AFU Common Entrance Exam: Agriculture

What the agriculture paper tests

The Agriculture section of the AFU Common Entrance Exam checks whether you can apply agronomy, soil science, horticulture and plant protection to farm decisions. Expect questions on soil pH and nutrient availability, seed quality, crop geometry, fertilizer grades, pest thresholds and cropping calendars. The exam favours calculations and cause-effect reasoning over recall alone.

Core rules to hold

• Fertilizer grades are quoted as N-P2O5-K2O percentages by mass, not elemental P or K. Urea is 46% N; DAP is 18% N and 46% P2O5.
• Pure live seed (PLS) = germination % x purity %; adjust seed rate by dividing the recommended PLS rate by the PLS fraction.
• In crop geometry, plant population per hectare = 10,000 / (row spacing in m x plant spacing in m). Keep units consistent.
• Soil pH controls availability: most macronutrients are most available near pH 6.0-7.0; lime raises pH, gypsum supplies Ca without raising pH much.

Worked example

A recommendation is 100 kg N/ha and 40 kg P2O5/ha. How much DAP and urea are needed?

1. Supply P first with DAP: 40 kg P2O5 / 0.46 = 87.0 kg DAP/ha.
2. DAP also supplies N: 87.0 x 0.18 = 15.7 kg N/ha.
3. Remaining N = 100 - 15.7 = 84.3 kg N/ha.
4. Urea = 84.3 / 0.46 = 183.3 kg urea/ha. Reasoning: P fixes the DAP rate; DAP's N credit reduces urea.

Traps

Using elemental P instead of P2O5; forgetting the N in DAP; mixing kg/ha with g/m2; treating germination as a percentage without converting to a fraction; assuming lime and gypsum are interchangeable.