Long-term effect of spruce bark ash fertilization on soil properties and tree biomass increment in a mixed scots pine-Norway spruce stand on drained organic soil
Latvian State Forest Research Institute Silava, Rigas Str. 111, LV-2169 Salaspils, Latvia
Ash contains all plant nutrients, except N, and is often used to facilitate forest growth and to prevent nutrient depletion potentially caused by harvesting. In this paper, we report effects of a large dose of spruce bark ash on soil properties and tree biomass increment in a mixed Scots pine-Norway spruce stand on drained organic soil in central Latvia, 12 years after ash application. Significant positive growth response after wood ash fertilization was recorded only for overstorey spruce. During the 12 years after fertilization the additional volume increment was 8.3 m3 ha-1 or 0.7 m3 ha-1 annually. The effect of wood ash application is long-term. Also 12 years after treatment fertilized overstorey spruces demonstrated 0.6 m3 ha-1 additional annual volume increment compared to the controls. Additional diameter increment increased during the first 10 years after treatment but started to decrease in 2012. Results demonstrate that ash fertilization did not change N availability in the soil, and additional growth can be explained with improved supply of P, Ca, Mg and other nutrients. Ash application did not significantly influence the chemical composition of the O layer.