Ecological Intensification of Irrigated Corn and Soybean Systems

Ecological Intensification of Irrigated Corn and Soybean Systems

A project supported by:

University of NebraskaPotash & Phosphate InstituteFluid Fertilizer FoundationIMC GlobalNebraska Corn Board

Definitions, Concepts, Considerations

Crop Yield Potential (Yp)

What is it? Theoretically achievable yield solely determined by genetic

characteristics and climate (solar radiation, temperature).How to measure it?

(a) Calculated from components of yield and radiation use efficiency.(b) Estimated by crop simulation models.

How to achieve it? Fully-controlled, small-scale experiment to eliminate all biotic and

abiotic stresses (water, nutrients, pests).How to increase it?

(a) Breeding/germplasm improvement(b) Management: optimization of planting date in relation to variation

in Yp due to the seasonal pattern of radiation and temperature.

Variability of Crop Yield Potential

Annual variation of the simulated corn yield potential at Lincoln, NE

Source: J. Lindquist & D. Walters, UNL Ecological Intensification Project

Year1965 1970 1975 1980 1985 1990 1995 2000

Yie

ld p

ote

nti

al (

bu

/acr

e)

160

180

200

220

240

260

280

300

320

340 Yield limited by temp. and radiationmodern hybrid, 114 d to maturityPlanting: April 11, 35,000 pl./acre

Variability of Crop Yield Potential

Effect of planting date on corn yield potential at Lincoln, NE

Source: J. Lindquist & D. Walters, UNL Ecological Intensification Project

Planting date4/10 4/24 5/08 5/22 6/05

Yie

ld p

ote

nti

al (

bu

/acr

e)

230

232

234

236

238

240

242

244

246

248

250

Yield limited by temp. and radiationmodern hybrid, 114 d to maturityPlanting: 35,000 pl./acre

Attainable Crop Yield Potential (Ya)

What is it? Yield that can be achieved by minimizing abiotic and biotic stresses through the best available technology at a given site in a typical production field.

How to measure it? (a) Yield achieved in high-quality research experiments.(b) Yield achieved by yield contest winners.

How to achieve it? Optimize all soil and crop management to achieve high use efficiencies of solar radiation, water and nutrients. Minimize yield losses due to insects, diseases, weeds.

How to increase it? (a) Improve soil quality (gradual process).(b) Improve crop management (learning process)

General Relationship Between:Yield and Inputs + Management

Inputs + Management

Yield

max profit = Y/X = 0

Year or Location

Optimal Rate of Input

Average optimalrateY

X

Why is it Important to Raise Yield Potential?

Inputs + Management

Yield

Yp 2Ya 2

Yp 1Ya 1

Improved variety

Inferior variety

Yield Potential, Actual Yield, Profit and Resource Use Efficiency

A average response curveB increase in yield potential (Yp)C increase in input use efficiencyD increase in Yp and input use efficiency

Prices:Corn $1.80/buN $0.15/lb NAppl. $6.00/acre/appl.

A & B: 1 N applicationC & D 2 N applications

N rate (lb/acre)

0 50 100 150 200 250

Co

rn y

ield

(b

u/a

cre)

80

100

120

140

160

180

200

220

B

A

D

C


N rate (lb/acre)

0 50 100 150 200 250

Gro

ss p

rofi

t ab

ove

N c

ost

($/a

cre)

180

200

220

240

260

280

300

320

340

360

Rat

e o

f re

turn

(R

OR

)($

pro

fit/

$in

pu

t)

-2

0

2

4

B

A

Max ROR Max Profit Max Y

ROR

A B increase in yield potential


A C increase in input use efficiencyA D increase in Yp and input use efficiency

N rate (lb/acre)

0 50 100 150 200 250

Gro

ss p

rofi

t ab

ove

N c

ost

($/a

cre)

180

200

220

240

260

280

300

320

340

360

Rat

e o

f re

turn

(R

OR

)($

pro

fit/

$in

pu

t)

-2

0

2

4

Max ROR Max Profit Max Y

D

CRORA


MAXIMUM PROFIT

A B C D

Gro

ss p

rofi

t ab

ove

N c

ost

($/a

cre)

200

220

240

260

280

300

320

340

360


Optimal N rate:A & B 162 lb/acreC & D 200 lb/acre



lb N/acre for max yield

lb N/acre for max profit

N RATE @ Max Profit and Max Yield

A B C D0

50

100

150

200

250



bu yield per lb N applied (PFP-N)

N Use Efficiency @ Max Profit

A B C D0.0

0.2

0.4

0.6

0.8

1.0

1.2

bu yield increase over unfertilized control per lb N applied (AE-N)

Why do we Need to Conduct Research on Understanding High Yields?

Average vs. Attainable Corn Yields

IOWA

Year1965 1970 1975 1980 1985 1990 1995 2000

Co

rn G

rain

Yie

ld (

bu

/acr

e)

0

50

100

150

200

250

300

350

400

IA, rainfed corn contest winner (4.1 bu/A/yr)IA, rainfed corn state average (1.5 bu/A/yr)

NEBRASKA

Year1965 1970 1975 1980 1985 1990 1995 20000

50

100

150

200

250

300

350

400

NE, rainfed corn contest winner (5.3 bu/A/yr)NE, rainfed corn state average (1.7 bu/A/yr)NE, irrigated corn contest winner (0 bu/A/yr)NE, irrigated corn state average (1.6 bu/A/yr)

12.1 million acres 8.6 million acres

Average vs. Attainable Soybean Yields

Source: modified from Specht et al., Crop Sci. 39 (1999), 1560-1570.

NEBRASKA

Year1970 1975 1980 1985 1990 1995 2000

So

ybea

n y

ield

(b

u/a

cre)

0

20

40

60

80

100

120NE, rainfed soybean contest winner (0.0 bu/A/yr)NE, rainfed soybean state average (0.4 bu/A/yr)NE, irrigated soybean contest winner (2.9 bu/A/yr)NE, irrigated soybean state average (0.6 bu/A/yr)Maximum yield research, USA

2.4 million acres rainfed1.1 million acres irrigated

Average vs. Attainable Corn Yields

IOWA

Year1965 1970 1975 1980 1985 1990 1995 2000

Co

rn G

rain

Yie

ld (

Mg

/ha)

0

5

10

15

20

25

IA, rainfed corn contest winner (257 kg/ha/yr)IA, rainfed corn state average (95 kg/ha/yr)

NEBRASKA

Year1965 1970 1975 1980 1985 1990 1995 20000

5

10

15

20

25

NE, rainfed corn contest winner (335 kg/ha/yr)NE, rainfed corn state average (107 kg/ha/yr)NE, irrigated corn contest winner (0 kg/ha/yr)NE, irrigated corn state average (98 kg/ha/yr)

4.9 million ha 3.5 million ha

Average vs. Attainable Soybean Yields

Source: modified from Specht et al., Crop Sci. 39 (1999), 1560-1570.

NEBRASKA

Year1970 1975 1980 1985 1990 1995 2000

So

ybea

n y

ield

(M

g/h

a)

0

1

2

3

4

5

6

7

8

9NE, rainfed soybean contest winner (0 kg/ha/yr)NE, rainfed soybean state average (27 kg/ha/yr)NE, irrigated soybean contest winner (197 kg/ha/yr)NE, irrigated soybean state average (37 kg/ha/yr)Maximum yield research

2.4 million acres rainfed1.1 million acres irrigated

How Does Soil Productivity Affect the Attainable Yield Potential?

Source: Johnson et al., 1999

Soil test K (lb/A)160 200 232 269 278

AE-N and PFP-N @ 160 lb N/A

0.2

0.4

0.6

0.8

1.0

1.2

1.4

N rate (lb/A)0 50 100 150 200 250 300 350

Yield (bu/A)

80

100

120

140

160

180

200

220

Soil test K 160 lb/A Soil test K 200 lb/A Soil test K 232 lb/A Soil test K 269 lb/A Soil test K 278 lb/A

PFP-N(bu/lb N)

AE-N(bu/lb N)

Corn, Ohio (1992-95)

What Causes the Variability of Yield in Relation to Inputs and Management?

Fertilizer N (lb/acre)0 50 100 150 200 250

Cor

n yi

eld

(bu/

acre

)

60

80

100

120

140

160

180

1996

19971999

1998

Same field in Lincoln, NE (1996-99)

Environmental Issues: Nitrate

Source: Broadbent & Carlton, 1978 N applied (kg/ha)0 100 200 300 400

Yield (bu/A) (t/ha)

0

2

4

6

8

10

12

0

30

60

90

120

150

180

N in crop or soil (kg/ha)

0

80

160

240

320

400

480

Yield

Inorganic N in soil

N in crop

Tagged N in soil

Irrigated corn, Davis, CA

Environmental Issues: Nitrate

Source: UNL, SCREC

Clay Center, NE, 18-yr LTE

0 200 400 600 800 1000 14001200 1600 1800 2000

0

2

4

6

8

10

12

1416

18

20

Cumulative Nitrate-N, kg ha-1

Dep

th,

m Continuous Corn

Corn-Soybean

Environmental Issues: C Sequestration

Source: T.O. West, ORNL, CSiTE project, 2000 (http://csite.esd.ornl.gov)

Average of long-term experiments, USA

Environmental Issues: C Sequestration

Source: Halvorson et al, Soil Sci. Soc. Am. J. 63 (1999), 912-917.

Dryland crop rotation, Akron, CO, 1984-94 (11 crops)

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

Mg

/ha

20

30

40

50

60

70

80

Total biomass

Total crop residues

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

So

il o

rgan

ic C

(M

g/h

a)

14

15

16

17

C-s

equ

estr

atio

n e

ffic

ien

cy (

%)

0

5

10

15

20

25

30

35Soil organic C

Increase in C-sequestration over control

Environmental Issues: N2O Emission

Sources: Bockman (1994), Eichner (1990)

Typical N2O emission from agricultural land:

1 to 2 kg N2O/ha per year

less than 1% of N applied

Median N2O emission (% of N applied):

Anhydrous ammonia 1.63% (range: 0.9-6.8)

Ammonium nitrate 0.40% (range: 0.04-1.7) Ammonium sulfate (chloride) 0.15% (range: 0.02-

1.7) Urea 0.11% (range: 0.01-0.6) Nitrate 0.05% (range: 0.01-1.8)

Global N fertilizer use (1999)

Million t N %World: Total N 83.0 100

Urea 39.6 48Ammonium nitrate 7.0 8Anhydrous ammonia 4.5 5Liquid N 4.2 5Other straight N 14.8 18Compound N 12.9 16

% of globalUSA: Total N 11.3 100 14

Urea 1.8 16 5Ammonium nitrate 0.6 5 9Anhydrous ammonia 3.6 32 80Liquid N 2.8 25 67Other straight N 0.3 3 2Compound N 2.2 19 17

Source: IFADATA, 2000

Kellogg Station, Michigan (1991-99)

-250

-200

-150

-100

-50

0

50

100

150C-W-S Chem & Till

C-W-S Chem, No-Till

C-W-S low inp/cov

C-W-S Organic/cov

Alfalfa

Poplar

Early Suc. (ab. 1989)

Mid Suc. (HT, ab. 1950)

Mid Suc. (NT, ab. 1959)

Forest

Relative net global warming potential (g CO2 equiv /m2/yr)*

Source: Robertson et al., Science 289 (2000), 1922-1925.

*Includes: soil C, N fertilizer, Lime, Fuel, N2O, CH4

Environmental Issues: Global Warming

What Do We Know About Growing Corn at Attainable Yield Potential Levels?

Yield contest winners: Continuous corn system (no rotation!) Deep soils with soil fertility built up to very high levels. Deep tillage (12-14’’). High plant density (41,000 to 44,000 plants/acre). Slow planting speed (2 mph); accurate plant spacing, less than 2%

skips. P, and K fertilizer inputs exceed average recommendations. Careful N management: Fall application for residue breakdown,

narrow band pre-plant N application (10’’ apart), starter fertilizer, sidedressing.

Frequent scouting and excellent pest control.

What Do We Know About Growing Corn at Attainable Yield Potential Levels?

Knowledge gaps:

Basic scientific understanding of yield-determining processes and how they are affected by management.

Solid scientific basis for efficient extrapolation to other locations (avoid trial and error).

Knowledge of how to design optimal systems managed at 70-80% of the yield potential.

Lack of studies that integrate productivity, profitability, and environmental consequences of high yield systems.

Research at UNL

Objectives

Quantify the yield potential of irrigated corn and soybean. Understand the physiological processes determining it.

Identify cost-effective and environmentally friendly crop management practices to achieve irrigated corn and soybean yields that approach potential levels.

Determine how changes in soil quality affect the ability to achieve yields that approach yield potential levels.

Quantify the energy use efficiency, soil C-sequestration and net radiative forcing potential of intensive corn and soybean management systems.

Ecological Intensification Project: Examples of the Questions Addressed

What is the yield and biomass potential of soybean and corn under irrigated conditions?

How much do current photosynthesis and stored carbohydrate stalk reserves contribute to grain yield at high yield levels?

Can we increase radiation and N use efficiency as we move yields up from present average yields to attainable yield levels?

What are the nutrient requirements to achieve genetic yield potential and how do they change with the yield level?

Do we need to increase soil quality to achieve optimal nutrient- and water-use efficiency at yield potential levels? How much?

What are the environmental consequences (nitrate loss, N2 emission, energy consumption, etc.) of high input systems required for achieving yields that approach yield potential levels?

What is the C-sequestration and net global warming potential of irrigated corn systems?

Key Investigators

Timothy J. Arkebauer Environmenal crop physiologyRobert M. Caldwell Soybean ecophysiology & modelingKenneth G. Cassman Crop physiology and plant nutritionRhae A. Drijber Soil microbial ecologyAchim Dobermann Soil fertility and plant nutritionJohn L. Lindquist Corn ecophysiology & modelingJohn P. Markwell BiochemistryLenis A. Nelson Plant breeding and crop production William Powers Soil physicsKenneth W. Russell Corn geneticsJames E. Specht Soybean geneticsDaniel T. Walters Soil fertility, C sequestration

Crop rotation (main plots)

CC Continuous corn CS Corn-soybean SC Soybean-corn

Plant population (subplots)

P1 corn: 30,000 plants/acre soybean: 150,000 plants/acreP2 corn: 37,000 plants/acre soybean: 185,000 plants/acreP3 corn: 44,000 plants/acre soybean: 220,000 plants/acre

Management intensity (sub-subplots) M1 recommend fertilizer management based on soil testing

corn: UNL recommendation for 200 bu/acre yield goal M2 intensive management aimed at yields close to yield potential

(higher fertilizer rates, micronutrients, N applied in 3 splits) Corn yield goal = 300 bu/acre

Irrigation:Drip irrigationSoil: siCL, pH 5.0-5.7, SOM 2.4-3.1%, P (Bray) 55-78 ppm, K 275-480 ppm

Experimental Details: Lincoln, NE

Experimental Design

SC CS CC CC SC CS

30,000 37,000 44,000 C|S 30,000 44,000 37,000 S|C 30,000 37,000 44,000 C|C 30,000 37,000 44,000 C|C 44,000 30,000 37,000 C|S 37,000 44,000 30,000

M1 M1 M2 | M2 M2 M1 | M2 M1 M2 | M1 M1 M2 | M2 M2 M1 | M2 M1 M2

202 204 206 | 208 210 212 | 214 216 218 | 402 404 406 | 408 410 412 | 414 416 418

30,000 37,000 44,000 | 30,000 44,000 37,000 | 30,000 37,000 44,000 | 30,000 37,000 44,000 | 44,000 30,000 37,000 | 37,000 44,000 30,000

M2 M2 M1 | M1 M1 M2 | M1 M2 M1 | M2 M2 M1 | M1 M1 M2 | M1 M2 M1201 203 205 | 207 209 211 | 213 215 217 | 401 403 405 | 407 409 411 | 413 415 417

37,000 44,000 30,000 C|S 44,000 37,000 30,000 S|C 37,000 30,000 44,000 C|C 44,000 37,000 30,000 C|S 37,000 30,000 44,000 S|C 30,000 37,000 44,000

M1 M2 M1 | M2 M2 M2 | M1 M1 M2 | M1 M2 M1 | M2 M1 M1 | M1 M1 M2

102 104 106 | 108 110 112 | 114 116 118 | 302 304 306 | 308 310 312 | 314 316 318

37,000 44,000 30,000 | 44,000 37,000 30,000 | 37,000 30,000 44,000 T 44,000 37,000 30,000 | 37,000 30,000 44,000 | 30,000 37,000 44,000

M2 M1 M2 | M1 M1 M1 | M2 M2 M1 40' M2 M1 M2 | M1 M2 M2 | M2 M2 M1101 103 105 | 107 109 111 | 113 115 117 L 301 303 305 | 307 309 311 | 313 315 317

CC CS SC SC CS CC

|--20'--|

Fertilizer Program (Corn)

Treatment Growth Stage1999 2000

C after S, M1 Pre-plant 65 103V6 65 35Total 130 138

C after S, M2 Pre-plant 105 103V6 60 100V10 60 95Total 225 298

C after C, M1 Pre-plant - 103V6 - 100Total - 203

C after C, M2 Pre-plant - 103V6 - 130V10 - 130Total - 363

M1: no other nutrients appliedM2: 44 kg P/ha, 85 kg K/ha, 21 kg S/ha

N rate (kg/ha)

Corn: Grain Yield 1999

Source: UNL Ecological Intensification Project (not for citation without permission).

Population density (plants/acre)

30000 37000 44000

Gra

in y

ield

(b

u/a

cre)

100

150

200

250

300

Gra

in y

ield

(M

g/h

a)

8

10

12

14

16

18M0 - C-S, ControlM1 - C-S, RecommendedM2 - C-S, Intensive


Corn: N uptake 1999


30000 37000 44000

To

tal N

up

take

(kg

/ha)

50

100

150

200

250

300

350



Corn: P uptake 1999


30000 37000 44000

To

tal P

up

take

(kg

/ha)

25

30

35

40

45

50

55



Corn: K uptake 1999


30000 37000 44000

To

tal K

up

take

(kg

/ha)

100

150

200

250

300



Nutrient Uptake Requirements

Based on 1999 data

Plant pop Management N P K S Mg

30,000 recommended (220 bu/a) 0.90 0.18 0.95 0.10 0.1244,000 intensive (260 bu/a) 0.98 0.16 1.19 0.09 0.11

30,000 recommended (220 bu/a) 0.30 0.14 0.19 0.06 0.0744,000 intensive (260 bu/a) 0.33 0.13 0.18 0.05 0.06

Nutrient uptake requirement (lb/bu)

Nutrient removal with grain (lb/bu)

July 21, 2000

July 21, 2000


Corn: Total Biomass 2000


30000 37000 44000

To

tal a

bo

veg

rou

nd

dry

mat

ter

(Mg

/ha)

10

15

20

25

30M0 - C-S, Control M1 - C-S, Recommended M2 - C-S, Intensive M0 - C-C, Control M1 - C-C, RecommendedM2 - C-C, Intensive


Corn: Grain Yield 2000


30000 37000 44000

Gra

in y

ield

(b

u/a

cre)

100

150

200

250

300

Gra

in y

ield

(M

g/h

a)

8

10

12

14

16



Corn: N uptake 2000


30000 37000 44000

To

tal N

up

take

(kg

/ha)

50

100

150

200

250

300

350


Corn: Biomass Dynamics

Source: J. Lindquist, UNL Ecological Intensification Project (not for citation without permission).

Development stage:

0.0 0.2 0.4 0.6 0.8 1.0 1.2 1.4 1.6 1.8 2.0

Dry

mat

ter

(kg

/ha)

0

5000

10000

15000

20000

25000 19992000

V10 Anthesis Phys. Maturity

V6

simulated total DM

simulated reprod. DM

Measured INTERCOM model37,000 plants/acreNo constraints other than T and radiation.

Possible Causes of Lower Attainable Yield in 2000 versus 1999?

Late-season high (night) temperatures causing increased maintenance respiration and shorter grain filling period?

Over-expression of vegetative biomass growth in relation to the actual yield potential?

Non-linear relationship between leaf-N, respiration rate, and temperature?

Mild water stress due to high vapor pressure deficit or imperfect irrigation?

Early insect damage? Subtle yield losses from undetected diseases?

Growth and Development


19992000

Emergence to anthesis 59 d 67 dAnthesis to maturity 56 d 45 d

Total growth period 115 d112 d

Average Daily Temperature

Development stage:

0.0 0.2 0.4 0.6 0.8 1.0 1.2 1.4 1.6 1.8 2.0

Ave

rag

e T

emp

erat

ure

(C

)

10

15

20

25

30

35

19992000


V6


Simulated Daily Crop Maintenance Respiration Rate


Development stage:

0.0 0.2 0.4 0.6 0.8 1.0 1.2 1.4 1.6 1.8 2.0

Mai

nte

nan

ce R

esp

irat

ion

(k

g d

ry m

atte

r h

a-1

d-1

)

0

100

200

300

400

500

19992000


V6

INTERCOM model37,000 plants/acreNo constraints other than T and radiation.

Nitrogen Use Efficiency: 1999


Corn after soybean Pop 30 Pop 37 Pop 44Partial factor productivity (PFP) M1 1.87 1.91 1.96

(bu yield/lb N applied) M2 1.15 1.20 1.26

Agronomic efficiency (AE) M1 0.49 0.54 0.59(bu yield increase/lb N applied) M2 0.36 0.41 0.47

Recovery efficiency (RE) M1 0.77 0.64 0.72(lb N uptake increase/lb N applied) M2 0.51 0.55 0.67

Physiological efficiency (PE) M1 0.64 0.84 0.82(bu yield increase/lb N uptake increase) M2 0.71 0.75 0.70

Internal efficiency (IE) M0 1.40(bu yield/lb N uptake) M1 1.07 1.18 1.16

M2 1.07 1.08 1.02

Nitrogen Use Efficiencies: 2000


Corn after soybean Corn after cornPop 30 Pop 37 Pop 44 Pop 30 Pop 37 Pop 44

Partial factor productivity (PFP) M1 1.83 1.90 1.88 1.16 1.17 1.15(bu yield/lb N applied) M2 0.85 0.92 0.86 0.68 0.69 0.66

Agronomic efficiency (AE) M1 0.92 0.98 0.97 0.55 0.56 0.54(bu yield increase/lb N applied) M2 0.43 0.50 0.44 0.34 0.35 0.32

Recovery efficiency (RE) M1 1.11 1.05 0.90 0.54 0.58 0.52(lb N uptake increase/lb N applied) M2 0.56 0.68 0.60 0.44 0.43 0.39

Physiological efficiency (PE) M1 0.83 0.94 1.08 1.03 0.96 1.04(bu yield increase/lb N uptake increase) M2 0.77 0.74 0.74 0.78 0.83 0.83

Internal efficiency (IE) M0 1.17 1.22(bu yield/lb N uptake) M1 0.99 1.06 1.14 1.12 1.08 1.13

M2 0.94 0.90 0.91 0.95 0.98 0.99

Nitrogen Use Efficiency: Corn 1999


30000 37000 44000Ag

ron

om

ic e

ffic

ien

cy o

f N

(b

u/lb

)

0.0

0.2

0.4

0.6

0.8

1.0M1 - C-S, RecommendedM2 - C-S, Intensive


30000 37000 44000Rec

ove

ry e

ffic

ien

cy o

f N

(lb

/lb)0.0

0.2

0.4

0.6

0.8

1.0

1.2

Nitrogen Use Efficiency: 2000


Population density (plants/acre)30000 37000 44000A

gro

no

mic

eff

icie

ncy

of

N (

bu

/lb)

0.0

0.2

0.4

0.6

0.8

1.0

M1 - C-S, Recommended M2 - C-S, Intensive

30000 37000 44000Rec

ove

ry e

ffic

ien

cy o

f N

(lb

/lb)

0.0

0.2

0.4

0.6

0.8

1.0

1.2

M1 - C-C, RecommendedM2 - C-C, Intensive

1999 Five farms in Nebraska

28,000 pl/A

155 lb N/A (all pre-plant)

sprinkler irrig.

Ecol. Int. expt. at UNL

30,000 pl/A

118 lb N/A (pre-plant+V6)

drip irrigation

Ecol. Int. expt. at UNL

44,000 pl/A

205 lb N/A (pre-plant,V6,V10) drip irrigation

Corn yield (bu/acre) 160 220 258

% of yield potential 52 73 86

Bushel yield per lb N applied (PFP N)

1.03 1.87 1.26

Bushel yield increase per lb N applied (AE N)

0.36 0.49 0.47

Recovery efficiency of applied N (%, RE N)

43 70 67

Gross return above fertilizer cost ($/acre)

291 410 461

Source: UNL Ecological Intensification Project; Prices: corn $2/bu, N $0.15/lb, $6/acre per N application

Crop Residue C After 2000 Harvest


M1-CS-30 M2-CS-44

To

tal C

in b

iom

ass

(Mg

/ha)

0

1

2

3

4

5

6

7

8

9

10Root Stalk+Leaf Cob 7.3 Mg C/ha

8.2 Mg C/ha

Soil CO2 flux for 37,000 plants per acre

Source: T. Arkebauer, UNL Ecological Intensification Project (not for citation without permission).

0.0

0.1

0.2

0.3

0.4

0.5

0.6

0 50 100 150 200 250 300 350 50 100 150 200 250 300 350Day of year

So

il C

O2

flu

x (m

g m

-2 s

-1) M2 - INTENSIVE MANAGEMENT

M1 - RECOMMENDED MANAGEMENT

1999 2000

N2O-N flux in Corn Treatments with Different

Levels of Fertility Management, 2000

Source: T. Arkebauer, UNL Ecological Intensification Project (not for citation without permission)

Control no N appliedM1 Recommended fertility management M2 Intensive fertility management

Treatment 23 May 12 July 24 August

g N ha-1 d-1

Control 0.8±0.5 a 0.6±0.6 a 1.9±0.9 a

M1 1.3±1.5 a 5.9±7.5 a 7.1±8.8 a

M2 4.2±3.3 b 24.0±19.7 b 20.6±11.4 b

Conclusions

Yield potential varies significantly from year to year.

Maximum profit is achieved at yield levels that approach the maximum attainable yield.

75 to 85% of the yield potential (220-260 bu/a) is likely to be the most efficient and profitable yield target for high-yielding systems.

Optimal plant density and N and K input depend on yield potential.

Maximum attainable yield requires higher plant density (37-44k plants/acre) and greater amounts K per bushel yield.

Some Challenges

Plant physiology & crop modeling: better understanding of processes governing fluctuation of yield potential in relation to climate and management.

Role of non-structural carbohydrates for grain filling? Quantitative estimates of root biomass and exudates. High N2O losses: how to improve N management in

combination with water management? Optimal timing and form of N? Use real-time N management?

Disease control at high yield levels. Hypothesis: maximum profit and enhanced

environmental quality are not mutually exclusive in high yield systems.

Key References

Broadbent, F.E., and A.B. Carlton. 1978. Field trials with isotopically labeled nitrogen fertilizer. p. 1-41. In Nitrogen in the environment. Vol. 1. Academic Press, New York.

Cassman, K.G. 1999. Ecological intensification of cereal production systems: Yield potential, soil quality, and precision agriculture. Proc. Natl. Academy of Science 96:5952-5959.

de Witt, C.T. 1992. Resource use efficiency in Agriculture. Agric. Systems 40:125-151.Duvick, D.N., and K.G. Cassman. 1999. Post-green revolution trends in yield potential of

temperate maize in the North-Central United States. Crop Sci. 39:1622-1630. Gifford, R.M. and L.T. Evans. 1981. Photosynthesis, carbon partitioning, and yield. Ann. Res. Plant

Physiol. 32:485-509. Greenwood, D.J., G. Lemaire, G. Gosse, P. Cruz, A. Draycott, and J.J. Neetson. 1990. Decline in

percentage N of C3 and C4 crops with increasing plant mass. Ann. Bot. 66:425-436. Loomis, R.S., and J.S. Amthor. 1999. Yield potential, plant assimilatory capacity, and metabolic

efficiencies. Crop Sci. 39:1584-1596. Specht, J.E., D.J. Hume, and S.V. Kumudini. 1999. Soybean yield potential - a genetic and

physiological perspective. Crop Sci. 39:1560-1570. Sinclair, T.R., and T. Horie. 1989. Leaf nitrogen, photosynthesis, and crop radiation use efficiency:

a review. Crop Sci. 29:90-98.

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Ecological Intensification of Irrigated Corn and Soybean Systems

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