Seasonal and spatial variations of N, P, K and Cd concentrations in water of the Mahakanumulla Cascade in the Dry zone of Sri Lanka

Systematic work on water quality aspects, particularly on the accumulation and fluctuation of plant nutrients and heavy metals, has not being carried out at the Mahakanumulla tank cascade in the dry zone of Sri Lanka. Therefore, the main objective of this research was to study the seasonal changes of the concentration of major plant nutrients viz., Nitrogen (NO^3-), Phosphorus (PO4^3-), Potassium (K⁺), and heavy metal Cadmium (Cd⁺²) in water along the cascade system. The concentrations of NO^3-, PO4^3-, K⁺ and Cd⁺² in water samples showed significant spatial and temporal variations over the study period and showed a bimodal pattern. The highest concentrations of the measured parameters were observed in months of April and May in the Yala season. Low nutrient concentration observed in the Maha season could be due to dilution effect caused by the comparativelyhigh volume of tank water. Spatial distribution of NO^{3 -} , PO4^3-, K⁺ and Cd⁺² concentrations in the water of three sampling locations of each paddy tract showed a significant increasing trend from the first sampling point to third point of the paddy field.

Tropical Agricultural Research Vol. 24 (3): 279 – 288 (2013)