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Master Thesis: Interactions of nitrogen use efficiency and lignin degradation in soils

13.05.2016 - Forschungszentrum Jülich, IBG-3 Agrosphäre, Jülich, Germany

The proposed work aims to explore the interactions between N fertilizer use efficiency and lignin decomposition.

© Forschungszentrum JülichCopyright: Forschungszentrum Jülich

As a three-dimensional biopolymer of high molecular weight, lignin is the most abundant aromatic compound on earth and constitutes a substantial fraction of soil organic matter (SOM). Its monomeric phenylpropanoid units are connected by nonhydrolyzable C-0-C and C-C bonds, forming complex structures which attribute largely to the high recalcitrance of lignin towards decomposition. Nitrogen (N) is the most important nutrient for agricultural production. Therefore, large quantities of nitrogen fertilizer are applied to cropland. However, the use efficiency of N fertilizer can be low due to N gas emissions, N leaching, and N retention through biotic and abiotic processes. N gas emission and retention in soils can occur through both biotic processes, such as nitrification, denitrification and microbial N immobilization, and abiotic reactions of reactive N intermediates (e.g., nitrite) with the mineral and organic fractions of the soil. SOM exerts a significant influence on abiotic N gas emissions and N retention. It has been reported that recalcitrant carbon (i.e. lignin, sawdust) tend to reduce soil N availability in the long term through either physical condensation or chemical substitution reactions of phenols (originating from partially degraded lignin and some fungal pigments) with either amino acids, NH3, NH2OH or nitrite, resulting in the formation of "brown, nitrogenous humates". Also, large amounts of NO and N2O emissions have been confirmed through reactions of nitrite with lignin derivatives. Theoretically, N availability should affect lignin decomposition to a large degree since nitrogen controls the physiological processes of microorganisms, especially in N-limited sites. Available nitrogen may function by modifying lignin-degrading enzyme activity, or by abiotic interactions with products of microbial degradation or synthesis, or by affecting the decomposer community. However, the comprehensive influences of lignin degradation on N fertilizer use efficiency still remain an open question.

The proposed work aims to explore the interactions between N fertilizer use efficiency and lignin decomposition. Incubation (e.g., litter-bag) experiments will be set up to explore the interactions of N use efficiency and lignin degradation in agricultural soils with the application of N fertilizer, plant litters, and lignin. Stable isotope tracing will be applied to detect the fate of N and lignin. We are looking for a master student who can conduct this work in the framework of his/her master thesis. Working location will be the Institute of Bio- and Geosciences, Agrosphere Institute (IBG-3) at Forschungszentrum Jülich.

Requirements:
(1) The candidate should have a major in Environmental Science, Agricultural Science, or related subjects.
(2) The candidate should be fluent in English.
(3) It will be preferred if the candidate can start the work in early July 2016.
Payment: We can pay a monthly compensation for a period of up to six months.

Contact:
Jing Wei
Forschungszentrum Jülich, IBG-3, Wilhelm-Johnen-Straße, 52428 Jülich
Email: ji.wei@fz-juelich.de
Phone: 02461-61-96647


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