1
G Higher maize population densities may increase yield potential due to more equidistant spacing in narrow rows and quicker canopy closure 1,2,5 . Modern maize hybrids are more efficient in nitrogen use than their previous counterparts 3,6,7 and are more tolerant to stresses such as high plant densities 4 . When maize is not limited by water or nutrients, especially nitrogen, light interception may become the most limiting factor to grain yields. Consequently, increased plant densities may take advantage of maximizing potential light interception in a high yielding environment. It is hypothesized that higher plant population densities will have higher yield potential but will demand higher nitrogen fertilizer compared to lower plant population densities. Narrow 38 cm rows were used to achieve high plant densities. Irrigation and other nutrients were supplied so as to not be limiting at three locations in Kentucky (Fig. 1) in 2014 and 2015. Conclusion Irrigated Maize Response to Nitrogen and Populations Julie Baniszewski and Chad Lee Plant and Soil Sciences Department, University of Kentucky, Lexington, KY [email protected] Introduction Harvest/Post-Harvest Lodging and stalk strength scales 0-10 and 1-5 Yield components kernel number/mass Four center rows harvested (Fig. 4) hand harvested sub-plot Partial return calculated (Eq. 1 & 2) Eq. 1 Partial Return = Gross Income ($15/100 kg) - Costs Eq. 2 Costs = Seed ($240/80 K seeds) + N ($1.10/kg N) + Fuel ($0.39/kg) Figure 1: Kentucky map showing Boone, Fayette and Hardin counties. Light Interception Normalized differential vegetative index (NDVI) of 0.6 - 0.8 indicates a healthy canopy. In both years, NDVI was increased with higher plant populations (Table 1). There was a greater difference in NDVI at earlier reproductive stages compared to later reproductive stages indicating an earlier canopy closure may be correlated with higher plant density (Fig. 9). Yield Response Population had a much larger effect on yield and yield components than nitrogen rate (Fig. 5). Kernel number ear -1 and kernel mass were decreased by higher populations (Fig. 6 & 7). Kernel number ha -1 was increased by population across all environments (Fig. 6). 0 -1 -2 -3 -5 -4 Figure 3: NDVI recorded by an active Crop Canopy Sensor (left). A corn plant with leaves numbered according to position below the ear leaf (right). This scale was used for nitrogen deficiency ratings. In-Season Pollination (tassel/silk) (VT/R1) NDVI recorded (R2-R5; Fig. 3) N deficiency rated (R5; Fig. 3) Nitrogen Deficiency Higher plant populations had nitrogen deficiency significantly higher on the plant, closer to the ear (p<0.0001; Fig. 10). Plant populations created a larger gradient of nitrogen deficiency than applied nitrogen rate (p<0.0001; data not shown). Figure 10: Nitrogen deficiency ratings are expressed as means ± SE for Boone and Fayette counties in both 2014 and 2015. The negative value indicates the number of leaves below the ear leaf to show visible nitrogen deficiency. Figure 8: Partial return was significantly affected by population and nitrogen rate for all locations in 2015 and Hardin in 2014 (α=0.1). There was a population*nitrogen rate interaction at Fayette in 2014 (p=0.0327) and no effect at Boone in 2014 (ANOVA, p=0.3605). Figure 2: A Wintersteiger pneumatic seeder with Kinze row units was used to plant four different corn populations (left). Nitrogen was applied as UAN with a backpack sprayer at V4-V6 (right). Planting Randomized split plot block design Nitrogen rates (196, 252, 308 & 364 kg N ha -1 ) applied pre-plant, side-dress, and at tassel Seed rates (74, 99, 124 & 148 K seeds ha -1 ) planted in 38 cm rows (Fig. 2) AgriGold A6517 Hybrid (flex ear) Yield response diminished after populations reached 99 K plants ha -1 due to reduced yield components. Partial return was maximized between 99 - 124 K plants ha -1 in most environments. Nitrogen above an adequate rate of 252 kg N ha -1 had little effect on yield, but decreased partial return. No population resulted in nitrogen deficiency at the ear leaf by R5, implying that nitrogen did not limit yield in these studies. NDVI shows increased light interception with higher population densities, but little effect from applied nitrogen. Thus, in a system not limited by water or nutrients, canopy closure could become the most limiting factor. Pollination suggests potential problems with pollination synchrony at high plant populations. Increasing plant density could maximize solar radiation and increase potential yield. However, populations greater than 99 K seeds ha -1 did not better utilize higher nitrogen rates as predicted. Instead, 99 K seeds with 252 kg N ha -1 maximized yield response while minimizing input costs. Partial Return Partial return diminished with higher applied nitrogen rates. A quadratic response was observed with planting rate in most environments, but there was a negative linear trend in Boone 2014 and a positive linear trend in Hardin 2014 (Fig. 8). Hardin, 2015 Fayette, 2015 Boone, 2015 Hardin, 2014 Fayette, 2014 Boone, 2014 Legend 2014 NDVI Population (Seeds ha -1 ) R3 R5 74,000 0.7360 0.6909 99,000 0.7291 0.6874 124000 0.7465 0.6923 148,000 0.7551 0.6990 p=0.0033 p=0.0002 Figure 5: Population significantly affected yield at all sites in 2015 and at Hardin in 2014. Fayette was significantly affected by applied nitrogen in 2015 as well and there was a population * nitrogen interaction at Fayette in 2014. There was no effect at Boone in 2014 (α=0.1). References 1 Andrade, FH, PA Calviño, A Cirilo, PA Barbieri. 2002. Yield responses to narrow rows depend on increased radiation interception. Agron. J. 94:975-980. 2 Barbieri, PA, H Echevarria, H Sainz Rozas, F Andrade. 2008. Nitrogen use efficiency in maize as affected by nitrogen availability and row spacing. Agron. J. 100:1094-1100. 3 Below, FE, M Uribelarrea, M Ruffo, SP Moose, AW Becker. 2007. Triple-stacks, genetics, and biotechnology in improving nitrogen use of corn. North Central Extension-Industry Soil Fertility Conference. Vol. 23. Des Moines, IA. 4 Boomsma, CR, JB Santini, M Tollenaar, TJ Vyn. 2009. Maize morphological responses to intense crowding and low nitrogen availability: an analysis and review. Agron. J. 101(6):1426-1452. 5 Bullock, DG, RL Nielsen, WE Nyquist. 1988. A growth analysis comparison of corn grown in conventional and equidistant plant spacing. Crop Sci. 28:254-258. 6 Burzaco, JP, IA Ciampitti, TJ Vyn. 2014. Nitrapyrin impacts on maize yield and nitrogen use efficiency with spring-applied nitrogen: field studies vs. meta-analysis comparison. Agron. J. 106 (2):753-760. 7 Crozier, CR, RJ Gehl, DH Hardy, RW Heiniger. 2014. Nitrogen management for high population corn production in wide and narrow rows. Agron. J. 106(1):66-72. 0.6 0.65 0.7 0.75 0.8 60000 80000 100000 120000 140000 NDVI Population (plants ha -1 ) NDVI in 2015 Fayette, R1 Fayette, R3 Fayette, R4 Hardin, R2 Boone, R2 Boone, R5 -5.08 -4.27 -3.57 -3.38 -6 -5 -4 -3 -2 -1 0 74 99 124 148 Nitrogen Deficiency Rating Population (K seeds ha -1 ) Nitrogen Deficiency Rating C A A B Pollination Pollen shed peaks around 3 days after tassel emergence and typically lasts 5 - 8 days, whereas silk longevity is only about 10 days. Data at Fayette indicate that peak pollen shed may occur before all silks emerge from high density populations (Fig. 11). Figure 11: Plant population densities are shown by symbols. Blue symbols indicate tassel emergence and black symbols indicate silk emergence. Data is shown for Fayette 2015. Tassel and silk emergence were only affected by population, not by nitrogen rate or their interaction ( α=0.1). Tassel emergence was significantly reduced with increased populations only 3 days after anthesis. Silk emergence was significantly reduced by population at both 3 and 6 days after anthesis. 0 10 20 30 40 50 60 70 80 90 100 0 1 2 3 4 5 6 7 Percent Emergence Days Post-Anthesis Pollination 74 99 124 148 *p=0.0185 *p=0.0004 * p=.0290 10 12 14 16 18 20 22 24 60000 80000 100000 120000 140000 Yield (Mg ha -1 ) Population (plants ha -1 ) Yield Response Hardin, 2015 Fayette, 2015 Boone, 2015 Hardin, 2014 Fayette, 2014 Boone, 2014 Figure 7: Kernel mass decreased with higher plant density but interacted with separate environments (p=0.0120). 35 40 45 50 55 60 65 70 75 475 525 575 625 675 725 775 60000 80000 100000 120000 140000 Kernels ha -1 (x 10 6 ) Kernels Ear -1 Population (plants ha -1 ) Kernel Number Kernels Ear-1 Kernels ha-1 Applied Nitrogen Table 1: In 2014, NDVI was significantly increased by higher plant populations across all sites at both R3 & R5. Figure 9: Data in 2015 confirms that higher populations increased NDVI at stages R2-R5 (α=0.1). Methods Figure 6: Kernel number per hectare was significantly increased with higher plant density (p<0.0001) across all environments. Kernel number per ear was decreased with higher plant densities with an environmental interaction (p=0.0831). 1200 1500 1800 2100 2400 150 250 350 450 550 Partial Return ($ ha -1 ) Nitrogen Rate (kg N ha -1 ) Figure 4: Measuring plot area and harvesting with a Wintersteiger plot combine. Results 0.24 0.26 0.28 0.3 0.32 0.34 60000 80000 100000 120000 140000 Kernel Mass (g) Population (plants ha -1 ) Kernel Mass Hardin, 2015 Fayette, 2015 Boone, 2015 Hardin, 2014 Fayette, 2014 Boone, 2014 1200 1700 2200 70 90 110 130 150 Target Population (K seeds ha -1 ) 1200 1400 1600 1800 2000 2200 2400 70 90 110 130 150 Partial Return ($ ha -1 ) Target Population (K seeds ha -1 ) 1200 1700 2200 70 90 110 130 150 Target Population (K seeds ha -1 ) Target Population Partial Return ($ ha -1 )

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Page 1: Irrigated Maize Response to Nitrogen and Populations

G

Higher maize population densities may increase yield potential due to more

equidistant spacing in narrow rows and quicker canopy closure1,2,5. Modern maize

hybrids are more efficient in nitrogen use than their previous counterparts3,6,7 and are

more tolerant to stresses such as high plant densities4 . When maize is not limited by

water or nutrients, especially nitrogen, light interception may become the most

limiting factor to grain yields. Consequently, increased plant densities may take

advantage of maximizing potential light interception in a high yielding environment.

It is hypothesized that higher plant population densities will have

higher yield potential but will demand higher nitrogen

fertilizer compared to lower plant population

densities. Narrow 38 cm rows were used

to achieve high plant densities.

Irrigation and other nutrients were

supplied so as to not be limiting

at three locations in Kentucky

(Fig. 1) in 2014 and 2015.

Conclusion

Irrigated Maize Response to Nitrogen and Populations Julie Baniszewski and Chad Lee

Plant and Soil Sciences Department, University of Kentucky, Lexington, KY

[email protected]

Introduction Harvest/Post-Harvest • Lodging and stalk strength

• scales 0-10 and 1-5

• Yield components

• kernel number/mass

• Four center rows harvested

(Fig. 4)

• hand harvested sub-plot

• Partial return calculated

(Eq. 1 & 2)

Eq. 1

Partial Return = Gross Income ($15/100 kg) - Costs

Eq. 2

Costs = Seed ($240/80 K seeds) + N ($1.10/kg N) + Fuel ($0.39/kg) Figure 1: Kentucky map showing Boone, Fayette and Hardin counties.

Light Interception Normalized differential vegetative index (NDVI) of 0.6 - 0.8

indicates a healthy canopy. In both years, NDVI was

increased with higher plant populations (Table 1). There was

a greater difference in NDVI at earlier reproductive stages

compared to later reproductive stages indicating an earlier

canopy closure may be correlated with higher plant density

(Fig. 9).

Yield Response Population had a much larger effect on yield

and yield components than nitrogen rate

(Fig. 5). Kernel number ear-1 and kernel

mass were decreased by higher populations

(Fig. 6 & 7). Kernel number ha-1 was

increased by population across all

environments (Fig. 6).

0

-1

-2 -3

-5 -4

Figure 3: NDVI recorded by an active Crop Canopy

Sensor (left). A corn plant with leaves numbered

according to position below the ear leaf (right). This

scale was used for nitrogen deficiency ratings.

In-Season • Pollination (tassel/silk) (VT/R1)

• NDVI recorded (R2-R5; Fig. 3)

• N deficiency rated (R5; Fig. 3)

Nitrogen Deficiency Higher plant populations had nitrogen deficiency

significantly higher on the plant, closer to the ear

(p<0.0001; Fig. 10). Plant populations created a larger

gradient of nitrogen deficiency than applied nitrogen

rate (p<0.0001; data not shown).

Figure 10: Nitrogen deficiency ratings are expressed as means ± SE for Boone and Fayette

counties in both 2014 and 2015. The negative value indicates the number of leaves below the ear

leaf to show visible nitrogen deficiency.

Figure 8: Partial return was significantly affected by population and nitrogen rate for all locations in 2015 and Hardin in 2014 (α=0.1).

There was a population*nitrogen rate interaction at Fayette in 2014 (p=0.0327) and no effect at Boone in 2014 (ANOVA, p=0.3605).

Figure 2: A Wintersteiger pneumatic seeder with Kinze row units was used to plant

four different corn populations (left). Nitrogen was applied as UAN with a

backpack sprayer at V4-V6 (right).

Planting • Randomized split plot block design

• Nitrogen rates (196, 252, 308 & 364 kg N ha-1

)

applied pre-plant, side-dress, and at tassel

• Seed rates (74, 99, 124 & 148 K seeds ha-1

)

planted in 38 cm rows (Fig. 2)

• AgriGold A6517 Hybrid (flex ear)

•Yield response diminished after populations

reached 99 K plants ha-1 due to reduced yield

components.

•Partial return was maximized between 99 -

124 K plants ha-1 in most environments.

•Nitrogen above an adequate rate of 252 kg N

ha-1 had little effect on yield, but decreased

partial return.

•No population resulted in nitrogen deficiency

at the ear leaf by R5, implying that nitrogen

did not limit yield in these studies.

•NDVI shows increased light interception with

higher population densities, but little effect

from applied nitrogen. Thus, in a system not

limited by water or nutrients, canopy closure

could become the most limiting factor.

•Pollination suggests potential problems with

pollination synchrony at high plant

populations.

•Increasing plant density could maximize solar

radiation and increase potential yield.

However, populations greater than 99 K seeds

ha-1 did not better utilize higher nitrogen rates

as predicted. Instead, 99 K seeds with 252 kg

N ha-1 maximized yield response while

minimizing input costs.

Partial Return Partial return diminished with

higher applied nitrogen rates. A

quadratic response was observed

with planting rate in most

environments, but there was a

negative linear trend in Boone

2014 and a positive linear trend in

Hardin 2014 (Fig. 8).

Hardin, 2015

Fayette, 2015

Boone, 2015

Hardin, 2014

Fayette, 2014

Boone, 2014

Legend

2014 NDVI

Population (Seeds ha-1) R3 R5

74,000 0.7360 0.6909

99,000 0.7291 0.6874

124000 0.7465 0.6923

148,000 0.7551 0.6990

p=0.0033 p=0.0002

Figure 5: Population significantly affected yield at all sites in 2015 and at

Hardin in 2014. Fayette was significantly affected by applied nitrogen in 2015

as well and there was a population * nitrogen interaction at Fayette in 2014.

There was no effect at Boone in 2014 (α=0.1).

References 1Andrade, FH, PA Calviño, A Cirilo, PA Barbieri. 2002. Yield responses

to narrow rows depend on increased radiation interception. Agron. J. 94:975-980. 2Barbieri, PA, H Echevarria, H Sainz Rozas, F Andrade. 2008. Nitrogen

use efficiency in maize as affected by nitrogen availability and row spacing. Agron.

J. 100:1094-1100. 3Below, FE, M Uribelarrea, M Ruffo, SP Moose, AW Becker. 2007. Triple-stacks, genetics, and biotechnology in improving nitrogen use of corn.

North Central Extension-Industry Soil Fertility Conference. Vol. 23. Des Moines,

IA. 4Boomsma, CR, JB Santini, M Tollenaar, TJ Vyn. 2009. Maize

morphological responses to intense crowding and low nitrogen availability: an

analysis and review. Agron. J. 101(6):1426-1452. 5Bullock, DG, RL Nielsen, WE Nyquist. 1988. A growth analysis

comparison of corn grown in conventional and equidistant plant spacing. Crop Sci.

28:254-258. 6Burzaco, JP, IA Ciampitti, TJ Vyn. 2014. Nitrapyrin impacts on maize

yield and nitrogen use efficiency with spring-applied nitrogen: field studies vs.

meta-analysis comparison. Agron. J. 106 (2):753-760. 7Crozier, CR, RJ Gehl, DH Hardy, RW Heiniger. 2014. Nitrogen

management for high population corn production in wide and narrow rows. Agron.

J. 106(1):66-72.

0.6

0.65

0.7

0.75

0.8

60000 80000 100000 120000 140000

ND

VI

Population (plants ha-1)

NDVI in 2015

Fayette, R1

Fayette, R3

Fayette, R4

Hardin, R2

Boone, R2

Boone, R5-5.08

-4.27

-3.57 -3.38

-6

-5

-4

-3

-2

-1

0

74 99 124 148

Nit

roge

n D

efic

ien

cy R

atin

g

Population (K seeds ha-1)

Nitrogen Deficiency Rating

C

A A

B

Pollination Pollen shed peaks around 3 days after tassel emergence

and typically lasts 5 - 8 days, whereas silk longevity is

only about 10 days. Data at Fayette indicate that peak

pollen shed may occur before all silks emerge from high

density populations (Fig. 11).

Figure 11: Plant population densities are shown by symbols. Blue symbols indicate tassel

emergence and black symbols indicate silk emergence. Data is shown for Fayette 2015. Tassel and

silk emergence were only affected by population, not by nitrogen rate or their interaction (α=0.1).

Tassel emergence was significantly reduced with increased populations only 3 days after anthesis.

Silk emergence was significantly reduced by population at both 3 and 6 days after anthesis.

0

10

20

30

40

50

60

70

80

90

100

0 1 2 3 4 5 6 7

Pe

rce

nt

Eme

rge

nce

Days Post-Anthesis

Pollination

74

99

124

148

*p=0.0185

*p=0.0004

* p=.0290

10

12

14

16

18

20

22

24

60000 80000 100000 120000 140000

Yie

ld (

Mg

ha-1

)

Population (plants ha-1)

Yield Response

Hardin, 2015

Fayette, 2015

Boone, 2015

Hardin, 2014

Fayette, 2014

Boone, 2014

Figure 7: Kernel mass decreased with higher plant density but interacted with separate

environments (p=0.0120).

35

40

45

50

55

60

65

70

75

475

525

575

625

675

725

775

60000 80000 100000 120000 140000

Ke

rne

ls h

a-1 (

x 1

06)

Ke

rne

ls E

ar-1

Population (plants ha-1)

Kernel Number

Kernels Ear-1

Kernels ha-1

Applied Nitrogen

Table 1: In 2014, NDVI was significantly

increased by higher plant populations

across all sites at both R3 & R5. Figure 9: Data in 2015 confirms that higher populations

increased NDVI at stages R2-R5 (α=0.1).

Methods

Figure 6: Kernel number per hectare was significantly increased with higher plant

density (p<0.0001) across all environments. Kernel number per ear was decreased

with higher plant densities with an environmental interaction (p=0.0831).

1200

1500

1800

2100

2400

150 250 350 450 550

Par

tial

Ret

urn

($

ha-1

)

Nitrogen Rate (kg N ha-1)

Figure 4: Measuring plot area and

harvesting with a Wintersteiger plot

combine.

Results

0.24

0.26

0.28

0.3

0.32

0.34

60000 80000 100000 120000 140000

Ke

rne

l Mas

s (g

)

Population (plants ha-1)

Kernel Mass

Hardin, 2015

Fayette, 2015

Boone, 2015

Hardin, 2014

Fayette, 2014

Boone, 2014

1200

1700

2200

70 90 110 130 150

Target Population (K seeds ha-1)

1200

1400

1600

1800

2000

2200

2400

70 90 110 130 150

Par

tial

Ret

urn

($

ha-1

)

Target Population (K seeds ha-1)

1200

1700

2200

70 90 110 130 150Target Population (K seeds ha-1)

Target Population

Par

tial

Ret

urn

($

ha-1

)