Salinity changes of tidal irrigation water of mangrove swamp at Warri, Nigeria

Salinity variations of the tidal water irrigating the rice fields at Warri mangrove swamp were studied for one calendar year. It was found that the mean pH is 7.24 for low tides and 7.14 for high tides, and pH is highest in July for both high and low tides. Sodium, calcium and magnesium, the major cationic constituents of the soluble salts in the saline tidal irrigation water, as well as potassium a minor ionic constituent were all found to be highest in June at both low and high tides. Also, both the Electrical Conductivity (EC) and the derived Sodium Adsorption Ration (SAR) were highest in June. Salinity at both high and low tides is highest in June but lowest in September for high tides and in October for low tides. The indications are that the adverse effects of salinity are largely responsible for the poor initial growth and survival of the rice variety MAS 2401 during early seedling stage. From salinity point of view, it would appear that October is the most favourable month to transplant rice at the Warri mangrove swamp.