Fig. 1
From: Late-season corn stalk nitrate measurements across the US Midwest from 2006 to 2018

Number of field-guided surveys (i.e., fields) across the US Midwest at the county level where corn stalk nitrate data were measured.
From: Late-season corn stalk nitrate measurements across the US Midwest from 2006 to 2018

Number of field-guided surveys (i.e., fields) across the US Midwest at the county level where corn stalk nitrate data were measured.