Observations of the microwave emissions at 1.413 GHz (L band) and 2.65
GHz (S band) from a silt loam soil exhibited an oscillatory behavior
in time as the soil was being irrigated. The oscillations are attribut
ed to interference between reflections from the air-soil interface and
the wet soil-dry soil interface as the latter moved down in the soil.
The magnitude of the first oscillation at L band was 56 K, and at S b
and it was 40 K, with oscillation damping out after about three cycles
to the brightness temperature expected for the wet soil. The emission
was modeled using a coherent model, and the results show qualitative
and quantitative agreement with the observations.