Result

Draft force is the least predictable quantity in this whole calculation: the reference figures per metre of width assume a typical working depth and reasonable implement condition, but soil moisture alone can shift the pull by a large margin, and a blunt or badly set share increases it further. Working depth matters as much as soil type for tillage implements, so a deep pass in the same field is a very different job from a shallow one. Tractive efficiency covers slip and rolling resistance and varies with tyre type, inflation, ballasting and surface condition, which is why the same implement needs a bigger tractor on soft ground than on firm — and why a heavily loaded rear axle behaves differently from a light one. The recommended horsepower class rounds up to commercially available sizes and deliberately leaves no margin beyond that, so allow additional headroom for hills, transport work, hydraulic loads and future implements rather than buying to the exact number. Field capacity assumes steady working and excludes refilling, adjustment and breakdown time. Use these figures for selection and planning, and confirm against the implement manufacturer's stated power requirement before committing to a purchase.