Distribution of nitrate, exchangeable and non-exchangeable ammonium in the soil-root interface
Following uptake by rape plants, the nitrate concentration decreased near the root surface. The gradient up to 4 mm from the root was greater when the initial concentration used was higher. In a similar way to exchangeable K+, the concentration of exchangeable NH 4 + in the soil decreased at the soil-root interface.
Native, non-exchangeable NH4/+ was not taken up by roots, so that its concentration in the soil close to the root remained unchanged. In contrast, recently fixed non-ecchangeable NH 4 + originating from fertilizer was absorbed by plants and almost completely extracted from the soil near the roots.
Key wordsConcentration gradients Nitrate Non-exchangeable ammonium Soil-root interface
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