Calibrated Passive Sampling - Multi-plot Field Measurements of NH3 Emissions with a Combination of Dynamic Tube Method and Passive Samplers

Summary

Ammonia emissions are a major threat to the environment by eutrophication, soil acidification and fine particle formation and stem mainly from agricultural sources. This method allows ammonia loss measurements in replicated field trials enabling statistical analysis of emissions and of relationships between crop development and emissions.

Abstract

Agricultural ammonia (NH₃) emissions (90% of total EU emissions) are responsible for about 45% airborne eutrophication, 31% soil acidification and 12% fine dust formation within the EU15. But NH₃ emissions also mean a considerable loss of nutrients. Many studies on NH₃ emission from organic and mineral fertilizer application have been performed in recent decades. Nevertheless, research related to NH₃ emissions after application fertilizers is still limited in particular with respect to relationships to emissions, fertilizer type, site conditions and crop growth. Due to the variable response of crops to treatments, effects can only be validated in experimental designs including field replication for statistical testing. The dominating ammonia loss methods yielding quantitative emissions require large field areas, expensive equipment or current supply, which restricts their application in replicated field trials. This protocol describes a new methodology for the measurement of NH₃ emissions on many plots linking a simple semi-quantitative measuring method used in all plots, with a quantitative method by simultaneous measurements using both methods on selected plots. As a semi-quantitative measurement method passive samplers are used. The second method is a dynamic chamber method (Dynamic Tube Method) to obtain a transfer quotient, which converts the semi-quantitative losses of the passive sampler to quantitative losses (kg nitrogen ha^-1). The principle underlying this approach is that passive samplers placed in a homogeneous experimental field have the same NH₃ absorption behavior under identical environmental conditions. Therefore, a transfer co-efficient obtained from single passive samplers can be used to scale the values of all passive samplers used in the same field trial. The method proved valid under a wide range of experimental conditions and is recommended to be used under conditions with bare soil or small canopies (<0.3 m). Results obtained from experiments with taller plants should be treated more carefully.

Introduction

Ammonia (NH₃) is the only atmospheric trace gas predominantly (90%) emitted from agricultural sources in the EU. Although agriculture is also a major source (>50% of EU emissions), these contribute only to about ~5% to the total of EU15 anthropogenic greenhouse gas emissions. In contrast, agricultural NH₃ emissions are responsible for about 45% of emission-derived eutrophication, 31% of acidification and 12% fine dust formation within the EU15¹. In addition to detrimental effects to ecosystems and human health, nitrogen (N) loss by NH₃ emission is an economic loss to farmers². Nitrogen fertilizer is essential for ....

Protocol

1. Experimental Design and General Operational Instructions

1. Use comparatively large plots (12 m x 12 m or 9 m x 9 m) as compared to the sizes usually applied in replicated field trials (e.g. 3 m x 8 m) to avoid effects of uneven fertilizer distribution on ammonia emissions (Figure 2). Use square plot shapes to avoid effects of shifting wind directions on ammonia uptake by the samplers. Reduce drift of NH₃ from one plot to the other to an acceptable degree by keeping a buffer area of 1 plot size between plots.

Results

In year 2014, a field trial was set up in the center of Denmark for testing the effects of several methods to reduce ammonia emissions after application of cattle slurry: incorporation with a rotary tiller, incorporation of acidified slurry and closed slot injection (injection of slurry in soil with subsequent coverage with soil). As a comparison with a high emission application technique and in particular for proper application of the chamber method trail hose application of slurry was also included. Altogether 24 plots were included in thi.......

Discussion

It was shown that the proposed method can be used to compare ammonia emissions from different fertilizer treatments in replicated field trials and to use the obtained statistically significant information from these measurements to improve management of N fertilizers. The quantity of emissions obtained by this approach has been validated in earlier studies by comparison with micrometeorological measurements^13,15,16. In this paper, the quantitative validity of this approach was indirectly demonstrated by a clos.......

Materials

List of materials used in this article

Name	Company	Catalog Number	Comments
stainless steel Dräger chamber + soil rings	Fa. Hofmann GmbH, Metallindustriewerk, Kiel, Germany	no number
roofs and stainless steel rod for passive sampler	Fa. Hofmann GmbH, Metallindustriewerk, Kiel, Germany	no number
ammonia electrode + bench	Thermo scientific	Cat. No. 9512BNWP or 951201
ammonia electrode filling solution	Thermo scientific	Cat. No. 951202
Ammonia calibration standards; 0.1 M ammonia chloride standard	Thermo scientific	Cat. No. 951006
Dräger pumps	Draeger Safety AG& Co Kg
Dräger tubes	Draeger Safety AG& Co Kg	types: 0.25/a; 2/a; 5/a
acid resistant passive sampling bottles (Azlon bottle, HDPE)	Dunn Labortechnik GmbH	Cat.No.: BGE230P
small vials (scintillation bottles PE 60 mm x 27 mm)	any laboratory store
PTFE tubing 7 mm x 1 mm WDG	any laboratory store
connectors PP Y-Form 6-7 mm	any laboratory store