Nitrogen Use Efficiency as Influenced by Crop Response

Index.

G.V. Johnson, W.R. Raun, R.W. Mullen, R.L. Westerman and B.B. TuckerDepartment of Plant and Soil SciencesOklahoma State University

R.A. OlsonDepartment of AgronomyUniversity of Nebraska

RI > 1.5

RI < 1.5

Higher NUE

LowerNUE

Apply more N

Apply less N

Potential for increased yield

Response Index

Improving Nitrogen Use Efficiency for Cereal Production

Raun and Johnson. 1999. Agron. J. 91:357-363.Worldwide NUE = 33 %1 % change = $234,658, 462

Improving Nitrogen Use Efficiency for Cereal Production

Potential Improvements Crop RotationsForage Production SystemsHybrid or CultivarConservation TillageNH4-N SourceIn-Season and Foliar-Applied NFertigationHigh Resolution Precision Management

Improving Nitrogen Use Efficiency for Cereal Production

Cause of low NUECause of low NUESoil-Plant system leaksSoil-Plant system leaks

Loss increases with excess mineral-NLoss increases with excess mineral-N

Leaching

Denitrification

NO, N2O

Fertilizers

Plant Uptake

Nitrification NO3

-

NHNH44++

N2

+ H2ONH3 + OH+ OH--

Harvest

+ OH+ OH--

NH3

Volatilization

Loss of N from soil-plant systemLoss of N from soil-plant system

Harvested-N1 - Harvested-N0 Fertilizer-N1

X 100 = NUE

Effect of N on Wheat Yield and NUE (1979-1998)502-Lahoma, OK

0500

10001500200025003000

0 20 40 60 80 100 120N rate (kg/ha)

Yiel

d (M

g/ha

)

102030405060708090

NUE(

%)Yld

NUE

Influence of year on NUE winter wheat receiving 90 kg N/ha.

y = 0.91x + 26.48

0102030405060708090

100

9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28Years

NU

E (%

)

NUE 90 kgN

0500

100015002000250030003500400045005000

1 3 5 7 9 11 13 15 17 19 21 23 25 27Years

Yiel

d (k

g/ha

)

No N

Unfertilized yield is variable over time.Unfertilized yield is variable over time.

y = -15.78x + 1910y = -15.78x + 1910C.V. = 30.4 %C.V. = 30.4 %

745745

19741974

Control plot yield of winter wheat (Lahoma, OK):Control plot yield of winter wheat (Lahoma, OK):

Fertilized yield is variable over time.Fertilized yield is variable over time.

0500

100015002000250030003500400045005000

1 3 5 7 9 11 13 15 17 19 21 23 25 27

Years

Yiel

d (k

g/ha

)

Max yld

Y = 23.95x + Y = 23.95x + 25812581C.V. = 20.5 %C.V. = 20.5 %

30453045 30883088

Maximum yield of winter wheat (Lahoma, OK)Maximum yield of winter wheat (Lahoma, OK)

Are fertilized and unfertilized wheat yields related?

y = 0.22x + 2562R2 = 0.04

0500

100015002000250030003500400045005000

0 500 1000 1500 2000 2500 3000Unfertilized Yield (kg/ha)

Max

Fer

tiliz

ed Y

ield

(kg/

ha)

What is the temporal variability of fertilizer-N response?

Response Index (RI) Response Index (RI) RI = Max yield NRI = Max yield Nxx / yield N / yield N00

RI = Indication of the degree to which RI = Indication of the degree to which N, external to the growing N, external to the growing environment, is needed to support environment, is needed to support potential yield.potential yield.

Temporal variability of wheat response to N

y = 0.04x + 1.37C.V. = 35

0.0

1.0

2.0

3.0

4.0

5.0

1 3 5 7 9 11 13 15 17 19 21 23 25 27

Years

Resp

onse

Inde

x

Relationship of fertilized and non fertilized yield to R.I.

R2 = 0.62 R2 = 0.17

0.0

1.0

2.0

3.0

4.0

5.0

0 1000 2000 3000 4000 5000Wheat yield (kg/ha)

Resp

onse

Inde

x

ControlMax Yld-N

Irrigated maize and sorghumIrrigated maize and sorghum

Effect of UAN-N on irrigated maize and sorghum yield and NUE (Mead, NE, 1969-83)

1.02.03.04.05.06.07.08.09.0

10.0

0 90 180 270N rate (kg/ha)

Yiel

d (M

g/ha

)

10

20

30

40

50

60

NU

E (%

)

Corn YldSorghum YldCorn NUESorghum NUE

Response Index for irrigated maize and sorghum over time.

0.51.01.52.02.53.03.54.0

69 71 73 75 77 79 81 83

Years

Res

pons

e In

dex Maize Sorghum

Conclusions

NUE of wheat is usually < 70 % at low NUE of wheat is usually < 70 % at low fertilizer-N rates and decreases with fertilizer-N rates and decreases with increasing N input.increasing N input.

NUE for maize and sorghum is usually NUE for maize and sorghum is usually < 50 %.< 50 %.

Supply of non-fertilizer N to crop Supply of non-fertilizer N to crop changes greatly from year to year.changes greatly from year to year.Soil moisture and temperature variability?Soil moisture and temperature variability?

Conclusions:

Response to fertilizer-N is influenced Response to fertilizer-N is influenced more by external N inputs and more by external N inputs and mineralized soil-N (Nmineralized soil-N (N00 yield) than by yield) than by potential yield, in a given year.potential yield, in a given year.

Since this is found for soil that has not Since this is found for soil that has not received fertilizer N for over 20 year, it is received fertilizer N for over 20 year, it is even more likely to occur in fields that have even more likely to occur in fields that have a history of receiving fertilizer-N each year.a history of receiving fertilizer-N each year.

Conclusions

NUE may be improved by knowing NUE may be improved by knowing the response index and avoiding the response index and avoiding excess fertilizer-N.excess fertilizer-N.

Identify potential yield each year.Identify potential yield each year. Identify non-fertilizer N contributions.Identify non-fertilizer N contributions. Apply fertilizer-N in-season.Apply fertilizer-N in-season.