Phosphatmobilisierende Wirkung verschiedener wurzelbzw. mikrobenbürtiger organischer Kohlenstoffverbindungen in unterschiedlichen Böden

Root derived organic carbon compounds and their microbial metabolites are of ecological importance for the nutrient supply of higher plants. An extraction method similar to the double-lactate (DL) method (2 g soil, 100 ml solution with 5 g l-1 substance, pH 3.7, 90 min) was used to measure the P-solubilizing ability of sugars and carboxylic acids in 10 different soils. Neutral extraction solutions were used to detect specific anion effects. Additionally a 24 h extraction at 28 °C was used to permit chemical and microbial changes of the substances in the soil.Sugars and sugar alcohols can contribute to P mobilization in insterile soils with a pH below 7. They have no effect under alkaline conditions. The acidic extraction with gluconic acid was as efficient as DL, although the buffer capacity of the solution is relatively low. The P release increased during 24 h. However, a neutral gluconate extraction was only comparable with sugar extraction. Succinic acid was only effective under acidic conditions.Citrate and oxalate, even in small concentrations, mobilized large P amounts under different soil conditions. Mainly the effectiveness of citrate increased with a longer incubation time. Specific anion effects are detectable with neutral extractions.It can be concluded, that the qualitative composition of root deposits has a higher influence on their P-mobilizing efficiency than their total amount.