Integrated Multi-Row Onion Production Under Contrasting Seasonal Conditions: Seeder Optimization, Nutrient Management, Crop Protection, and EIQ-Adjusted Sustainability

Reliable establishment of direct-seeded onion requires coordinated control of sowing geometry, nutrient supply, crop protection, and resource use. This study combined Hartley-4 optimization of a four-section, multi-row ridge seeder with a two-year randomized complete block experiment comprising ten fertilization × crop-protection treatments. Engineering tests at 5.2, 6.4, and 7.6 km h−1 identified a central operating setting at 6.4 km h−1 that maintained a sowing depth of 1.5–2.0 cm and depth variability below 0.5 cm. In field plots, chemical protection with vermicompost produced the highest mean total yield (25.54 t ha−1), whereas chemical split NPK maximized marketable and standard yields. Biological split NPK showed the greatest two-season yield retention (0.780), although biological protection was associated with higher downy mildew severity. The biological biocomplex treatment ranked highest under the author-defined EIQ-adjusted resource-efficiency screening index, but sensitivity analysis showed that intermediate rankings depended on aggregation assumptions. The optimized design provides manufacturers with validated parameter ranges and gives users a constant-speed platform for comparing crop-management programs. Future research should test the seeder across contrasting soil textures and speeds and directly measure field capacity, fuel use, and long-term agronomic performance.