Field-scale variability of field moisture capacity and mineral nitrogen in the vadose zone of sandy soils in northeast Germany

摘要

On sandy Pleistocene sites the variability of springtime soil moisture content (field capacity) and mineral nitrogen in pore water were analysed down to 4.2 m depth under different land use systems. The average of the field capacity was about 10 cm~3/100 cm~3. Their large site-specific variability (variation coefficients of 26-63 percent) is mainly due to the substrate heterogeneity of the pedogenesis. End moraines had the highest total variability, aeolic sand layers were strongly spatially dependent. The sandy outwash area had the lowest variability of field capacity, lower than the glacial tills. Considering sampling distances of 10 m, the autocorrelation length was also in the range of decametres. Areas of aeolic sands and outwash sands showedrelatively large ranges of autocorrelation (> 140 m), end morains and glacial tills neighboured to end moraines are structured into smaller areas (range of autocorrelation < 20 - 40 m). The amounts of mineral nitrogen in the vadose zone reflect the landuse and show larger variability than the field capacities. Highest amounts were found in arable land of former intensive slurry application. High nitrogen concentration were also measured under a pine forest. Not fertilized grassland had the lowest amounts and concentrations of mineral nitrogen.