to the graduate council - university of tennessee at martin · to the graduate council: i am...

To the Graduate Council:

I am submitting herewith a thesis written by April R. Tutor entitled “Effect of Soybean Planting Date in North and South Carolina on Advancing Soybean Varieties in Soybean Breeding.” I have examined the electronic copy of this thesis for form and content and recommend that it be accepted in partial fulfillment of the requirements for the degree of Master of Science, with a major in Agriculture and Natural Resources Systems Management.

Dr. Eric Walker Major Professor

We have read this thesis and recommend its acceptance:

Dr. Jesse Gilsinger

Dr. Barbara Darroch

Dr. Joey Mehlhorn

Accepted for the Council

Dr. Victoria S. Seng Associate Vice Chancellor for Academic Affairs and Dean of Graduate Studies

(Original signatures are on file with official student records)

Effect of Soybean Planting Date in North and South Carolina on Advancing Soybean

Varieties in Soybean Breeding

A Thesis Presented for

the Master of Science Degree

The University of Tennessee at Martin

April R. Tutor

May 2012

ii

Acknowledgements

There are many people that I would like to acknowledge for their support and insight

throughout this project. First of all, I would like to thank Monsanto for providing the resources

and funding that allowed me to complete this project. I would like to thank Dr. Eric Walker and

Dr. Joey Mehlhorn for their insight and for helping to make my thesis what it is today. I would

like to thank Dr. Jesse Gilsinger for his time, guidance, and insight throughout the project. I

would also like to thank all my co-workers at Monsanto for their help with packaging, planting,

note-taking, and harvesting; their assistance was an integral part of this project. I would like to

thank Dr. Barbara Darroch for her guidance and direction throughout my years in the MSANR

program, for editing my paper, and for all the help with the statistical analysis of the project. I

would also like to thank my husband, Kevin Tutor, for his continued and never-ending support

and for assisting with the care of our two daughters, Bailey and Parker, while I worked on this

project.

iii

Abstract

Soybean [Glycine max (L) Merr.] is an important crop on many farms in North and South

Carolina. The planting date and maturity group (MG) that a farmer chooses can vary from farm

to farm. Therfore, it is important that soybean breeding stations test soybean varieties under the

same planting conditions and dates under which the farmers will grow them. Many soybean

breeding stations utilize winter nurseries to advance generations more quickly and may get the

harvested seed shipped to them later in the spring than desired. This may result in a later than

optimal planting date. If a significant genotype by planting date interaction is present, this could

have an impact on selections. The objective of this was were to provide local soybean breeders,

as well as breeding stations, with information on the effects of soybean planting date on the

selection of lines that are advanced in a breeding program.

For this study, trials were conducted in 2010 at five locations across North and South

Carolina, two of which were irrigated. Each trial consisted of three randomized, ten-entry tests

representing MGV, MGVI, and MGVII across two planting dates, one in late May/early June

and one in late June/early July. A split plot randomized complete block design with three

replications was used. Main plots consisted of planting dates and subplots consisted of maturity

groups. Varieties were nested within maturity groups. Yield data, as well as data on lodging and

plant height, were collected and analyzed to determine whether or not a genotype by planting

date interaction existed.

A significant (P < 0.05) date by variety (within group) interaction existed at four of the

five locations for both yield and plant height. For lodging, a significant interaction was noted at

all three locations where lodging was observed. Changes in rank were also noted for each

iv

planting date for all three variables. These results indicate that advancing lines based on an

undesirable planting date could exclude high-performing lines; therefore, planting date should be

taken into consideration when breeders advance lines within their breeding programs. We

suggest decreasing selection pressure on late planted soybean trials, especially for MG V and VI.

This would help buffer the effects of genotype by planting date interaction.

v

Table of Contents

Page

Chapter I Introduction ......................................................................................................................1 Research Objectives .............................................................................................................2 Chapter II Literature Review ...........................................................................................................3 Overview of Soybean Production ........................................................................................3

Soybean Maturity Groups ....................................................................................................4 Planting Date ........................................................................................................................4 Planting Date by Genotype Interactions ..............................................................................6

Chapter III Research Methods .........................................................................................................7 Chapter IV Results .........................................................................................................................11 Yield ...................................................................................................................................11 Lodging ..............................................................................................................................23 Plant Height .......................................................................................................................26 Chapter V Discussion ....................................................................................................................29 Chapter VI Conclusions .................................................................................................................30 Literature Cited ..............................................................................................................................31 Appendices .....................................................................................................................................33 Appendix A ANOVA Tables .............................................................................................34 Appendix B Weather Data .................................................................................................42 Vita .................................................................................................................................................48

vi

List of Tables

Page

Table 1. Planting and harvest dates for test sites in 2010. ..............................................................9 Table 2. Probability (P) Values for the main effects and interaction terms in the analysis of variance for soybean trials at Benson (NCBN), Calypso (NCCO), Hugo (NCHU), and Mount Olive (NCMO), North Carolina, and Hartsville (SCHA), South Carolina in 2010............................................................................................................................................... 12 Table 3. Average yield and yield rankings (in parentheses) by planting date across five locations (Benson, Calypso, Hugo, and Mount Olive, North Carolina, and Hartsville, South Carolina) in 2010. ............................................................................................................... 14 Table 4. Average yield and yield rankings (in parentheses) by irrigation type across five locations (Benson, Calypso, Hugo, and Mount Olive, North Carolina, and Hartsville, South Carolina) in 2010. ............................................................................................................... 15 Table 5. Average yield and yield rankings (in parentheses) for PDS5 (soybean varieties in maturity group 5.5 to 5.9) across five locations (Benson, Calypso, Hugo, and Mount Olive, North Carolina, and Hartsville, South Carolina) in 2010. ............................................................ 16 Table 6. Average yield and yield rankings (in parentheses) for PDS6 (soybean varieties in maturity group 6.0 to 6.7) across five locations (Benson, Calypso, Hugo, and Mount Olive, North Carolina, and Hartsville, South Carolina) in 2010. ............................................................ 17 Table 7. Average yield and yield rankings (in parentheses) for PDS7 (soybean varieties in maturity group 6.8 to 7.7) across five locations (Benson, Calypso, Hugo, and Mount Olive, North Carolina, and Hartsville, South Carolina) in 2010. ............................................................ 18 Table 8. Effect of planting date on mean soybean yield for trials at Benson (NCBN), Calypso (NCCO), Hugo (NCHU), and Mount Olive (NCMO), North Carolina, and Hartsville (SCHA), South Carolina in 2010. ................................................................................ 22

Table 9. Average lodging score by planting date across three locations (Calypso and Mount Olive, North Carolina, and Hartsville, South Carolina) in 2010. ...................................... 24 Table 10. Average lodging score by irrigation type across three locations (Calypso and Mount Olive, North Carolina, and Hartsville, South Carolina) in 2010. ...................................... 25 Table 11. Average plant height by planting date across five locations (Benson, Calypso, Hugo, and Mount Olive, North Carolina, and Hartsville, South Carolina) in 2010. .................... 27

vii

Table 12. Average plant height by irrigation type across five locations (Benson, Calypso, Hugo, and Mount Olive, North Carolina, and Hartsville, South Carolina) in 2010. .................... 28 Table A.1. Results of the ANOVA for the effect of seeding date, maturity group, and variety on lodging of soybean varieties at Calypso, North Carolina in 2010. ............................. 35 Table A.2. Results of the ANOVA for the effect of seeding date, maturity group, and variety on lodging of soybean varieties at Mount Olive, North Carolina in 2010. ...................... 35 Table A.3. Results of the ANOVA for the effect of seeding date, maturity group, and variety on lodging of soybean varieties at Hartsville, South Carolina in 2010. .......................... 36 Table A.4. Results of the ANOVA for the effect of seeding date, maturity group, and variety on plant height of soybean varieties at Benson, North Carolina in 2010. ....................... 36 Table A.5. Results of the ANOVA for the effect of seeding date, maturity group, and variety on plant height of soybean varieties at Calypso, North Carolina in 2010. ...................... 37 Table A.6. Results of the ANOVA for the effect of seeding date, maturity group, and variety on plant height of soybean varieties at Hugo, North Carolina in 2010. .......................... 37 Table A.7. Results of the ANOVA for the effect of seeding date, maturity group, and variety on plant height of soybean varieties at Mount Olive, North Carolina in 2010. ............... 38 Table A.8. Results of the ANOVA for the effect of seeding date, maturity group, and variety on plant height of soybean varieties Hartsville, South Carolina in 2010. ....................... 38 Table A.9. Results of the ANOVA for the effect of seeding date, maturity group, and variety on yield of soybean varieties at Benson, North Carolina in 2010. .................................. 39 Table A.10. Results of the ANOVA for the effect of seeding date, maturity group, and variety on yield of soybean varieties at Calypso, North Carolina in 2010. ................................. 39 Table A.11. Results of the ANOVA for the effect of seeding date, maturity group, and variety on yield of soybean varieties at Hugo, North Carolina in 2010. ..................................... 40 Table A.12. Results of the ANOVA for the effect of seeding date, maturity group, and variety on yield of soybean varieties at Mount Olive, North Carolina in 2010. .......................... 40 Table A.13. Results of the ANOVA for the effect of seeding date, maturity group, and variety on yield of soybean varieties at Hartsville, South Carolina in 2010. ............................... 41

viii

List of Figures

Page Figure 1. Map of test site locations in 2010 (Test Site Image, 2012). .............................................8 Figure 2. Average monthly temperature and total monthly rainfall at Benson, North Carolina in 2010. ............................................................................................................................19 Figure 3. Average monthly temperature and total monthly rainfall at Calypso, North Carolina in 2010. ............................................................................................................................19 Figure 4. Average monthly temperature and total monthly rainfall at Hugo, North Carolina in 2010. ............................................................................................................................20 Figure 5. Average monthly temperature and total monthly rainfall at Mount Olive, North Carolina in 2010. ............................................................................................................................20 Figure 6. Average monthly temperature and total monthly rainfall at Hartsville, South Carolina in 2010. ............................................................................................................................21 Figure B.1. Daily precipitation for Benson, North Carolina; May-October 2010. ........................43 Figure B.2. Average maximum and minimum daily temperatures for Benson, North Carolina; May-October 2010. ........................................................................................................43 Figure B.3. Daily precipitation for Calypso, North Carolina; May-October 2010. .......................44 Figure B.4. Average maximum and minimum daily temperatures for Calypso, North Carolina; May-October 2010. ........................................................................................................44 Figure B.5. Daily precipitation for Hartsville, South Carolina; May-October 2010. ....................45 Figure B.6. Average maximum and minimum daily temperatures for Hartsville, South Carolina; May-October 2010. ........................................................................................................45 Figure B.7. Daily precipitation for Hugo, North Carolina; May-October 2010. ...........................46 Figure B.8. Average maximum and minimum daily temperatures for Hugo, North Carolina; May-October 2010. ........................................................................................................46 Figure B.9. Daily precipitation for Mount Olive, North Carolina; May-October 2010. ...............47

ix

Figure B.10. Average maximum and minimum daily temperature for Mount Olive, North Carolina; May-October 2010. ........................................................................................................47

1

Chapter I

Introduction

Soybean [Glycine max (L) Merr.] is an important crop in North and South Carolina. Most

soybeans planted in North and South Carolina are planted from mid-May to mid-June. The date

that a farmer chooses to plant soybeans will determine which soybean maturity group (MG) will

be planted. Soybeans planted in North Carolina can range from MG IV to MG VII, while those

planted in South Carolina can range from MG V to MG VIII.

Several public and private soybean breeding programs are currently in operation across

the Southeastern United States. These breeding programs are responsible for producing high-

yielding soybeans with resistance to insects and diseases commonly found in the region. These

programs focus primarily on developing MG V, VI, and VII soybean varieties and germplasm.

Across North and South Carolina, a majority of the MG V and early MG VI soybeans are planted

in May and early June as a full season soybean. Later maturing soybeans (late MG VI and MG

VII) are typically planted later in the season (mid June through early July), often as a double crop

after wheat. From a breeding program perspective, it would be more efficient to plant all

breeding material (MG V-MG VII) at the same time rather than using multiple planting dates for

the different maturity groups. However, if genotype by planting date interactions are significant,

then it may be difficult to select the best lines for a given maturity group if the data are collected

from a trial planted outside of its normal planting date range. In addition, many breeding

programs utilize winter nurseries to advance lines more quickly. As a result, researchers may be

forced to plant later in the season because materials coming back from winter nurseries may be

delayed. This is more of a concern for the earlier maturity groups (MG V) which are typically

2

planted earlier in the season. If significant genotype by planting date interactions exist, then it is

possible that selection would be for MG V lines that performed well after being planted later

than normal, but may not have been the best selection under a normal planting date regime.

With increased fuel and input costs and lower profit margins, it is important that farmers

choose a variety and maturity group that suits their needs and maximizes their profit. Whether

the farmer wants to plant soybeans as a full season crop or after wheat, or whether the farmer

needs to plant a variety that will mature early or late due to other crops on the farm, choosing the

correct maturity group will provide the necessary flexibility.

Because farmers need a variety of soybeans from which to choose, it is important that

local breeding stations produce varieties that meet the needs of farmers and maximize farmers’

profits. Also, because the seed market is so competitive, it is important that breeding stations

produce the best quality, highest-yielding soybean varieties possible.

Research Objectives

This research project evaluated the effect of two soybean planting dates, one in late

May/early June and one in late June/early July, on the soybean characteristics that a breeder uses

to choose lines to advance for further testing in a breeding program. Furthermore, the objective

of this study was to increase efficiency in making soybean selections in soybean breeding

programs by making breeders aware of the impact that planting date has on selections.

3

Chapter II

Literature Review

Overview of Soybean Production

Soybeans are the 2nd largest cash sales crop in the United States and were planted on 30%

of the cropland in the United States during 2010 (Soy Stats, 2011). Soybeans have edible and

industrial uses, are consumed by both humans and animals, and are used in making products

such as crayons and paint strippers. Known as the “miracle crop,” soybeans are the foremost

provider of protein and oil for the United States and provided 68% of the edible consumption of

fats and oils in the United States in 2010 (Soy Stats, 2011).

In 2010, farmers in North Carolina produced 40.3 million bushels of soybeans on

1,580,000 acres with a crop value of $496 million (Soy Stats, 2011). Farmers in South Carolina

produced 10.47 million bushels of soybeans on 465,000 acres with a crop value of $120 million

(Soy Stats, 2011). Because many farmers utilize soybeans as a major crop on their farms, it is

important that farmers have a diverse platform of soybean varieties and traits from which to

choose when selecting varieties for their farms. There are a large number of varieties that are

commercially available to farmers and variety selection can be both complicated and

overwhelming. Farmers must consider soil type, weather patterns, desired planting and harvest

dates, beneficial traits such as disease, insect, and weed resistance, and even desired physical

characteristics when choosing varieties to plant on their farms (Wiatrak et al., 2011b).

4

Soybean Maturity Groups

Soybean varieties are classified into one of 13 maturity groups ranging from MG 000 to

MG X. The maturity group of a particular soybean variety represents the geographical location

to which it is adapted. Because soybeans are facultative photoperiod sensitive, their growth and

development is directly related to the environment in which they are grown, making it important

for farmers to choose soybeans with a maturity group that corresponds to their desired planting

and harvest dates. Soybean breeders assign a maturity group to a cultivar based on the cultivar’s

adaptation to the conventional planting practices in a particular region (Boerma and Specht,

2004). Because soybean breeders have to assign a MG to each cultivar that is released for

production, it is important that their research program has tested the varieties under the same

conditions for which they are intended, as well as for the intended planting date. New releases

are assigned a MG based on a comparison of maturity date with a well established cultivar of a

known maturity.

Planting Date

Soybeans are facultative photoperiod sensitive, meaning that their flowering period is

directly linked to day length and temperature. Early soybean varieties bloom when days are long

and nights are short. Soybeans with a later maturity date, on the other hand, bloom when days

are short and nights are long. Soybean maturity groups planted by North Carolina farmers range

from MG IV to MG VII and are typically planted from May 1 to July 18 and harvested from

October 10 to December 20 (Baker et al., 2005). In South Carolina, farmers focus on soybeans

with a maturity ranging from MG V to MG VIII. For South Carolina farmers, MG V and VI

5

soybeans should be planted between May 1 and June 10 (Wiatrak et al., 2011a). Soybeans

planted after June 10 should be MG VII and VIII (Wiatrak et al., 2011a).

The date that farmers choose to plant their soybeans can affect profit because planting

outside normal planting dates can reduce yield or cause harvest conflicts with other crops such as

cotton and tobacco. With rising input costs, it is more important than ever that farmers try to

minimize costs and losses to maximize profit. Recent research in the southeastern United States

has concluded that, for every day after mid-June that planting occurs, about a one-half bushel

loss in yield is incurred for MG’s V-VIII (Wiatrak et al., 2011a). DeBruin and Pederson (2008)

support planting early and suggest that farmers can utilize planting date to maximize yield and

increase profits. In a study conducted in the upper midwestern part of the United States, yield

benefits of early planting became more apparent when compared to soybeans planted in late May

or early June (DeBruin and Pedersen, 2008).

A similar study concluded that planting soybeans after May 27th in the southeastern

United States resulted in a rapid decline in grain yield, regardless of maturity group (Chen and

Wiatrak (2010). Furthermore, Chen and Wiatrak (2010) also noted that, for MG V to VII, later

planting dates resulted in a shortened vegetative and reproductive stage. The shortened

vegetative and reproductive stages were most prominent during the stages of flowering and pod-

setting. In addition, Chen and Wiatrak (2010), noted a significant interaction of planting date and

maturity group on yield for MG’s V to VIII and explained the variation in soybean yield among

different planting dates to be a result of changes to the plant and environment.

6

Planting Date by Genotype Interactions

While studies have been conducted in the United States concerning soybean planting date

and its effect on soybean yield, little research has been conducted on the effects of planting date

on soybean selections in a breeding program. In 1979, however, a study was conducted on the

effects that row spacing and genotype by planting date interactions have on soybean

development in double-cropped environments (Carter and Boerma, 1979). The study focused on

determining whether or not there was a need to develop a breeding program to select for double-

cropped cultivars because the cultivars farmers were planting as double-cropped were

commercialized based on data from full-season environments (Carter and Boerma, 1979). After

noting the significant interactions among genotypes, planting date, and row spacing with regard

to yield, Carter and Boerma (1979), concluded that there is a need for the development and

testing of double-cropped cultivars.

Another study focused on the impact that planting date and environmental conditions had

on soybean development and yield (Chen and Wiatrak, 2010). Chen and Wiatrak (2010)

concluded that planting date, along with environmental conditions and the cultivar’s genetic

potential, did affect the growth, development, and yield of soybeans. Furthermore, the study

found that later planting dates shortened the vegetative and reproductive stages of the plants and

that a positive correlation existed between yield and the length of the growing season (Chen and

Wiatrak, 2010).

Akhter and Sneller (1996) studied genotype by planting date interaction and selection of

early maturing soybean genotypes. The study, which focused on MG IV in Arkansas, concluded

that a selection advantage may exist in the early plantings of indeterminate lines.

7

Chapter III

Research Methods

Soybean test plots were planted at five locations across North and South Carolina:

Mount Olive, NC; Calypso, NC; Benson, NC; Hugo, NC; and Hartsville, SC (Figure 1). The soil

series at the Benson and Hartsville sites was a Norfolk Loamy Sand. The Mount Olive site was

established on a Rains Sandy Loam, the Calypso site was established on a Lucy Loamy Sand,

and the soil series at the Hugo site was a Lynchburg Sandy Loam. The Mount Olive, NC and

Hartsville, SC sites were irrigated. Each location had two planting dates: one in late May/early

June and one in late June/early July (Table 1). Due to a heavy rain and weather conditions,

however, the site in Hartsville, SC was re-planted. Therefore, the planting dates were staggered

by only 26 days. Each planting date consisted of three randomized ten-entry groups with three

replications (blocks). The same varieties were tested at each location. The first group, PDS5,

consisted of soybean varieties ranging from maturity group 5.5-5.9; the second group, PDS6,

consisted of maturity groups 6.0-6.7; and the third group, PDS7, consisted of maturity groups

6.8-7.7. The first two groups represented soybean maturities that are typically planted in late

May or early June, while the third group represented soybeans that are typically planted in mid to

late June. The experimental design for each test was a split-plot randomized complete block

design with planting date as the main plot and maturity group as the subplot. Varieties were

nested within each maturity group. Each plot consisted of two rows with 108 seeds per row;

rows were 76.2 cm (30 inches) apart. Each plot was 3.66 m (12 feet) long and separated by a

1.22 m (4 feet) alley.

8

Figure 1. Map of test site locations in 2010 (Test Sites Image, 2012).

9

Table 1. Planting and harvest dates for test sites in 2010.

Location Planting Dates Harvest Dates

Early Late Early Late

Benson, NC 5/20/2010 7/08/2010 11/12/2010 11/13/2010

Calypso, NC 6/03/2010 7/09/2010 11/10/2010 11/23/2010

Hugo, NC 5/22/2010 7/07/2010 11/09/2010 11/11/2010

Mount Olive, NC 5/11/2010 7/09/2010 10/29/2010 11/11/2010

Hartsville, SC 6/12/2010 7/07/2010 11/11/2010 11/19/2010

10

Observations were recorded for yield, seed moisture, seed size, lodging, plant height,

maturity, planting date, seedling vigor, stand count, phenotypic score, canopy rating, flower

color, and pubescence color. These observations are representative of the selection criteria most

breeding programs use to advance breeding lines. This study focused on lodging, yield, and

plant height. Lodging and phenotypic score ratings were based on a scale of one to nine; one

being the most desirable and 9 being the least desirable. Plant height observations were based on

the average height of the plot and were determined by selecting a minimum of four random

plants within each row and averaging the heights. Daily weather data were also collected from

weather stations in close proximity to each location. The amount of water that was applied by

irrigation was not available; however, irrigation was applied as needed to keep plants from

showing water deficit stress. Plots were monitored periodically and treated for weed and insect

problems as needed and managed for weed and insect control by utilizing standard agricultural

practices common to North and South Carolina. Plots were harvested with Almaco SPC 40 plot

combines. Data were analyzed using the GLM Procedure in SAS (SAS Institute Inc., Cary,

N.C.).

11

Chapter IV

Results

Yield

Significant (P < 0.05) date by variety (within group) interactions were observed for yield

at Benson, Hugo, and Mount Olive (Table 2). At Calypso, the date by variety (within group)

interaction was significant at the 10% significance level (Table 2). The lack of a significant

interaction at the Hartsville location was most likely due to the planting dates, which were

staggered by only 26 days (Table 1). The significance level observed at the Calypso location is

most likely due to the later planting date of the early planting as well. The first planting date for

the Benson, Hugo, and Mount Olive locations occurred in mid to late May (Table 1). The early

planting date for the Calypso location was early June, and Hartsville was planted in mid June

(Table 1). The observed date by variety interactions at all but one location indicate that yield

response to seeding date was not uniform across varieties. Therefore, selection using only one

planting date could mean that valuable genotypes are missed. These data also suggest that the

closer the planting dates, the less significant the date by variety (within group) interaction, as

expected.

A significant date by group interaction was observed at Calypso at the 5% significant

level and at Hugo at the 10% level (Table 2). Varieties within each group respond differently to

different environments and different planting dates. When this difference is averaged together, an

interaction may exist under certain environments and not as much under others.

12

Table 2. Probability (P) Values for the main effects and interaction terms in the analysis of variance for soybean trials at Benson (NCBN), Calypso (NCCO), Hugo (NCHU), and Mount Olive (NCMO), North Carolina, and Hartsville (SCHA), South Carolina, in 2010.

Location Interaction Term Yield Lodging Plant Height

--------------------P > F-------------------- NCBN Date 0.0010 -† 0.0572 Group 0.0032 - <0.0001 Date*Group 0.1867 - 0.6717 Variety(Group) 0.0015 - <0.0001 Date*Variety(Group) 0.0021 - <0.0001 NCCO Date 0.0014 0.0118 0.0033 Group 0.0018 <0.0001 0.0001 Date*Group 0.0001 0.0011 0.3838 Variety(Group) 0.0495 <0.0001 <0.0001 Date*Variety(Group) 0.0954 0.0163 <0.0001 NCHU Date 0.0003 - 0.0133 Group 0.1478 - <0.0001 Date*Group 0.0522 - 0.0059 Variety(Group) 0.0020 - <0.0001 Date*Variety(Group) 0.0094 - <0.0001 NCMO Date 0.0160 0.0338 0.0128 Group 0.1315 0.1905 <0.0001 Date*Group 0.8442 0.2888 0.0006 Variety(Group) <0.0001 <0.0001 <0.0001 Date*Variety(Group) <0.0001 <0.0001 <0.0001 SCHA Date 0.0068 0.0023 0.0002 Group 0.0006 0.0005 0.0073 Date*Group 0.6735 0.0005 0.5773 Variety(Group) <0.0001 <0.0001 <0.0001 Date*Variety(Group) 0.1053 <0.0001 0.7289

†Plants at NCBN or NCHU were not lodged so lodging ratings did not change with planting date.

13

In addition to a significant planting date by variety interaction, changes in rank for yield

were also observed (Table 3). However, there appears to be less change in ranking for later

maturities. For PDS5, the top three early non-irrigated varieties across all sites were entries 5, 6,

and 9 (Table 4). The top three late non-irrigated varieties across all sites were entries 3, 8, and

10. Because the top three varieties were different at each planting date, a breeder could have

failed to advance a good genotype if the decision had been made solely on one planting date.

Similar rank changes were also noted in PDS6 and PDS7, regardless of the irrigation type

(Table 4). Rank changes were also noted within location across the two planting dates and across

locations (Tables 5-7). However, the planting date affected certain cultivars more than others.

For example, entry 3 in PDS6 ranked 4th regardless of planting date when averaged across all

locations (Table 3). However, entry 9 in PDS 6 ranked 7th in the early planted group and 3rd in

the late planted group when averaged across all locations (Table 3). Therefore, certain cultivars

may be less affected by planting date than others.

All research sites experienced consistent rainfall until September, at which time all sites

were fairly dry (Figures 2 to 6). October was accompanied by a large rainfall and a significant

drop in temperature. The rainfall most likely benefited the late planted PDS7 varieties and

provided them with the needed water to mature towards the end of the growing season. Irrigation

amounts for Mount Olive and Hartsville are not available; however, the sites were irrigated as

needed.

For PDS5, PDS6, and PDS7, the mean yield was higher for the early planting date than

the late planting date at all locations except Mount Olive (Table 8). The mean yield for the late

planting date at Mount Olive for PDS5 and PDS6 was higher than the early planting date (Table

8). Data for the early PDS7 group at Mount Olive was lost due to a harvest error.

14

Table 3. Average yield and yield rankings (in parentheses) by planting date across five locations (Benson, Calypso, Hugo, and Mount Olive, North Carolina, and Hartsville, South Carolina) in 2010.

Maturity Group Entry Early Late -------------kg/ha----------

PDS5† 1 2866(10) 2504(8) 2 3060(7) 2163(10) 3 3117(6) 2753(3) 4 3266(3) 2599(5) 5 3387(1) 2586(6) 6 3182(4) 2625(4) 7 2893(9) 2486(9) 8 2973(8) 2765(2) 9 3363(2) 2533(7) 10 3178(5) 3083(1) Mean 3128 2610

PDS6 1 2670(10) 2492(10)

2 2787(9) 2647(6) 3 3005(4) 2707(4) 4 2976(5) 2603(8) 5 3229(1) 2705(5) 6 2906(8) 2619(7) 7 2960(6) 2597(9) 8 3021(2) 2874(1) 9 2948(7) 2729(3) 10 3016(3) 2850(2) Mean 2952 2683

PDS7 1 3192(6) 2798(4)

2 3111(8) 2679(9) 3 3235(5) 2743(6) 4 3096(9) 2584(10) 5 3266(4) 2707(8) 6 3369(1) 2982(1) 7 3344(3) 2842(3) 8 3006(10) 2738(7) 9 3365(2) 2938(2) 10 3115(7) 2749(5)

Mean 3210 2776 LSD₀.₀₅

‡ 243.4 243.4 †PDS5 = soybean varieties in maturity group 5.5-5.9; PDS6 = soybean varieties in maturity group 6.0-6.7; PDS7= soybean varieties in maturity group 6.8-7. ‡The LSD applies to entry means, not overall group means.

15

Table 4. Average yield and yield rankings (in parentheses) by irrigation type across five locations (Benson, Calypso, Hugo, and Mount Olive, North Carolina, and Hartsville, South Carolina) in 2010.

†Mount Olive, North Carolina and Hartsville, South Carolina were irrigated. Hugo, Benson, and Calypso, North Carolina were non-irrigated. ‡PDS5 = soybean varieties in maturity group 5.5-5.9; PDS6 = soybean varieties in maturity group 6.0-6.7; PDS7= soybean varieties in maturity group 6.8-7.7 βThe LSD applies to entry means, not overall group means.

Maturity Group Entry

Irrigated† Non-Irrigated Early Late Early Late

-----------------------------------kg/ha (rank)----------------------- PDS5‡ 1 2831(10) 2979(10) 2890(9) 2189(4)

2 3142(6) 3069(8) 3005(7) 1558(10) 3 3206(5) 3484(4) 3059(6) 2265(2) 4 3406(3) 3310(5) 3174(4) 2125(7) 5 3574(2) 3234(6) 3262(1) 2155(6) 6 3083(7) 3539(3) 3249(2) 2015(9) 7 2920(9) 3192(7) 2876(10) 2015(8) 8 3073(8) 3621(2) 2906(8) 2194(3) 9 3634(1) 3053(9) 3182(3) 2186(5) 10 3239(4) 3892(1) 3137(5) 2545(1) Mean 3210.8 3337.3 3074 2124.7

PDS6 1 2613(10) 2921(10) 2708(9) 2207(8) 2 2946(8) 3305(2) 2681(10) 2208(7) 3 3287(2) 3204(7) 2817(8) 2377(3) 4 3130(5) 3220(5) 2874(6) 2192(9) 5 3411(1) 3215(6) 3108(1) 2365(4) 6 2925(9) 3147(8) 2894(3) 2266(6) 7 3061(6,7) 3294(4) 2892(5) 2132(10) 8 3213(3) 3295(3) 2893(4) 2592(1) 9 3061(6,7) 3096(9) 2872(7) 2484(2) 10 3169(4) 3648(1) 2915(2) 2313(5) Mean 3081.6 3234.5 2865.4 2313.6

PDS7 1 4193(6) 3487(3) 2858(7) 2338(7)

2 3226(10) 3214(6) 3073(1) 2323(8) 3 4306(4) 3301(5) 2878(6) 2371(5) 4 3849(9) 3089(10) 2844(8) 2248(10) 5 4217(5) 3212(7) 2949(3) 2371(6) 6 4728(1) 3741(1) 2916(4) 2475(2) 7 4629(2) 3206(8) 2915(5) 2599(1) 8 4181(7) 3170(9) 2615(10) 2451(3) 9 4319(3) 3739(2) 3047(2) 2404(4) 10 4075(8) 3442(4) 2795(9) 2286(9) Mean 4172.3 3360.1 2889 2386.6

LSD₀.₀₅

β 384.1 384.1 302.6 302.6

16

Table 5. Average yield and yield rankings (in parentheses) for PDS5 (soybean varieties in maturity group 5.5 to 5.9) across five locations (Benson, Calypso, Hugo, and Mount Olive, North Carolina, and Hartsville, South Carolina) in 2010.

Benson

Calypso

Hugo

Mount Olive

Hartsville

Entry Early Late Early Late Early Late Early Late Early Late

----------------------------------------------------kg/ha (rank)-------------------------------------------------------

1 3053(9) 2508(4) 3304(5) 2245(7) 2311(3) 1809(5) 2300(8) 3114(8) 3360(9) 2843(9)

2 3761(4) 1522(10) 3100(6) 2085(9) 2154(7) 1069(10) 2408(5) 2964(10) 3876(5) 3174(5)

3 3533(8) 2170(7) 3512(4) 2762(1) 2130(8) 1863(3) 2133(10) 3714(3) 4277(1) 3253(4)

4 3596(7) 2387(6)(0) 3734(1) 2174(8) 2190(5) 1814(4) 2914(2) 3549(4) 3898(4) 3071(6)

5 4582(1) 1984(9) 3046(9) 2576(3) 2159(6) 1905(1) 2900(3) 3006(9) 4248(2) 3461(3)

6 4154(2) 2587(3) 3065(8) 1843(10) 2529(1) 1614(9) 2394(6) 3519(5) 3771(8) 3560(1)

7 2993(10) 2091(8) 3616(2) 2278(6) 2018(10) 1677(7) 2580(4) 3443(6) 3260(10) 2941(8)

8 3654(5) 2601(2) 2988(10) 2327(5) 2076(9) 1656(8) 2336(7) 4241(2) 3811(7) 3001(7)

9 3999(3) 2468(5) 3089(7) 2408(4) 2459(2) 1683(6) 3412(1) 3277(7) 3855(6) 2829(10)

10 3640(6) 2988(1) 3571(3) 2761(2) 2199(4) 1885(2) 2262(9) 4259(1) 4217(3) 3526(2)

Mean 3697 2324 3303 2346 2223 1698 2564 3509 3857 3166

LSD₀.₀₅ 99.9 99.9 65.2 65.2 53.3 53.3 68.4 68.4 86.4 86.4

17


Benson

Calypso

Hugo

Mount Olive

Hartsville


----------------------------------------------------kg/ha (rank)-------------------------------------------------------

1 3486(9) 2677(5) 2789(6) 2310(9) 1849(4) 1634(9) 1794(10) 2769(10) 3432(10) 3073(9)

2 3562(7) 2675(6) 2663(8) 2411(6) 1818(6) 1540(10) 2184(8) 3248(5) 3707(7) 3360(2)

3 3808(5) 2802(4) 2829(5) 2477(3) 1814(7) 1851(4) 2560(3) 3127(8) 4013(3) 3280(5)

4 4506(1) 2480(9) 2325(10) 2228(10) 1791(8) 1870(3) 2574(2) 3143(7) 3687(8) 3297(4)

5 4365(3) 2981(2) 3139(1) 2374(8) 1820(5) 1740(6) 2654(1) 3156(6) 4167(1) 3273(6,7)

6 3519(8) 2643(8) 2959(3) 2475(4,5) 2204(1) 1681(8) 2219(7) 3120(9) 3629(9) 3174(8)

7 3477(10) 2186(10) 3089(2) 2401(7) 2112(2) 1809(5) 1991(9) 3250(4) 4131(2) 3338(3)

8 3694(6) 3374(1) 2907(4) 2475(4,5) 2078(3) 1928(1) 2493(5) 3317(3) 3932(4) 3273(6,7)

9 4371(2) 2827(3) 2486(9) 2730(1) 1757(10) 1896(2) 2305(6) 3452(2) 3818(5) 2739(10)

10 4176(4) 2643(7) 2779(7) 2580(2) 1789(9) 1715(7) 2531(4) 3658(1) 3806(6) 3636(1)

Mean 3896 2728 2796 2442 1903 1767 2330 3224 3833 3244

LSD₀.₀₅ 99.9 99.9 65.2 65.2 53.3 53.3 68.4 68.4 86.4 86.4

18


Benson

Calypso

Hugo

Mount Olive

Hartsville


----------------------------------------------------kg/ha (rank)-------------------------------------------------------

1 4102(4) 2925(6) 2493(9) 2300(9) 1979(4) 1789(3) NA 3396(4) 4193(6) 3578 (5)

2 4198(3) 2972(5) 2851(2) 2283(10) 2167(3) 1715(5) NA 2898(9) 3226(10) 3529 (6)

3 3943(6) 2737(10) 2811(5) 2552(3) 1881(7) 1824(2) NA 3008(7) 4306(4) 3593 (4)

4 3746(9) 2892(7) 2816(4) 2381(7) 1970(6) 1473(10) NA 3055(6) 3849(9) 3122 (10)

5 4223(1) 3107(3) 2396(10) 2399(6) 2228(2) 1605(8) NA 2553(10) 4217(5) 3872 (1)

6 3923(7) 3391(1) 2957(1) 2535(4) 1868(8) 1500(9) NA 3681(1) 4728(1) 3802 (3)

7 4210(2) 3275(2) 2564(8) 2766(1) 1972(5) 1757(4) NA 3181(5) 4629(2) 3230 (9)

8 3562(10) 3060(4) 2621(7) 2640(2) 1661(10) 1654(7) NA 2972(8) 4181(7) 3367 (8)

9 4075(5) 2806(9) 2784(6) 2531(5) 2282(1) 1874(1) NA 3640(2) 4319(3) 3838 (2)

10 3849(8) 2833(8) 2827(3) 2318(8) 1710(9) 1706(6) NA 3512(3) 4075(8) 3371 (7)

Mean 3983 3000 2712 2470 1972 1690 NA 3190 4172 3530.2

LSD₀.₀₅ 99.9 99.9 65.2 65.2 53.3 53.3 NA 68.4 86.4 86.4 †Data for Mount Olive, North Carolina-Early is not available due to a harvest error.

19

Figure 2. Average monthly temperature and total monthly rainfall at Benson, North Carolina in 2010.

Figure 3. Average monthly temperature and total monthly rainfall at Calypso, North Carolina in 2010.

0

5

10

15

20

25

30

0

50

100

150

200

250

300

May June July August September October

Average

Temperature (⁰C)

Precipitation (mm)

Precipitation (mm) Average Temperature (⁰C)

0

5

10

15

20

25

30

0

50

100

150

200

250

300


Average

Temperature (⁰C)

Precipitation (mm)


20

Figure 4. Average monthly temperature and total monthly rainfall at Hugo, North Carolina in 2010.

Figure 5. Average monthly temperature and total monthly rainfall at Mount Olive, North Carolina in 2010.

0

5

10

15

20

25

30

0

50

100

150

200

250

300


Average

Temperature (⁰C)

Precipitation (mm)


0

5

10

15

20

25

30

0

50

100

150

200

250

300


Average

Temperature (⁰C)

Precipitation (mm)


21

Figure 6. Average monthly temperature and total monthly rainfall at Hartsville, South Carolina in 2010.

0

5

10

15

20

25

30

0

50

100

150

200

250

300

May June July August September OctoberAverage

Temperature (⁰C)

Precipitation (mm)


22

Table 8. Effect of planting date on mean soybean yield for trials at Benson (NCBN), Calypso (NCCO), Hugo (NCHU), and Mount Olive (NCMO), North Carolina, and Hartsville (SCHA), South Carolina in 2010.

Location

Planting Date Group Overall Mean

PDS5† PDS6 PDS7

Early Late Early Late Mean Early Late Mean Early Late Mean ------------------------------------------------kg/ha------------------------------------------------

NCBN 3699 2347 3046b‡ 3894 2730 3315a 3981 2999 3490a 3860A 2703B

NCCO 3302 2381 2892a 2798 2441 2636b 2710 2482 2609b 2939A 2434B

NCHU 2226 1695 1964a 1903 1769 1836a 1970 1688 1829a 2031A 1722B

NCMO 2576 3510 3046a 2334 3221 2777a -§ 3181 -§ 2448B 3309A

SCHT 3860 3167 3510b 3833 3241 3537b 4176 3531 3840a 3948A 3315B †PDS5 = soybean varieties in maturity group 5.5-5.9; PDS6 = soybean varieties in maturity group 6.0-6.7; PDS7= soybean varieties in maturity group 6.8-7.7 ‡Letters within a location for planting date group mean and letters within a location for overall mean followed by the same letter are not significantly different by Ryan-Einot-Gabriel-Welsch Multiple Range Test (P<0.05). §Data for PDS7-Early at Mount Olive, North Carolina is not available due to a harvest error.

23

Lodging

Overall, lodging scores were quite low and were not significant enough to cause concern

with regards to quality or yield. With regard to lodging, a significant (P < 0.05) planting date by

variety (within group) interaction was observed at all three locations where lodging occurred:

Calypso, Mount Olive, and Hartsville (Table 2). At Hugo and Benson, the plots were not lodged

and therefore, lodging ratings did not change with planting date. For PDS5, the varieties that

received the best lodging score for the early planting date were entries 1, 7, and 8 (Table 9). The

entries that received the best lodging score under late planting conditions for PDS5 were entries

2, 6, and 8 (Table 9). For PDS6, the lodging score rankings did not change by planting date as

much as the PDS5 and PDS7 groups. In fact, entries 2 and 7 both ranked in the top three for

lodging regardless of planting date in PDS6 (Table 9). For PDS7, however, entries 1, 8, and 9

had the best lodging score for early planting conditions while entries 6, 8, and 10 received the

best lodging score for the later planting conditions (Table 9). Furthermore, all entries for PDS7

received a higher lodging score when planted early. This was directly related to the taller plant

height observed for all PDS7 entries under early planting conditions. The overall mean lodging

scores averaged across all locations for PDS6 and PDS7 were lower for the later planting date

than the earlier planting date (Table 9). This is most likely due to the increased plant height that

both the PDS6 and PDS7 varieties experienced in the early planting date due to a longer growing

season. For PDS5, however, lodging scores were greater for the late planting date than the early

planting date (Table 9). Overall means were similar for both irrigated and non-irrigated sites

(Table 10).

24

Table 9. Average lodging score by planting date across three locations (Calypso and Mount Olive, North Carolina, and Hartsville, South Carolina) in 2010.

Maturity Group Entry Early Late

PDS5† 1 1.6 ‡ 1.9 2 2.0 1.6 3 1.7 2.1 4 2.0 2.7 5 2.3 2.1 6 2.3 1.7 7 1.7 2.0 8 1.6 1.8 9 2.3 1.9 10 1.9 2.3

Mean 1.9 2.0 PDS6 1 2.2 2.1 2 1.8 1.9 3 2.5 2.2 4 2.5 2.3 5 2.8 2.4 6 2.2 2.4 7 1.6 1.6 8 2.1 1.8 9 2.0 2.0 10 2.3 2.2

Mean 2.2 2.1 PDS7 1 2.4 2.1 2 3.0 2.7 3 2.7 2.2 4 2.7 2.2 5 2.7 2.3 6 2.5 1.8 7 2.7 2.2 8 2.3 1.6 9 2.3 1.9 10 2.6 1.87 Mean 2.6 2.1 LSD₀.₀₅

β 0.6 0.6 †PDS5 = soybean varieties in maturity group

5.5-5.9; PDS6 = soybean varieties in maturity group 6.0-6.7; PDS7= soybean varieties in maturity group 6.8-7.7 ‡Lodging was rated on a 1-9 scale, with 1 being not lodged and 10 being flat on the ground.

βThe LSD applies to entry means, not overall group means.

25

Table 10. Average lodging score by irrigation type across three locations (Calypso and Mount Olive, North Carolina, and Hartsville, South Carolina) in 2010.

Maturity Group

Entry Irrigated† Non-Irrigated

Early Late Early Late PDS5‡ 1 1.0β 2.0 2.0 1.9 2 2.3 1.7 1.8 1.6 3 1.7 2.0 1.8 2.2 4 1.7 3.0 2.2 2.6 5 2.3 2.3 2.2 2.0 6 2.7 1.7 2.0 1.7 7 1.7 2.0 1.7 2.0 8 1.2 1.5 1.9 2.0 9 2.5 1.8 2.1 1.9 10 1.5 2.5 2.1 2.1

Mean 1.9 2.1 2.0 2.0 PDS6 1 2.0 1.7 2.3 2.3 2 1.5 1.8 2.0 2.0 3 2.5 2.0 2.4 2.3 4 2.7 2.2 2.3 2.3 5 3.0 2.3 2.7 2.4 6 1.8 2.5 2.4 2.3 7 1.3 1.3 1.8 1.8 8 1.7 1.7 2.3 1.9 9 2.0 2.0 2.0 2.0 10 2.0 2.5 2.4 2.0

Mean 2.1 2.0 2.3 2.1 PDS7 1 2.5 2.0 2.3 2.2 2 3.5 2.8 2.7 2.6 3 2.8 2.2 2.7 2.2 4 2.8 2.2 2.7 2.2 5 2.7 2.0 2.8 2.4 6 2.3 1.8 2.6 1.8 7 2.7 1.8 2.8 2.4 8 2.0 1.5 2.4 1.7 9 2.2 2.3 2.4 1.7 10 2.2 1.8 2.9 1.9 Mean 2.6 2.1 2.6 2.1 LSD₀.₀₅

δ 0.7 0.7 1.1 1.1 †Mount Olive, North Carolina and Hartsville, South Carolina were Irrigated and Calypso, North Carolina was non-irrigated.

‡PDS5 = soybean varieties in maturity group 5.5-5.9; PDS6 = soybean

varieties in maturity group 6.0-6.7; PDS7= soybean varieties in maturity group 6.8-7.7. βLodging was rated on a 1-9 scale, with 1 being not lodged and 10 being flat on the ground. δThe LSD applies to entry means, not overall group means.

26

Plant Height

A significant ( P < 0.05) planting date by variety (within group) interaction was observed

for plant height at Benson, Calypso, Hugo, and Mount Olive (Table 2). At Hartsville, a

significant interaction did not exist, which was most likely due to the close planting dates. For

varieties in PDS7, consisting of varieties with a maturity group of 6.8 to 7.7, the average plant

height for the early planting date was consistently higher than the later planted material across all

10 varieties (Table 11) due to the longer growing season. For varieties in maturity groups 5.5 to

6.7 (PDS5 and PDS 6), however, plant height response to planting date differed by variety but

not consistently across all 10 lines in each group. For example, in PDS5, the tallest entries under

early planting conditions were entries 2, 6, and 9 (Table 11). For the late planting date in PDS5,

entries 5, 6, and 10 were the tallest varieties (Table 11). Irrigation also affected plant height and

consistently increased plant height across PDS5, PDS6, and PDS 7 (Table 12). The irrigated

overall plant height mean averaged across all locations for PDS5, PDS6, and PDS7 was higher

than the non-irrigated sites for both planting dates (Table 12). This was a direct result of the

increased water the plants received, which allowed the soybeans to grow taller. Plant height is

important because taller plants often lodge more but do not necessarily yield more.

27

Table 11. Average plant height by planting date across five locations (Benson, Calypso, Hugo and Mount Olive, North Carolina, and Hartsville, South Carolina) in 2010.

Maturity Group Entry Early Late ---------cm--------

PDS5† 1 75 81 2 94 81 3 69 78 4 81 84 5 88 86 6 103 87 7 66 71 8 66 74 9 98 83 10 77 84 Mean 82 81

PDS6 1 80 83

2 90 88 3 84 86 4 92 87 5 97 93 6 81 85 7 79 81 8 90 87 9 88 82 10 97 92 Mean 88 86

PDS7 1 97 92

2 98 94 3 95 93 4 90 85 5 97 95 6 89 87 7 92 88 8 89 83 9 86 83 10 94 86

Mean 93 89 LSD₀.₀₅

‡ 1.0 1.0 †PDS5 = soybean varieties in maturity group 5.5-5.9; PDS6 = soybean varieties in maturity group 6.0-6.7; PDS7= soybean varieties in maturity group 6.8-7.7.

‡The LSD applies to entry means, not overall group means.

28

Table 12. Average plant height by irrigation type across five locations (Benson, Calypso, Hugo, and Mount Olive, North Carolina, and Hartsville, South Carolina) in 2010.

Maturity Group Entry Irrigated † Non-Irrigated

Early L:ate Early Late -----------------------cm---------------------- PDS5‡ 1 80 87 72 77 2 102 91 89 74 3 70 82 69 75 4 83 89 80 80 5 91 94 86 80 6 110 98 98 80 7 66 75 66 68 8 66 77 67 72 9 108 95 91 75 10 78 86 76 83 Mean 85 87 79 76 PDS6 1 78 86 82 81 2 88 91 91 86 3 85 89 84 85 4 94 92 92 84 5 101 96 95 90 6 80 92 81 80 7 77 84 80 78 8 93 88 88 85 9 88 86 88 80 10 99 94 95 91 Mean 88 90 88 84 PDS7 1 100 94 95 91 2 104 97 94 92 3 101 102 91 88 4 95 88 87 84 5 103 98 94 93 6 94 87 85 87 7 95 89 91 87 8 93 83 86 83 9 92 86 82 81 10 98 86 91 86 Mean 97 91 90 87 LSD₀.₀₅

β 2.8 2.8 1.9 1.9 †Mount Olive, North Carolina and Hartsville, South Carolina were irrigated. Hugo, Benson, and Calypso, North Carolina were non-irrigated. ‡PDS5 = soybean varieties in maturity group 5.5-5.9; PDS6 = soybean varieties in maturity group 6.0-6.7; PDS7= soybean varieties in maturity group 6.8-7.7.

βThe LSD applies to entry means, not overall group means.

29

Chapter V

Discussion

Chen and Wiatrak (2010) concluded that planting date influences the development and

yield of soybeans in the Southeastern Coastal Plains, United States. The current study also

demonstrated that soybean yield is influenced by the genetic potential of the cultivar as well as

the planting date, thus supporting the conclusions of Chen and Wiatrak (2010). Soybean breeders

should be particularly cautious when making soybean selections on varieties that were planted

outside the normal planting regime because the lines they choose to advance may not perform

well under normal planting conditions. Also, making selections in soybeans that were planted

outside the normal planting regime may exclude lines that would have been selected and

advanced if planted under normal planting conditions as seen in the changes in rank observed in

this study. This is especially true for MGV and decreased with later MG’s. This seems logical

given that there would be less physiological impact on a later MG due to the decreasing

photoperiod after June 21.

Similar to this study, a study in Arkansas found planting soybean cultivars at later dates

consistently resulted in premature flowering of MG’s V-VIII caused by shorter photoperiods,

which results in yield loss (Board and Hall, 1984).

Carter and Boerma (1979) investigated the need for a breeding program to select lines

based on double-cropped environments. The current study supports the study by Carter and

Boerma (1979) that noted a significant genotype x planting date interaction that resulted in

changes in rank of genotypes at different planting dates.

30

Chapter VI

Conclusions

This study was intended to advise soybean breeders on whether or not there is significant

genotype by planting date interaction and if planting date should be taken into account when

advancing lines for further testing. After collecting and analyzing the data from five

environments, and noting the number of planting date by variety interactions that were

significant and the rank changes that caused these interactions, it is evident that planting date

should be considered when breeders advance lines in their breeding programs. Therefore,

selecting genotypes on the basis of just one planting date may exclude good genotypes,

especially with regard to yield. Based on these results, if trials are planted outside of the target

planting date, we suggest decreasing selection pressure to help buffer changes in rank. By

making breeders aware of this, they can improve their breeding strategy and continue to offer

farmers improved varieties for increased profitability.

31

Literature Cited

32

Literature Cited

Akhter, M. and C. H. Sneller. 1996. Genotype x planting date interaction and selection of early maturing soybean genotypes. Crop Sci. 36:883-888.

Baker, J.R., S.R. Koenning, J.W. Van Duyn, A.C. York, and S.J. Toth, Jr. 2005. Crop Profile for Soybeans in NC. http://www.ipmcenters.org/CropProfiles/docs/NCsoybeans.pdf

Board, J.E. and W. Hall. 1984. Premature flowering in soybean yield reductions at nonoptimal planting dates as influenced by temperature and photoperiod. Agronomy Journal 76: 700-704.

Boerma, H.R. and J.E. Specht. 2004. Soybeans: Improvement, Production, and Uses, 3rd Ed. Madison, Wisconsin: American Society of Agronomy, Inc., Crop Science Society of America, Inc., & Soil Science Society of America, Inc.

Carter, T.E. Jr., and H.R. Boerma. 1979. Implications of genotype x planting date and row spacing interactions in double-cropped soybean cultivar development. Crop Sci. 19:607-610.

Chen, G. and P. Wiatrak. 2010. Soybean development and yield are influenced by planting date and environmental conditions in the Southeastern Coastal Plain, United States. Agronomy Journal. 102: 1731-1737.

De Bruin, J. L. and P. Pedersen. 2008. Soybean seed yield response to planting date and seeding rate in the Upper Midwest. Agronomy Journal 100:696-703.

Wiatrak, P., J. Dunphy, and J. Norsworthy. 2011a. Planting dates and populations production guide. Clemson University. http://www.clemson.edu/extension/rowcrops/soybeans/guide/planting_dates_and_populations.html

Wiatrak, P., E. Shipe, and J. Norsworthy. 2011b. Selecting the Right Varieties Production Guide. Clemson University. http://www.clemson.edu/extension/rowcrops/soybeans/guide/varieties.html

Soy Stats. 2011. The American Soybean Association. http://www.soystats.com/2011/Default-frames.htm

Test Sites Image, 2012. 34°44’18.11”N 78°33’25.53”W. Google Earth. Created March 1, 2012.

33

Appendices

34

Appendix A

ANOVA Tables

35

Table A.1. Results of the ANOVA for the effect of seeding date, maturity group, and variety on lodging of soybean varieties at Calypso, North Carolina in 2010.

Source of Variation DF Sum of

SquaresMean

SquareF Value Pr>F

Block 2 1.34 0.67 1.33 0.2680Date 1 18.05 18.05 83.31 0.0118Error a 2 0.43 0.22 Group 2 40.14 20.07 36.31 <.0001Date*Group 2 19.63 9.82 17.76 0.0011Error b 8 4.42 0.55 Variety (Group) 27 69.02 2.56 5.07 <.0001Date*Variety (Group) 27 24.82 0.92 1.82 0.0163Error 108 54.47 0.50 Corrected Total 179 232.33

Table A.2. Results of the ANOVA for the effect of seeding date, maturity group, and variety on lodging of soybean varieties at Mount Olive, North Carolina in 2010.


SquaresMean

SquareF Value Pr>F

Block 2 0.31 0.16 0.40 0.6734Date 1 62.42 62.42 28.09 0.0338Error a 2 4.44 2.22 Group 2 4.58 2.29 2.05 0.1905Date*Group 2 3.24 1.62 1.46 0.2888Error b 8 8.91 1.11 Variety (Group) 27 48.00 1.78 4.54 <0.0001Date*Variety (Group) 27 32.67 1.21 3.09 <0.0001Error 108 42.33 0.39 Corrected Total 179 206.91

36

Table A.3. Results of the ANOVA for the effect of seeding date, maturity group, and variety on lodging of soybean varieties at Hartsville, South Carolina in 2010.


SquaresMean

SquareF Value Pr>F

Block 2 0.41 0.21 1.81 0.1686Date 1 91.02 91.02 442.81 0.0023Error a 2 0.41 0.21 Group† 2 5.21 2.61 22.88 0.0005Date*Group 2 5.21 2.61 22.88 0.0005 Error b 8 0.91 0.11 Variety (Group) 27 13.77 0.51 4.49 <0.0001Date*Variety (Group) 27 13.77 0.51 4.49 <0.0001Error 108 12.27 0.11 Corrected Total 179 142.98

†Group interactions are similar because the late planting date at Hartsville, South Carolina was not lodged, therefore, all entries received a score of 1 for the late planting date.

Table A.4. Results of the ANOVA for the effect of seeding date, maturity group, and variety on plant height of soybean varieties at Benson, North Carolina in 2010.


SquaresMean

SquareF Value Pr>F

Block 2 33.14 16.57 2.82 0.0638Date 1 93.89 93.89 15.99 0.0572Error a 2 11.74 5.87 Group 2 1507.41 753.71 74.40 <0.0001Date*Group 2 8.48 4.24 0.42 0.6717Error b 8 81.04 10.13 Variety (Group) 27 1164.57 43.13 7.35 <0.0001Date*Variety (Group)

27 470.97 17.44 2.97 <0.0001

Error 108 634.07 5.87 Corrected Total 179 4005.31

37

Table A.5. Results of the ANOVA for the effect of seeding date, maturity group, and variety on plant height of soybean varieties at Calypso, North Carolina in 2010.


SquaresMean

SquareF Value Pr>F


Table A.6. Results of the ANOVA for the effect of seeding date, maturity group, and variety on plant height of soybean varieties at Hugo, North Carolina in 2010.


SquaresMean

SquareF Value Pr>F

Block 2 2.88 1.44 1.03 0.3597Date 1 10.27 10.27 73.96 0.0133Error a 2 0.28 0.14 Group 2 474.01 237.01 146.10 <0.0001Date*Group 2 33.88 16.94 10.44 0.0059Error b 8 12.98 1.62 Variety (Group) 27 1356.88 50.25 36.06 <0.0001Date*Variety (Group) 27 255.68 9.47 6.79 <0.0001Error 108 150.53 1.39 Corrected Total 179 2297.39

38

Table A.7. Results of the ANOVA for the effect of seeding date, maturity group, and variety on plant height of soybean varieties at Mount Olive, North Carolina in 2010.


SquaresMean

SquareF Value Pr>F

Block 2 2.41 1.21 0.28 0.7597Date 1 464.01 464.01 76.41 0.0128Error a 2 12.14 6.07 Group 2 613.21 306.61 40.71 <0.0001Date*Group 2 327.01 163.51 21.71 0.0006Error b 8 60.24 7.53 Variety (Group) 27 2416.95 89.52 20.46 <0.0001Date*Variety (Group) 27 1093.82 40.51 9.26 <0.0001Error 108 472.53 4.38 Corrected Total 179 5462.33

Table A.8. Results of the ANOVA for the effect of seeding date, maturity group, and variety on plant height of soybean varieties at Hartsville, South Carolina in 2010.


SquaresMean

SquareF Value Pr>F

Block 2 36.40 18.2 9.10 0.0002Date 1 728.02 728.02 4680.14 0.0002Error a 2 0.31 0.16 Group 2 101.73 50.87 9.70 0.0073Date*Group 2 6.18 3.09 0.59 0.5773Error b 8 41.96 5.24 Variety (Group) 27 1422.40 52.68 26.34 <0.0001Date*Variety (Group) 27 43.80 1.62 0.81 0.7289Error 108 216.00 2.00 Corrected Total 179 2596.80

39

Table A.9. Results of the ANOVA for the effect of seeding date, maturity group, and variety on yield of soybean varieties at Benson, North Carolina in 2010.

Table A.10. Results of the ANOVA for the effect of seeding date, maturity group, and variety on yield of soybean varieties at Calypso, North Carolina in 2010.


SquaresMean

SquareF Value Pr>F

Block 2 50.86 25.43 1.41 0.2483Date 1 2194.77 2194.77 719.66 0.0014Error a 2 6.10 3.05 Group 2 362.00 181.00 15.41 0.0018Date*Group 2 806.59 403.29 34.34 0.0001Error b 8 93.96 11.74 Variety (Group) 27 782.35 28.98 1.61 0.0495Date*Variety (Group) 27 708.36 26.24 1.46 0.0954Error 90 1617.49 17.97 Corrected Total 161 6986.74


SquaresMean

SquareF Value Pr>F


40

Table A.11. Results of the ANOVA for the effect of seeding date, maturity group, and variety on yield of soybean varieties at Hugo, North Carolina in 2010.


SquaresMean

SquareF Value Pr>F


Table A.12. Results of the ANOVA for the effect of seeding date, maturity group, and variety on yield of soybean varieties at Mount Olive, North Carolina in 2010.


SquaresMean

SquareF Value Pr>F


41

Table A.13. Results of the ANOVA for the effect of seeding date, maturity group, and variety on yield of soybean varieties at Hartsville, South Carolina in 2010.


SquaresMean

SquareF Value Pr>F

Block 2 83.75 41.88 1.56 0.2153Date 1 3990.82 3990.82 145.24 0.0068Error a 2 54.96 27.48 Group 2 903.61 451.80 21.19 0.0006Date*Group 2 17.71 8.86 0.42 0.6735Error b 8 170.53 21.32 Variety (Group) 27 2199.92 81.48 3.03 <0.0001Date*Variety (Group)

27 1032.71 38.25 1.42 0.1053

Error 106 2849.09 26.88 Corrected Total 177 11332.14

42

Appendix B

Weather Data

43

Figure B.1. Daily precipitation for Benson, North Carolina; May-October 2010.

Figure B.2. Average maximum and minimum daily temperatures for Benson, North Carolina; May-October 2010.

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Figure B.3. Daily precipitation for Calypso, North Carolina; May-October 2010.

Figure B.4. Average maximum and minimum daily temperatures for Calypso, North Carolina; May-October 2010.

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Figure B.5. Daily precipitation for Hartsville, South Carolina; May-October 2010.

Figure B.6. Average maximum and minimum daily temperatures for Hartsville, South Carolina; May-October 2010.

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Figure B.7. Daily precipitation for Hugo, North Carolina; May-October 2010.

Figure B.8. Average maximum and minimum daily temperatures for Hugo, North Carolina; May-October 2010.

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Figure B.9. Daily precipitation for Mount Olive, North Carolina; May-October 2010.

Figure B.10. Average maximum and minimum daily temperatures for Mount Olive, North Carolina; May-October 2010.

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48

Vita

April Rouse Tutor was born in Seven Springs, North Carolina on April 7, 1986. She

graduated from South Lenoir High School in 2004. In May 2007, she graduated from Mount

Olive College in Mount Olive, North Carolina with a B.S. in Agribusiness and accepted a

position with Monsanto as a Research Assistant in soybean breeding. In 2008, she started on her

Master’s program in Agriculture and Natural Resources Systems Management with a

concentration in Systems Science in Agriculture at The University of Tennessee at Martin.

to the graduate council - university of tennessee at martin · to the graduate council: i am...

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