Strengths: Looking for climate change signals is a current concern. The studied relationship between acreage and climate has problematic interpretation, which is recognized in the project.
Points for consideration:
Differenced corn and soy should not have a negative trend - this is a visual artifact from comparison with temperature.
“No clear seasonality” should be the case for annual data
The construction of the 0.0698 p-value is not clearly explained.
$\epsilon_n$ is missing from the equations for $Y_n$
Careful discussion of confounding is needed when considering any causal inferences between temperature and crop acreage.