CALIBRATION LESSON 1 - NO FORMULAS SIMPLE ARITHMETIC

CALIBRATION - To some a four letter word. LESSON 1

If you don't understand the arithmetic or the formulas you have arrived at the right place.

Here's where the proverbial light goes on.

If you need to determine the amount of spray-mix going down per treated hectare** you need a starting point. That starting point is the product label. For example let's use a herbicide. We'll call it DESTROY.

Destroy is applied at a specific rate in 100 to 300 litres spray-mix per hectare -- ha.

** A hectare is a square with sides 100 metres long. So the area is 100 x 100m = 10'000 m² (ten thousand square metres) Be very careful when dealing with row crops and calculating litres per field hectare.  If you are only treating 5'000 m² for every field hectare then a treated hectare will obviously mean every 2 field hectares.

IN PRACTICE IT IS ASSUMED YOU HAVE THE CORRECT NOZZLE TIPS FITTED TO THE SPRAYER.   THE FARMER OR CHEMICAL REP THEN HAULS OUT A FORMULA AND DRIVING OR WALKING AT A SPECIFIC SPEED CALCULATES THE SPRAY-VOLUME PER HECTARE.   IF YOUR HAPPY WITH FORMULAS, GOOD BUT THIS BLOG POST IS ABOUT UNDERSTANDING WHAT IS ACTUALLY HAPPENING.

This image courtesy of R Steenkamp

To be efficient you want to spray the least amount of spray-mix which in this case is 100 l/ha. (litres for each hectare)     Transporting water costs money so cutting down on refill times is crucial.  It is vital that you know how many actual practical working minutes you have in a day.   I have demonstrated in field that is possible to spray 30 l/ha using a boom-sprayer and therefore possible to spray 20 hectares with a 600 litre tank.   But there may  not be enough spraying time in a day to empty the tank. So, be careful.  Another important point is  as spray-volumes go down management goes up.   You can't afford to make errors with high concentrates!

You know what volume you need to put down but you also need to know the speed you are travelling at. When determining speed make sure you are doing it in the situation you will be spraying.   WHY?    BECAUSE WE ARE TRYING TO DETERMINE THE FLOW RATE OF THE NOZZLE WE NEED TO MATCH THE SPRAY VOLUME YOU WANT!!   READ THAT AGAIN.

SPEED AND AREA

We'll assume that you have a 100 m tape measure and a stop watch. Mark off accurately 100 metres in field. You can also use 50 metres.   Determine the time taken to travel the distance. Do it both ways and if needs be do it in a different area in the field to be treated.

You end up with seconds to cover the distance. EXAMPLE: It takes 50 seconds to cover 100 metres. You also know the number of nozzle positions and their spacing on the boom.

TIP: THE EFFECTIVE SWATH (HOW WIDE THE RIG SPRAYS) IS SIMPLY THE NUMBER OF POSITIONS MULTIPLIED BY THE SPACING.   EXAMPLE : 20 NOZZLE POSITIONS AND SPACING IS 50 CENTIMETRES OR 0.5 METRE. THE EFFECTIVE SWATH IS 0.5 m X 20 nozzle positions =10 METRES.

Next posting we determine speed in kilometres per hour and the area covered in a specific time. 

Questions?  chemicon@multispray.com