Long-term effect of wood and peat ash fertilization on nutrient content in peat and trees on a drained peatland

Abstract

ABSTRACTTotal and soluble nutrients in peat were studied after ash fertilization on an oligotroph peatland in southeast Norway. Plots 15 m × 15 m in size were fertilized with 0, 4, 7, and 10 tons ha1 of wood or peat ash in 1944. Chemical analyses after 18, 35 and 48 years showed a gradual reduction of phosphorus (P) and calcium (Ca) from the 0 to 10 cm surface peat layer. Some of the leached Ca was recovered in the layers 10–20 and 20–40 cm, while hardly any of the lost P was recovered in this way. The amount of potassium (K) in the surface layer declined by 75% over the first 18 years, and remained stable thereafter. Nothing of the lost K was recovered in deeper layers. The pH reflected the Ca levels. Over the years, an increasing proportion of the applied P, K and Ca was retrieved in the trees. Needle analyses indicated that declining tree vigor on plots fertilized with 4 and 7 tons of ash ha−1 was due to P limitations. After 48 years, the peat content of P and Ca was still significantly higher in fertilized than in control plots, thus demonstrating the long-lasting effect of ash fertilization.