aim for a spray volume of around 200 sqm only for most medium sprays.

You can have the best most expensive knapsack in the world but the effectivness of it depends upon the choice of nozzle and the operator working in harmony together and calibrating it. The process can take just a few minutes.

See this post were at the bottom you can print out or save for future use a calibration sheet. Knapsack Calibration Sheet or see the uploaded files.

Hope this helps. Basically once you know your knapsack output (volume per Ha) there is a simple formula you can use to work out how much product to put in a full tank thus:

Amount of concentrate to put into a full tank = Tank Capacity multiplied by the Dose Rate divided by the Spray Volume TC x DR / SV

Example - 15 (Litres) x 5 Lts (Per Ha) divided by 200 = 0.38 (litres) or 380 ml

You can check your figures of any calibration process by quickly working out how much water and chemical is required per SINGLE SQUARE METRE. Let's assume you have a 200 sqm lawn to treat -

How much Chemical per single square metre = Chemical Dose Rate per Hectare (Ha) divided by 10,000 (number of sqm in a Hectare) x 200 (area to be treated in square metres)

Chemical Example = 5 divided by 10,000 multiply by 200 - 0.10 (Litres) or 100ml

How much water per single square metre = Spray Volume per Hectare (Ha) divided by 10,000 (number of sqm in a Hectare) x 200 (area to be treated in square metres)

Water Example = 200 divided by 10,000 multiply by 200 = 4 Litres

So you need 100ml of product in 4 Litres of water to treat 200 sqm.

The critical bit to know with any calibration is the Spray Volume (mix of chemical and water) which for most products for lawn is within a range of 200 - 400 lits per Ha. Armed with this information, you can quickly look at any product label and use the formulas above to determine how much goes into a full tank and how much per each singel square metre or multiple of. You should also be able to know how many square metres on a good day your knapsack can cover.

Too much or too little will give inconsistent results.

Weed Free provide NPTC training and qualifications in the use of PA1, PA2A and PA6A. We are happy to help you get it right otherwise if gets a bit costly if mistakes are made. Email us
PRO

Gary RK August 21, 2012 at 6:46pm

Mike, a comment..

If you plan to spray hard surfaces, most suitable pesticide products have been removed for use in 'blanket spraying' scenarios from this April.

See : http://www.landscapejuicenetwork.com/forum/topics/blanket-pesticide...

Ie the current PSD guidance is use 'targeted' application - and most have taken that to mean spot spraying. It maybe semantics, however treating hard surfaces is expensive when 90% of the surface is what you DON'T want to spray...:-(

My guys have instructions to spot spray on all hard surfaces using similar methods as Brian states above.

Totally agree tho' about calibration for wide area application...
PRO

Brian www.mibservices.co.uk August 21, 2012 at 7:28pm

How can you blanket spray if your spot spraying in and around shrub beds or treating a clump of giant hog or japanese knotweed / individual weeds or small clumps of weeds in hard standing etc etc how can you possibly work out the calibration / hectare rate ? As long as you are mixing the correct amount of chemical to the correct amount of water and applying it to the spot / weed or small area and not spraying to run off then you wont be over dosing the area.