Spray pressure influences spraying effectiveness in crops by 3 ways:
- Pressure influences the spray angle: the higher the pressure the wider the spray angle. If the pressure is too low (below 21.75 PSI for flat fans and 43.50 PSI for INJET) the spray angle is not wide enough to ensure full overlap on the boom and optimum liquid distribution.
- The higher the pressure, the smaller the droplets and the more they are likely to be deposited within the upper canopy of the foliage. These smaller drops are also more sensitive to wind movement.
- The higher the pressure, then the more: â—¦surrounding air is entrained that helps penetration of larger droplets within the canopy â—¦air turbulence which may increase under leaf deposit of smaller droplets especially when using low output conventional nozzles
Pressures recommended for field spraying with standard and lowdrift nozzles
- Pressures of 29 to 43.5 PSI for normal flat fan and lowdrift nozzles can be recommended for most applications.
- Only for well developed dense canopies where penetration is needed – such as spraying weeds that are concealed at the base of a vigorous crop – the pressure could be increased to 72.5 PSI with larger nozzles (03, 04 and bigger).
Pressures recommended for field spraying with INJET nozzles
- INJET nozzles require a minimum of 43.50 PSI to have a full spray angle but can be used up to 116 PSI.