Denitrification associated N loss in mangrove soil

The effect of salinity and nitrogen (NO3- and NH4+) on growth, nutrition and nitrogen uptake in Kandelia candel (L) Druce was investigated in phytroton condition. The experimental design was 4 × 2 factorial with four salinities (0, 0.88, 1.75 and 3.30 % NaCl) and two nitrogen sources (NO3- and NH4+). Nitrogen uptake rates were measured using 15N stable isotope technique. Biomass of shoot and root reduced with increasing salinity. Biomass ratio of root/shoot increased from 0.71 to 1.22 with increasing salinity (0 to 3.30 % NaCl salt) indicating reduction in the flux of water and nutrient transport. It was appeared that young seedlings of K. candel were salt tolerant and hypoctoyl acts as a buffer, regulate salt and nutrients. Increase in NaCl concentration from 0 to 3.30 % significantly reduced nitrogen content of leaf and root by 20 % and 57 % respectively. Nitrogen uptake was significantly reduced with increase in salinity. Nitrate and ammonium were utilized in more or less equal proportion at low salinity whereas NH4+ appears to be major source only at high salinity levels. N uptake patterns support the hypothesis that K. candel can utilize NO3- and NH4+ simultaneously as N source but salinity has strong bearing on it.