Long-term effect of wood and peat ash on the growth of Pinus sylvestris on drained peatland

Abstract

The effect of ash fertilization on height growth and volume production of Scots pine (Pinus sylvestris L.) was studied on oligotroph peatland in southeast Norway. In the year 1944, plots 15 m × 15 m size were fertilized with 0, 4, 7, and 10 tons ha−1 of wood or peat ash. The area was treeless, but a satisfactory number of pine seedlings were present. All measurements were confined to the central inner plot, 10 m × 10 m area. Most plots were re-fertilized with 10 tons of wood ash ha−1 in the year 1993. Wood ash had higher content of nutrients, and generally, it had greater growth enhancement effect than peat ash. When the amount of ash was increased, volume production significantly increased for the age period 38–50 years and the total production at age 50 years. The mean annual increment during the first 50 years was about 6 m3 ha−1 for the plots applied with 10 tons of ash ha−1. Trees on plots fertilized with 7 or 10 tons in 1944 and replenished with 10 tons ha−1 at age 50 years (1993) had a mean annual increment of 14 m3 ha−1 for the stand age period 51–68 years. Over time some tree roots from control plots and plots fertilized with 4 tons ha−1 have captured nutrients from richer plots. Such effect is to a smaller extent relevant for treatment 7 tons. It is concluded that the content of mineral nutrients of wood and peat ash makes these ashes well suited as fertilizers on peatland.