Agriculture Reference
In-Depth Information
percolation in the fields (Bhutta and Smedema, 2007). Even though much
of this lost water is now captured by extensive groundwater pumping and
used downstream, this does not apply to the saline groundwater zone. From
a basin perspective, improvements in farm irrigation efficiency may result
in little gain in saving water except for those areas where groundwater is
saline (Clemmens and Allen, 2005). Nevertheless, reducing water deliv-
ery to farms and improving farm water use efficiency are important from
the perspective of other considerations like reducing energy consumption,
costs and improving production (Karimi et al., 2012).
Farmers' current irrigation practices in Pakistan are aimed at apply-
ing the maximum amount of water in an attempt to maximize their crop
yields. Farmers having access to groundwater in addition to canal water
tend to apply more water compared to those who are fully dependent on
canal water. Due to uncertainties in canal water supplies, farmers usually
do not plan their irrigations in advance. Their decision to irrigate mainly
depends upon the crop water need and availability of water in the canal
system and/or access to groundwater. The water requirements of different
crops depend upon environmental conditions, soil types and other factors
that are equal across all the farms. However, different studies have shown
that the number of irrigations applied to a wheat crop varies from 4 to
7, to cotton from 4 to 8, and to rice from 16 to 25 (Vlotman et al., 1994;
Raza and Choudhry, 1998). The depth of individual irrigation applications
has been the subject of many research studies. Vehmeyer (1992) found
that it ranged from 60 to 90 mm. Vlotman and Latif (1993) determined
the average depth applied per irrigation at between 70 and 80 mm. On the
basis of fi eld measurements, Raza and Choudhry (1998) reached a value
of 60-90 mm with an average of about 85 mm per irrigation. If, on aver-
age, 6 irrigations to wheat and cotton and 20 irrigations to rice crop are
considered with an amount of 80 mm per irrigation, irrigation water ap-
plied to wheat and cotton will be equal to 480 mm whereas for rice it will
be 1600 mm. The average irrigation application in the Indus basin is 36%
(Ahmad, 2009).
Considering the water scarcity in the Indus basin, many researchers
have tried to fi nd optimal irrigation schedules for different crops. The
modelling work of Qureshi and Bastiaanssen (2001) has suggested that
