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

ABSTRACT

Total 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.

KEYWORDS:

• Ash fertilizer
• nutrient deficiency
• nutrient elements
• peatland
• pine

Acknowledgements

I thank Mr. Hans Odde for expert technical assistance with the fieldwork, and Drs. Douglas Sheil and Ola M. Heide for their helpful linguistic and scientific comments on the manuscript. I am especially grateful to Ola who helped me finishing the manuscript during my long period of serious illness.

Disclosure statement

No potential conflict of interest was reported by the author.