The Impact of Traffic-Induced Compaction on Soil Bulk Density, Soil Stress Distribution and Key Growth Indicators of Maize in North China Plain

The traffic-induced soil compaction in the field has gradually become an important constraint to sustainable agricultural development. A field experiment was conducted to acquire the stress transmitted caused by multiple passes with different types of tractors and to investigate the impact of these stresses on soil bulk density and crop growth. The experiment applied two tractors with different masses: LOVOL M904 (HC) and John Deer 280 (LC), and six different treatments of 0 (C0), 1 (C1), 3 (C3), 5 (C5), 7 (C7), and 9 (C9) tractor passes for each tractor. The results showed that at each number of passes, tractors with small axle-loads at 0–20 cm depth generated higher soil additional stress, while tractors with large axle-loads at 20–80 cm depth generated higher soil additional stress. In the 0–20 cm soil layer, when the number of continuous passes is less than 7 times, the passes of a small axle-load tractor lead to larger soil bulk density, and when the number of continuous passes is more than 7, the compaction of large axle-load tractor leads to larger soil bulk density. At depths of 20–80 cm, compaction by large axle-load tractors results in larger soil bulk density. In this study, different levels of tractor compaction inhibited key growth indicators of maize, resulting in yield reductions. The effect of different tractor load compaction on maize yield increased significantly with the number of compaction passes, with 1–5 tractor passes having no significant effect on yield and 7–9 passes producing greater yield reductions for HC. This study will provide a theoretical basis and technical support for the selection of agricultural machinery and reasonable tillage technology.