Management of Salt-Affected Soils - Practices of Irrigation and On-farm Water Management - page 290

sodium measured but not exchangeable. Once this correction is made, the results
are expressed as percent exchangeable sodium.

Estimation of SAR

After determining the ionic concentrations of Na, Mg, and Ca; SAR value can be
calculated using standard formula as described in an earlier section.

Interpretation of the Results

The general interpretation of the results is summarized in Tables 8.6 and 8.7 .

Table 8.6 Interpretation of salinity hazard based on EC value

EC of saturation
extract (dS/m) Salt rank Interpretation

0-2 Low Very little chance of injury on all plants

2-4 Medium Sensitive plants and seedlings of other plants may show

injury

4-8 High Most non-tolerant plants will show injury

8-16 Excessive Salt tolerant plants will grow, other crops will show severe

injury

>16 Very excessive Very few plants will tolerate and grow

Table 8.7 Interpretation of sodicity hazard based on Na, SAR, ESP, and Ca:Na ratio

Parameter Value Alkali rank Interpretation

Sodium percent (%) 0-10 Low No adverse effect on soil

>10 Excessive Soil dispersion results in poor soil physical

condition and plant growth is restricted

SAR > 13 Indicates sodic soil

ESP >15 Indicates sodic soil

Ca:Na < 10:1 Sodium may begin to cause soil structural

problems

8.3.4 Salinity Mapping and Classification

8.3.4.1 Salinity Mapping

The purpose of classifying and mapping salinity is to identify various types and
extent to quantify the issue and move toward recommended management practices.
The maps provide an excellent extension tool to local agents and let farmers know
the extent of salinity issues beyond their property. Analyses of the data allow policy