Management of Salt-Affected Soils - Practices of Irrigation and On-farm Water Management - page 300

Fig. 8.3 Schematic
representation of relative
yield versus EC

1

S

EC t EC 0

where

Y r = relative yield reduction (%)

EC e = salinity of the saturation extract of field soil (dS/m)

EC t = threshold salinity level of the soil above which yield starts to decline

(maximum EC value for 100% yield potential) (dS/m)
EC 0 = salinity level of soil above which yield is zero (dS/m)

S = slope of the response function between EC t and EC 0 (Fig. 8.3 )

1
EC 0 −

=

EC t

Yields of most crops are not significantly affected where salt levels are 0-2 dS/m.
Generally, a level of 2-4 dS/m affects some crops (slightly tolerant). Levels of 4-5
dS/m affect many crops (moderately tolerant) and above 8 dS/m affect all but the
very tolerant crops.

8.5.5 Sample Examples

Example 8.1
In a saline area, the EC of a wheat field during its growth period was found 7.0
dS/m. Estimate yield reduction due to salinity, if the wheat cultivar can maintain
potential yield up to 4 dS/m, and the yield at EC>22 dS/m is zero.

Solution

Here, EC e = 7 dS/m

EC 0 = 22 dS/m

EC 100 =

4 dS/m
We get, relative yield, Y r =

EC 0 − EC e

×

100

EC 0 − EC 100

Putting the above values, Y r = 83.33%

Yield reduction = (100-83.33)% = 16.67% (Ans.)