Outflows and nitrogen cascade

Introduction

What is on of the main difference between phosphorus, potassium and nitrogen ?

Nitrate goes from the biosphere to the environment by nitrate leaching, gaseous emissions.

Nitrate leaching

Nitrate leaching is highly dependent on rainfall, soil type and soil nitrogen content.

Video to watch

https://www.youtube.com/watch?v=-6e_iF9d2F0

Ammonia volatilization

The presence of ammoniacal nitrogen in a solution in contact with air systematically leads to the volatilization of ammonia.

Volatilization depends very strongly on the physical and chemical conditions of the environment.

  • the nitrogen content of the substrate in contact with the air ;

  • the proportion of nitrogen present in the form of ammonia ;

  • the contact surface between the solution containing ammoniacal nitrogen and the atmosphere ;

  • the dispersion of the air in contact with the emission zone.

Nitrogen oxides and nitrous oxide emissions

The parameters which are likely to intervene to regulate the proportion of nitrous oxide formed during denitrification are :

  • the pH of the environment ;

  • the nitrate concentration ;

  • the soil aeration, often characterized by the water saturation rate ;

  • the availability of reducing agents.

In addition to nitrous oxide emissions, there are nitric oxide emissions, rather observed in dry environments, and associated with nitrification situations.

Nitrogen oxides, mainly NOx (NO2 and NO) and nitrous oxide (N2O) are emitted during nitrification and/or denitrification reactions, both in the field and in livestock buildings (bedding, effluent storage areas).

The nitrogen cascade

Simplified view of the nitrogen cascade, highlighting the major anthropogenic sources of reactive nitrogen (Nr) from atmospheric dinitrogen (N2), the main pollutant forms of Nr (orange boxes) and nine main environmental concerns (blue boxes). Estimates of anthropogenic N fixation for the world (Tg /yr for 2005, in black) are compared with estimates for Europe (Tg /yr for 2000, in blue italic). Blue arrows represent intended anthropogenic Nr flows; all the other arrows are unintended flows.

QCM

1) Nitrogen is characterized by a great ability to leave the soil-plant-animal cycle

  • True

  • False

2) Nitrate leaching losses increase when fertilizer applications are in excess of the crop need.

  • True

  • False

3) What is the physical and chemical condition of the environment on which the volatilization of ammonia depends?

  • the nitrogen content of the substrate in contact with the air.

  • the proportion of nitrogen present in the form of ammonia.

  • the proportion of nitrogen present in the form of nitrate.

  • the contact surface between the solution containing ammoniacal nitrogen and the atmosphere.

  • the soil aeration.

  • the dispersion of the air in contact with the emission zone.

Medias