Time and method of application of N fertilizer is a major
agronomic practice contributing to the rapid growth in rice
production even under submergence. In a study, Gautam et al.
(2014a) reported that pre-submergence N application was
harmful for submerged rice, whereas, post-submergence N
application positively influenced the survival and growth of rice.
In this study, results revealed that foliar application of post-flood
N was better than broadcast application of post-flood N. Pande
et al. (1979) suggested that use of N through foliar spray after
flash
flooding resulted in better recovery and higher productivity
of rice under waterlogged conditions. Basal P and post-flood N
application either though broadcasting or foliar spray resulted in
significantly higher leaf N concentration, Pn rate, effective tillers
and ultimately yield. The recovery of plants subjected to simulate
flash
flooding was better with top dressing of N fertilizer after
floods, as some of the partially damaged tillers regained growth
and produced more dry matter (Sharma, 1995). Mae (1997)
reported that a large amount of absorbed N increases leaf N
content, which leads to enhancement of photosynthetic capacity
of plants. At the end of the recovery period, the difference in leaf
N concentration among plants from the three
flooding depth
treatments was small, indicating that previously accumulated
photosynthetic products in leaves may have been transported to
roots, rhizomes, and shoot base for plant recovery (Miao and Zou
2012; Chen et al., 2013). Delay in
flowering and reduced
photosynthetic rate might be resulted in reduced yield; this is
reflected in correlation between Pn rate, delay in
flowering and
grain yield (Fig. 4b). Sharma (1995) reported that the grain yield
decreased due to
flash
flooding by 1.16–1.21 t ha1 but the adverse
effect was less pronounced in the crop with application of N after
flash
flooding.