|Components of NUE|
|Moll, R.H., E.J. Kamprath, and W.A. Jackson. 1982. Analysis and interpretation of factors which contribute to efficiency to nitrogen utilization. Agron. J. 74:562-564.|
1. Uptake efficiency Eup=Nf/Ns
Unlike the description by Moll et al. (1982), uptake efficiency should be partitioned into two separate components since plant N loss (from flowering to maturity) can be significant.
Fraction of N translocated to the grain should be estimated as Ng/Nf and not Ng/Nt as proposed by Moll et al. (1982) since more N was accumulated in the plant at an earlier stage of growth.
Plants losing significant quantities of N as NH3 would have very high fractions of N translocated to the grain when calculated using Nt instead of Nf.
In terms of plant breeding efforts, this could be a highly misleading statistic.
A second component, the translocation index is proposed that would reflect the ability of a plant genotype or management practice to incorporate N accumulated at flowering into the grain.
2. fraction of N translocated to the grain
3. translocation index Eti=Ng/Nf * (1/Nl)
Ability of the soil-plant system to utilize outside sources of N for food production (grain or forage) depends on the efficiency of storage in the soil. The efficiency of the soil to supply N to plants is strongly influenced by immobilization and mineralization with changing climate and environment.
Over a growing season, storage efficiency will be equal to the difference between fertilizer N added (Ns) minus maximum plant uptake (Nf) plus the difference between total soil N at the beginning and end of the season, all divided by fertilizer N added.
Esg = [(Ns-Nf)-(St1-St2)]/Ns
4. soil (management system) supply efficiency, Es=Ns/(Sv+Sd+Sl) where Sv, Sd and Sl are estimates of soil volatilization, denitrification and leaching losses from the soil, respectively.
Lastly, a composite estimate of efficiency for the entire system (soil and plant) can be estimated as follows
5. composite system efficiency Ec=Eup*Es=Nf/(Sv+Sd+Sl)
|Grain weight||Gw||kg ha-1|
|Nitrogen supply (rate of fertilizer N)||Ns||kg ha-1|
|Total N in the plant at maturity (grain + stover)||Nt||kg ha-1|
|N accumulation after silking||Na||kg ha-1|
|N accumulated in grain at harvest||Ng||kg ha-1|
|Growth stage where N accumulated is at a maximum, at or near flowering||Nf||kg ha-1|
|Total N accumulated in the straw at harvest||Nst||kg ha-1|
|Estimate of gaseous loss of N from the plant||Nl =Nf-(Ng+Nst)||kg ha-1|
|Flowering uptake efficiency||Eup=Nf/Ns|
|Harvest uptake efficiency (Uptake efficiency)||Eha=Nt/Ns|
|Translocation index (accumulated N at flowering translocated to the grain)||Eti =Ng/Nf * (1/Nl)|
|Soil supply efficiency||Es=Ns/(Sv+Sd+Sl)|
|Composite system efficiency||Ec=Eup*Es=Nf/(Sv+Sd+Sl)|
|Efficiency of use||Gw/Ns|
|Grain produced per unit of grain N||Gw/Ng|
|Fraction of total N translocated to grain||Et=Ng/Nt|
|Fraction of total N accumulated after silking||Na/Nt|
|Ratio of N translocated to grain to N accumulated after silking||Ng/Na|
Moll, R.H., E.J. Kamprath, and W.A. Jackson. 1982. Analysis and interpretation of factors which contribute to efficiency to nitrogen utilization. Agron. J. 74:562-564.
Raun, W.R., G.V. Johnson, and R.L. Westerman. 1998. Soil-plant nutrient cycling and environmental quality. Dept. Plant and Soil Sciences. Oklahoma State University, Stillwater, OK.