Danish Institute of Agricultural Sciences Department of Agroecology

Danish Institute of Agricultural Sciences Department of Agroecology Research Centre Foulum Denitrification in the root zone N 2 N O N N 2 O 2 2 N 2 O Finn P. Vinther, Danish Institute of Agricultural Sciences, Department of Agroecology, Research Centre Foulum

Measuring denitrification Denitrification In the field: NO 3 (nitrate) N 2 O (nitrous oxide) In the lab: N 2 (atmospheric nitrogen) Denitrification Acetylene NO 3 N 2 O N 2

Measuring or modelling? • Resource demanding and difficult to measure • Modelling often the only possibility • Most models, however, often needs more input information than what is available • Simple model for estimation of N 2 O emission and denitrification – Sim. Den…. . which only needs information about • amount and type of added nitrogen • clay content of the soil

Principles of Sim. Den: Denitrification = N 2 O * (N 2/N 2 O) Fertilizer N 2 O emission Bouwman, 1996 Background N 2 O emission Total N 2 O emission = Background N 2 O emission + EF 1. 25 * N-input Inorganic N: EF 0. 8 Organic N: EF 2. 5

Principles of Sim. Den: Denitrification = N 2 O * (N 2/N 2 O) Literature values (app. 500): Avg. N 2/N 2 O-ratio: app. 3 WFPS* < 60% N 2/N 2 O-ratio 0 -3 60% < WFPS < 80% N 2/N 2 O-ratio 3 -5 WFPS > 80% N 2/N 2 O-ratio 5 - 10 * Water filled pore space

Principles of Sim. Den: Denitrification Sim. Den Water filled pore space (WFPS) Soil texture (clay content)

How to use Sim. Den Example 1: Background denitrification

How to use Sim. Den Example 2: Background + fertilizer denitrification

How to use Sim. Den Example 3: Background + fertilizer denitrification at higher clay content

How does Sim. Den perform Danish studies

How does Sim. Den perform Other studies Canada (Paul & Zebarth, 1997) Spain (Vallejo et al. , 2004) Sweden (Dahlin et al. , 2005) The Netherlands (Zwart et al. , 2004)

How does Sim. Den perform Other studies

How does Sim. Den perform Other studies

How can Sim. Den be used? Regional mapping, as for example as shown here, where Sim. Den has been implemented into ”CTtools”, Con. Terra Ap. S, which use databases with information about soil types, fertiliser use, etc. Herning

Ending remarks • Sim. Den is based on average values, and the denitrification is calculated for a climatically ‘normal’ year, or an average denitrification over years. • If more detailed estimates about the annual variation of the denitrification is wanted, dynamic models as for example Daisy must be used. • Sim. Den can be downloaded from www. agrsci. dk/simden • Wish you good luck and thank you for your attention!