Subtopic: Calculation of performance parameters – field capacity, efficiency, performance index, application rate and losses
Question Statement:
A precision seed planter can plant 10 seeds per revolution of the metering plate with a row to row distance of 450 mm at a speed of 6 km h⁻¹. A plant population of 36 plants per square meter is desired for the crop. The germination percentage of the seed is 90 %. If the planter ground wheel has a rolling radius of 350 mm, the speed ratio of metering plate to the ground wheel required to obtain the desired plant population is ________.
Official Answer Key:
3.90 to 4.10
Step-by-Step Solution & Explanation
Plants required per metre of row = population × row spacing = 36 × 0.45 = 16.2 plants m⁻¹.
Allowing for 90 % germination, seeds to be dropped = 16.2/0.90 = 18 seeds m⁻¹.
Ground-wheel circumference = 2πr = 2π(0.35) = 2.199 m per revolution.
Let k = N_plate/N_wheel. Seeds per wheel revolution = 10k; distance covered = 2.199 m.
Seeds per metre = 10k/2.199 = 18 ⇒ k = 18 × 2.199/10 = 3.96 — within the official range 3.90–4.10.
Note: the forward speed of 6 km h⁻¹ is redundant data — plant spacing depends only on the gear ratio and wheel circumference (no-slip assumption).
Section 3 — Farm Power
9 questions · 15 marks
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