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INPLAMINT Subproject G

Christian-Albrechts-University
Institute of Crop Science and Plant Breeding
Agronomy and Crop Science

Prof. Dr. Henning Kage
Dr. Ingo Pahlmann
Steffen Rothardt, MSc

Central research object in this sub-project is a field trial established in 2015 on the experimental farm Hohenschulen near Kiel. The aim of this experiment is to evaluate whether organic soil amendments can conserve a temporal autumnal nitrogen (N) surplus and improve the transfer of residual N from the preceding crop to the subsequent crop.

Three factors are implemented: 2 crop rotations (winter oilseed rape (WOSR) – winter wheat (WW) – winter barley (WB) and faba beans (FB) – WW – WB), 4 soil managements after WOSR and FB (original crop residues, removal of crop residues, application of WW straw and application of spruce saw dust), as well as 4 different N rates in the following WW. The latter experimental factor allows for the assessment of the N transfer effects. A sub-optimum N rate in WB allows observation of long-term effects. All elements of the crop rotations are four-times replicated and present in every year, arranged in a split-plot design containing 528 plots on 2.4 ha.

Subproject G1 Experiment overview, blocks of one crop rotation element are marked red; photography by K. Sieling 2016

Subproject G2 A block after substrate treatment, red squares mark the 4 different treatments before winter wheat sowing; photography by S. Rothardt 2015

Monitoring includes sampling of soil mineral nitrogen (SMN), N2O-emissions, biomass (destructive and hyperspectral measurements) and yield analysis. As a proxy for decomposition activity the tea bag index (Keuskamp et al., 2013) has been determined in post-harvest period 2016 and will be will be repeated in the ongoing vegetation period. In parallel we strive to simulate mineralization, leaching and N-uptake processes after harvest using the obtained experimental data for model parametrization and validation.

Project partners at the FZ Jülich study the decomposition rate of the substrates under lab conditions. They also measure the potential N2O-emission in-vitro parallel to our field measurements.

The findings might be used for model improvement. At the Leuphana University soil from the experimental farm and the amendments are used in mesocosm experiments focusing on plant functional traits (e.g. root architecture).

Main scientific questions:

  • Can microbial immobilization reduce N-leaching?
  • How to control and quantify immobilization processes in field scale?
  • Will the tested strategies increase N use efficiency?
  • Can a dynamic model help to assess possible strategies under varying environmental conditions (e.g. climate change, different soils)?

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