Moderate reductions in water and nitrogen inputs enhance lodging resistance of spring wheat under a novel drip...

Drip irrigation improves water and fertilizer use efficiency in wheat. However, it may promote excessive stem elongation and shallow root development, increasing lodging risk. Although optimized water and nitrogen management can enhance lodging resistance in drip-irrigated wheat, the regulatory thresholds and underlying mechanisms remain unclear, particularly under the novel TR6S pattern.

A two-year field experiment was conducted in 2024-2025 to systematically investigate the effects of water-nitrogen interactions on the lodging resistance of spring wheat under the TR6S pattern. Four irrigation levels were applied: 4500, 4200, 3900, and 3600 m³·ha^-1, designated as W4500, W4200, W3900, and W3600, respectively. Three nitrogen application levels were applied: 300, 270, and 240 kg·ha^-1, designated as N300, N270, and N240, respectively.

Wheat lodging rate exhibited a decreasing-increasing trend with reductions in both irrigation and nitrogen inputs. Compared with the traditional treatment (N300-W4500) (CK), moderate reductions in water-nitrogen inputs (N270-W4200) significantly increased the grain yield by 7.88-8.35% and reduced the lodging rate by 56.18-56.99%, achieving a favorable balance between yield (8.65-8.87 t·ha^-1) and lodging rate (12.14-14.20%). Further reductions in water and nitrogen inputs decreased the lodging rate to some extent, and grain yield declined concurrently. The PLS-SEM model verified the reasons for the optimal lodging resistance performance of N270-W4200. Moderate nitrogen reduction enhanced the activities of key enzymes involved in lignin synthesis in basal stems, increased lignin content and stem firmness, and strengthened the mechanical properties against lodging, playing a major role in enhancing wheat lodging resistance. Moderate reduction in irrigation primarily increased root weight in the 30-60 cm soil layer, thereby enhancing root anchorage strength. However, as the irrigation volume did not efficiently regulate root growth in the middle soil layer (30-60 cm), it played only a secondary role in enhancing wheat lodging resistance.

This study quantified the optimal water-nitrogen input threshold for the TR6S pattern, with an irrigation volume ranging from 4203.55 to 4237.14 m³·ha^-1 and the nitrogen application amount ranging from 264.49 to 283.16 kg·ha^-1. These results provide a theoretical basis for promoting the TR6S pattern and technical references for studying crop lodging resistance in arid and semi-arid regions.