128 Layer limit superior / inferior
The upper (lower) limit of the layer depth (in cm).
The limit between the organic and mineral layer corresponds to 0 cm.
For organic layers (OL, OF, OH, OFH, Hf, Hfs, Hs), the limits are negative values.
For mineral layers (M05, M01, M51, M12, M24, M48) the limits are positive numbers.