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With the introduction of the small four‐wheel tractors (ST), agricultural mechanization has developed rapidly in China. In this study, we investigated the impact of these relatively small tractors on soil compaction of a silty clay loam (fine‐silty, mixed, superactive, mesic Typic Argiboroll) in northeast China using soil penetration resistance (PR) and bulk density as soil compaction indicators. The relationship between soil water content and PR, the comparison of soil compaction induced by ST and the medium power tractor (MT), the effect of tractor mass on compaction, the effect of number of tractor passes and tillage on PR, and the effect of compaction on crop yield were studied. Compared with MT‐powered tillage, the ST‐powered tillage system created a more compacted plow layer due to increased passes required with this system. Small four‐wheeled tractors had a statistically significant higher PR than MT in the topsoil and subsoil. The PR had a significant negative correlation ( r = − 0.640, P < 0.01) with soil water content at time of PR measurement. After trafficking in a wheat ( Triticum aestivum L.) field, the highest PR values were found in the 5‐ to 14‐cm depth interval. Crop yield decreased with increasing numbers of tractor passes. There were different yield‐loss responses to compaction for spring wheat and corn ( Zea mays L.). With the development of mechanical tillage in China, the problem of soil compaction may be significantly increased, causing potential yield reductions.
Zhang et al. (Mon,) studied this question.