Farm Structures and Environmental Control
Farm Structures and Environmental Control examines functional farm buildings and the microclimate inside them. The exam tests site selection, layout, ventilation, space allowances, grain storage and control of temperature, humidity and gases for livestock and produce.
Core rules
- Site selection: well-drained, elevated land, away from flooding, with access, water, power and wind direction considered; keep manure and odour sources downwind of dwellings.
- Orientation: long axis generally east–west in hot climates reduces direct solar gain on side walls; local wind and rainfall also matter.
- Ventilation removes heat, moisture, dust and gases. Ridge openings, side openings and fans provide stack and wind-driven air exchange.
- Floor space and feeder/waterer space must match species, age and body weight; overcrowding raises humidity, disease and stress.
- Grain stores need a damp-proof floor, rodent-proof walls, weather-tight roof, and ventilation or aeration to prevent moisture migration.
- Roof slope should shed heavy rain; gutters and drains protect foundations.
Worked example
Store 10 t of paddy at about 600 kg/m³. Required volume = 10,000 ÷ 600 = 16.7 m³. A cylindrical bin of diameter 3 m has cross-sectional area π × 1.5² = 7.07 m². Required grain height = 16.7 ÷ 7.07 = 2.36 m. Add freeboard, say 0.5 m, so the bin wall is about 2.9 m. Reasoning: use bulk density to convert mass to volume, then divide by floor area; never design exactly to the grain height because filling and aeration need space.
Traps
Do not use floor area alone when mass and bulk density are given. Do not ignore freeboard or the angle of repose in hopper-bottom bins. In ventilation questions, distinguish air changes per hour from air velocity. A roof that is weather-tight but unventilated can still allow condensation and mould.