At small scale, choosing spraying machinery is mostly a question of budget and convenience. At commercial scale it becomes an operational calculation: can this machine deliver the required coverage inside the spray window, at the lowest cost per hectare, without creating a new bottleneck somewhere else in the system?

That reframing matters, because it changes what you compare. Two machines with identical boom widths can have completely different effective capacities once refill logistics, field geometry, and control technology are taken into account — and the cheaper one is often the one that costs more per hectare.

This guide walks through the selection decision in the order it should actually be made. It is the third part of a series; Agricultural Sprayer Specifications Explained covers what the individual specifications mean, and Agricultural Sprayer Maintenance: Essential Checks for Reliable Operation covers keeping the chosen machine accurate.

1. Start With the Spray Window, Not the Machine

The spray window is the number of workable days you realistically have to cover a given area, given weather, crop stage, product label intervals, and re-entry constraints. Everything else in this guide is downstream of it.

The selection question is: how many hectares per hour must be covered to stay inside the window?

Worked example. A 500 ha program where a critical application must be completed within a 5-day window:

• Required pace: 500 ÷ 5 = 100 ha per day

• Assume 10 productive hours per day (weather, dew, wind, travel): 10 ha/h required

• With a realistic field efficiency of about 0.75 (turns, filling, headlands): a machine must be theoretically capable of roughly 13–14 ha/h

Theoretical work rate is straightforward: width (m) × speed (km/h) ÷ 10 = ha/h. So 13–14 ha/h could come from a 12 m boom at 11–12 km/h, an 18 m boom at 7–8 km/h, or a 24 m boom at about 6 km/h. All three are valid answers — and each points to a different machine class, tractor requirement, and budget.

Run this arithmetic before talking to a supplier. It eliminates most of the range for you.

2. The Machine Classes and What Each Is Actually For

Read the table as a decision ladder, not a ranking. Each row steps up in work rate and capital, and each step is only justified when the row above genuinely fails your situation. Buying a self-propelled machine for 120 ha of mixed ground is rarely a capacity decision — it is usually a labour or timeliness decision, which may or may not apply to you.

Note the airblast row carefully. Orchard and vineyard spraying is delivered by air, not by boom height, and a wide boom is not an upgrade path to it. If your area splits between arable and tree crops, expect to be selecting two different machines rather than one compromise.

3. The Four Numbers That Decide the Class

Before comparing models, establish these four figures from your own operation:

1. Hectares per spray window — from section 1. This sets the work-rate floor.

1. Water required per pass — area × application rate. A 500 ha block at 150 L/ha needs 75,000 L of spray mix in total. How you supply that volume determines tank size and whether you need a water tender.

1. Field geometry — field size, shape, and obstacles. This drives both boom width and, crucially, section count. Irregular fields reward section control far more than they reward extra width.

1. Crop form and canopy — low broadcast crop, row crop, or dense tree canopy. This selects the application technology (boom, shielded/banded, airblast) before it selects a model.

If you cannot answer these four, you are not ready to compare machines — you are comparing brochures.

4. Tank Size: At Commercial Scale, Water Logistics Decides

Tank capacity is usually discussed as "range between refills," but at scale it is better understood as the difference between a machine's theoretical and effective capacity.

Worked example. A 24 m boom at 12 km/h gives a theoretical 28.8 ha/h. With 0.75 field efficiency that is about 21.6 ha/h. Now add refills:

• Tank 1,500 L, rate 150 L/ha → 10 ha per fill

• 10 ha at 21.6 ha/h ≈ 27.8 minutes of spraying

• Plus a 10-minute refill stop → 37.8 minutes per 10 ha

Effective capacity: about 15.9 ha/h — 26% below the field-efficiency figure, purely because of tank size.

Change the tank to 3,000 L and the same machine holds 20 ha per fill: 55.6 minutes of spraying plus one 10-minute stop, giving roughly 18.3 ha/h. Bigger tank, same boom, 15% more output per hour.

Two implications for selection:

• Do not size the tank from the brochure range — size it from refill distance. If your water source is 20 minutes away, small tanks destroy capacity far faster than a narrow boom does. A water tender or nurse tank at the field edge is often cheaper than a larger sprayer and recovers the same lost time.

• Ask what agitation the tank provides and whether it runs independently of spraying. Suspension products settle during long refill stops, and settling is a rate error that no calibration will catch.

5. Boom Width, Section Control, and Automation — Where the Real Differentiation Lives

Boom width is the most visible specification and the least decisive one once you are above roughly 18 m. Above that point, the value is in control technology, not steel.

• Section control. More individually switched sections reduce overlap on headlands, wedges, and point rows. On irregular fields the saving is immediate and measurable in product; on large rectangular fields it matters much less. This is the single highest-return option on the list for most commercial operations.

• Satellite guidance with automatic section switching. Closes the tramline and overlap problem, and reduces operator fatigue on long days — which matters most precisely when windows are tight.

• Per-nozzle pulse-width modulation (PWM). Holds application rate constant as ground speed varies, and effectively decouples rate from speed. Worth specifying if your speeds vary widely through the day, or if you spray at higher speeds; less important on flat, uniform fields at steady speed.

• Automatic boom height control. Keeps nozzle-to-target distance constant over rolling ground, which supports both uniformity and drift management. The benefit grows with boom width and speed.

• Turn compensation and auto-section on curves. Relevant where you have many turns and irregular headlands.

The honest test: estimate the overlap and turn waste on your own fields. If you cannot quantify a saving, the automation is a comfort feature — pleasant, but not a selection driver.

6. Match the Machine to the Tractor and the Fleet

A sprayer under-specified at the tractor end is a bad machine regardless of its own specification sheet. Check:

• Three-point lift capacity and rear axle load — a full mounted tank transfers a large share of its mass to the rear axle, which affects steering, braking, and soil compaction.

• PTO rating and shaft type for pump drive; confirm the pump's demand at working pressure, not at idle.

• Hydraulic flow and outlets if the machine uses hydraulics for boom folding, height control, or drive.

• Tractor mass and braking for trailed units. A full 3,000 L trailed sprayer plus its own mass is a substantial pushed load on braking and on downhill terrain; tractor weight is a safety specification here, not a preference.

• Wheel track and tyre width to match row spacing and tramlines, and to keep axle loads within the limits that protect your soil.

• Transport dimensions. Folded width, height, and length must comply with the road-transport rules where you operate — verify locally rather than assuming.

7. Match the Application Technology to the Crop

The droplet-size decision sits inside this table and is easy to overlook: coarser droplets reduce drift but can reduce coverage on difficult-to-wet surfaces; finer droplets improve coverage and increase drift risk. Two nozzles of the same size can differ meaningfully here, so choose nozzle families deliberately rather than by habit. The pressure-versus-droplet relationship is covered in the specifications article.

8. Compare Cost Per Hectare, Not Purchase Price

For a commercial operation the relevant metric is total cost per hectare over the machine's life:

• Labour hours per hectare. The largest swing factor. Higher-capacity machinery, or automation that lets one operator work longer safely, reduces this directly.

• Water hauling and refill labour. Often the hidden cost, and the reason a nurse tank frequently beats a bigger sprayer.

• Fuel and wear items. Nozzles, seals, filters, and pumps are consumables; abrasive mixes and high volumes accelerate them.

• Downtime risk. A missed spray window is a crop loss, not a maintenance cost — weight reliability and parts availability accordingly.

• Residual value and asset utilisation. A high-capacity machine used 15 days a year is expensive per hour of actual use.

And consider the alternative honestly. On smaller or highly seasonal areas, contract spraying is often the correct selection: you convert capital and labour into a variable cost and gain access to machinery capacity you could not justify owning. Run the numbers before assuming you must buy.

9. Decision Scenarios

Small mixed farm, ~60 ha, varied fields, some orchard. One tractor-mounted sprayer, 600–1,000 L, 8–12 m boom with at least 3–5 sections, plus an airblast unit or contractor for the tree crop. Priorities: manoeuvrability, modest weight, section control on irregular ground. Watch for: tank too small relative to distance to water, and one machine asked to do two incompatible jobs.

Arable block, 300–600 ha. Trailed sprayer, 2,000–4,000 L, 18–24 m boom, guidance with automatic section control, clean water tank, good filtration. Priorities: effective capacity (see the refill arithmetic in section 4), tramline fit, and tractor mass to match. Watch for: sizing the tank for the brochure rather than for refill distance.

Orchard or vineyard, ~50 ha. Airblast / air-assisted machine sized to canopy and row spacing, with calibration appropriate to air-delivered application. Priorities: canopy penetration, adjustable air direction and volume, row-spacing fit. Watch for: evaluating it on boom-sprayer criteria, which do not apply.

1,000+ ha or contract work. Self-propelled, 3,000 L+, 24–36 m, full guidance and section control, auto boom height, high-capacity refill or tender support. Priorities: timeliness and labour efficiency above all; the machine's justification is windows and operators, not litres. Watch for: paying for width you cannot keep stable, and for transport-rule limits on folded dimensions.

Terraced, steep, or flood-prone ground. UAV where local rules and product labels permit, combined with ground equipment for accessible areas. Priorities: regulatory compliance first, then coverage rate. Watch for: assuming aerial application is permitted or label-approved in your jurisdiction — verify before purchasing.

10. Questions to Put to Suppliers

1. What is the machine's documented operating pressure band, and which nozzle tables apply?

1. How many independently switched sections, and does section control integrate with my guidance system?

1. What is the pump output at working pressure, and how much headroom remains for agitation and bypass?

1. What are the tank material, agitation type, and rinse-tank capacity?

1. What is the filtration chain, and what mesh does it specify?

1. What are the folded transport dimensions and mass, full and empty?

1. Is PWM or auto boom height available, and is it retrofit or factory-only?

1. What documentation ships with it — calibration guide, nozzle charts, parts diagrams?

1. What is the spare-parts and service network in my region, and typical response time?

1. Can you demonstrate it on my ground, with my crop and my water source?

The last question is the most valuable and the least often asked. A demonstration on your own field geometry will reveal more than any specification comparison.

FAQ

How do I decide on tank size?From refill logistics, not from the brochure. Calculate effective capacity including refill stops (section 4). If your water source is distant, a nurse tank or water tender at the field edge usually recovers capacity more cheaply than a larger tank.

Is a wider boom always better?No. Above roughly 18 m the binding constraints become boom stability, transport dimensions, and the value of section control. On irregular fields, section count and guidance typically return more than extra width.

Trailed or self-propelled?Trailed if you already have a suitably sized tractor and your windows are manageable. Self-propelled earns its premium where areas are large, windows are tight, and labour hours per hectare are the dominant cost — or where contract work justifies high annual utilisation.

Do I need satellite guidance and section control?Quantify the overlap and turn waste on your own fields. On irregular or many-cornered ground the saving is normally clear and fast; on large rectangular blocks at steady speed it is smaller.

Can a drone replace my sprayer?Not generally. Aerial application suits steep, terraced, waterlogged, or urgent spot situations — and is subject to regulatory approval and product label coverage that vary by country. Verify locally before relying on it.

Related Reading

• Agricultural Sprayer Specifications Explained: Tank, Boom, Pressure, Flow and Speed — what tank, boom, pressure, flow and speed mean, and how to calculate application rate.

• Agricultural Sprayer Maintenance: Essential Checks for Reliable Operation — the daily, weekly and seasonal checks that keep a selected machine delivering to specification.