A new finding by Agricultural Research Service soil scientist Stewart B. Wuest has stunned many plant scientists. Until recently, it was generally believed that seeds must be in direct contact with soil to obtain liquid water needed for germination. Then Wuest discovered the importance of water vapor.
From his research on wheat seeds at ARS' Columbia Plateau Conservation Research Center in Pendleton, Ore., as well as from studying previously published data, Wuest concluded that water vapor in the soil is actually what makes seeds germinate. With a relative humidity of close to 99 percent in soil, the seeds didn't need to be tightly compacted in the soil to grow. In fact, seeds that were separated from the soil by crop residue still germinated, because the vapor was able to reach them.
Wuest also found that, thanks to water vapor, seeds separated from soil by a layer of fiberglass cloth germinated just as well as those touching the soil. He was even able to germinate seeds suspended in air above water, using just the vapor rising from it.