Quantification and reduction of ammonia emissions after mineral fertilizer application

Background and Objective

Agriculture is facing multiple challenges such as adaptation to climate change, providing high sustainable yields while concomittantly reducing ammonia emission and increasing nitrogen use efficiency. About 15% of the total agricultural ammonia emissions in Germany originate from application of synthetic nitrogen fertilizers. The emissions are affecting environment, climate and health and they are reducing nitrogen use efficiency of fertilization. This joint research project is analysing and assessing measures to reduce ammonia emission from application of synthetic fertilizers and to increase the nitrogen use efficiency.  The project is focussing on the following fertilizers that are responsible for about 85% of the total ammonia emissions from synthetic fertilizer application in Germany and represent about 70% of the total amount of nitrogen applied with synthetic fertilizers: urea, calcium ammonium nitrate (CAN), ammonium nitrate urea solution (UAN), and ammonium sulfate urea. The evaluation of the fertilizers is based on field experiments wirh application of various NH₃ measurement systems, the quantitative accuracy of which is checked and verified by the research consortium. Recommendations are developed to optimize application of synthetic nitrogen fertilizers with respect to nitrogen use efficiency, yields, and mitigation of ammonia emission. The working program includes a network of field experiments across Germany as well as knowledge transfer to farmers and agricultural extension services.

Target Group

• researchers
• regulatory authorities
• farming advisors and extension services
• agricultural holdings
• fertilizer producers

Approach

The project is divided into two phases:

In the first year (phase 1) we compare different measurement methods for ammonia (NH₃) emissions after mineral fertilizer application. The focus is on the evaluation of common and newly developed measurement methods for plot experiments with field replications for statistical evaluation and comparison of fertilization treatments.

In the second phase (year 2 to 4) NH₃ emissions after application of different synthetic nitrogen fertilizers are quantified in a representative German network of field experiments (8 sites distributed over Germany). Methods validated in phase 1 will be used. We evaluate of the nitrogen use efficiency of different synthetic N fertilizers and application systems in crop field trials. We calculate site-specific NH₃ emission factors for synthetic N fertilizers and  German production conditions.

Winter wheat is the model crop used at all study sites

Data and Methods

Phase 1:

Micrometeorological methods are used to evaluate the plot methods. All plots are fertilized with urea.

We combine the micrometeorological mass balance methods with Leuning passive samplers installed on a large circular plot of 0.125 ha  with 3 evaluation approaches: a) the classical Integrated Horizontal Flux Method, b) the ZINST evaluation, and c) the backwards Lagrangian stochastic dispersion model (bLs). In addition, we establish eddy covariance measurement with a laser sensor technology on a large plot of 1 ha.

Three measuring methods will be  compared in a plot trial approach (8 treatments with 4 repetitions each). The following techniques will be used: a) the dynamic chamber method: Draeger Tube Method (DTM), b) passive samplers with sulphuric acid scaled with DTM measurements (calibrated passive sampling) and c) passive samplers for determination of atmospheric NH₃ concentration, flow calculation with bLs approach (CEH Alpha-Sampler).

Phase 2:

At each site NH₃ flux quantification will be measured on a large circular plot fertilized with urea using micrometeorological mass balance measurements with Leuning passive samplers. Ammonia measurement in the plot experiment will be done with a plot measurement method that was evaluated as valid in phase 1.

Our Research Questions

• How high are ammonia (NH₃) emissions after application of various synthetic N fertilizers?
• How high are the site-specific NH₃ emissions of different synthetic N fertilizers aggregated over different application dates?
• How much can the emission of ammonia be reduced by application techniques (e.g. incorporation/injection), fertilizer type or the use of inhibitors (urease inhibitor)?
• How do different fertilizer-dependent NH₃ emissions affect yields, N uptake and nitrogen utilization efficiency in winter wheat?