Water Resources Management - Practices of Irrigation and On-farm Water Management - page 157

Soil-Crop-Weather Management
Manipulation of Seedling Age In transplanted rice, seedlings 25-45 days old are
normally used. Recent research results showed that up to 55-65-day-old seedlings
can be used for Boro (Kharif) season (BINA, 2005 ) . The older seedlings (55-65
days) could reduce crop duration up to 15 days. That means that total crop dura-
tion in the field (from transplanting to maturity) can be reduced by 30 days (15 days
late transplanting +15 days early maturing), which obviously reduces the crop water
requirement, and increases water productivity. Ali et al. (1992) obtained the high-
est yield with 60-day-old seedling for Aman (monsoon) season. Singh and Sharma
(1993) and Paul (1994) observed insignificant yield difference for 30-60-day-old
seedling for monsoon rice.
Priming or Soaking of Seed The technique of seed priming, where the seed is
soaked in water (usually 10-12 hrs), then surface dried and sown, has been shown to
improve plant stands and provide benefits in terms of earlier maturity and increased
seed yield in a range of crops (wheat, maize, lentil, chickpea, etc.) in rainfed, as well
as irrigated crops grown on normal soils. This technique reduces the post-sowing
or pre-sowing irrigation needs and saves water. Besides, priming had a significant
positive effect on yield. Thus, the water productivity is increased. Kahlon et al.
( 1992 ) observed that soaking wheat for 24 or 48 h in water or pre-germinating seed
sowing increased grain yield by 10.3, 16.3, and 21.2%, respectively, compared to
sowing untreated seeds.
Crop Sowing Based on Weather Analysis or Forecast With the probability anal-
ysis of long-term rainfall data or the use of the short- or medium-term weather
forecast, dry spell can be avoided and thus the need of irrigation can be avoided.
Chahel et al. ( 2007 ) observed that with the shifting of transplanting dates of rice at
Punjab, India, from higher (mid-May) to lower (end of June onward) evaporative
demand, there was an increase in grain yield, while there was a reduction in ET and
irrigation water applied.
Changing Crops Another method for reducing evapotranspiration in irrigated
areas is to alter cropping patterns. In climates with hot summers and mild win-
ters, summer crops can be minimized, and more winter crops (vegetables, flowers)
can be grown. In addition, crops with lower water requirements can be introduced.
Where there is some rainfall, dryland farming systems with supplemental irrigation
(if necessary) can replace conventional irrigated agriculture.
Use of Anti-transpirants Spraying plants with anti-transpirants may have some
application for ornamental plants (lawns and shrubs) where production or fast
growth is not important. For agricultural crops, however, a reduction in transpira-
tion usually also means a reduction in yield. Thus, anti-transpirants generally are
not feasible for reducing water use of agricultural crops.