559and December 23 in 2013–2014, under two water regimes—rainfed and supplemen-
tal irrigation. Data showed that late planting under rainfed conditions reduced 1000-
seed weight from 38.7 to 32.3 g and from 45.6 to 26.8 g. This corresponded to yield
reductions from 2.5 to 1.2 t ha−^1 in 2012–2013 and from 2.8 to 0.3 t ha−^1 in 2013–
- However, with supplemental irrigation, yields from early and late plantings
were similar in both years. Supplemental irrigation in the 2012–13 growing season
increased yield from 2.5 to 4.3 t ha−^1 (72 %) with early planting and from 1.2 to 4.4
t ha−^1 (266 %) with late planting. In 2013–2014, the corresponding values were
from 2.8 to 5.4 t ha−^1 (93 %) with early planting and from 0.3 to 5.3 t ha−^1 with late
planting. Under rainfed conditions, two-year average evapotranspiration ranged
from 236 to 330 mm under early planting and from 181 to 232 mm under late plant-
ing. Under SI, it ranged from 396 to 593 mm with most of the water lost as transpi-
ration as evident from the biomass gains. On average of the three watering treatments,
water productivity for early and late planting was, respectively, 9.2 and 7.8 kg ha−^1
mm−^1 in 2012–2013 and 10.5 and 5.1 kg ha−^1 mm−^1 in 2013–2014. But the effect of
SI on WP was not consistent. It was only positive in 2012–2013 under both early
and late planting dates, ranging from 144 % to 218 %, respectively. The authors
concluded that early planting and supplemental irrigation with late planting were
options for mitigating drought and heat stress which are exacerbated by the effects
of climate change in the dry areas in WANA.
3 Discussion
3.1 Supplemental Irrigation to Alleviate Moisture Stress
Unlike full irrigation, the time for SI irrigation cannot be determined in advance.
This is because the basic source of water for rainfed crops is rainfall which, being
variable in amount and distribution, is difficult to predict. Since SI water is best
given when the soil moisture drops to a critical level, the time for irrigation can be
best determined by measuring soil moisture on a regular basis. There is no simple,
low-cost device that an average, low-educated farmer can use for this purpose. The
well-known tensiometers are not suitable since SI management allows a lower soil
moisture potential than these instruments can read. Other more sophisticated meth-
ods are either costly or too complex for farmers to use. Instead, most farmers in the
region rely on personal experiences related to the amount of rainfall received and
crop appearance. They tend to irrigate earlier and more frequently than necessary
when a water supply is available.
ICARDA has developed a methodology, through modeling, which analyzes his-
torical rainfall records in the area, together with soil and crop parameters, to deter-
mine the most probable conditions after set rainfall amounts at any time during the
season. Research in the WANA region has shown that the amount of rain falling
before the end of February is a good indicator of what will occur later in the season.
Supplemental Irrigation: A Promising Climate-Resilience Practice for Sustainable...