THE PENETRATION OF RADIOACTIVE SUPERPHOSPHATE INTO A PODZOL SOIL

Abstract

The penetration into the soil of phosphorus, applied as superphosphate, was determined under various conditions in a field experiment on Cornwallis sand. Monocalcium phosphate containing P32 was thoroughly incorporated in the surface inch, and the activity was later determined in 1-inch segments of core samples.Movement downward of applied phosphorus was very slight in spite of the coarse texture of this soil. In 2 weeks an average of 5.2 per cent was located in the 2–6 inch zone and only 8.5 per cent had reached this depth in 4 weeks. Application of 2 inches of water per week (rainfall plus irrigation) produced no significant difference from 1 inch per week. Neither adjustment of pH levels with dolomitic limestone, nor increasing the organic matter levels with anthraxylate (a. humus-like material prepared from coal) had any significant effect on phosphorus migration.There was some evidence that increased rates of superphosphate resulted in greater penetration of phosphorus but the effect was not statistically significant. Even the heaviest rate of phosphorus used (800 lb./ac. of P2O5) did not saturate this soil appreciably, as it has a high phosphorus retention capacity (28.7 tons/acre).