Land, Water and Environmental Management
Soil as a managed resource
Candidates must understand soil texture (sand, silt, clay proportions) versus structure (aggregation, porosity), cation exchange capacity, pH and nutrient availability, organic matter and soil biology. Link these to erosion processes: sheet, rill, gully, wind and tunnel erosion, and to control measures such as contour banks, stubble retention, cover crops, windbreaks and controlled trafficking to limit compaction.
Water and nutrients
Know the water cycle on farm: infiltration, drainage, evaporation, transpiration, runoff and storage in soil. Understand plant available water, field capacity and permanent wilting point, plus irrigation scheduling by evapotranspiration replacement. Nutrient management requires knowledge of the nitrogen cycle (fixation, mineralisation, nitrification, leaching, denitrification, volatilisation), phosphorus movement in runoff, and the difference between soil testing and plant tissue testing. Be ready to discuss salinity, waterlogging, acidification and nutrient stratification.
Environment and regulation
Understand catchment thinking, riparian zones, buffer strips, nutrient balances, effluent and manure management, and off-site impacts such as eutrophication. Know the purpose of environmental management frameworks: nutrient management plans, water entitlements, native vegetation retention, and monitoring for continuous improvement.
Traps in questions
- Confusing soil texture (fixed property) with structure (manageable).
- Assuming lime fixes all acidity instantly; it reacts slowly and may not reach subsoil.
- Treating leaching and runoff as the same loss pathway; one is downward through soil, the other across the surface.
- Recommending more fertiliser when the constraint is water, pH or compaction.
- Forgetting that riparian and buffer zones work by slowing water and trapping sediment, not by filtering dissolved nutrients completely.
Worked example: irrigation scheduling rule
If reference evapotranspiration is 6 mm/day, crop coefficient is 0.8 and effective rainfall is 2 mm, crop water use = 6 x 0.8 = 4.8 mm; deficit = 4.8 - 2 = 2.8 mm/day. Over 5 days the deficit is 14 mm, roughly 140 m³/ha (1 mm = 10 m³/ha). Rule of thumb: irrigate to replace the deficit in the root zone, and check soil moisture before irrigating rather than following a fixed calendar.