  The Mapper of the IGM Spin Temperature (MIST) is a new ground-based,
single-antenna, radio experiment attempting to detect the global 21 cm signal
from the Dark Ages and Cosmic Dawn. A significant challenge in this measurement
is the frequency-dependence, or chromaticity, of the antenna beam directivity.
MIST observes with the antenna above the soil and without a metal ground plane,
and the beam directivity is sensitive to the electrical characteristics of the
soil. In this paper, we use simulated observations with MIST to study how the
detection of the global 21 cm signal from Cosmic Dawn is affected by the soil
and the MIST beam directivity. We simulate observations using electromagnetic
models of the directivity computed for single- and two-layer models of the
soil. We test the recovery of the Cosmic Dawn signal with and without beam
chromaticity correction applied to the simulated data. We find that our
single-layer soil models enable a straightforward recovery of the signal even
without chromaticity correction. Two-layer models increase the beam
chromaticity and make the recovery more challenging. However, for the model in
which the bottom soil layer has a lower electrical conductivity than the top
layer, the signal can be recovered even without chromaticity correction. For
the other two-layer models, chromaticity correction is necessary for the
recovery of the signal and the accuracy requirements for the soil parameters
vary between models. These results will be used as a guideline to select
observation sites that are favorable for the detection of the Cosmic Dawn
signal.
