Tank Loads to Cover a Field

The companion to the previous calculation, asked the other way round: not how much ground a tank covers, but how many tanks a field will take. A 50 hectare field at 120 L/ha needs 6,000 litres of spray solution, which is seven and a half loads from an 800 litre tank.

The half is the interesting part. Fractional loads are the normal case, not the exception, and the last one should be mixed to the partial volume rather than filled and part-used. Mixing a full tank and applying half of it leaves several hundred litres of made-up pesticide solution with nowhere legitimate to go. It cannot be kept — most tank mixes begin separating, settling or degrading within hours, and adjuvants can make that faster — and disposal of surplus spray is regulated in every jurisdiction that regulates pesticides at all.

Two adjustments make the planning honest. Add the boom's own priming volume to the first load, since several litres are needed just to fill the plumbing before anything reaches the ground. And treat field area as sprayed area: headlands get double coverage where passes overlap, point rows and awkward corners waste solution, and buffer zones along water reduce the area but complicate the pattern. Most operators find real usage runs 3 to 8 percent above the geometric field area, which is very nearly the whole margin between seven and a half loads and eight.