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N-Expert – Fertiliser recommendations for field vegetables


1992 - today

Several field grown vegetables require high amounts of nitrogen (N) while having a short cultivation time compared to many agricultural crops. Therefore, these vegetables need to receive high amounts of N over a comparatively short period to ensure high yield and good quality.

Cooperation Partners

Kai Katroschan
Gartenbaukompetenzzentrum (GKZ), Gülzow
Karin Rather
Staatliche Lehr- und Versuchsanstalt für Gartenbau (LVG)
Hermann Laber
Sächsisches Landesamt für Umwelt, Landwirtschaft und Geologie, Dresden
Klaus Strohmeyer
Gesellschaft für Bodenanalysen, Laboruntersuchung und Qualitätsprüfung (BOLAP)
Joachim Ziegler
Dienstleistungszentrum Ländlicher Raum (DLR) Rheinpfalz, Neustadt a.W.

The estimation of N fertiliser demand is based on the prediction of N demand of the plant and N supply of the soil. Since both are strongly influenced by weather and site properties, prediction errors cannot be excluded. An overestimation of the fertiliser demand is of low economic risk, given that fertilisers are not expensive. An underestimation on the other hand can lead to high economic losses, since already a small lack of nutrients could result in yield and quality losses causing substantial deficits.
Therefore, in practice, insecurity in the prediction of the fertiliser demand, is usually overcome by adding a safety margin, which often leads to excessive fertilisation.
Analyses at IGZ and in independent field experiments revealed that by using N-Expert, a fertilisation advisory system developed at IGZ, safety margins can be reduced and nitrogen losses decreased, without losing yield.


The N-Expert software supports growers and fertilizer advisers both to calculate fertilizer demand of vegetable crops and to compile nutrient balances as required by the German Fertilizer Ordinance. The program published by the Leibniz Institute of Vegetable and Ornamental Crops (IGZ) was completely revised in 2015 and has been continuously developed since then. The new edition comes with an updated database on nutrient demand of all relevant field vegetable crops and nutrient demand of many other crops that are grown in crop rotations with vegetables. 



  1. The computer program ‘N-Expert – Fertilizer advice and nutrient balances for field vegetables’.
    For Windows operating systems we provide an installer that installs the N-Expert program, the N-Expert database and the Java runtime environment on your computer: N-Expert – installation programm for Windows (ca. 135 MB).
    Both the installer and the program do not require Windows administrator rights.
    Please note the latest information on the N-Expert software.
    Note: The default language of the N-Expert program is German. Click on “Einstellungen” – “Sprache” – “English” to change the language setting.
  2. An extensive description of the data used for the N-Expert database (the data is partly obsolete, but the description of the recommendation system is up to date): PDF (in German)
  3. A current table with Nmin target values for field vegetable cultivation: PDF (in German)
  4. A current table with nutrient offtakes of crop products and harvest residues: PDF (in German)
  5. A current table of nutrient contents and N mineralization of organic fertilizers in harvested products and in crop residues of vegetable crops: PDF (in German)
  6. A manual for the application of N-Expert: PDF (in German)

A click guide in six videos to help to get started with the N-Expert software (which is also available on YouTube), in German:

  1. Structure of the Program (.mp4)
  2. Creating a culture (.mp4)
  3. Creating a crop sequence (.mp4)
  4. Fertilization and soil analysis (.mp4)
  5. N-fertilization recommendation according to N-Expert(.mp4)
  6. Other possible uses (.mp4)

This work was financially supported by


 the German Federal Ministry of Food and Agriculture (BMEL) through the Federal Office for Agriculture and Food (BLE), Grant number 28I4HSO15.

We gratefully acknowledge the code development by

Wieczorek IT Service

Marcel Wieczorek IT-Services

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