Summary Several agricultural problems are associated with the presence of certain levels of CaCO
3 in soils. The level of CaCO
3 at which the phosphate fixation becomes an apparent agricultural problem, is thought to be an appropriate margine at which the soil can be considered calcareous. Thus, a set of soil mixtures, ranging in CaCO
3 content from 1 to 96% was prepared and used in a column study to determine the level at which the CaCO
3 fraction becomes a dominant factor controlling. P
32 movement and distribution.Increasing the percentage of oolitic sand, in the soil mixture, from 1 to 10% caused a sharp drop in P
32 movement with soil solution and any increase in CaCO
3 content above 10% did not show any further drop in P
32 movement. The amount of P
32 removed with the soil solution was generally low compared to that retained in soil columns. Studying the distribution of P
32 in soil columns, after five displacements, has indicated that the migration of P
32 from the top soil increased by increasing CaCO
3 from 1 and 2 to 6%. The amount of P
32 removed was however retained in lower sections. A very sharp decrease in P
32 migration from the top soil was observed when CaCO
3 content was raised from 8 to 10%.A similar picture was shown when the CaCO
3 material used was in clay size fraction. However the sharp increase in phosphate retention in top soil sections took place at CaCO
3 content of 8% rather than at 10%. A limit of 8 to 10% CaCO
3 was proposed as an appropriate margine for defining calcareous soils.
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