Climate impact of liming arable soil -effect on N2O emissions in a life cycle perspective

• Agricultural soils are limed primarily to maintain high yields. Limed soils, with higher pH, often have lower emissions of the strong greenhouse gas nitrous oxide (N2O), but also increased emissions of soil CO2. In this study, data from the long-term Ultuna outdoor frame trials were used to estimate the impact of increasing pH on agricultural soils, by comparing treatments with higher soil pH (7.2, representing liming) and lower pH (6.6). Climate impact was calculated in a life cycle perspective up to farm gate, meaning that impacts from producing inputs and field emissions were included. Measured field data were used to estimate effects on soil N2O emissions. In addition, three existing empirical models for estimating soil N2O emissions were applied. Field data from the Ultuna trials showed that soil N2O emissions from the treatment with higher soil pH were 71% lower than those from the treatment with lower soil pH. Assessed in a life cycle perspective, the results indicated that liming to increase soil pH can decrease the overall climate impact from crop production, by around 28% in this case. The reduction was mainly due to lower soil N2O, but also increased soil organic carbon content. The climate impact from production and application of additional lime needed to maintain the higher soil pH was around 10% of the total climate impact assessed on a per-hectare basis. Different models for estimating soil N2O gave very different results, illustrating the uncertainty in estimates, which is crucial to consider in interpretation of results. The contribution of soil N2O emissions to the overall climate impact varied between 18% and 43%, depending on the model used to estimate N2O emissions. Model development is needed to enable more accurate estimation of N2O emissions and more accurate prediction of the effects of management changes on soil N2O.

Ämnesord

LANTBRUKSVETENSKAPER  -- Lantbruksvetenskap, skogsbruk och fiske -- Markvetenskap (hsv//swe)

AGRICULTURAL SCIENCES  -- Agriculture, Forestry and Fisheries -- Soil Science (hsv//eng)

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