Effects of Soil Compaction on Straw N Utilization Under Conservation Tillage: A 15 N Tracer Study

ABSTRACT The widespread adoption of agricultural machinery has led to significant soil compaction, a critical constraint on farmland productivity. Utilizing 15 N isotopic tracing and simulated compaction experiments, this study investigated the effects of different compaction levels on the fate of straw‐derived nitrogen (N) in corn under conservation tillage with deep straw mixing incorporation (0–40 cm). Three compaction treatments were established: non‐compaction (A1, 1.21 g/cm 3 ), light compaction (A2, 1.35 g/cm 3 ), and heavy compaction (A3, 1.43 g/cm 3 ). We assessed the straw‐derived 15 N utilization efficiency by crops ( 15 NUE (%)) and the 15 N soil retention rate ( 15 NRR (%)). Results indicated that soil compaction significantly inhibited root development, leading to reductions in grain yield, 15 NUE (%), and 15 NRR (%). Over the three‐year period (2019–2021), the cumulative 15 NUE (%) in A2 and A3 decreased by 23.9% and 44.5%, respectively, compared to A1. Corresponding decreases in 15 NRR (%) ranged from 12.5% to 28.6% in 2019, 8.3% to 17.0% in 2020, and 19.0% to 35.5% in 2021. These findings demonstrate that soil compaction from conventional farming practices adversely affects corn root systems, thereby diminishing grain yield, straw‐N utilization efficiency, and soil N retention. Our study underscores the necessity of mitigating compaction through optimized field management (e.g., controlled traffic farming) while concurrently improving soil structure via organic amendments to enhance nutrient recycling from incorporated straw. This work provides critical empirical evidence for developing integrated straw‐return strategies that synergistically enhance agricultural productivity and soil sustainability.