On the Dynamics of Phosphorus Added to Fishponds in Israel

The fate of phosphate added to fishponds and the inorganic processes of phosphorus fixation were studied in Israel. Conditions in these ponds are different from those of the more humid climatic zones in having alkaline water and high calcium content. In these condi tions most of the phosphorus added is precipitated as Ca3(P04)2. rctical aspects of this are discussed. The quantitative theobottom mud. Another factor in the phosphorus fixation is the This fixation in the alkaline conditions prevailing is believed to be partly due to anion exchange reaction of the colloids and partly to reaction with calcium carbonate and not with heavy metals. The fixation of phosphorus to the mud is affected by the composition of the mud, becoming greater when the content of calcium carbonate and total colloids is higher. Fixation of phosphorus is lower with the accumulation of organic matlor in the mud because of the low phosphorus adsorption capacity of organic colloids. Phosphorus fixation is higher when the mud is mixed with the water of the pond. In the fishpond this is done by the carp in its search for food in the bottom mud.