Field studies conducted in 1993 on an Eel loam soil compared the growth and yield response of direct-seeded cabbage, cucumber, snap bean, and sweet corn, and transplanted cabbage, to a compacted soil layer (>2.5 MPa penetrometer resistance) at the 15 - 30 cm depth. Direct-seeded cabbage and snap bean were most severely affected by compaction, with 50% yield losses, and much smaller cabbage head size in compacted plots. Transplanted cabbage had a 30% lower yield in compacted compared to uncompactcd plots. Early vegetative growth of cucumber was less stunted by compaction compared to snap bean and cabbage, but compaction nevertheless resulted in a 50% reduction in total cucumber yield. Compaction delayed maturity and reduced early yield of cabbage, snap bean, and cucumber. Sweet corn yield was reduced by only 10% when grown on compacted soil, and there was no delay in maturity. Sweet corn responded more negatively to compaction in a 1992 field experiment,
Greenhouse studies found a reduction in total plant biomass at 21 days after planting of 30%, 14%, 1%. and 3% for snap bean, cabbage, cucumber, and sweet corn, respectively, in pots compacted at the 10 cm depth. Sweet corn had a significantly higher proportion of root biomass in the compacted zone compared to the other crops. For all species, the growth reductions could not be attributed to reductions in leaf turgor, photosynthetic rate per unit leaf area or leaf nutrient status.