Short term impact of application of different doses of wood ash on greenhouse gas (GHG) emissions from peat

Abstract

Wood ash contains most of the nutrients necessary for development of plants, as well as soil microorganisms. It is well studied that application of wood ash improves forest growth in peatlands and significantly increases biomass production in the forest floor; however, there is limited knowledge on the shortterm impact on the soil GHG (CO2, N2O, CH4) fluxes after application of wood ash, specifically, if different doses of the wood ash are applied. The scope of the study is to determine short term (2 months) effect of application of 2, 5 and 10 tons·ha of hardened and fresh wood ash in peat from abandoned peatland – southern part of Kaigu mire (former raised bog). The study is implemented in controlled conditions (temperature and moisture) in a greenhouse. Peat from abandoned peatland is filled into 50 cm deep plastic boxes (area 50 x 70 cm) simulating 50 cm deep peat layer. The same amount of water is added regularly in all boxes to ensure that moisture level in peat remains close to natural conditions at the beginning of the experiment in control boxes. GHG fluxes are measured using Gasmet DX4040 FTIR analyser and opaque chambers. Measurement period 30 min. Measurements are repeated at least once per week. According to the study results directly after application of fresh wood ash peat acts as net sink of CO2 due to consumption of CO2 in chemical reactions; however, already in the second week after the application CO2 emissions from soil increase, while carbon losses from treated boxes in average were smaller by 59% in comparison to control boxes. No significant effect of wood ash is found on CH4 and N2O emissions and no significant difference was found between hardened and fresh wood ash.