SoilSoc Research

Research projects Thesis abstracts

Nitrogen gains and losses from agro-ecosystems

Institute / Organisation / Unit: Agricultural University of Iceland ( and Agroscope Reckenholz-Tänikon Research Station ART (

Research director / Project Leader: Dr. Áslaug Helgadóttir Agricultural University of Iceland.

Other researchers: Dr. Andreas Lüscher Professor ETH- Zurich, Head of research group at Agroscope Reckenholz-Tänikon Research Station ART, Dr. Rannveig Anna Guicharnaud Agricultural University of Iceland, Dr. Ţorsteinn Guđmundsson Agricultural University of Iceland.

PhD-student responsible: Ţórey Ólöf Gylfadóttir (starting date summer 2009)

Discription: The project will study the effects of nitrogen on species diversity and N fluxes in grass-clover mixtures under Icelandic conditions with the ultimate aim of identifying management practices that maximize yield and fodder quality and, at the same time, improve nitrogen use efficiency and minimize environmental footprint. The effects of sward diversity and level of nitrogen application on yield and fodder quality will be investigated in a field experiment in Iceland where we systematically vary the relative abundance of four agronomic plant species belonging to different functional groups (two grass species and two legume species). On the same plots we measure N fluxes of legume based grassland compared to grass monoculture. This entails N2 fixation, ammonification and nitrification in the soil, N leaching, C and N incorporated within the soil microbial biomass and soil microbial biomass functionality. The project will yield new information on the interaction effects of species diversity and nitrogen fertilisation on forage yield and quality, nitrogen fixation and nitrogen losses through leaching in a northern environment. The combined knowledge of soil N turnover and N leaching from the same plots will add to our knowledge of the sources of N lost from agricultural systems. The results obtained in the project can be directly used in simulation work to identify optimal grass-clover management and its impact on the N fluxes of the system.