Soil acidification as caused by the nitrogen uptake pattern of Scots pine (Pinus sylvestris) |
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Authors: | Gert Arnold |
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Institution: | (1) Department of Soil Science and Plant Nutrition, Wageningen Agricultural University, P.O. Box 8005, 6700 EC Wageningen, The Netherlands |
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Abstract: | Three-year-old Scots pine (Pinus sylvestris) trees were grown on a sandy forest soil in pots, with the objective to determine their NH4/NO3 uptake ratio and proton efflux. N was supplied in three NH4-N/NO3-N ratios, 3:1, 1:1 and 1:3, either as 15NH4+14NO3 or as 14NH4+15NO3. Total N and 15N acquisition of different plant parts were measured. Averaged over the whole tree, the NH4/NO3 uptake ratios throughout the growing season were found to be 4.2, 2.5, and 1.5 for the three application ratios, respectively.
The excess cation-over-anion uptake value (Ca-Aa) appeared to be linearly related to the natural logarithm of the NH4/NO3 uptake ratio. Further, this uptake ratio was related to the NH4/NO3 ratio of the soil solution. From these relationship it was estimated that Scots pine exhibits an acidifying uptake pattern
as long as the contribution of nitrate to the N nutrition is lower than 70%. Under field circumstances root uptake may cause
soil acidification in the topsoil, containing the largest part of the root system, and soil alkalization in deeper soil layers. |
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Keywords: | cation-anion uptake balance 15N labelling NH4/NO3 uptake ratio nitrogen source Pinus sylvestris soil acidification soil solution |
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