Managed Land

Nutrient Management Model, surface balance

Surface balance

The annual surface N balance includes the N inputs and outputs for a given area of land, here represented by 0.5 by 0.5 degree grid cells. N inputs include biological N fixation (N_fix), atmospheric N deposition (N_dep), application of synthetic N fertilizer (N_fert) and animal manure (N_man). Outputs in the surface N balance include N removal from the field by crop harvesting, hay- and grass-cutting, and grass consumption by grazing animals (N_exp). The surplus of the surface N balance (N_sur) is calculated as follows:

N_sur = N_fix + N_dep + N_fert + N_man - N_exp

For further reading approach we refer to a set of peer-reviewed publications (Bouwman et al., 2005c; Bouwman et al., 2005b; Bouwman et al., 2006; Eickhout et al., 2006).

Fate of the nutrient surplus

The Surface N balancing is a steady state approach, not taking into account change of N in soil organic matter. N_sur  is subject to NH³ volatilization, denitrification and leaching. 
The same method is used For P, with the exception that the surplus of P is primarily fixed in soils.

• see  carbon nitrogen and water cycle
• see  land use emissions       

For further reading we refer to two peer-reviewed publications (Van Drecht et al., 2003; Bouwman et al., 2005a).

• to  Carbon Plantations Model, input and output
• to  external references
• to  MNP references