VI. Acknowledgements

Corn Yield Responses to Plant Height Variability for Various Tillage Systems and Crop Rotations

Christopher R. Boomsma, Jason C. Brewer, Judith B. Santini, Terry D. West, and Tony J. Vyn

Department of Agronomy; Purdue University; West Lafayette, IN 47907

IV. Preliminary Conclusions• The continuous corn, no-till treatment shows a significantly lower grain yield compared to

the other three treatments in 10 out of 14 years (Figure 4).

• For the continuous corn, no-till treatment, 8 week plant height mean and variability are not

associated with lower grain yield when grain yields are below an annual grand mean grain

yield of ≈ 175 bu A-1, but may influence grain yield when grain yields are above an annual

grand mean grain yield of ≈ 175 bu A-1 (Figures 4-6).

• An increase in 8 week plant height mean for the continuous corn, no-till treatment is

associated with a decrease in grain yield (Figure 7).

• An increase in 8 week plant height variability for the continuous corn rotation is associated

with a decrease in grain yield for the combined no-till and plow tillage treatments

(Figure 8).

• A variety of non-treatment factors, such as temperature, rainfall, and planting date, may also

influence plant height, plant height variability, and subsequently grain yield, and will

therefore be investigated in future research.

I. IntroductionBackground:The effects of various tillage systems and crop rotations on corn (Zea mays L.) growth

and development have been studied extensively over the past twenty-five years. Many

previous studies were conducted on a short-term basis (Wilhelm et al., 2004); however, a

number of long-term studies were also performed. Many of these have principally

focused on the effects of tillage and crop rotation on grain yield and mean plant height

(Griffith et al., 1988; Kapusta et al., 1996; Vyn et al., 2000; West et al., 1996). As a

result of past research, many agronomists and growers believe that lower corn grain

yields in no-till versus conventional-till systems are generally associated with reduced

mean plant heights at critical developmental stages throughout the growing season.

However, mean plant heights may not be accurate morphometric indicators of decreased

grain yields in no-till corn. This research, conducted over a 14 year period, therefore

examines the early-season effects of both mean plant heights and plant height variability

on grain yields using multiple tillage systems and two crop rotations.

Hypotheses:1) No-till grain yield reductions are greatest when plant height variability is high.

2) Early-season plant height variability is a more accurate indicator or predictor of grain

yield response to tillage and crop rotation than early-season mean plant heights.

Objective:• To determine the effects of early-season plant height variability and mean plant heights

on grain yields for various tillage systems and crop rotations.

V. Literature CitedGriffith, D.R., E.J. Kladivko, J.V. Mannering, T.D. West, and S.D. Parsons. 1988. Long-term tillage and rotation effects on corn growth and yield on high and low organic matter, poorly drained soils. Agron. J. 80:599-605.

Kapusta, G., R.F. Krausz, and J.L. Matthews. 1996. Corn yield is equal in conventional, reduced, and no tillage after 20 years. Agron. J. 88:812-817.

Vyn, T.J., T.D. West, and G.C. Steinhardt. 2000. Corn and soybean response to tillage and rotation systems on a dark prairie soil: 25-year review. p. 1–10. In Proc. 15th Int. Soil Tillage Res. Org. Conf., Fort Worth, TX. 2–6 July 2000. Published by Int. Soil Tillage Organization. CD-ROM available from Soil Sci. Dep., Univ. of Wisconsin, Madison, WI.

West, T.D., D.R. Griffith, G.C. Steinhardt, E.J. Kladivko, and S.D. Parsons. 1996. Effect of tillage and rotation on agronomic performance of corn and soybean: Twenty-year study on dark silty clay loam. J. Prod. Agric. 9:241-248.

Wilhelm, W.W., J.M.F. Johnson, J.L. Hatfield, W.B. Voorhees, and D.R. Linden. 2004. Crop and soil productivity response to corn residue removal: A literature review. Agron. J. 96:1-17.

II. Materials and Methods

Figure 3: Fall plowing of soybean residue in preparation for a corn crop.

Experimental Setup:• Layout:

• Split-plot Split-block Design

• Four Blocks

• Hybrid: Beck’s 65X (114 Day)

• Seeding Rate: 26,100 plants A-1

• Planting Date:

• Range: April 25 to May 22

• Mean: May 5

Measurements:• Grain Yield (bu A-1)

• Grain Moisture Content (%)

• Plant Population (plants A-1)

• 4 and 8 Week (after planting) Plant Heights (in)

Statistical Analyses:• All analyses were conducted using SAS®

PROC GLM.

• Years were considered a fixed effect.

• Block 1 plant measurements were omitted from analysis due to frequent flooding.

• 8 week plant height measurements were omitted in 1981 and 1987 due to data problems.

Treatments:• Crop Rotation (whole unit):

• Corn-Soybean (CS)

• Corn-Corn (CC)

• Tillage System (subunit):

• No-Till (NT)

• Plow (PL)

• Chisel

• Ridge-Till

• Year (split block):

• 1981 – 1994

• 8 week plant height coefficient of variation (CV) was log-transformed prior to analysis.

• All error terms were pooled (P>0.25) within even- and odd-year analyses.

• Even- and odd-year analyses were combined into a single 12- or 14-year model since the even- and odd-year error variances were homogeneous.

• Figures 4-8 present results for no-till and plow tillage treatments only.

Figure 1: Spring, pre-plant comparison of a plow (left) and no-till (right) tillage treatment following a previous corn crop.

Figure 2: Spring, pre-plant comparison of all tillage treatments following a previous corn crop.

Figure 8:

Figure 8 describes the relationship between annual grain yield and 8 week plant

height CV for 12 years of the study.

Key Results:

• Large 8 week plant height CVs are associated with predicted grain yields of approximately

145 bu A-1 or less.

• Yield is not influenced by the 8 week plant height CV for the corn-soybean rotation.

• Yield is not influenced by the 8 week plant height CV for the continuous corn rotation when

only CVs less than 16% are considered.

Mean Grain Yield vs. Eight Week Plant Height CV for Two Crop

Rotations and Two Tillage Systems (1982 - 1986, 1988 - 1994)

Eight Week Plant Height CV (%)

0 5 10 15 20 25 30

Gra

in Y

ield

(b

u A

-1)

20

40

60

80

100

120

140

160

180

200

220

240

CB-NT,PLCC-NT,PLCB-NT,PL (Yield = 179.91 + 0.30*Ht8CV)CC-NT,PL (Yield = 179.91 - 1.94*Ht8CV)

R2 = 0.2074**

III. Results

Figure 4:

Figure 4 presents the annual grain yield

for each rotation-tillage treatment for all

14 years of the study. The years are

ranked according to the grain yield grand

mean of all four treatments.

Key Results:

• The continuous corn, no-till treatment has

a significantly lower yield for most years

of the study.

• The continuous corn, no-till yields vary

tremendously relative to the yields of all

other treatments.

Important Note: Error bars equal one-half of the least significant difference (LSD) at probability level 0.05. Means are significantly different where error bars do not overlap.

Figure 5:

Figure 5 presents the 8 week plant height

mean for each rotation-tillage treatment for

12 years of the study. The years are ranked

according to the grain yield grand mean of

all four treatments.

Key Results:

• The continuous corn, no-till treatment has a

significantly lower 8 week plant height

mean for 11 out of the 12 years of the study.

• The continuous corn, no-till 8 week plant

height means vary relative to the means for

all other treatments.

Figure 6:

Figure 6 displays the 8 week plant height

CV (log10[%]) for each rotation-tillage

treatment for 12 years of the study. The

years are ranked according to the grain

yield grand mean of all four treatments.

Key Results:

• The continuous corn, no-till treatment

shows a significantly higher 8 week plant

height CV in 2 out of 12 years of the study.

Figure 7:

Figure 7 describes the relationship between

annual grain yield and 8 week plant height

mean for 12 years of the study.

Key Results:

• Yield decreases 0.91 bu A-1 for each 1 inch

increase in 8 week plant height mean for the

continuous corn, no-till treatment.

• Yield is not influenced by the 8 week plant

height mean for all other treatments.

• Factors other than the treatments may be

influencing the continuous corn, no-till

regression line.

Mean Grain Yield vs. Eight Week Plant Height Mean for Two Crop

Rotations and Two Tillage Systems (1982 - 1986, 1988 - 1994)

Eight Week Plant Height Mean (in)

20 30 40 50 60 70 80 90

Gra

in Y

ield

(bu

A-1

)

20

40

60

80

100

120

140

160

180

200

220

240

CC-NTCC-PL, CB-NT, CB-PLCC-NT (Yield = 185.43 - 0.91*Ht8Mean)CC-PL, CB-NT, CB-PL (Yield = 185.43 - 0.10*Ht8Mean)

R2 = 0.2815**

Mean Grain Yield for Two Crop Rotations and

Two Tillage Systems (1981 - 1994)

Rank Order of Annual Grand Mean Grain Yield

1 2 3 4 5 6 7 8 9 10 11 12 13 14

Gra

in Y

ield

(b

u A

-1)

80

100

120

140

160

180

200

220

240

CS-NTCS-PLCC-NTCC-PL

Eight Week Plant Height Means for Two Crop Rotations

and Two Tillage Systems (1982 - 1986, 1988 - 1994)

Rank Order of Annual Grand Mean Grain Yield

1 2 3 4 7 8 9 10 11 12 13 14

Eig

ht

Wee

k P

lan

t H

eigh

t M

ean

(in

)

20

30

40

50

60

70

80

90

CS-NT CS-PL CC-NT CC-PL

Eight Week Plant Height CVs for Two Crop Rotations

and Two Tillage Systems (1982 - 1986, 1988 - 1994)

Rank Order of Annual Grand Mean Grain Yield

1 2 3 4 7 8 9 10 11 12 13 14

Eig

ht

Wee

k P

lan

t H

eigh

t C

V (

log 10

[%])

0.25

0.50

0.75

1.00

1.25

1.50

1.75

2.00

CS-NT CS-PL CC-NT CC-PL

Equipment and Materials:• Beck’s Hybrids

• Purdue University Agronomy Center

for Research and Education (ACRE)

Funding:• Purdue University Andrews Fellowship

• Purdue University Research Foundation