Components of the N fertilizer recommendation

The N-Expert system builds on the approaches of the Nmin system and the KNS system. The N target value in N-Expert is not determined in fertilizer trials, but calculated.

This allows the N target value to be adjusted for yield expectation, soil characteristics and field history.

The N target value is calculated as follows:

+ N in the crop
+ Soil mineral n (Nmin) minimum
+ Immobilization (N-fixing in organic soil substance)
+ Unavoidable N losses
- N-mineralization of soil organic matter
- N mineralization from organic fertilizers
- N mineralization from crop residues
---------------------------
= N setpoint

Then, the N fertilizer requirement is calculated by subtracting the Nmin supply from the N target value.

 + Nmin target value
- Nmin supply
---------------------
= N-fertilizer requirement

We recommend to determine soil mineral N (Nmin) with a soil sample.
If no soil samples are available, the N-Expert software can also estimate Nmin from the data entered (preculture, fertilization measures, soil temperature, etc.) ( How does N-Expert estimate the Nmin supply of soil? )