The efficiency of refilling operations can have a major impact on the cost-effectiveness of spraying as well as the lifespan of the spray machinery.
The ability to maximise the area sprayed in a day is determined by:

  • how efficiently the sprayer can be filled
  • the time taken getting to and from the paddock
  • the operation of the sprayer itself – ground speed, opening/closing of boom.

Spraying hours are mostly limited due to meteorological conditions specified on the product labels. This includes surface temperature inversions, high wind speed, frosts, heat and rain.
Growers want to maximise the hectares sprayed with the available time and labour and the ways to achieve this will vary from operation to operation.
Making spraying as efficient as possible has the twin benefits of increasing the likelihood of better control through better timing of application which in turn leads to lower costs.
Increasing travel speed can increase the area sprayed per day, however this introduces problems such as:

  • increasing the potential for spray drift via updraft behind the boom.
  • increasing wear on the machine, particularly the boom and drive system.
  • reducing spray coverage. Boom auto-height improves spray deposition and helps protect the boom but does not fully overcome updrafts behind the machine.

Other methods for increasing spray efficiency may pose fewer issues regarding spray effectiveness and drift.
Increase hectares per load
To increase the area sprayed per load, the options are to reduce application volume per hectare and/or increase tank size.
Reducing application volume requires a good understanding of the different products being used – how they work (mode of action), the target weeds, the effect of meteorological conditions and the spray quality being used. Lower water volumes with large droplets (less than 70 litres per hectare) may only suit the use of highly water soluble pre-emergent herbicides in low levels of stubble, or translocated herbicides such as 2,4-D as per the APVMA guidelines ( https://apvma.gov.au/node/15581 ) on moderate to larger target weeds.
Products that require good to excellent coverage or which are not well translocated, such as herbicides from groups A, C, D, F, G, H and L, as well as fungicides and some insecticides, require higher water volumes (80 to 100-plus L/ha). These require 10 to 20 per cent coverage, which can be checked using water sensitive paper and the SnapCard® app ( https://www.agric.wa.gov.au/grains/snapcard-spray-app ) or fluorescent dye and UV lights.
A larger spray tank is another way to improve the area sprayed per day as it reduces the number of fills per day. However, this can affect the stability of the spray unit. Paddock evenness and soil type such as loose sand or heavily ploughed fields will have a significant effect on spray rig behaviour.
Another factor that needs to be considered if considering larger tanks is pump size as too small a pump will not be able to run the boom and give enough agitation to keep all the products in solution.
Take water and product to the paddock

More efficient methods to improve productivity will come from decreasing the distance to fill points.
For example, a four-kilometre fill station round trip at 20km/h takes 12 minutes per load. With four to five loads per day, up to 60 minutes will be spent travelling and one less tankful sprayed that day. This doesn’t include the time taken to fold and unfold the boom.
Many growers are now using portable mixing and transfer systems and water carts to reduce time the sprayer is out of the paddock, which also reduces the engine hours of the sprayer or tractor. Having enough product for at least a full day’s spraying on a batching trailer enables it to be moved to each refill site either close to a watering point or moved with a water truck. If the tanker isn’t big enough to hold water for a full day’s spraying, a separate batching trailer enables it to be left behind while the water tanker is refilled.
Large operations will use semi-trailer/road-train set-ups while small to medium operations may have a similar set-up fitted to a large trailer or truck.
A simple tanker and batching set-up for servicing spraying operations on multiple fa