The Application of Fertilizers to Drained Peat 1. Nutrient Losses in Drainage

An experiment to follow the fate of applied fertiliser was installedon a newly-drained raised bog near Edinburgh. Sixteen lysimeters(2.25 m²) were constructed to isolate blocks of peat to 0.8m depth and were allocated to four treatments; untreated control,+ 50 kg P ha^–1 (as rock phosphate), + 100 kg K ha^–1(as KCl), P and K together at these same rates. Fertiliserswere applied in May 1977 and for the following three years drainagewas collected weekly for chemical analysis. The hydrologicalbehaviour of the lysimeters was checked by monitoring run-offfrom an enclosed 2.5 ha catchment. Losses of K in drainage were rapid but declined over the perioduntil they were only slightly greater than control values; lossesof P began after 24 weeks and were greatest in winter with noapparent decline; Ca was not leached and no significant releaseof N was detected. Control lysimeters showed a net loss of Nand P following drainage. When K and P were applied separatelylosses were 39 and 16 per cent respectively but in combinationthe losses were reduced to 26 and 7 per cent. Concentrationsof dissolved P in leachates exceeded 1.0 mgl^–1 on occasionand K fertiliser initially reduced water pH.