Management of Salt-Affected Soils - Practices of Irrigation and On-farm Water Management - page 314

8.6.2.9 Increasing Water Use of Annual Crops and Pastures

In some areas, salinity is caused by change in vegetation. Native vegetation is
cleared and replaced with annual crop and pasture species, which allow a larger
proportion of rainfall to remain unused by plants and to enter the groundwater. As
a result, groundwater tables have risen; bringing dissolved accumulated salts to the
surface. In such areas, increasing the water use of existing annual crops and pas-
tures may play an important rule to minimize salt accumulation at surface. But this
practice alone may not sufficient.

8.6.2.10 Policy Formulation

Land-use planning should be done at the national level, indicating what crops should
be grown at each soil and/or agro-ecological zone. Based on the salinity problem,
suggested specific crop(s) must be grown and it should be monitored and mate-
rialized. This would enhance the best utilization of the land and optimize crop
production.

8.6.2.11 Overall Discussion

Salinity problems may often more complex. Management of salt-affected lands for
agricultural use is largely dependent on the water availability, climatic conditions,
period of salinity, crop standing, and the availability of resources (capital, inputs).
It may require a combination of agronomic and engineering management practices,
depending on careful definition of the main production constraints and requirements
based on a detailed, comprehensive investigation of soil characteristics, water mon-
itoring (rainfall, irrigation water and water table), and a survey of local conditions
including climate, crops, economic, social, political and cultural environment, and
existing farming system. Proper management procedures (soil moisture, irrigation
system uniformity and efficiency, local drainage, and the right choice of crops),
combined with periodic soil tests, can improve the conditions (i.e., prolong the
productivity) in salt-affected soils to a certain extent.

8.6.2.12 Sample Examples

Example 8.3

A pond water has the salinity level 2.0 dS/m. The groundwater salinity level at that
area is 15 dS/m, which is marginal for wheat irrigation. Find out the mixing ratio of
pond water to groundwater to lower the salinity to 8.0 dS/m.

Solution

Given,

EC of pond water, EC p = 2.0 dS/m

EC of groundwater, EC g = 15 dS/m