Soil is the foundation of both the built environment and the food production systems of a regenerative community. Before development, a systematic soil survey should characterize the texture, structure, depth, drainage, and chemistry of soils across the site.

Field soil assessment methods include: the jar test (mixing a soil sample with water and watching silt, sand, and clay settle out to determine texture), the ribbon test (squeezing moist soil between thumb and forefinger to assess clay content), percolation tests (measuring how quickly water infiltrates for drainage design), and profile excavations (digging test pits to observe soil horizon depth, structure, and the presence of caliche or hardpan).

Laboratory soil tests provide more precise information about pH, nutrient levels, organic matter percentage, and the presence of contaminants (especially important on previously developed or agricultural sites with potential pesticide residues). These tests guide soil amendment strategies for food production zones.

Caliche: A Southwest Building Reality

Caliche is a calcium carbonate hardpan layer found widely in arid southwestern soils. It forms as calcium leaches downward through alkaline soils and precipitates out at the depth where moisture penetration typically ends.

Caliche layers typically occur 6–36 inches below the surface and can be from a few inches to several feet thick. They can impede drainage, block root penetration, and make excavation difficult.

In community design, caliche has both challenges and advantages. It impedes infiltration (important for septic and wetland system design) but creates a natural hard layer that can be used for road base or worked around for cistern foundations.

Identify caliche early in site assessment — it affects building foundation design, water system design, and agricultural zone selection.