Potassium budget for inland, saline water shrimp ponds in Alabama

Potassium budgets were prepared for inland shrimp ponds in Alabama in which saline water was supplemented with potassium ion by additions of two fertilizers, potassium chloride and potassium magnesium sulfate. The study was conducted during the first shrimp crop in newly constructed ponds. A total of 1021.2 kg/ha of potassium were applied to the ponds, and the main input was the fertilizers. The total loss of potassium from ponds was 456.5 kg/ha, and of this, seepage and harvest effluent accounted for 101.2 and 347.9 kg/ha, respectively. Based on the potassium budgets, bottom soil apparently adsorbed 564.7 kg/ha of exchangeable potassium. However, the potassium increase was only 374 kg/ha in the upper 15-cm layer of bottom soil during the first growing season in which the ponds were used. The discrepancy possibly resulted from potassium fixation by non-exchange processes. Potassium also may have been adsorbed to a greater depth, and some may have been contained in suspended particles discharged in draining effluent. Soil uptake was an important sink for added potassium in the new ponds, so further studies should be conducted to determine the rate at which the potassium binding capacity of the bottom soil will be filled. Water reuse is the only practical way of lessening the loss of potassium from inland shrimp ponds.