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To improve onion ( Allium cepa L.) productivity and soil health, optimizing cultural practices such as drip tape placement, straw mulching, and onion seed depth are crucial in semiarid environments. In 2023, a field experiment was conducted at Malheur Experiment Station in Ontario, OR, USA, using a split-split plot design. The treatments include two drip tape depths (3 and 5 inch) as the main plot, three mulching placements (none, tape row, and nontape row) as the split plot, and two seeding depths (0.5 and 1.0 inch) as the split-split plot. Planting onions at 0.5 inch increased stand establishment significantly compared with 1.0-inch seeding, whereas plant height and leaf number were unaffected by treatments. Thrips ( Thrips tabaci L.) populations were strongly influenced by the interaction between drip tape placement and seeding depth. More shallow drip placement (3 inch) combined with deeper seeding (1.0 inch) resulted in the greatest mean thrips densities (13.7–13.9 adults + larvae per plant). Deeper drip placement with shallow seeding reduced thrips pressure consistently. Total and marketable onion yields were unaffected by drip tape placement; however, a significant interaction between drip tape and seeding depth influenced bulb size distribution, and total and marketable onion yield. Installing drip tape at 3 inch and planting onion seeds at 0.5 inch, or at 5 inch and 1 inch, maximized total and marketable onion yields. Applying mulch at the tape row increased supercolossal bulb production, whereas nontape row mulching improved soil fertility and microbial activity. To optimize onion production, when using the more shallow drip tape (3 inch), planting onion seeds at a depth of 0.5 inch is ideal. Conversely, if the drip tape is placed deeper (5 inch), the ideal planting depth for the onion seeds is 1 inch.