Die Bodenkultur - Journal for Land Management, Food and Environment
Effects of a Fertilization Pulse on Migration of Nutrient and Trace Elements in Chernozem Soil Columns within a Vegetation Period
Topsoils of a Calcic, a Haplic and a Gleyic Chernozem were packed to columns of about 30 cm length and 125 cm2 area in 3 layers and 4 replicates each, in order to investigate the vertical migration of nutrients and trace elements, added as a fertilization pulse. The columns were gradually eluted in the dark with about 5 pore volumes of water within 2 months to simulate natural rainfall. After passage of about one pore volume, pH in the eluate dropped and a pulse of non-added species Mg/Sr/Ba/Li appeared in the eluates, explainable from ion exchange and acidification.
Then, most median concentrations in the eluates approached a level higher than obtained from standard water extracts 1 + 9. Similarly, the eluted loads did hardly correlate with solubilities obtained from water extracts.
Substantial amounts of added phosphorus eluted only from the Haplic Chernozem samples, whereas added molybdenum and vanadium were almost completely retained. Added boron was rapidly eluted from the Haplic, and still within 5 pore volumes from the Gleyic chernozem columns, but largely retained on the Calcics. Elevated Cu from former use of the Calcic Chernozem as a wineyard soil, was not mobilized to the eluates, but clearly extractable into oxalate pH 3 and 1 M NaOH. Simple mathematical modelling of desorption after the ion exchange peak could be only achieved for Na.
After the experiment, the solids remaining in the columns were let dry and sliced into 6 fractions, which were characterized by aqua regia, oxalate, and NaOH like the original materials, to reveal pedogenic oxides and humics as target phases of adsorption/desorption within the profiles. Oxalate soluble Fe increased in the Calcic and Haplic Chernozem samples to double amounts, whereas oxalate soluble non-added Co-Ni-Pb-Zn tended to decrease; in the Gleyics no changes in these pedogenic oxide fraction occurred. Though no organics were added nor formed by photosynthesis, alkali mobile forms of the remaining solids tended to increase. The target phases for the additional loaded fertilizer anions varied considerably between the 3 soil types, but alkali mobile recoveries were preferred over oxalate mobiles.
Key words: soil columns, phosphorus, molybdenum, boron, vanadium.