Items from the nitrogen balance forecast mat_mws 24 mars 2015

Items from the nitrogen balance forecast

Comifer champs1The references to key balance sheet items are compiled from knowledge gained on a given date. They are extracted or complete the methodological guide for the calculation of nitrogen fertilization.


They can be used in France, but the use of locally established references cannot be encouraged (Chapter 7 of the methodological guide). These references have no binding legal value. COMIFER reserves the right to update them on its website as necessary.



Nitrogen needs of crops

The calculation of nitrogen fertilization requires the determination of the nitrogen needs of the crop. These needs are defined by the amounts of nutrients removed by a crop that are necessary and sufficient to achieve a production target (or yield) and the level of quality set.


Pi: quantity of nitrogen absorbed by the crop at the opening balance sheet


Ri: Quantity of mineral nitrogen in the soil at the opening balance sheet

Several tools available on the French market offer to estimate the Ri term through agro-climate models. They generally use an estimate of drainage and mineral nitrogen available sources (mineral nitrogen stocks from the previous harvest, mineralization of organic matter …).

The use of such models can be a solution to estimate the R position in environments where a measure is not easily achievable, or in the absence of an observatory to extrapolate some ad hoc measures for all crop situations.


Mh: Net mineralization of soil humus

The proposed calculation tool for regional agronomists allow the exploration of a range of N mineralization of the soil Mh values according to different climatic conditions (27 weather stations) and soil types.

For questions and remarks about the use of the tool, click here


Mhp: additional net mineralization due to prairie reversals


Mr: Mineralization of the previous crop residue


MRCI: Mineralization of intermediate crop residues


Nitrogen supplies by PRO


L: Losses by leaching of nitrate


Rf: Quantity of mineral nitrogen in the soil at the balance sheet closing