Agricultural Engineering and Farm Machinery
What the exam tests
Agricultural Engineering and Farm Machinery tests power sources, tillage implements, seed drill calibration, irrigation and pumps, threshing, and machinery selection and cost.
Core rules
- Draft is the force required to pull an implement; power = force × speed. Use consistent units: kW = kN × m/s.
- Field capacity is the area a machine can cover per unit time. Theoretical field capacity = width × speed; effective field capacity is lower because of turns, refilling and breakdowns.
- Seed drill calibration: collect seed over a known area, then scale to one hectare. Area covered = number of wheel revolutions × wheel circumference × effective working width.
- Irrigation efficiency = water stored in the root zone ÷ water delivered.
Worked example
A 4-row seed drill has a 2.0 m effective width; the drive wheel circumference is 2.0 m. After 10 wheel revolutions, 0.80 kg seed is collected. Area covered = 10 × 2.0 × 2.0 = 40 m². Seed rate = 0.80 kg ÷ 40 m² × 10,000 m²/ha = 200 kg/ha. Reasoning: convert the calibration area to one hectare before scaling; do not multiply by the number of rows again because the effective width already includes them.
Traps
Using wheel diameter instead of circumference; double-counting row width; mixing hp and kW; and reporting theoretical rather than effective field capacity.