Agricultural Engineering and Farm Machinery
Farm power and implements
Farm power comes from human, animal, mechanical, electrical and renewable sources. Primary tillage implements include the mouldboard plough, disc plough and chisel plough; secondary implements include harrows, cultivators and levellers. Sowing and planting equipment includes seed drills, dibblers and transplanters. Sprayers, threshers, combine harvesters, pumpsets, drip and sprinkler systems are also tested.
Principles
- Draft and power requirement depend on soil type, depth, width and speed.
- Theoretical field capacity (ha/h) = width (m) × speed (km/h) ÷ 10.
- Field efficiency = actual field capacity ÷ theoretical field capacity × 100.
- Seed drills and sprayers must be calibrated before use.
Worked example
A 3 m wide cultivator works at 5 km/h. Theoretical field capacity = 3 × 5 ÷ 10 = 1.5 ha/h. At 80% field efficiency, actual capacity = 1.5 × 0.8 = 1.2 ha/h. The reasoning is that the formula converts width and speed into area per hour, while efficiency allows for turns, refilling and minor repairs.
Traps that cost marks
Using width in centimetres in the field-capacity formula; forgetting field efficiency; confusing horsepower with kilowatt (1 hp = 0.746 kW); using a rotavator as a primary tillage tool; and spraying without calibrating the nozzle output.