Nitrogen Use Efficiency, Nitrogen Fertilizers, NUE, Nitrogen and the EnvironmentNitrogen Use Efficiency Definitions
  NUE Flow Chart                                                                          Quick links:
Nitrogen use efficiency and/or fertilizer recovery in crop production systems can be computed using many different methods.  Those specifically designated for crop production systems follow.  In addition, nitrogen use efficiency has been estimated using world N consumption and crop production, but on macro scales (Agron. J. 91:357-363). Other methods (Difference Method, Isotopic Method (Enriched and Depleted)) follow below.  Finally, the components of Nitrogen Use Efficiency are also discussed, initially discussed by Moll et al. (1982).  Regardless of the method, almost all result in estimated NUE for cereal production from 30 to 35%.  Topdress or sidedress N applications in the middle of the season can result greater NUE's (>50%).  Because the risk of N loss is greater with fall N application, N should be applied in the spring to minimize risk and optimize profitability regardless of tillage system (Vetsch and Randall, 2004).
  • 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.
  • Olson, R.V., and C.W. Swallow. 1984. Fate of labeled nitrogen fertilizer applied to winter wheat for five years. Soil Sci. Soc. Am. J. 48:583-586.

Olson and Swallow, 1984 (27-33% of the applied N fertilizer was removed by the grain following 5 years)

Calculating N Use Efficiency using The Difference Method -

 Moll et al. (1982)
Presence of two primary components of N use efficiency:
(1)Efficiency of absorption or uptake (Nt/Ns)
(2)Efficiency with which N absorbed is utilized to produce grain (Gw/Nt)
Nt = total N in the plant at maturity (grain + stover)
Ns = nitrogen supply or rate of fertilizer N
Gw = grain weight (all expressed in the same units)

Consideration of additional parameters not discussed in Moll et al. (1982) *plant N loss 

  • Maximum N accumulation has been found to occur at or near flowering in wheat and corn and not at harvest. 
  • In order to estimate plant N loss without the use of labeled N forms, the stage of growth where maximum N accumulation is known to occur needs to be identified. 
  • The amount of N remaining in the grain + straw or stover, is subtracted from the amount at maximum N accumulation to estimate potential plant N loss (difference method). 
  • Use of difference methods for estimating plant N loss are flawed since continued uptake is known to take place beyond flowering or the point of maximum N accumulation.
Davis, R.L., J.J. Patton, R.K. Teal, Y. Tang, M.T. Humphreys, J. Mosali, K. Girma, J.W. Lawles, S.M. Moges, A. Malapati, J.Si, H. Zhang, S. Deng, G.V. Johnson, R.W. Mullen, and W.R. Raun. 2003. Nitrogen balance in the Magruder Plots following 109 years in continuous winter wheat. J. Plant Nutr. 26(8):1561-1580.

 Nitrogen Use Efficiency (Recovery) Using Isotopic Methods


Enriched 15N:

Materials with a greater than natural concentration of 15N % plant N derived from fertilizer = %15N excess in sample  % 15N excess in fertilizer
 

Depleted 15N:

Materials with a lower than natural concentration of 15N (0.003 - 0.01 atom % 15N) or (< 0.01 atom % 15N)

Use of isotopic 14N

Studies involving residual soil nitrogen are not practical with depleted materials due to the high dilution factor.
 

% plant N derived from the fertilizer =

(Nu - Nt)/(Nu - (Nf/n))
Nu =atom % 15N in unfertilized plants
Nt = atom % 15N in fertilized plants
Nf = atom % 15N in the fertilizer (for example 0.006%)
n = the plant discrimination factor between 14N and 15N.

If it is assumed that there is no discrimination between 14N and 15N, then n = 1.

 

  Fertilizer N Recovery (Varvel and Peterson, 1990)

1. Difference method

PFR = (NF)-(NC) / R

NF = total N uptake in corn from N fertilized plots
NC = total N uptake in corn from unfertilized plots
R = rate of fertilizer N applied
PFR = percent fertilizer recovery

2. Isotopic method (Depleted material)

PFR = ((NF) x (C-B)/D) / R

NF = total N uptake in corn from N fertilized plots
B = atom % 15N of plant tissue from N fertilized plots
C = atom % 15N of plant tissue from unfertilized plots (0.366%)
D = depleted atom % 15N in applied N fertilizer
R = rate of applied 15N-labeled fertilizer

3. Isotopic method (Enriched material, Sanchez et al., 1987)

F = As-Ar/Af-Ar
F= fraction of total N uptake derived from 15N enriched fertilizer
As = atom % 15N measured in the harvested plant sample
Af = atom % 15N in the enriched fertilizer
Ar = atom % 15N of the reference harvested plant material from non 15N enriched fertilizer treatments

Ef = F x total N uptake
Ef = uptake of 15N enriched fertilizer

Shearer and Legg (1975) found that d15N of wheat plants decreased as the N application rate increased.

d15N = atom % 15N (sample) - atom % 15N (standard) x 1000 / atom % 15 N (standard)

15N composition of the total N of grain and leaf samples of corn (Zea mays L.) decreased systematically as N fertilizer rates increased (Kohl et al., 1973). This result was considered to be consistent with increasing contributions of fertilizer N to plants as the rate of applied N increased.

Hauck and Bremner, 1976

percent nitrogen recovered (plant or soil) =

= 100P (c-b) / f(a-b)

P = total N in the plant part or soil in kg ha-1
f = rate of 15N fertilizer applied
a = atom percent 15N in the labeled fertilizer
b = atom percent 15N in the plant part or soil receiving no 15N
c = atom percent 15N in the plant part or soil that did receive 15N

unlabeled N uptake = (total N uptake in grain and straw) -

[N rate(% recovery of 15N in grain and straw)]

 

 

  References

Davis, R.L., J.J. Patton, R.K. Teal, Y. Tang, M.T. Humphreys, J. Mosali, K. Girma, J.W. Lawles, S.M. Moges, A. Malapati, J.Si, H. Zhang, S. Deng, G.V. Johnson, R.W. Mullen, and W.R. Raun. 2003. Nitrogen balance in the Magruder Plots following 109 years in continuous winter wheat. J. Plant Nutr. 26(8):1561-1580.

Raun, W.R. and G.V. Johnson. 1999. Improving Nitrogen Use Efficiency for Cereal Production. Agron. J. 91:357-363

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.

Olson, R.V., and C.W. Swallow. 1984. Fate of labeled nitrogen fertilizer applied to winter wheat for five years. Soil Sci. Soc. Am. J. 48:583-586.

Vetsch, Jeff, and Gyles Randall. 2004. Corn production as affected by nitrogen application timing and tillage. Agron. J. 96:502-509.

Varvel, G.E., and T.A. Peterson. 1990. Nitrogen fertilizer recovery by corn in monoculture and rotation systems. Agron. J. 82:935938.

 

Journals
    PDF  version from Agronomy Journal (91:357-363)
    Components of Nitrogen Use Efficiency (added discussion of the Moll et al. 1982) manuscript