Abstract
Salinity of soil and water severely hinders rice cultivation in the coastal regions
of many countries. Conjunctive use of fresh water and saline water under
suitable management practice(s) may mitigate this limitation. This study
investigated such possibility by conducting three experiments at Field
Lysimeter Yard of the Bangladesh Institute of Nuclear Agriculture (BINA),
Mymensingh during 2014-15, 2015-16 and 2016–17. The experiments were laid
out in split-split plot design arrangement in a completely randomized design
(CRD) with three replications. The first experiment identified sensitivity of
growth stages of four rice cultivars (Binadhan-8, Binadhan-10, BRRI dhan28 and
BRRI dhan47) to salinity by imposing four salinity levels of irrigation water
(fresh water as control, and saline water of 6, 9 and 12 dS m1) on six growth
stages (establishment, tillering, panicle formation, flowering, maturity and all
growth stages together). The second experiment evaluated effectiveness of four
amendments (no amendment as control, cowdung manure @ 6 t ha 1, gypsum@
150 kg ha 1 and combination of cowdung manure and gypsum at these rates) in
ameliorating salinity stress on the rice cultivars. The last experiment evaluated
four irrigation-drainage management practices (2-5 cm continuous ponding,
continuous saturation, and changing irrigation water after 3 and 5 days of
application by maintaining 2-5 cm ponding depth) for minimizing the effect of
saline-water irrigation on the rice cultivars. The establishment and flowering
stages were found the most critical to saline-water irrigation. Gypsum and
combination of gypsum and cow dung most effectively ameliorated salinity
stress on the rice cultivars, which could tolerate up to 12 dS m-1 irrigation-water
salinity without appreciable yield loss. Replacing saline irrigation water after 3
days of application by maintaining a 2-5-cm ponding depth was the best
irrigation-drainage management practice to produce Boro rice with conjunctive
use of fresh water and saline water. Therefore, irrigation with fresh water in
sensitive stages and saline water in other stages of salt-tolerant rice cultivars
with intermittent replacement of saline irrigation water would be a good
strategy for rice cultivation in the coastal saline regions.