University of Natural Resources and Life Sciences, Vienna (BOKU) - Research portal
Gewählte Master / Diploma Thesis:
Eva Oburger
(2007):
The Fate of Organic Acids in the Plant-Soil Environment.
Master / Diploma Thesis,
BOKU-Universität für Bodenkultur,
pp 43.
UB BOKU
obvsg
- Abstract:
- Organic acids released by roots are assumed to perform many beneficial functions in rhizosphere soil including enhanced nutrient acquisition, metal detoxification, stimulation of microbial activity and accelerated mineral weathering. As plants release various organic acids simultaneously, it has been suggested that some organic acids (e.g. malonate, as it is well known for its inhibiting effect on the TCA-cycle) might act as a deterrent to microbial activity. Also preferential mineralisation and sorption of some organic acids in these mixtures might enhance the longevity and nutrient mobilization capacity of others. Hence, the objective of this study is: (1) to sum up the current knowledge about organic acids in the plant-soil environment in a literature review; (2) to directly evaluate interaction reactions of three organic acids implicated in phosphate (P) mobilization (i.e. citrate, malate, oxalate) in the presence of two other organic acids (malonate and shikimate) in biodegradation, adsorption and phosphate desorption. Our results show that organic acid biodegradation was not influenced by the presence of other carboxylates. An inhibiting effect of malonate on the microbial community could not be observed disproving malonate’s assumed function as deterrent for microbial activity. Adsorption of organic acids in the mixture as well as a single compound was generally determined by the valency of the carboxylate (the higher the charge the stronger the adsorption) and the concentration in the solution. The P desorption efficiency of organic acids in soils was low if a high number of unsaturated sorption sites were present or the general concentration of P in the solution was relatively high. Nevertheless organic acids in the mixture tend to have an additive effect on P desorption.
- Beurteilende(r): Wenzel Walter