Effect of various kinds of phosphorus fertilizers on a peat soil

Results are reported from a field trial on acid fen peat soil in which the effects of superphosphate and ground soft rock phosphate were compared as annual surface dressing on an old timothy ley. Until 1948 basic slag was used instead of rock phosphate; since that rock phosphate had been applied for ten years. Owing to the large variation in the results from the replicate plots the differences in the phosphorus conditions between the various treatments were less distinct than could have been expected. The accumulation of phosphorus quite in the surface layer was demonstrated. The hay yield produced by the annual dressing with 100 kg/ha of superphosphate in 1957 was equal to that produced by 130 kg/ha of rock phosphate. Also the yields from the treatments with 200 kg/ha of superphosphate or 260 kg/ha of rock phosphate were equal in size, but a significant difference was found in the phosphorus content of hay. In the superphosphate plots the P-content was about 0.21—0.23 per cent of dry matter, whereas in the rock phosphate plots only 0.14—0.15 per cent P in the dry matter was found