Wide-narrow row spacing reduces mechanical harvest losses in rice by optimizing panicle distribution: evidence from five-year field trials integrating density and cultivar variables.

Objective: The aim of this study was to establish a mechanized rice production technique that simultaneously increases grain yield and reduces harvest loss. Methods: Large-scale field trials were conducted comparing two planting methods, the traditional farmers' equal-row spacing method (FM) and the wide-narrow row spacing method (WNM), and investigated their effects on yield, yield components, plant uniformity at maturity, mechanical harvest loss, and varietal performance. Results: The results demonstrate that WNM enhances yield through two complementary mechanisms. First, it significantly increases the number of productive panicles per unit area, with the high-yield cultivar Lijiang 419 exhibiting a greater response (average yield increasing of 5.5%). Second, WNM markedly reduces mechanical harvest loss by decreasing panicle dropping. The wider row spacing of WNM (36 cm vs. 30 cm in FM) provides larger corridors for the combine header, minimizing incidental contact with adjacent plants and thereby reducing dropped panicles. Additionally, WNM improves panicle neck height uniformity by 4.7-5.0%, ensuring that more panicles are positioned above the cutting height and further mitigating losses. Conclusion: Consequently, the integration of optimized agronomic practices (WNM) with suitable machinery effectively boosts both yield and harvest efficiency, making WNM a promising planting pattern for mechanized rice production areas seeking high yield and low loss.