## 2.19.5. Nitrogen allocation[¶](#nitrogen-allocation "Permalink to this headline")
---------------------------------------------------------------------------------

The total flux of nitrogen to be allocated is given by the FUN model (Chapter [2.18](https://escomp.github.io/ctsm-docs/versions/master/html/tech_note/FUN/CLM50_Tech_Note_FUN.html#rst-fun)). This gives a total N to be allocated within a given timestep, \\(N\_{supply}\\). The total N allocated for a given tissue \\(i\\) is the minimum between the supply and the demand:

(2.19.26)[¶](#equation-19-26 "Permalink to this equation")\\\[NF\_{alloc,i} = min \\left( NF\_{demand, i}, NF\_{supply, i} \\right)\\\]

The demand for each tissue, calculated for the tissue to remain on stoichiometry during growth, is:

(2.19.27)[¶](#equation-19-27 "Permalink to this equation")\\\[NF\_{demand,leaf} \\\_ =\\frac{CF\_{alloc,leaf\\\_ tot} }{CN\_{leaf} } f\_{cur}\\\]

(2.19.28)[¶](#equation-19-28 "Permalink to this equation")\\\[NF\_{demand,leaf\\\_ stor} \\\_ =\\frac{CF\_{alloc,leaf\\\_ tot} }{CN\_{leaf} } \\left(1-f\_{cur} \\right)\\\]

(2.19.29)[¶](#equation-19-29 "Permalink to this equation")\\\[NF\_{demand,froot} \\\_ =\\frac{CF\_{alloc,leaf\\\_ tot} a\_{1} }{CN\_{fr} } f\_{cur}\\\]

(2.19.30)[¶](#equation-19-30 "Permalink to this equation")\\\[NF\_{demand,froot\\\_ stor} \\\_ =\\frac{CF\_{alloc,leaf\\\_ tot} a\_{1} }{CN\_{fr} } \\left(1-f\_{cur} \\right)\\\]

(2.19.31)[¶](#equation-19-31 "Permalink to this equation")\\\[NF\_{demand,livestem} \\\_ =\\frac{CF\_{alloc,leaf\\\_ tot} a\_{3} a\_{4} }{CN\_{lw} } f\_{cur}\\\]

(2.19.32)[¶](#equation-19-32 "Permalink to this equation")\\\[NF\_{demand,livestem\\\_ stor} \\\_ =\\frac{CF\_{alloc,leaf\\\_ tot} a\_{3} a\_{4} }{CN\_{lw} } \\left(1-f\_{cur} \\right)\\\]

(2.19.33)[¶](#equation-19-33 "Permalink to this equation")\\\[NF\_{demand,deadstem} \\\_ =\\frac{CF\_{alloc,leaf\\\_ tot} a\_{3} \\left(1-a\_{4} \\right)}{CN\_{dw} } f\_{cur}\\\]

(2.19.34)[¶](#equation-19-34 "Permalink to this equation")\\\[NF\_{demand,deadstem\\\_ stor} \\\_ =\\frac{CF\_{alloc,leaf\\\_ tot} a\_{3} \\left(1-a\_{4} \\right)}{CN\_{dw} } \\left(1-f\_{cur} \\right)\\\]

(2.19.35)[¶](#equation-19-35 "Permalink to this equation")\\\[NF\_{demand,livecroot} \\\_ =\\frac{CF\_{alloc,leaf\\\_ tot} a\_{2} a\_{3} a\_{4} }{CN\_{lw} } f\_{cur}\\\]

(2.19.36)[¶](#equation-19-36 "Permalink to this equation")\\\[NF\_{demand,livecroot\\\_ stor} \\\_ =\\frac{CF\_{alloc,leaf\\\_ tot} a\_{2} a\_{3} a\_{4} }{CN\_{lw} } \\left(1-f\_{cur} \\right)\\\]

(2.19.37)[¶](#equation-19-37 "Permalink to this equation")\\\[NF\_{demand,deadcroot} \\\_ =\\frac{CF\_{alloc,leaf\\\_ tot} a\_{2} a\_{3} \\left(1-a\_{4} \\right)}{CN\_{dw} } f\_{cur}\\\]

(2.19.38)[¶](#equation-19-38 "Permalink to this equation")\\\[NF\_{demand,deadcroot\\\_ stor} \\\_ =\\frac{CF\_{alloc,leaf} a\_{2} a\_{3} \\left(1-a\_{4} \\right)}{CN\_{dw} } \\left(1-f\_{cur} \\right).\\\]

After each pool’s demand is calculated, the total plant N demand is then the sum of each individual pool \\(i\\) corresponding to each tissue:

(2.19.39)[¶](#equation-19-39 "Permalink to this equation")\\\[NF\_{demand,tot} = \\sum \_{i=tissues} NF\_{demand,i}\\\]

and the total supply for each tissue \\(i\\) is the product of the fractional demand and the total available N, calculated as the term \\(N\_{uptake}\\) equal to the sum of the eight N uptake streams described in the FUN model (Chapter [2.18](https://escomp.github.io/ctsm-docs/versions/master/html/tech_note/FUN/CLM50_Tech_Note_FUN.html#rst-fun)).

(2.19.40)[¶](#equation-19-40 "Permalink to this equation")\\\[NF\_{alloc,i} = N\_{uptake} NF\_{demand,i} / NF\_{demand,tot}\\\]
