Phosphorus movement in some calcareous and noncalcareous Manitoba soils

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Lewis, Errol T.
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Manitoba contains large acreages of calcareous soils as well as noncalcareous soils. Most of these soils are deficient in available phosphorus and phosphorus fertilization is an important aspect in crop production. The behaviour of applied phosphorus in Manitoba soils, especially the movement of phosphorus in soils, is not well known. This project was initiated to study the movement of applied phosphorus in some Manitoba soils. Ten surface soils varying in texture and calcium carbonate content were selected for the studies. Phosphorus movement from a monoammonium phosphate pellet was found to be slightly greater than from a diammonium phosphate pellet... The movement of phosphorus was slightly retarded in both a calcareous and a noncalcareous soil when P32 "tagged" monoammonium phosphate was mixed with CaCl2, MgCl2, KCl, NaCl and NH4Cl... Rate of phosphorus movement studies indicated that movement of phosphorus was more rapid in noncalcareous soils than in calcareous soils. Solubility studies showed that the soil solutions of the phosphorus treated calcareous soils contained greater amounts of calcium and magnesium than did the soil solutions of phosphorus treated noncalcareous soils. It is suggested that the large amounts of calcium and magnesium in the calcareous soils precipitated the added phosphorus very close to the pellet site and thus the movement of phosphorus was restricted. Since the supply of calcium and magnesium in the noncalcareous soils was not as great as in the calcareous soils, added phosphorus was able to move farther away from the pellet site before it was precipitated by calcium and/or magnesium.