Springer Online Journal Archives 1860-2000
Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
Abstract Main objective of this study was to test the effects of Mg(OH)2-fertilization in a Norway spruce ecosystem showing severe symptoms of Mg-deficiency. The site is characterized by high atmospheric inputs with deposition rates of 1.25 kg H, 42 kg S, and 32 kg N per ha and year. The typic Dystrochrept derived from granite is acidified down to greater depths. The pH-values in soil solution of the organic surface layer and the upper mineral soil are around 3.5. Concentrations of Al, SO4 2-, and especially NO3 - and DOC are very high. The element balance indicates a significant influence of N-inputs and processes of N-turnover on the chemical status of the soil and probably on tree nutrition. Nitrification in the upper mineral soil leads to a transformation of a major part of NH4 + into NO3 -, which is quantitatively leached, resulting in an ecosystem-internal H+-production of 1.8 keq ha-1yr-1. NO3 - and SO4 2- govern the seepage output from the ecosystem. Mg(OH)2 fertilization resulted in manifold increased Mg2+ concentrations in soil solution down to 70 cm soil depth and to a significant increase of pH down to 25 cm mineral soil depth. Nitrate concentrations were elevated after fertilization, but decreased within 15 months below the level of the control plot. As a mean over the whole experimental period, N-output was not increased by fertilization. Despite an elevated internal proton production due to nitrification, acid buffering in the soil was clearly increased, but enhanced Al-mobilization was not observed. Mg/Al- and Ca/H-ratios in soil solution indicate much more favourable conditions for fine root growth. Fertilization also increased the amount of exchangeable Mg down to 40cm mineral soil depth. Mg contents in current-year needles increased after three vegetation periods. Thirty months after application, only 10% and 4% of the fertilized Mg had left the organic surface layer and the mineral soil with seepage water output, respectively.
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