BIO-CYCLING OF PHOSPHORUS IN SOIL BY PLANT ROOTS
Plants cycle nutrients in soil by bringing minerals from the subsurface to the surface soil. This paper presents evidence that phosphorus, a relatively immobile nutrient, can be moved to the subsoil by the roots under cereals that have received high rates of P. Residual effects of phosphatic fertilizer have been studied at Swift Current, Saskatchewan since 1966. Single applications of 0, 100, 200 and 400 kg P/ha were applied in 1966. Soil samples taken in the fall of 1967, 1974 and 1979 showed that there is more NaHCO3-extractable P under the plots that received 100, 200 or 400 kg of P than under the unfertilized plots. At depths below 30 cm the differences were greater in 1979 than in 1974, particularly under the 400 kg P/ha treatment. This indicates a gradual downward movement of P, probably in the tissue of the plant roots.