Septic soil in Greene County, MS, by the numbers
Very limited
83.4% of Greene County, MS's surveyed soil comes back "Very limited" in USDA's own SSURGO data, the county's dominant condition for a septic absorption field. Practically, that rules out a simple gravity system for most of the county - 83.4% of it sits in USDA's most-constrained bucket. Greene County, MS is 712.738 square miles with a population of 13,675.
What Greene County's reading doesn't cover
Greene County's rating is an average across the whole county, not a promise about any one lot inside it. A local percolation test, typically $750-$1,850 (around $1,300 typical), is the only way to know what one lot in Greene County will actually do.
What a system would cost here
With 83.4% of Greene County rating "Very limited", a standard gravity system is not a safe assumption here. The engineered-system range, $10,000-$40,000 (mound or aerobic treatment), is the more realistic number to plan around, against $3,000-$8,000 for a conventional system on the rare lot that passes.
How Greene County, MS compares
Nationally, Greene County, MS is the 1,832-most-constrained of 3,058 rated counties for septic soil. Within Mississippi alone it ranks 65 of 82.
Further reading
How this rating is built, and its real limits · Conventional vs. engineered septic systems