Oklahoma State University Department of Plant and Soil Sciences Oklahoma State University Department...

Oklahoma State UniversityDepartment of Plant and Soil SciencesOklahoma State UniversityDepartment of Plant and Soil Sciences

Nitrogen Loss from Urea Fertilizer Applications on Hot,

Dry Soils

Nitrogen Loss from Urea Fertilizer Applications on Hot,

Dry Soils

R.W. Mullen, G.V. Johnson, K.W.Freeman,K.J. Wynn,

W.E. Thomason, and W.R. Raun

R.W. Mullen, G.V. Johnson, K.W.Freeman,K.J. Wynn,

W.E. Thomason, and W.R. Raun

Urea is the most widely used solid Urea is the most widely used solid fertilizer N source in the world; fertilizer N source in the world; 23,610,991 Mt used for cereal 23,610,991 Mt used for cereal production in 1998 (www.FAO.org).production in 1998 (www.FAO.org).

Volatilization losses from surface Volatilization losses from surface applications of urea-based fertilizers applications of urea-based fertilizers are thought to occur in sizeable are thought to occur in sizeable quantities (Ernst and Massey, 1960; quantities (Ernst and Massey, 1960; Fenn and Hossner, 1985).Fenn and Hossner, 1985).

Urea is the most widely used solid Urea is the most widely used solid fertilizer N source in the world; fertilizer N source in the world; 23,610,991 Mt used for cereal 23,610,991 Mt used for cereal production in 1998 (www.FAO.org).production in 1998 (www.FAO.org).

Volatilization losses from surface Volatilization losses from surface applications of urea-based fertilizers applications of urea-based fertilizers are thought to occur in sizeable are thought to occur in sizeable quantities (Ernst and Massey, 1960; quantities (Ernst and Massey, 1960; Fenn and Hossner, 1985).Fenn and Hossner, 1985).

IntroductionIntroduction

Urea fertilizers must be hydrolyzed Urea fertilizers must be hydrolyzed by the enzyme urease before urea-by the enzyme urease before urea-N becomes plant available.N becomes plant available. Increases in urease activity can result Increases in urease activity can result

in more N loss due to volatilization.in more N loss due to volatilization. Urease activity is moisture and Urease activity is moisture and

temperature dependent.temperature dependent.

Urea fertilizers must be hydrolyzed Urea fertilizers must be hydrolyzed by the enzyme urease before urea-by the enzyme urease before urea-N becomes plant available.N becomes plant available. Increases in urease activity can result Increases in urease activity can result

in more N loss due to volatilization.in more N loss due to volatilization. Urease activity is moisture and Urease activity is moisture and

temperature dependent.temperature dependent.



Urea hydrolysis is maximized when Urea hydrolysis is maximized when moisture levels are optimum for moisture levels are optimum for plant growth (Havlin et al., 1999).plant growth (Havlin et al., 1999). Volk (1966) reported that 14 d after Volk (1966) reported that 14 d after

application of prilled urea to air-dry soil application of prilled urea to air-dry soil 80% had not been hydrolyzed.80% had not been hydrolyzed.

McInnes et al. (1986) found hydrolysis was McInnes et al. (1986) found hydrolysis was minimal following urea application to dry minimal following urea application to dry soil, but following wetting, urea hydrolysis soil, but following wetting, urea hydrolysis increased. increased.

Urea hydrolysis is maximized when Urea hydrolysis is maximized when moisture levels are optimum for moisture levels are optimum for plant growth (Havlin et al., 1999).plant growth (Havlin et al., 1999). Volk (1966) reported that 14 d after Volk (1966) reported that 14 d after

application of prilled urea to air-dry soil application of prilled urea to air-dry soil 80% had not been hydrolyzed.80% had not been hydrolyzed.

McInnes et al. (1986) found hydrolysis was McInnes et al. (1986) found hydrolysis was minimal following urea application to dry minimal following urea application to dry soil, but following wetting, urea hydrolysis soil, but following wetting, urea hydrolysis increased. increased.


Urease activity has been observed from Urease activity has been observed from 2ºC to 37ºC 2ºC to 37ºC (Havlin et al., 1999).(Havlin et al., 1999). Urease activity is positively correlated with Urease activity is positively correlated with

temperature (Clay et al., 1990)temperature (Clay et al., 1990) Fisher and Parks (1958) found that Fisher and Parks (1958) found that

hydrolysis was 50 and 85% complete at hydrolysis was 50 and 85% complete at temperatures temperatures 10 and 20ºC, respectively, 10 and 20ºC, respectively, two weeks after urea application.two weeks after urea application.

Urease activity has been observed from Urease activity has been observed from 2ºC to 37ºC 2ºC to 37ºC (Havlin et al., 1999).(Havlin et al., 1999). Urease activity is positively correlated with Urease activity is positively correlated with

temperature (Clay et al., 1990)temperature (Clay et al., 1990) Fisher and Parks (1958) found that Fisher and Parks (1958) found that

hydrolysis was 50 and 85% complete at hydrolysis was 50 and 85% complete at temperatures temperatures 10 and 20ºC, respectively, 10 and 20ºC, respectively, two weeks after urea application.two weeks after urea application.


Mechanical incorporation of urea fertilizers can effectively decrease N-loss due to volatilization. Increased soil surface area to absorb

released NH3 (Havlin et al., 1999). Palma et al. (1998) reported N-loss

decreased from 8.6% to 5.4% when urea was incorporated.

Mechanical incorporation of urea fertilizers can effectively decrease N-loss due to volatilization. Increased soil surface area to absorb

released NH3 (Havlin et al., 1999). Palma et al. (1998) reported N-loss

decreased from 8.6% to 5.4% when urea was incorporated.

Rainfall or irrigation can result in Rainfall or irrigation can result in subsurface incorporation thus subsurface incorporation thus minimizing volatilization losses.minimizing volatilization losses. Significant precipitation (>.25 cm) 3 to 6 d Significant precipitation (>.25 cm) 3 to 6 d

after application can efficiently reduce after application can efficiently reduce volatilization losses (Havlin et al., 1999).volatilization losses (Havlin et al., 1999).

Rainfall or irrigation can result in Rainfall or irrigation can result in subsurface incorporation thus subsurface incorporation thus minimizing volatilization losses.minimizing volatilization losses. Significant precipitation (>.25 cm) 3 to 6 d Significant precipitation (>.25 cm) 3 to 6 d

after application can efficiently reduce after application can efficiently reduce volatilization losses (Havlin et al., 1999).volatilization losses (Havlin et al., 1999).


ObjectivesObjectives

To determine decreases in winter wheat yield which could be attributed directly to N-loss via volatilization.

To determine the effect of surface application or incorporation on winter wheat N uptake.

To determine decreases in winter wheat yield which could be attributed directly to N-loss via volatilization.

To determine the effect of surface application or incorporation on winter wheat N uptake.

Materials and MethodsMaterials and Methods

Two experimental sites: Stillwater and Tipton, OK

Experimental design: RCBD Eight treatments with three replications

Three N sources both surface applied and incorporated and one injected source Urea (46-0-0), Urea ammonium nitrate (AN;

28-0-0), and ammonium nitrate (AN; 34-0-0) AA (82-0-0)

Two experimental sites: Stillwater and Tipton, OK

Experimental design: RCBD Eight treatments with three replications

Three N sources both surface applied and incorporated and one injected source Urea (46-0-0), Urea ammonium nitrate (AN;

28-0-0), and ammonium nitrate (AN; 34-0-0) AA (82-0-0)


All N was applied at a 112 kg N ha-1 rate. Urea and AN were applied using conventional

dry-fertilizer spreader. UAN was broadcast applied using spray

applicator. AA was injected 15 cm below soil surface using

custom built applicator. Incorporated treatments received a 15-cm

tillage pass.

All N was applied at a 112 kg N ha-1 rate. Urea and AN were applied using conventional

dry-fertilizer spreader. UAN was broadcast applied using spray

applicator. AA was injected 15 cm below soil surface using

custom built applicator. Incorporated treatments received a 15-cm

tillage pass.

Winter wheat variety ‘Jagger’ planted in Winter wheat variety ‘Jagger’ planted in 21-cm rows at a rate of 88 kg ha21-cm rows at a rate of 88 kg ha-1-1..

Harvested area: 2.0 x 6.1 m.Harvested area: 2.0 x 6.1 m. Grain sample taken from each plot for Grain sample taken from each plot for

N analysis using Carlo-Erba dry N analysis using Carlo-Erba dry combustion analyzer (Schepers et al., combustion analyzer (Schepers et al., 1989)1989)

Winter wheat variety ‘Jagger’ planted in Winter wheat variety ‘Jagger’ planted in 21-cm rows at a rate of 88 kg ha21-cm rows at a rate of 88 kg ha-1-1..

Harvested area: 2.0 x 6.1 m.Harvested area: 2.0 x 6.1 m. Grain sample taken from each plot for Grain sample taken from each plot for

N analysis using Carlo-Erba dry N analysis using Carlo-Erba dry combustion analyzer (Schepers et al., combustion analyzer (Schepers et al., 1989)1989)


Results and DiscussionResults and Discussion

1998-1999 Yield response at Stillwater 1998-1999 Yield response at Stillwater

0

500

1000

1500

2000

2500

3000

3500

Check Urea UAN AN AA

Surface

Incorporated

0

500

1000

1500

2000

2500

3000

3500


Surface

Incorporated

SED=26SED=2666SED=26SED=2666

N SourceN Source

Yie

ld k

g h

a-1Y

ield

kg

ha-1


1998-1999 N uptake at Stillwater 1998-1999 N uptake at Stillwater

0

20

40

60

80

100

120

140

160


Surface

Incorporated

0

20

40

60

80

100

120

140

160


Surface

Incorporated

SED=8.SED=8.11SED=8.SED=8.11

N SourceN Source

N U

pta

ke k

g h

a-1N

Up

take

kg

ha-1


1998-1999 Yield response at Tipton 1998-1999 Yield response at Tipton

0

500

1000

1500

2000

2500


Surface

Incorporated

0

500

1000

1500

2000

2500


Surface

Incorporated


N SourceN Source

Yie

ld k

g h

a-1Y

ield

kg

ha-1

1998-1999 N uptake at Tipton 1998-1999 N uptake at Tipton

0

10

20

30

40

50

60

70

80

90


Surface

Incorporated

0

10

20

30

40

50

60

70

80

90


Surface

Incorporated


N SourceN Source

N U

pta

ke k

g h

a-1N

Up

take

kg

ha-1


1999-2000 Yield response at Stillwater 1999-2000 Yield response at Stillwater


0

500

1000

1500

2000

2500

3000

3500

4000


Surface

Incorporated

0

500

1000

1500

2000

2500

3000

3500

4000


Surface

Incorporated


N SourceN Source

Yie

ld k

g h

a-1Y

ield

kg

ha-1

1999-2000 N uptake at Stillwater 1999-2000 N uptake at Stillwater


0

10

20

30

40

50

60

70

80

90


Surface

Incorporated

0

10

20

30

40

50

60

70

80

90


Surface

Incorporated

SED=9.1SED=9.1SED=9.1SED=9.1

N SourceN Source

N U

pta

ke k

g h

a-1N

Up

take

kg

ha-1

1999-2000 Yield response at Tipton 1999-2000 Yield response at Tipton


0

500

1000

1500

2000

2500

3000

3500

4000


Surface

Incorporated

0

500

1000

1500

2000

2500

3000

3500

4000


Surface

Incorporated


N SourceN Source

Yie

ld k

g h

a-1Y

ield

kg

ha-1

1999-2000 N uptake at Tipton 1999-2000 N uptake at Tipton

0

20

40

60

80

100

120


Surface

Incorporated

0

20

40

60

80

100

120


Surface

Incorporated


N SourceN Source

N U

pta

ke k

g h

a-1N

Up

take

kg

ha-1


ConclusionsConclusions

Incorporation of urea fertilizers tended to increase yields when compared to surface applications.

Losses due to volatilization may have been depressed due to rainfall within a week of fertilizer application in both years.

Incorporation of urea fertilizers tended to increase yields when compared to surface applications.

Losses due to volatilization may have been depressed due to rainfall within a week of fertilizer application in both years.

Oklahoma State University Department of Plant and Soil Sciences Oklahoma State University Department...

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