Abstract
Twin-row planting arrangements are commonly used in agronomic crops to improve production and enhance disease management, but little information exists on their application in onion production. This study evaluated the impact of twin-row arrangements at high planting density on yield and bulb size distribution of short-day onion (‘Sweet Magnolia’). Treatments combined within-row and between-row distances and the number of rows per bed top to achieve the desired planting arrangement and resultant planting densities. Treatments were four single rows of plants per bed top spaced 6 inches × 12 inches (within by between row), four single rows spaced 4 inches × 12 inches, or four twin rows (eight rows in total) spaced 6 inches × 4 inches among twins with 12 inches between twin-row pairs from middle to middle, resulting in planting densities of 58,000, 87,000 (commercial standard), and 116,000 plants per acre, respectively. Onion total and marketable yields increased while bulb size decreased as planting density rose. The twin-row high planting density was equivalent to the commercial standard in both total and marketable yield. Most important, twin rows had a favorable bulb size distribution, with both the highest yield and percentage of jumbo bulbs (≥3 inches in diameter) at 998.3 40-lb bags per acre and 80.2%, respectively. Culls decreased with increased planting density with no difference between twin-row high planting density and the commercial standard. Significant bolting was observed in 2024 at high planting density in conjunction with cooler weather. Our data indicate that twin-row planting arrangements do not outperform the commercial standard planting density in marketable yield but have potential applications for targeting specific bulb sizes by altering the bulb size distribution to favor smaller bulbs.