The assumption that seed–soil contact is important for germination of seeds has influenced imbibition research and equipment design but has not been tested. This study compared germination with and without seed–soil contact. Over a temperature range from 3 to 28°C, wheat (Triticum aestivum L.) seed was either provided with good seed–soil contact or separated from soil by fiberglass cloth. The germination system was sealed to prevent evaporation. At soil water potentials of −4.5 and −2.3 MPa, no seeds germinated in either treatment. When the soil water potential was −1.1 to −0.15 MPa, the average increase in germination time due to the absence of seed–soil contact was 0.3 d (5.6%). Days to germination ranged from 1.1 d at −0.15 MPa and 28°C, to 18.3 d at −1.1 MPa and 3°C. These results show that vapor transport may be the most important mechanism for imbibition and that liquid transport through seed–soil contact may make little contribution. Recognition of vapor transport as a sufficient, and perhaps dominant, mechanism for water transport between seed and soil should improve modeling efforts and planting equipment designs.

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