Airblast Calibration

Tree Row Volume • Sprayer Output • Spray Mixture

Farm Details

Tree Measurements

Sprayer Setup

Product & Tank

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Calibration Questions

Airblast calibration questions

It works out how much spray your machine puts onto a hectare at a given speed, pressure and nozzle set, so the rate printed on the product label is the rate the tree actually receives. Two numbers multiply together here — water volume per hectare and product concentration in the tank — and an error in either one carries straight through to the tree.

Tree Row Volume sizes the spray to the canopy you are treating rather than to the ground beneath it. It combines tree height, tree width and row spacing, adjusted for tree shape and canopy density, to describe how much canopy there is per hectare. A young block and a mature block on identical spacing cover the same hectares but hold very different volumes of tree, and Tree Row Volume is what accounts for the difference.

From the orchard: tree height, tree width, tree spacing and row spacing in metres, plus tree shape and canopy density. From the sprayer: the seconds taken to cover 100 m at working speed, the number of nozzles, the operating pressure in bar, and the discharge rate per nozzle in litres per minute. If you do not have manufacturer figures for the nozzles, the discharge reference table on this page runs from 2.07 L/min at 5 bar to 4.13 L/min at 20 bar.

At the start of every spray season, whenever you fit new nozzles, and whenever tractor speed or operating pressure changes. Nozzles wear, and worn nozzles pass more liquid than new ones, so a sprayer calibrated two seasons ago is very likely applying more water and more product than you think it is.

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Overview

Fill in all the fields and press Calculate once. The results bar shows your Tree Row Volume, target vs actual application rate, and how much product to add per tank — all in one step.

Tree Measurements

Measure your trees in the orchard and enter the values.

  • Tree Height — ground to the top of the canopy
  • Tree Width — widest point of the canopy across the row
  • Tree Spacing — distance between trees within the row
  • Row Spacing — distance between rows (also used for the sprayer output calculation)

Shape guide:

  • 2/3 Cylinder + 1/3 Dome — most common for mature orchard trees
  • Block — hedgerow plantings with flat tops
  • Dome — rounded canopy, wider than tall
  • Sphere — roughly equal height and width
  • Cone — conical canopy, narrowing at the top

Density guide:

  • Very Dense (1.0) — fully covered rows, no gaps
  • Dense (0.8) — mostly closed canopy
  • Moderate (0.6) — some gaps between trees
  • Sparse (0.4) — young trees or wide gaps

Sprayer Setup

  • Seconds to Cover 100 m — time your tractor over 100 metres at normal spraying speed. The calculator converts this to km/h automatically (shown below the field as you type)
  • Number of Nozzles — total active nozzles on the sprayer
  • Discharge Rate per Nozzle (L/min) — the actual output of one nozzle at your operating pressure. Measure by collecting water from a single nozzle for 60 seconds, or check the nozzle manufacturer’s chart. A reference table appears below the results for common disc nozzle rates

Product & Tank

  • Tank Capacity — your spray tank size in litres
  • Product Name — for your reference in the results
  • Product Rate — the label rate in L/ha (or kg/ha)
Always follow the product label. The calculator converts the per-hectare rate into the correct amount for your tank based on the actual sprayer output.

Reading the Results

After pressing Calculate, the results bar shows four values:

  • Tree Row Volume — canopy volume per hectare (m³/ha)
  • Target Water Volume — how many L/ha your canopy needs (TRV × 0.06)
  • Actual Sprayer Output — what your sprayer delivers at the current settings (L/ha)
  • Product per Tank — how much product to add to your spray tank

A green or amber indicator tells you whether your sprayer output is close to the TRV target. If they are more than 15% apart, adjust your speed, pressure or nozzle count and recalculate.

Tips

  • Recalibrate at the start of each spray season or when changing nozzles
  • Adjust nozzle selection before changing pressure — pressure changes affect droplet size
  • Run a test pass and measure actual water use to confirm your calibration
  • Record your settings so you can replicate them next time
Calibrating a knapsack instead? Use the knapsack calibration calculator — same principle, walked rather than driven.