Field-Scale Evaluation of Seed Placement Quality in No-Till Sunflower Sowing: Operating Speed, Soil Moisture, and Compliance with Seeder Settings

Achieving stable seed placement under No-Till conditions remains challenging because the seeding units operate directly in undisturbed soil with spatially variable properties and surface residues. This study evaluated seed-placement quality and compliance with predefined seeder settings during field-scale No-Till sunflower sowing under three operating regimes. A CASE IH Quadtrac 620 tractor coupled with an AMAZONE Primera DMC 9001-2C pneumatic seeder was evaluated in three separate field areas. Each area was associated with one nominal operating regime: 8, 10, or 12 km h−1, designated as S8, S10, and S12, respectively. A total of 135 sampling positions were evaluated for displayed operating speed, sowing depth, seed spacing, missing placements, double placements, and soil moisture. The mean sowing depths recorded for the S8, S10, and S12 zone–regime combinations were 5.97, 9.42, and 6.02 cm, respectively. The S8 field area showed the highest compliance with the target depth, with 92.1% of the measured seeds positioned within 4–6 cm. The proportions of seed-spacing observations within the target range of 20–25 cm were 0% for S8 and S10 and 17.8% for S12. Missing and double placements were numerically more frequent in the areas associated with the higher nominal speeds. However, because each operating regime was evaluated in a separate field area, the observed differences cannot be attributed separately to operating speed, soil moisture, or spatial field variability. The findings are therefore limited to the sampled field areas and provide a descriptive assessment of seeder performance under the specific operating conditions.