When purchasing a seeder, how to verify metering accuracy and calibration method?

• Seeding accuracy measured by qualified seed spacing rate, must be ≥90%.
• Require metering type: mechanical or pneumatic; pneumatic needs stable vacuum.
• Calibrate at rated forward speed; accuracy must hold within ±10% speed change.
• Check seed plate hole count matches seed size to avoid double/missed seeding.
• Obtain test report showing row-to-row discharge CV ≤5%.