mmho/cm
millimho per centimeter
Electrical conductivityexact by definition
The millimho per centimetre is exactly 0.1 siemens per metre, and it is identical to the decisiemens per metre that soil science uses today. It is the classic unit of irrigation water and soil salinity, where a saturated paste extract above about 4 mmho/cm begins to depress yield in salt-sensitive crops. The conversion is exact.
| 1 mmho/cm | 1,000 μS/cm |
Where the unit came from
The US Salinity Laboratory Handbook 60 of 1954 set the framework for salinity classification in millimhos per centimetre, and the thresholds in it were carried unchanged into the decisiemens per metre when the units were renamed. That is why agricultural salinity classes still land on round numbers.
Solvers that use electrical conductivity