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dissertation entitled

Weed Composition and Forage Production in Alfalfa
Seeded with Oat and Perennial Forage Grasses

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Eric Spandl

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WEED COMPOSITION AND F ORAGE PRODUCTION IN ALFALFA SEEDED
WITH OAT AND PERENNIAL FORAGE GRASSES

By

Eric Spandl

A DISSERTATION

Submitted to
Michigan State University
in partial fulfillment of the requirements
for the degree of

DOCTOR OF PHILOSOPHY

Department of Crop and Soil Sciences

1996

ABSTRACT

WEED COMPOSITION AND F ORAGE PRODUCTION IN ALFALF A SEEDED
WITH OAT AND PERENNIAL FORAGE GRASSES

By

Eric Spandl

Establishing alfalfa with a perennial forage grass may reduce weed invasion.
Including a small grain companion crop with the mixtures at establishment may also
suppress weed growth. This study documented the effects of seeding alfalfa with a forage
grass and an oat companion crop on weed and component yields, weed and alfalfa density,
and forage quality. Alfalfa was seeded alone, with weeds controlled (weed-free alfalfa) and
without weed control (weedy alfalfa), and in binary mixtures with bromegrass, orchardgrass,
timothy, or Kentucky bluegrass. All forages were seeded with and without oat in sites with
low and high weed pressure. In an existing study, measurements were taken in the third and
fourth years of the stand where alfalfa was seeded alone and with bromegrass, orchardgrass,
or timothy.

In new stands, forage grasses had no consistent effect on yields, plant densities, or
forage quality in the seeding year. Bromegrass and timothy were nearly eliminated from the
stand after the first harvest in the second year. In established stands, orchardgrass and
Kentucky bluegrass often decreased alfalfa yields. Total forage yields of mixtures were often
greater than the weedy alfalfa at the spring harvest and similar at subsequent harvests.
Orchardgrass and Kentucky bluegrass reduced weed yield at one harvest in the second year

and more consistently the following year. Both grasses reduced dandelion density in the fall

of the third year. Alfalfa density was usually unaffected by the grasses in the first three years
of the stand.

Responses of the mixtures, weedy alfalfa, and weed-free alfalfa to the oat companion
were often similar. Oat reduced weed yield at both harvests in the seeding year. Seeding
with oat increased forage yields at the first harvest and decreased yields at the second
harvest. Forage quality was reduced by the oat at first harvest and increased at the second
harvest. Few residual effects of the oat were seen on weed invasion or alfalfa density in an
environment with adequate soil moisture.

In the existing stand, orchardgrass consistently reduced weed yields. Average weed
content was 24, 17, 2, and 15% for the weedy alfalfa, alfalfa-bromegrass, alfalfa-
orchardgrass, and alfalfa-timothy, respectively. Crude protein was decreased, and acid and
neutral detergent fiber increased by the orchardgrass at the spring harvest and neutral

detergent fiber increased at subsequent harvests.

ACKNOWLEDGMENTS

I can not name just a few when so many have contributed their time and effort
towards the completion of this work. My sincere appreciation is extended to my fellow
graduate students and friends, committee members, technicians and secretaries, and

undergraduate employees.

iv

TABLE OF CONTENTS

Page
LIST OF TABLES ................................................................................................... viii
CHAPTER ONE: AN OAT COMPANION CROP INFLUENCES
WEED INVASION, COMPONENT YIELDS, FORAGE QUALITY,
AND PLANT DENSITY IN ALF ALFA SEEDED WITH
PERENNIAL FORAGE GRASSES ..................................................................... 1
ABSTRACT ............................................................................................................. 1
INTRODUCTION .................................................................................................... 2
MATERIALS AND METHODS ............................................................................. 6
RESULTS AND DISCUSSION ............................................................................... 9
Component Yields ........................................................................................ 9
Seeding year ..................................................................................... 9
Low weed pressure ............................................................... 9
High weed pressure .............................................................. 10
One year after seeding ...................................................................... 11
Low weed pressure ............................................................... 1 1
High weed pressure .............................................................. 12
Two years afier seeding .................................................................... 12
Low weed pressure ............................................................... 12
High weed pressure .............................................................. 12
Forage Quality .............................................................................................. 13
Low weed pressure ........................................................................... 13
High weed pressure .......................................................................... 13
Plant Density ................................................................................................ 15
Low weed pressure ........................................................................... 15
High weed pressure .......................................................................... 16
SUMMARY ............................................................................................................. 17
REFERENCES ......................................................................................................... 20

TABLES ...................................................................................................................

CHAPTER TWO: WEED INVASION IN NEW STANDS OF ALF ALF A
SEEDED WITH PERENNIAL FORAGE GRASSES ........................................

ABSTRACT .............................................................................................................
INTRODUCTION ....................................................................................................
MATERIALS AND METHODS .............................................................................

RESULTS AND DISCUSSION ...............................................................................
Component Yields ........................................................................................
Seeding year .....................................................................................

Low weed pressure ...............................................................

High weed pressure ..............................................................

One year after seeding ......................................................................

Low weed pressure ...............................................................

High weed pressure ..............................................................

Two years after seeding ....................................................................

Low weed pressure ...............................................................

High weed pressure ..............................................................

Forage Quality ..............................................................................................
Low weed pressure ...........................................................................

High weed pressure ..........................................................................

Plant Density ................................................................................................
Low weed pressure ...........................................................................

High weed pressure ..........................................................................

SUMMARY .............................................................................................................
REFERENCES .........................................................................................................
TABLES ...................................................................................................................
CHAPTER THREE: WEED INVASION IN ESTABLISHED

STANDS OF ALF ALF A SEEDED WITH PERENNIAL

FORAGE GRASSES ..............................................................................................
ABSTRACT .............................................................................................................
INTRODUCTION ....................................................................................................

MATERIALS AND METHODS .............................................................................

vi

25

40

4O

42

43

46
46
46
46
47
48
48
50
51
51
53
55
55
56
57
57
58

6O

62

65

78

78

79

82

RESULTS AND DISCUSSION ...............................................................................
Component Yields ........................................................................................
Forage Quality ..............................................................................................

SUMMARY .............................................................................................................

REFERENCES .........................................................................................................

TABLES ...................................................................................................................

APPENDIX ..............................................................................................................

vii

84
84
86
87
88
93

97

LIST OF TABLES

CHAPTER ONE: AN OAT COMPANION CROP INFLUENCES

WEED INVASION, COMPONENT YIELDS, FORAGE QUALITY,

AND PLANT DENSITY IN ALFALFA SEEDED WITH

PERENNIAL FORAGE GRASSES

Table 1. Dates of field operations for 1993 seedings ..............................................
Table 2. Dates of field operations for 1994 seedings ..............................................
Table 3. Weed density in the year of seeding .........................................................

Table 4. Total and component yields in the year of seeding (average of 1993
and 1994 seedings) with low weed pressure .............................................

Table 5. Total and component yields in the year of seeding (average of 1993
and 1994 seedings) with high weed pressure ............................................

Table 6. Total and component yields one year after seeding (average of 1993
and 1994 seedings) with low weed pressure .............................................

Table 7. Total and component yields one year after seeding (average of 1993
and 1994 seedings) with high weed pressure ............................................
Table 8. Total and component yields two years afier seeding (1993 seeding

only) with low weed pressure ....................................................................

Table 9. Total and component yields two years after seeding (1993 seeding
only) with high weed pressure ..................................................................

Table 10. Forage quality characteristics in the seeding year (average of 1993
and 1994 seedings) with low weed pressure ............................................

Table 11. Forage quality characteristics in the seeding year (average of 1993
and 1994 seedings) with high weed pressure ...........................................

viii

Page

25
26

27

28

29

30

31

32

33

34

35

Table 12. Plant density in the seeding year (average of 1993 and 1994
seedings) at sites with low weed pressure .................................................

Table 13. Plant density in the seeding year (average of 1993 and 1994
seedings) with high weed pressure ............................................................

Table 14. Alfalfa plant density in fall with low weed pressure ................................
Table 15. Alfalfa plant density in fall with high weed pressure ...............................

CHAPTER TWO: WEED INVASION IN NEW STANDS OF ALF ALF A
SEEDED WITH PERENNIAL F ORAGE GRASSES

Table 1. Component yields in the year of seeding (average of 1993 and 1994
seedings) with low weed pressure .............................................................

Table 2. Component yields in the year of seeding (average of 1993 and 1994
seedings) with high weed pressure ............................................................

Table 3. Component yields one year after seeding (average of 1993 and 1994
seedings) with low weed pressure .............................................................

Table 4. Component yields one year after seeding (average of 1993 and 1994
seedings) with high weed pressure ............................................................

Table 5. Component yields two years after seeding (1993 seeding only) with
low weed pressure .....................................................................................

Table 6. Component yields two years after seeding (1993 seeding only) with
high weed pressure ....................................................................................

Table 7. Forage quality characteristics in the seeding year (average of 1993
and 1994 seedings) with low weed pressure .............................................

Table 8. Forage quality characteristics in the seeding year (average of 1993
and 1994 seedings) with high weed pressure ............................................

Table 9. Plant density in the seeding year (average of 1993 and 1994
seedings) with low weed pressure .............................................................

Table 10. Alfalfa plant density in fall with low weed pressure ................................

Table l 1. Dandelion density in fall two years afier establishment
(1993 seedings only) .................................................................................

ix

36

37

38

39

65

67

69

7O

71

72

73

74

75

75

76

Table 12. Plant density in the seeding year (average of 1993 and 1994
seedings) with high weed pressure ............................................................ 77

Table 13. Alfalfa plant density in fall with high weed pressure ............................... 77

CHAPTER THREE: WEED INVASION IN ESTABLISHED STANDS
OF ALF ALFA SEEDED WITH PERENNIAL FORAGE GRASSES

Table 1. Component yields three years after seeding (1993) .................................. 93
Table 2. Component yields four years after seeding (1994) .................................... 94
Table 3. Forage quality characteristics three years after seeding (1993) ................ 95
Table 4. Forage quality characteristics four years afier seeding (1994) .................. 96
APPENDIX

Table A1. Soil fertility at seeding ........................................................................... 97
Table A2. Fertilization information ......................................................................... 97

Table A3. Component percentages in the seeding year (average of 1993
and 1994 seedings) with low weed pressure .......................................... 98

Table A4. Component percentages in the seeding year (average of 1993
and 1994 seedings) with high weed pressure ......................................... 99

Table A5. Component percentages in the year after seeding (average of 1993
and 1994 seedings) with low weed pressure .......................................... 100

Table A6. Component percentages in the year after seeding (average of 1993
and 1994 seedings) with high weed pressure ......................................... 101

Table A7. Component percentages two years after seeding (1993 seeding
only) with low weed pressure ................................................................. 102

Table A8. Component percentages two years afier seeding (1993 seeding

only) with high weed pressure ............................................................... 103
Table A9. Component percentages three years afier seeding (1993) ...................... 104
Table A10. Component percentages four years after seeding (1994) ....................... 105

CHAPTER ONE
An Oat Companion Crop Influences Weed Invasion, Component Yields, Forage
Quality, and Plant Density in Alfalfa Seeded with Perennial Forage Grasses.
ABSTRACT

Small grain companion crops are widely used in spring establishment of forages.
Potential advantages of seeding with a companion crop include weed suppression, soil and
water conservation, and increased forage yield. Most research has focused on the effects of
companions on pure seeded alfalfa. There are, however, many producers that grow mixtures
of alfalfa with a perennial forage grass. These studies determined what effects an oat
companion crop had on weed yield and density, component yields, forage quality, and alfalfa
density. Field experiments were seeded in spring of 1993 and 1994 at sites with high and
low weed pressure. Treatments included alfalfa seeded alone, with and without weed
control, and in binary mixtures with bromegrass, orchardgrass, timothy, or Kentucky
bluegrass. All forages were seeded with and without an oat companion. Measurement were
taken during the first three years of the stand. Oat significantly reduced weed yield at both
harvests in the seeding year but had little effect on weed yields in subsequent years. Weed
density was, at times, reduced by the oat during the initial growth and not affected in
regrowth or established stands. Under high weed pressure, forage quality and plant density
was less consistent in response to oat. Yield of components, forage quality, and plant density
response to seeding with oat was often similar in the mixtures, the weed-free alfalfa, and the
weedy alfalfa. Oat consistently suppressed weed growth but effects on forage yield and
quality were harvest dependent in the seeding year. Few effects of oat were noted on plant

density afier establishment or alfalfa density in an environment with adequate soil moisture.

INTRODUCTION

Companion crops, primarily small grains, are widely used in spring seedings of
alfalfa (Medicago sativa L.). An estimated 60% of alfalfa acreage planted in the north
central and north eastern USA is seeded with a companion crop (55). In Minnesota,
companion crops are used by up to 85% of forage producers (48).

Potential advantages of including companion crops with forages at seeding include
reduced soil erosion, increased economic return, increased forage yield, reduced insect pests,
and suppression of weeds. Reduced erosion was given as the primary reason Minnesota
forage producers used companion crops (48). Companion crops are also seeded with forages
to provide economic return from the silage or grain and straw (6,21). Seeding alfalfa with
companion crops generally results in greater forage yield compared to alfalfa seeded alone
with herbicides (23,25,43,49). Forage yields when alfalfa is seeded without weed control
vary, depending on weed growth, but may even exceed that of the oat (Avena sativa
L.)/alfalfa (46). Lamp (24) found that seeding alfalfa with oat reduced potato leafliopper
(Empoascafabae) numbers.

A companion crop may be seeded with the forage to suppress weed growth. Weed
competition can reduce alfalfa yield in the seeding year and in established stands
(14,26,33,39,44,46,58). Total forage yield, however, may not be affected (3 4) but the weeds

may compose a large proportion of the dry matter (33,53). Also, intense weed competition

3

in the seeding year may result in a stand failure (45). Forage quality may or may not be
reduced by the presence of weeds (12,13,16,20,27,29,31,33,36,47). Additionally, weeds
may reduce palatability (29), have potentially toxic levels of nitrates (5), decrease the rate
of drying (11), and provide seeds or vegetative propagules that result in increased weed
pressure in subsequent crops (30).

During the initial growth of the forages in the seeding year, weed yield (content) and
density may be reduced by the companion crop (25,28,49). Residual effects of the
companion on weed density or content in subsequent harvests in the seeding year and
establishment years are inconsistent. Lanini et al. (25) found weed content in the second year
of an alfalfa stand was reduced 30 to 50% depending on alfalfa seeding rate. In contrast,
weed content was greater in established stands of alfalfa-bromegrass (Bromus inermis
Leyss.)(35) and timothy (Phleum pratense L.)(28) when seeded with a companion crop.

Alternative methods of weed control in the seeding year include using herbicides,
clipping (mowing), or altering the seeding date. Herbicides effectively control weeds
(17,19,20,43,59) and are used increasingly as a method of weed control in pure alfalfa
seedings (55). Clipping requires accurate timing to reduce broadleaf competition and
minimize damage to the forage (25,32). Grass weeds may not be controlled since their
growing point is often below the height of cutting.

Altering seeding date is also an effective method for controlling weeds. In the North
Central region, spring seedings have heavy weed pressure primarily from summer annuals
such as common lambsquarters (Chenopodium album L.), redroot pigweed (Amaranthus

retroflexus L.), and giant foxtail (Setariafaberi Hermm.) In late summer seedings, summer

4

annual weed pressure is lower and of less concern since frost will kill those weeds. Winter
annual weed pressure, however, will be greater (15). Inadequate soil moisture in summer
may result in stand failure (40). Spring seedings may be preferred to maximize forage and
nutrient yields in the year of establishment.

Seeding forages with a companion crop also has potential disadvantages.
Competition provided by the companion may reduce alfalfa yield and density in the seeding
year (3 5,49,25,57,37,46) and alfalfa yield or persistence in subsequent years (3,35,38,41).
Additionally, forage quality may be reduced at the initial harvest. Forage quality of
companion crops decreases as the plants mature (2,8,22). Companion crops are generally
lower in quality and their inclusion will reduce forage quality unless harvested at the flag leaf
stage (2). Harvest at the early boot stage may provide forage that is 50% higher in feeding
value than that harvested for grain (55). Producers must also have a use for the silage or
grain and straw.

Seeding alfalfa with a companion crop also requires special considerations and
changes in management practices. Reduced seeding rates of the companion are often
recommended to decrease the competitiveness with alfalfa (9,55). Reduced rates of the
companion may, however, result in greater weed density or content (25,52). Timing of
harvest is also critical to the alfalfa density (establishment). As the companion crop matures,
initial and subsequent alfalfa yields and plant density may be reduced (22,49). Often, it is
recommended that the forage (companion, alfalfa, and weeds) be removed in the boot stage
or at 60 to 70 days after seeding regardless of growth stage ( 1,55). Early removal may allow

for an additional harvest in the seeding year and provide higher quality forage at the initial

harvest.

The most commonly used companion crop is oat (38,48,52). Oat has been the
preferred companion crop due to reduced competitiveness compared to other companions
(37,55). Familiarity and experience with the companion also contribute to crop selection
(48). Plant morphology and maturity influence the competitiveness of the companion.
Cultivars with a less dense canopy, shorter stature, or earlier maturity may be less
competitive with the forage and more resistant to lodging (3 7,49,5 1). However, under severe
weed pressure, greater weed growth may result (4). In addition, other companions may
provide forage that is greater in nutritive value than that of oat (2,7,8).

An oat companion is generally recommended for use only in spring seedings of
forages. Use of a companion crop in summer provides excessive competition at a time when
soil moisture is limiting and may result in a failed stand (54). One exception is to seed
alfalfa with oat in summer and then kill the oat with a herbicide before 15 cm of growth.
This method had been shown to be effective and may reduce potential for erosion while
providing acceptable stand establishment (1).

To date, most research using companion crops in forage establishment has focused
on pure seeded alfalfa. There are, however, many producers that grow mixtures of forages
such as alfalfa with a perennial forage grass. In the North Central region, up to 20% of
alfalfa is seeded with a grass (50).

Options for weed control when seeding alfalfa with grasses are limited. Few, if any,
herbicides are labeled in the US. for application to alfalfa-grass mixtures (10). Weed control

by clipping or delayed seeding are viable options but may not maximize economic return in

the seeding year.

Using a companion crop at seeding may be an effective way to reduce weed
competition in alfalfa-grass mixtures. Limited data are available to define how weeds,
yields, forage quality, and plant density of alfalfa-perennial forage grass mixtures are
affected by seeding with a companion crop. These studies were designed to determine how
an oat companion crop influences the weeds, and subsequently forage yield, quality, and
plant density in alfalfa seeded with smooth bromegrass, orchardgrass (Dactylis glomerata

L.), timothy, or Kentucky bluegrass (Poa pratensis L.).

MATERIALS AND METHODS

Field experiments were established in the spring of 1993 and 1994 at the Michigan
State University Agronomy Farm in East Lansing, Michigan on a Capac Loam soil (fine-
loamy, mixed, mesic, Aerie Ochraqualfs). Two studies were seeded in each year. Sites were
chosen on the basis of weed pressure. These sites will be referred to as low and high weed
pressure. Prior to seeding, fertilizer was applied to fields based on soil test recommendations
(Appendix Table A1). In established stands, annual additions of fertilizer were applied in
spring based on soil tests (Appendix Table A2). Seedbed preparation included conventional
tillage and cultipacking. Treatments were established in mid-May with a drill using 18 cm
rows followed by press wheels in 3.3 by 6.1 m plots (Tables 1 and 2). In 1994, recently
seeded plots were irrigated due to droughty conditions.

Each study was arranged as a randomized complete block with a split-plot

arrangement. Whole plots consisted of seeding with or without an oat companion crop.

7

Sub-plots included alfalfa seeded alone, with weeds controlled (weed-free alfalfa) and
without weed control (weedy alfalfa), and in binary mixtures with bromegrass, orchardgrass,
timothy, or Kentucky bluegrass. Bromegrass, orchardgrass, and timothy were included
because they are commonly used in mixtures with alfalfa. Kentucky bluegrass was included
since it often invades established stands of alfalfa. Identical studies were established under
low and high weed pressure in both years. Dominant weed species present at seeding were
redroot pigweed and common lambsquarters (Table 3). Weed control in the weed-free alfalfa
plots consisted of 1.12 kg ha" of 2,4-DB [4-(2,4-Dichlorophenoxy) butyric acid] applied
postemergence, supplemented with handweeding. Hexazinone [3 -cyclohexyl-6-
(dimethyslamino)-l-methyl-1,3,5-triazine-2,4(1H,3H)-dione] was applied in spring in the
first or second year after seeding to remove additional weed growth. Insecticides were
applied as needed to control potato leafhopper and alfalfa weevil (Hypera postica).

Seeding rate for ‘Newdak’ oat was 54 kg ha". ‘Apollo Supreme’ alfalfa was seeded
in all plots at 17.9 kg ha“. ‘Common’ bromegrass, ‘Common’ orchardgrass, ‘Climax’
timothy, and ‘Common’ Kentucky bluegrass were seeded at 3.4, 1.1, 4.5, and 6.7 kg ha",
respectively. In studies with high weed pressure, combine screenings which were composed
mostly of pigweed species were overseeded by hand at 3.1 kg ha‘1 prior to cultipacking to
ensure high numbers of summer annual weeds.

Weed, perennial forage grass, and alfalfa densities were measured on each plot six
weeks after seeding (6WAS). Newly germinated weeds were also counted four weeks after
the first harvest (4WAH). A 0.25 m2 quadrat was randomly placed at two locations within

each plot and densities were determined within that area. Alfalfa density was also counted

8

in the fall of the seeding year and one and two years after seeding. Two rows one meter in
length were selected from within each plot. Plants were excavated and only live plants were
counted. Dandelion ( T araxacum officinale Weber) density was counted in the fall two years
after seeding on fields seeded in 1993. A 1 m2 quadrat was placed within each plot and the
number of live plants were counted.

Forage was harvested in the seeding year at 60-70 days after seeding when the cat
was in late boot to soft dough stage and again approximately 60 days later. In the years
following establishment, plots were harvested four times annually when alfalfa reached the
bud to one-tenth bloom stage. A flail mower was used to harvest the forage . A 0.9 x 15.5
m strip was harvested from each plot and weighed. A 500 g subsample was taken by hand,
weighed fresh, dried in a forced air dryer at 60°C for 72 h, and weighed again. Fresh and dry
weights were used to calculate yields on a dry matter basis.

Weed, perennial grass, and alfalfa content (% of total dry matter) were determined
by hand separations on samples taken from each plot at all harvests. A 0.5 m2 area was
selected within each plot and all plant material above 5 cm collected. Half the sample was
used for hand separations and the remaining used for forage quality analysis. Once
separated, components were dried and weighed.

Forage samples for quality analyses were dried immediately afier sampling and
ground to pass a 2 mm screen in a cyclone mill. Forage quality analyses included
determinations of crude protein (CP), acid detergent fiber (ADF), and neutral detergent. fiber
(NDF) concentration. Micro Kjeldahl procedures were used to determine total N which was

multiplied by 6.25 to get crude protein concentration. Fiber concentration was determined

9

by using the sequential fiber analysis procedures of Van Soest et al. (56).

All data were analyzed using PROC ANOVA procedures of SAS (42). Data were
combined across seeding years since any interactions present between seeding year and
treatments did not alter the results or conclusions. Tables with data from two years afier
seeding contain data from 1993 seedings only. Comparisons were made between the weed-
free alfalfa, weedy alfalfa, and binary mixtures seeded with eat and those seeded without oat.

Differences were considered significant at P<0.05.

RESULTS AND DISCUSSION
Component Yields

Seeding year
We. At the first harvest in the seeding year, all forages seeded with oat were
greater in total forage yield and lower in alfalfa yield than those seeded without oat (Table
4). Yields of forage grass were lower in mixtures seeded with oat than in those seeded
without oat. Total weed yield was lower in the weedy alfalfa and in the mixtures when
seeded with oat. When oat was seeded with the forages, the oat composed 95% or greater
of the total yield. Data of Peters (41) confirms that, in the initial harvest, the oat component
dominates alfalfa and weeds. Seeding with oat reduced weed content to 2% or less of total
yields. Without oat, weed content was 65% in the mixtures and 70% in the weedy alfalfa.

At the second harvest, all forages seeded with oat were lower in forage yield than
those seeded without oat (Table 4). Alfalfa yield was lower in the weed-free alfalfa when

seeded with oat but not reduced in the weedy alfalfa or in the mixtures. Forage grass yield

10

in the mixtures and weed yield in the weedy alfalfa were lower when planted with oat.
Reductions in alfalfa yields at subsequent harvests in the seeding year were noted by Lanini
et al. (25). Weed yield was reduced in the mixtures by seeding with oat from 27% to 15%.
Weed yield (content) in the weedy alfalfa was reduced from 42% to 18%. In both harvests,
oat was effective at reducing weed content. Simmons et a1. (49) found that barley (Hordeum
vulgare L.) and oat companion crops greatly suppressed weed growth in the establishment
year. Weed yield in forages established with oat increased from the first to second harvest.
Although alfalfa yield in the mixtures was greater in plots established with oat, forage yield
was reduced due to the reductions in forage grass and weeds. In the weedy alfalfa,
reductions in forage yield were attributed to lower weed yield. Reduced yield of the weed-
free alfalfa may be due primarily to previous competition with oat but may also have been
reduced due to the 2,4-DB which showed injury after application. Second harvest forage
yields were reduced by residual effects of oats, but large increases in forage yields at first
harvest resulted in annual forage yields which were greater in all forage types seeded with
the oat companion.

Wm. At the first harvest, all forages seeded with oat were greater in total
forage yields than those seeded without oat (Table 5). Alfalfa yield was reduced by seeding
with oat in the weed-flee alfalfa and weedy alfalfa. Yield of alfalfa was not reduced in the
mixtures by seeding with oat. Forage grass yield was also reduced in mixtures seeded with
oat. Seeding with oat reduced weed yields in the weedy alfalfa and the mixtures. Inplots
seeded with oat, the oat comprised 94% or greater of the total yield. Weed yields did not

exceed 5% of the total yields. Without oat, weed content in the mixtures was 91% and in the

ll

weedy alfalfa was 93%.

At the second harvest, seeding with oat reduced forage yields in the weed-free alfalfa,
weedy alfalfa, and in the mixtures (Table 5). Reduced forage yields in the mixtures and
weedy alfalfa were attributable mostly to a reduction in weed yields, although, forage grass
yields were also reduced. Seeding with oats reduced alfalfa yields in the weed-free alfalfa
but not in the weedy alfalfa or the mixtures. Forage grass yields in the mixtures were
reduced by seeding with cat. Total weed yields in the weedy alfalfa and in the mixtures were
also reduced when seeded with oat. Weed yields comprised 13% of the mixtures and 11%
of the weedy alfalfa when seeded with oat. Seeded without oat, weed yield comprised 39%
of the mixtures and 34% of the weedy alfalfa. The large increase in forage yields due to the
oat at the first harvest overcame the reduction in yields at the second harvest resulting in
greater annual yield for all forages seeded with oat.

One year after seeding

W. In the year afier seeding, there were no residual effects of companion
crop on forage yield in any individual harvest or annually (Table 6). With one exception,
alfalfa yields in all harvests also were not affected by seeding with the oat companion.
Seeding with oat reduced forage grass yield in the first and third harvests but not in the
second and fourth harvests. At all harvests, total weed yields were similar when mixtures
or the weedy alfalfa were initially seeded with or without oat. Weed content at any harvest
did not exceed 3% of the total forage. Residual effects of seeding the forage with an oat

companion crop appeared primarily at the first harvest in the year following establishment.

 

12

W. Seeding with oat had no residual effects on forage, alfalfa, or weed
yields in any individual harvest or for the annual totals (Table 7). Weed yields did not
exceed 4% of the total yields at any harvest. Forage grass yield, however, was reduced by
seeding with oat at the first and second harvests. Grass yields in the third and fourth harvests
were not affected by initially seeding with the oat companion crop. Total yields of weeds
were greatest at the first harvest but accounted for no more than 3% of the total yield.
Two years after seeding

Wm. Establishing with cat had no effect on forage, alfalfa, or perennial grass
yield in any individual harvest or for annual totals (Table 8). Weed yields were different in
only one instance. Mixtures seeded with oat were lower in weed yield than those seeded
without oat at the first harvest. The reduction in weed yield was 31 kg ha" which is
negligible considering the total forage yield involved. In contrast, data from Canada (35)
showed weed yields in the second through fourth years of an alfalfa-bromegrass stand were
increased as a result of seeding with barley. Weed content did not exceed 5% at any given
harvest.

Wm. Seeding with cat had no effect on forage, alfalfa, grass, or weed yields
two years afier seeding (Table 9). The weed yield was less than 7% of the total at any given
harvest. Effects of companion crop may be seen in spring in the first year after seeding but

are often not found beyond that time.

l3

Forage Quality

Low weed pressure

At the first harvest in the seeding year, planting with cat reduced CP and increased
ADF and NDF in the weed-free alfalfa, weedy alfalfa, and the mixtures (Table 10).
Therefore, seeding with an oat companion reduced forage quality. A reduction in forage
quality at the first harvest is common since oat comprises a majority of the forage and may
be lower in quality than alfalfa. When plants were harvested at the dough stage of the oat,
the alfalfa was greater in CP than was oat (41). At the second harvest, all forages seeded
with cat were higher in CF and lower in ADF and NDF and thus forage quality was greater
than in forages initially seeded without oat. Increased forage quality may be attributed to
alfalfa maturity and weed content. In all plots, alfalfa seeded with oat was less mature at the
first harvest and subsequently less mature at the second harvest (visual observations). As
alfalfa matures, quality declines (18). Since alfalfa in the forage seeded with oat was less
mature, the forage quality was higher. Alfalfa maturity probably had the greatest effect on
the difl‘erence in forage quality at the second harvest since it comprised the largest part or all
of the forages. Weed content was also lower in mixtures and the weedy alfalfa seeded with
oat.
High weed pressure

Seeding with oat reduced forage quality in most but not all cases at the first harvest
in the seeding year. Planting with oat reduced CP in the weed-free alfalfa, weedy alfalfa, and
the mixtures (Table 11). Seeding with oat increased ADF in the weed-free alfalfa plots but

had no effect in the weedy alfalfa or mixtures. Weedy alfalfa and mixtures contained

14

perennial grasses and/or weeds which can be greater in ADF than alfalfa. The weed and/or
grass content increased ADF in the weedy alfalfa and mixtures to levels similar to forages
seeded with oat. Neutral detergent fiber was higher for all forages when seeded with oat.
Crude protein and ADF were at times similar between forages seeded with or without oat.
In these cases, the forages with weeds (seeded without oat) had similar chemical composition
to that of the forages seeded with oats. However, NDF was reduced by the oat companion
in all forages. A clear reduction in NDF may be attributed to a greater hemicellulose level
in oat than in weeds. Marten and Andersen (29) found that grassy weeds and oat contained
greater levels of hemicellulose than the forbs which included redroot pigweed and common
lambsquarters. The result is reduced quality in forages seeded with oat even though the
forages seeded without oat were composed of over 91% weeds.

At the second harvest, all forages seeded with oat were higher in CP and lower in
ADF and NDF (Table 11). Thus, forage quality was greater in forages initially seeded with
oat. As stated previously, the difference in forage quality may be attributed to alfalfa
maturity and weed content. Alfalfa seeded with oat was less mature at both harvests and
consequently higher in quality. Alfalfa maturity probably influenced forage quality more
than did the reduced weed content, although, both contributed to an increase in forage quality

in plots established with oat.

15

Plant Density
Low weed pressure

At 6WAS, seeding with an oat companion reduced alfalfa plant density in the weed-
free alfalfa, weedy alfalfa, and mixtures (Table 12). Perennial forage grass density in the
mixtures was also reduced by seeding with oat. Competition provided by the oat reduced
alfalfa and grass density. Simmons et a1. (49) showed increased alfalfa mortality during
establishment when seeded with oat or barley. Total weed density, however, was not
affected by the oat in the weedy alfalfa or in the mixtures. Effects of companion crops on
weed density are less consistent than effects on alfalfa or grass density. The forage plants
are swded at the same time as the oat and often germination is relatively uniform. Therefore,
competition among plant species occurs throughout the growth cycle. The weed seed bank
provides an ample supply of seeds that may germinate opportunistically throughout the
forage growth cycle. The uneven germination of weeds through this cycle resulted in a large
range of weed maturity from seedling emergence to firll maturity at the time when density
was determined.

At 4WAH, seeding with oat had no residual effect on weed density in the weedy
alfalfa or in the mixtures. A reduction in weed density as a result of initially seeding with
oat was not expected since weeds counted at 4WAH were those that germinated after the first
harvest and no companion was present to provide competition.

The oat companion crop had no effect of alfalfa plant density measured in fall of the
seeding year in the weed-free alfalfa, weedy alfalfa, or mixtures (Table 13). This was

consistent for all three fall measurements. Alfalfa densities in the year after establishment

16

were also similar, whether seeded with or without oat at 18 kg ha" , in a study by Lanini et
a]. (25). By the late fall measurement in the seeding year, the differences seen at 6WAS had
diminished. Alfalfa density in plots seeded without oat declined due to seedling mortality.
Density apparently increased from 6WAS to the late fall period in plots seeded with oat.
Additional alfalfa seed may have germinated after the first count at 6WAS resulting in the
increase in density. Alfalfa plant density decreased in all plots, after the initial fall
measurement, as the stand aged.

Oat had no effect on dandelion density, two years afier seeding, in the weedy alfalfa
or in the mixtures. In the weedy alfalfa, the were 6.3 and 8.3 dandelions m2 when seeded
without or with oat. Dandelion density was 4.1 and 6.1 plants m2 in mixtures seeded without
and with oat. In both cases, these differences were not significant. In established stands,
efl‘ects of a companion crop are not commonly seen on weed density or content. Although,
Moyer et al. (35) found that weed yields in established stands (primarily dandelions) were
greater as a result of companion crop.

High weed pressure

At 6WAS, seeding with oat increased alfalfa plant density in the weedy alfalfa but
did not affect the density in the weed-free alfalfa or in the mixtures (Table 14). Perennial
forage grass density was not reduced by seeding with oat. A reduction in alfalfa and grass
density may be expected as occurred in the low weed pressure experiment. Weed
competition, however, may have been of equal or greater intensity than that of the oat
resulting in similar or lower forage plant densities. Weed density was lower when seeded

with oats in the weedy alfalfa and in the mixtures. At 4WAH, seeding initially with oat did

17

not affect weed density in the weedy alfalfa or mixtures.

Vlfrth one exception, the oat companion crop had no effect on alfalfa plant density in
the weed-free alfalfa, weedy alfalfa, or mixtures at all three fall measurements (Table 15).
The exception was in the fall of the seeding year where the weedy alfalfa initially seeded
with oats had higher alfalfa plant density than that seeded without oat. This also occurred
at 6WAS. Again, it may not be an effect of oat increasing alfalfa density but weed
competition reducing alfalfa density more than that of the oat. Only in weed‘free alfalfa
seeded with oats did alfalfa density appear greater at the fall timing than at 6WAS. Alfalfa
plant density for all forages, afier the first fall, decreased as the stand aged.

Oat had no effect on dandelion density, two years after seeding, in the weedy alfalfa
or in the mixtures. The weedy alfalfa seeded without oat had 12.5 dandelions m2 while
seeding with oat resulted in 9.5 plants m2 . In mixtures, dandelion density was 6.6 and 7.3
plants m2 when seeded without and with oat. These differences in density were not

significant.

SUMMARY
Yield, forage quality, and plant density response to seeding with oat was often similar
in weed-free alfalfa, the weedy alfalfa, and in the binary mixtures regardless of weed
pressure at seeding. Inconsistencies in response between high and low weed pressure
experiments occurred for seeding year measurements on plant density and forage quality.
Inconsistencies among the forages in response to the oat companion occurred most often

during initial growth.

l8

Seeding with oat increased forage yields in the first harvest, lowered yields in the
second harvest, and increased annual yields in the seeding year. Alfalfa yields were ofien
reduced by oat at the first harvest but not consistently affected in the second harvest of the
seeding year. Perennial forage grass and weed yields were reduced at both harvests as a
result of the oat companion. Total and component yields one and two years after seeding
were seldom affected by the initial oat companion. If yield was reduced, as a residual effect
of oat, it ofien occurred in the early harvests in the year following seeding.

Seeding with oat ofien reduced forage quality at the initial harvest in the seeding
year. In the experiment with high weed pressure, CP and ADF levels were at times similar
among forages seeded with and without oat. As such, seeding with oat was not always
disadvantageous to forage quality. At the second harvest, forages initially seeded with oat
were higher in quality than those seeded alone. In the experiment with low weed pressure,
alfalfa and grass density in the initial growth were reduced by the oat companion. Weed
densities and subsequent alfalfa densities were not altered as a result of seeding with oat.
Under high weed pressure, differences in plant densities due to oat during the initial grth
were inconsistent. In most cases, oat did not affect alfalfa or grass density. Weed density
tended to be lower in forages seeded with oat. After the initial growth weed and alfalfa
density were usually not affected by seeding with the oat companion.

In general, the response of the binary mixtures to the oat companion was similar to
that of the weed-free alfalfa or weedy alfalfa. Weed pressure appeared to affect the
consistency of response to the companion crop. Forages seeded under high weed pressure

were more variable in response to the oat companion in forage quality and plant density

19

measurements. Seeding with oat significantly reduced weed content at both harvests in the
seeding year while the effects of oat on forage quality and yield varied by specific harvest.
Few residual effects of seeding with oat on yields or plant densities were seen one or two
years after seeding. Producers considering an oat companion for seeding with alfalfa-
perennial grass mixtures or alfalfa alone must take into account the oats effect on forage

yield and quality, the weed pressure, and the potential use of the forage.

LIST OF REFERENCES

10.

11.

12.

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Brink, GE, and G.C. Marten. 1986. Barely vs. oat companion crops. 11. Influences
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Buxton, DR, and WP. Wedin. 1970. Establishment of perennial forages 1.
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Carlisle, R.J., V.H. Watson, and AW. Cole. 1980. Canopy and chemistry of pasture
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Chastain, T.G., and BF. Grabe. 1989. Spring establishment of orchardgrass seed
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Cherney, J.H., and G.C. Marten. 1982. Small grain crop forage potential: 1.
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Cherney, J.H., and G.C. Marten. 1982. Small grain crop forage potential: 11.
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determinants of quality. Crop Sci. 22:240-245.

Copeland, L.O., O.B. Hesterrnan, F.J. Pierce, and MB. Tesar. Seeding practices for
Michigan crops. Mich. Coop. Ext. Serv. Bull. E-2107.

Crop Protection Reference. 1996. 12th Ed. Chemical and Pharmaceutical Press.
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Doll, JD. 1984. Effects of common dandelion on alfalfa drying time and yield.
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Dutt, T.E., R.G. Harvey, and RS. Fawcett. 1982. Feed quality of hay containing

20

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perennial broadleaf weeds. Agron. J. 74:673-676.

Dutt, T.E., R.G. Harvey, RS. Fawcett, N.A. Jorgensen, H.J. Larsen, and DA.
Schlough. 1979. Forage quality and animal performance as influenced by
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Fawcett, R.S., R.G. Harvey, D.A. Schlough, and LR. Block. 1978.
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Fischer, Al, J .H. Dawson, and AP. Appleby. 1988. Interference of annual weeds
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Hall, M.S., W.S. Curran, E.L. Werner, and LE. Marshall. 1995. Evaluation of weed
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Harvey, R.G. 1991. Bentazon for annual weed control in newly seeded alfalfa
(Medicago sativa L.). Weed Tech. 52154-158.

Kalu, B., and G.W. Pick. 1983. Morphological stage of development as a predictor
of alfalfa herbage quality. Crop Sci. 23:1167-1172.

Kapusta, G. 1973. Common chickweed control in established alfalfa. Weed Sci.
21:119-122.

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Kilcher, M.R., and DH. Heinrichs. 1960. The use of cereal grains as companion
crops in dryland forage establishment. Can. J. Plant Sci. 40:81-93.

Klebesadel, LI, and D. Smith. 1961. Effects of harvesting an oat companion crop
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moisture, and on the establishment of alfalfa. Agron. J. 53:627-630.

Kust, CA. 1968. Herbicides or oat companion crops for alfalfa establishment and
forage yields. Agron. J. 60:151-154. -

Lamp. W.O. 1991. Reduced Empoasca fabae (Homoptera: Cicadellidae) density in
oat-alfalfa intercrop systems. Env. Ento. 20:118-126.

Lanini, W.T., S.B. Orloff, R.N. Vargas, J.P. Orr, V.L. Marble, and SR. Gratten.

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Lemieux, C., AK. Watson, and J.M. Deschenes. 1987. Effect of barley, red clover
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Lemieux, C., AK. Watson, and J .M. Deschenes. 1987. Weed population dynamics
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Marten, G.C. and RN. Andersen. 197 5. Forage nutritive value and
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Table 1. Dates of field operations for 1993 seedings.

25

 

 

 

 

 

 

 

 

 

Weed pressure

Operation Low High

1 993
Seeded 13 May 15 May
Herbicide applied 12 June 12 June
Plant density measured 29 June 1 July
Insecticide applied 21 July 21 July
First harvest 27 July 28 July
Insecticide applied 18 August 18 August
Weed density measured 24 August 25 August
Second harvest 30 September 1 October
Alfalfa density measured 4 November 16 November

1994
Fertilizer applied 11 April 11 April
First harvest 3 June 7 June
Second harvest 13 July 14 July
Insecticide applied 8 August 8 August
Third harvest 30 August 30 August
Fourth harvest 13 October 13 October
Alfalfa density measured 8 November 10 November

1995
Herbicide applied 30 March 30 March
Fertilizer applied 1 April 1 April
First harvest 31 May 31 May
Second harvest 11 July 11 July
Insecticide applied 25 July 25 July
Third harvest 18 August 18 August
Fourth harvest 10 October 10 October
Alfalfa density measured 23 October 23 October
Dandelion density measured 25 October 25 October

 

Table 2. Dates of field operations for 1994 seedings.

26

 

 

 

 

 

 

 

Weed pressure

Operation Low High

1994
Seeded 10 May 13 May
Irrigation 19 May 19 May
Herbicide applied 9 June 9 June
Irrigation 10 June 10 June
Plant density measured 22 June 23 June
Insecticide applied 20 June 25 June
First harvest 20 July 22 July
Weed density measured 16 August 18 August
Second harvest 29 September 29 September
Alfalfa density measured 10 November 1 1 November

1995
Herbicide applied 30 March 30 March
Fertilizer applied 1 April 1 April
First harvest 30 May 30 May
Insecticide applied 3 July 3 July
Second harvest 11 July 11 July
Insecticide applied 25 July 25 July
Third harvest 16 August 16 August
Fourth harvest 10 October 10 October
Alfalfa density measured 23 October 23 October

 

27

Table 3. Weed density in the year of seeding.

 

 

 

 

 

Low weed pressure High weed pressure
Timing Weed 1993 1994 1993 1994
plants / m2
6WASa Broadleavesb 1 53° 28 257d 1 46d
Grasses 0 3 2 3 3
4WAH Broadleaves 42 26 49 32
Grasses 2 l 8 8

 

‘ 6WAS, 6 weeks after seeding; 4WAH, 4 weeks after first harvest.

b Dominant weeds: common lambsquarters (C henopodium album L.) and redroot pigweed (Amaranthus
retroflexus L.)

° Dominant weed: common lambsquarters.

‘ Dominant weed: redroot pigweed.

28

Table 4. Total and component yields in the year of seeding (average of 1993 and 1994 seedings) with low
weed pressure.

 

 

 

 

 

Harvest Annual
Component Forage Oat l 2 total
kgha’l
Total forage mixtures no 3396 2780 6176
with 6595 2235* 8830*
weedy alfalfa no 3451 2688 6139
with 6357* 2167* 8524*
weed-free no 1 907 2693 4600
with 6490* 2130* 8620*
Alfalfa mixtures no 903 1 53 3 -
with 116* 1718* -
weedy alfalfa no 1073 1558 -
with 104* 1769 -
weed-free no 1 907 2693 -
with 175* 2130* -
Forage grass mixtures no 284 446 -
with 6* 215* -
Weeds mixtures no 2209 737 -
with 126* 336* -
weedy alfalfa no 2378 1130 -
with 196* 3 98* -

 

* Statistical difference (P<0.05) between levels of oat companion.

29

Table 5. Total and component yields in the year of seeding (average of 1993 and 1994 seedings) with high
weed pressure.

 

 

 

 

 

Harvest Annual
Component Forage Oat 1 2 total
kg ha'1
Total forage mixtures no 3 3 34 2609 5943
with 6216* 1999* 8215*
weedy alfalfa no 3 3 3 3 2434 5767
with 6407* 1917* 8324*
weed-free no 499 2413 2912
with 7081* 1776* 8857*
Alfalfa mixtures no 255 1 3 86 -
with 75 1699 -
weedy alfalfa no 238 1600 -
with 68* 1700 -
weed-free no 499 241 3 -
with 96* l 776* -
Forage grass mixtures no 49 1 93 -
with 1 4* 44* -
Weeds mixtures no 3030 l 030 -
with 290* 256* -
weedy alfalfa no 3095 834 -
with 237 * 217 * -

 

* Statistically different (P<0.05) between levels of oat companion.

30

Table 6. Total and component yields one year after seeding (average of 1993 and 1994 seedings) with low

 

 

 

 

 

weed pressure.
Harvest Annual
Component Forage Oat 1 2 3 4 total
kg ha'1

Total forage mixtures no 5 1 96 2966 2440 143 1 12033
with 5089 31 15 2584 1452 12240

weedy alfalfa no 4566 3273 2568 1547 11954

with 4670 3134 2509 1437 11750

weed-free no 4701 3418 2647 1519 12285

with 4378 3342 2583 1526 11829

Alfalfa mixtures no 3567 2600 2175 1281 -
with 4022* 283 9 2402 1344 -

weedy alfalfa no 4526 3205 2540 1540 -

with 4581 3061 2470 1425 -

weed-free no 4701 3418 2647 1519 -

with 4378 3342 2583 1526 -

Forage grass mixtures no 1556 360 247 142 -
with 1017* 255 146* 104 -

Weeds mixtures no 73 6 18 8 -
with 50 21 36 4 -

weedy alfalfa no 40 68 27 7 -

with 89 73 39 12 -

 

* Statistically different (P<0.05) between levels of oat companion.

31

Table 7. Total and component yields one year after seeding (average of 1993 and 1994 seedings) with high

 

 

 

 

 

weed pressure.
Harvest Annual
Component Forage Oat 1 2 3 4 total
kg ha"

Total forage mixtures no 5147 297 l 2606 1680 1 2404
with 4938 3049 2598 1663 12248

weedy alfalfa no 4634 3020 2501 1642 l 1797

with 4770 3171 2724 1751 12416

weed-free no 4521 31 18 2802 1707 12148

with 4428 3243 2616 1637 1 1924

Alfalfa mixtures no 4038 2651 2408 1568 -
with 4188 2803 2444 1570 -

weedy alfalfa no 4479 2967 2441 1628 -

with 4620 3147 2710 1748 -

weed-fi'ee no 4521 31 18 2802 1707 -

with 4428 3243 2616 1637 -

Forage grass mixtures no 1025 267 176 104 -
with 686* 222* 122 82 -

Weeds mixtures no 84 1 0 22 8 -
with 64 24 32 11 -

weedy alfalfa no 155 53 6O 14 -

with 150 24 14 3 -

 

* Statistically different (P<0.05) between levels of oat companion.

32

Table 8. Total and component yields two years after seeding year (1993 seeding only) with low weed

pressure.

 

 

 

 

 

Harvest Armual
Component Forage Oat 1 2 3 4 total
kg ha’l

Total forage mixtures no 4138 2628 1433 859 9058
with 4060 2525 1424 83 3 8842

weedy alfalfa no 3894 3015 1707 928 9544

with 3733 2623 1556 961 8873

weed-free no 3390 3431 2056 1090 9967

with 3532 3113 1921 1003 9569

Alfalfa mixtures no 3476 2316 1283 693 -
with 3502 2289 1246 690 -

weedy alfalfa no 3775 2963 1680 925 -

with 3572 2559 1495 941 -

weed-free no 3 3 90 343 1 2056 1090 -

with 3532 3113 1921 1003 -

Forage grass mixtures no 577 253 144 163 -
with 504 220 160 138 -

Weeds mixtures no 85 59 6 3 -
with 54* 17 18 5 -

weedy alfalfa no 119 53 27 l -

with 161 64 61 20 -

 

* Statistically different (P<0.05) between levels of oat companion.

33

Table 9. Total and component yields two years after seeding year (1993 seeding only) with high weed

 

 

 

 

 

pressure.
Harvest Annual
Component Forage Oat 1 2 3 4 total
kg ha'1

Total forage mixtures no 41 15 2510 2004 1272 9901
with 4135 2557 2065 1363 10120

weedy alfalfa no 3786 2538 2042 1290 9656

with 3948 2500 2092 1384 9924

weed-free no 3345 2777 2258 1413 9793

with 3585 2536 2037 1289 9447

Alfalfa mixtures no 3 348 223 3 1796 1089 -
with 3504 2198 1852 1155 -

weedy alfalfa no 3539 2473 1953 1259 -

with 3817 2399 2047 1360 -

weed-free no 3585 2777 2258 1413 -

with 3345 2536 2037 1289 -

Forage grass mixtures no 683 242 196 169 -
with 568 281 203 193 -

Weeds mixtures no 84 35 12 14 -
with 63 78 10 15 -

weedy alfalfa no 247 65 89 31 -

with 131 101 45 24 -

 

* Statistically different (P<0.05) between levels of oat companion.

34

Table 10. Forage quality characteristics in the seeding year (average of 1993 and 1994 seedings) with low
wwd pressure.

 

 

Characteristic Forage Oat Harvest 1 Harvest 2
.................. g kg‘1 -----------------
CP‘ mixtures no 139 183
with 92* 210*
weedy alfalfa no 145 182
with 95* 218*
weed-free no 1 7 5 1 83
with 93* 21 1*
ADF mixtures no 281 314
with 348* 288*
mixtures no 272 320
with 341* 299*
weedy alfalfa no 244 344
with 346* 299*
NDF mixtures no 453 476
with 586* 415*
weedy alfalfa no 436 466
with 57 9* 41 8*
weed-free no 353 469
with 587* 417*

 

' CP, crude protein concentration; ADF, acid detergent fiber concentration; NDF, neutral detergent fiber
concentration.
* Statistically different (P<0.05) between levels of oat companion.

35

Table 11. Forage quality characteristics in the seeding year (average of 1993 and 1994 seedings) with high

weed pressure.

 

 

Characteristic Forage Oat Harvest 1 Harvest 2
------------------ g kg ------------------
CP' mixtures no 99 1 81
with 82* 289*
weedy alfalfa no 96 166
with 81* 236*
weed-free no 1 47 209
with 85* 232*
ADF mixtures no 3 1 8 304
with 334 276*
weedy alfalfa no 310 310
with 330 262*
weed-free no 1 74 308
with 329* 272*
NDF mixtures no 5 l 6 497
with 570* 404*
weedy alfalfa no 505 474
with 566* 388*
weed-free no 283 428
with 573* 385*

 

‘ CP, crude protein concentration; ADF, acid detergent fiber concentration; NDF, neutral detergent fiber

concentration.

* Statistically different (P<0.05) between levels of oat companion.

36

Table 12. Plant density in the seeding year (average of 1993 and 1994 seedings) at sites with low weed
pressure.

 

 

Component Forage Oat 6WAS' 4WAH
-------------- plants / m2 --------------
Alfalfa mixtures no 267 -
with 162* -
weedy alfalfa no 298 -
with 144* -
weed-free no 336 -
with 148* -
Forage grass mixtures no 101 -
with 44* -
Weeds mixtures no 97 29
with 95 39
weedy alfalfa no 101 32
with 83 39

 

' 6WAS, 6 weeks after seeding; 4WAH, 4 weeks after first harvest.
* Statistically different (P<0.05) between levels of oat companion.

37

Table 13. Alfalfa plant density in fall with low weed pressure.

 

Years after seeding

 

 

 

 

Forage Oat O 1 2
plants / m2

Mixtures no 224 1 36 1 08
with 251 142 106

Weedy alfalfa no 222 169 148
with 222 1 56 101

Weed-free no 2 10 1 7 8 106
with 222 171 102

 

* Statistically different (P<0.05) between levels of oat companion.

38

Table 14. Plant density in the seeding year (average of 1993 and 1994 seedings) with high weed pressure.

 

 

Component Forage Oat 6WAS‘ 4WAH
-------------- plants / m2 --------------
Alfalfa mixtures no 255 -
with 262 -
weedy alfalfa no 231 -
with 276* -
weed-free no 300 -
with 259 -
Forage grass mixtures no 66 -
with 56 -
Weeds mixtures no 2 10 43
with 182* 48
weedy alfalfa no 253 46
with 185* 52

 

‘ 6WAS, 6 weeks after seeding; 4WAH, 4 weeks after first harvest.
* Statistically different (P<0.05) between levels of oat companion.

39

Table 15. Alfalfa plant density in fall with high weed pressure.

 

 

 

 

 

Years after seeding
Forage Oat 0 1 2
plants / m2
Mixtures no 251 160 124
with 262 174 1 l7
Weedy alfalfa no 229 163 123
with 274* 178 134
Weed-free ‘ no 280 171 129
with 276 174 137

 

* Statistically different (P<0.05) between levels of oat companion.

CHAPTER TWO

Weed Invasion in New Stands of Alfalfa Seeded with Perennial Forage Grasses.

ABSTRACT

Weed invasion in alfalfa may be reduced by seeding with a perennial forage grass.
This study documented the effects of perennial forage grasses on weed and component
yields, plant densities, and forage quality. Alfalfa was seeded alone (weedy alfalfa) and in
binary mixtures with bromegrass, orchardgrass, timothy, or Kentucky bluegrass. All forages
were established with and without an oat companion crop in sites with low and high weed
pressure in 1993 and 1994. Measurements were taken during the first three years of the
stand. Seeding grasses with alfalfa had no consistent effect on total or component yields or
plant densities in the seeding year. Grasses had little effect on forage quality in the seeding
year. Crude protein was not altered and, in a few cases, fiber content was changed by the
grasses. Most differences in fiber content occurred at the second harvest. There were a few
instances in which alfalfa-grass mixtures were lower in weed density or content than that of
the weedy alfalfa. After the first harvest in the second year, bromegrass and timothy
contributed little to total yields. In the established stands, orchardgrass and Kentucky
bluegrass often reduced alfalfa yields and occasionally reduced alfalfa plant density.
However, total forage yields were often greater in the mixtures than the weedy alfalfa at the
spring harvest and similar at subsequent harvests. Seeding alfalfa with Kentucky bluegrass
resulted in reduced forage yields in the third year of the stand. Orchardgrass or Kentucky
bluegrass with alfalfa reduced weed content at one harvest in the second year and more

consistently in the third year of the stand. In the third year, the maximum weed content of

the weedy alfalfa did not exceed 5% of the total dry matter and maximum reduction in weed
yield by any forage grass was 182 kg ha“. Dandelion density was also reduced in the third
year of the stand by these two grasses. Seeding alfalfa with forage grasses can be effective
at reducing weed invasion. This effect likely will become more evident as the stand ages and
is dependent upon grass species and harvest management. Orchardgrass and Kentucky
bluegrass were able to persist with four annual harvests and subsequently reduced weed
invasion. Therefore, stands must be managed appropriately and grass maintained as a large
component of the forage for effective reduction in weed invasion. The effects of the forage

grass on quality and yield must also be considered prior to seeding.

INTRODUCTION

Seeding perennial forage grasses with alfalfa (Medicago sativa L.) may help to
reduce weed invasion. Weed competition can reduce alfalfa yield in seeding year and
established stands (7,11,17,20,25,26,33). Total forage yield may not be affected (18) but the
weeds may compose a large proportion of the dry matter (17,30).

Forage quality may or may not be reduced by the presence of weeds
(4,5,6,8,10,12,13,l 5,17,19,27). The degree to which forage quality is affected is dependent
on the weed species, maturity, and proportion in the forage. Weeds also may be less
palatable (13), toxic to animals (2), and slow the drying rate of the forage (4). Additionally,
weeds may provide seeds or vegetative propagules that invade subsequent crops (14).

Weeds may be controlled or suppressed by tillage, herbicides, mowing, altering the
seeding date, or using companion crops. An annual or perennial crop may be seeded with
the forage to suppress weed growth. Annual companion crops, primarily small grains, are
widely used in spring seedings of alfalfa to reduce soil erosion and suppress weeds.
Perennial forage grasses may also reduce weed invasion in alfalfa. A reduction in weed
invasion or enhanced weed control has been given as a potential advantage of including a
forage grass (3) but little data is available to support this statement. In one study, seeding

annual ryegrass (Lolium spp.) or a fescue (F estuca spp.) into established alfalfa showed a

42

43

trend towards reducing weed competition (1). Willard (34) and Sollenberger et a1. (29) also
found that growing orchardgrass (Dactylis glomerata L.) with alfalfa was effective at
keeping weeds out of the stand. As alfalfa stands age, plant density decreases (16) thereby
allowing favorable conditions for weed growth. As alfalfa-grass stands age, the alfalfa plant
density decreases and grasses become dominant (28,31) which may reduce weed invasion.

Including grass in mixture with alfalfa may reduce forage quality (22). The extent to
which forage quality is reduced is dependent on the specific harvest, grass species, and
proportion of grass in the forage. Earlier harvest of mixtures may be required to maintain
high forage quality.

The potential for interseeded perennial forage grasses to reduce weed invasion has
been mentioned in numerous articles as a potential advantage. Data to support this
statement, however, are not abundant. Objectives of this research were to determine how
interseeding smooth bromegrass (Bromus inermis Leyss.), orchardgrass, timothy (Phleum
pratense L.), or Kentucky bluegrass (Poa pratensis L.) with alfalfa affect weed and

component yields, plant densities, and forage quality.

MATERIALS AND METHODS
Field experiments were established in the spring of 1993 and 1994 at the Michigan
State University Agronomy Farm in East Lansing, Michigan on a Capac Loam soil (fine-
loamy, mixed, mesic, Aeric Ochraqualfs). Two studies were seeded in each year. Sites were
chosen on the basis of weed pressure. These sites will be referred to as low and high weed

pressure. Prior to seeding, fertilizer was applied to fields based on soil test recommendations

44

(Appendix Table A1). In established stands, annual additions of fertilizer were applied in
spring based on soil tests (Appendix Table A2). Seedbed preparation included conventional
tillage and cultipacking. Treatments were established in mid-May with a drill using 18 cm
rows followed by press wheels in 3.3 by 6.1 m plots (See Tables 1 and 2 in Chapter 1). In
1994, newly seeded plots were irrigated due to droughty conditions.

Each study was arranged as a randomized complete block with a split-plot
arrangement. The whole plot consisted of seeding with or without an oat companion crop.
Sub-plots included alfalfa seeded alone without weed control (weedy alfalfa), and in binary
mixtures with bromegrass, orchardgrass, timothy, or Kentucky bluegrass. Bromegrass,
orchardgrass, and timothy were included because they are commonly used in mixtures with
alfalfa. Kentucky bluegrass was included since it often invades established stands of alfalfa.
Identical studies were established under low and high weed pressure in both years.
Dominant weed species present at seeding were redroot pigweed and common lambsquarters
(See Table 3 in Chapter 1). Insecticides were applied as needed to control potato leafliopper
(Empoascafabae) and alfalfa weevil (Hypera postica).

Seeding rate for ‘Newdak’ oat was 54 kg ha“. ‘Apollo Supreme’ alfalfa was seeded
in all plots at 17.9 kg ha". ‘Common’ bromegrass, ‘Common’ orchardgrass, ‘Climax’
timothy, and ‘Common’ Kentucky bluegrass were seeded at 3.4, 1.1, 4.5, and 6.7 kg ha",
respectively. In studies with high weed pressure, combine screenings which were composed
mostly of pigweed species were overseeded by hand at 3.1 kg ha‘l prior to cultipacking to
ensure high numbers of summer annual weeds.

Weed, perennial forage grass, and alfalfa densities were measured on each plot six

45

weeks after seeding (6WAS). Newly germinated weeds were also counted four weeks after
the first harvest (4WAH). A 0.25 m2 quadrat was randomly placed at two locations within
each plot and densities determined within that area. Alfalfa plants were also counted in the
fall of the seeding year and one and two years after seeding. Two rows one meter in length
were selected from within each plot. Plants were excavated and only live plants were
counted. Dandelion (T araxacum oflicinale Weber) density was determined in the fall two
years after seeding on fields seeded in 1993. A l m2 quadrat was placed within each plot and
the number of live plants were counted.

Forage was harvested in the seeding year at 60-70 days after seeding when the oat
was in late boot to soft dough stage and again approximately 60 days later. In the years
following establishment, plots were harvested four times annually when alfalfa reached the
bud to one-tenth bloom stage. A 0.9 x 15.5 m strip was harvested from each plot with a flail
mower and weighed. A 500 g subsample was taken by hand, weighed fresh, and after drying
in a forced air dryer at 60°C for 72 h. Fresh and dry weights were used to calculate yields
on a dry matter basis.

Weed, perennial grass, and alfalfa content (% of total dry matter) were determined
by hand separations on samples taken from each plot at all harvests. A 0.5 m2 area was
selected within each plot and all plant material above 5 cm collected. Half the sample was
used for hand separations and the remaining used for forage quality analysis. Once
separated, components were dried and weighed.

Forage samples used for quality analyses were dried immediately after sampling and

ground to pass a 2 mm screen in a cyclone mill. Forage quality analyses included

46

determinations of crude protein (CP), acid detergent fiber (ADF), and neutral detergent fiber
(NDF) concentration. Micro Kjeldahl procedures were used to determine total N which was
multiplied by 6.25 to get crude protein concentration. Fiber concentration was determined
by using the sequential fiber analysis procedures of Van Soest et al. (32).

All data were analyzed using PROC AN OVA procedures of SAS (24) and the means
separated using Duncans multiple range test. Differences were considered significant at
P<0.05. Data were combined across seeding years or whole plots where interactions were
not present or when combining did not alter the results or conclusions. All tables with data
from two years after seeding contain information from the 1993 seedings only. Percentages
of each component are included in Appendix tables A3 through A8 and are given in the same

format as the component yields.

RESULTS AND DISCUSSION
Component Yields
Seeding year
W. At the first harvest in the seeding year, including a forage grass had no

effect on total, alfalfa, or weed yields (content) in plots seeded with or without an oat
companion crop (Table 1). Yield of bromegrass was greater than that of the other three
grasses when seeded without oat. Grass yields seeded with oat were similar but negligible.

At the second harvest, total and alfalfa yields were not influenced by interseeding
grass. In plots established without oat, weed yields were lower in plots seeded with

bromegrass, orchardgrass, and timothy than in the weedy alfalfa or alfalfa-Kentucky

47

bluegrass. When these forages were seeded with oat, weed yields were similar between the
alfalfa and the mixtures. Weed yields were, however, lower in the mixture with orchardgrass
than in the one with timothy. Among the grasses, Kentucky bluegrass was lower yielding
than the others in plots established without oat and lower yielding than orchardgrass in plots
seeded with oat.

Individual harvest and total yields in the seeding year were similar among all forages.
Seeding the grasses with alfalfa had no influence on forage yields. The maximum
contribution by grass at the first harvest was by bromegrass, in mixtures seeded without oat,
which comprised 20% of the total forage. This appears to be an exception since orchardgrass
is usually more competitive than bromegrass. Weed yields comprised up to 74% of the total
forage in plots seeded without oat and 3% of the forage in plots seeded with oat. The grasses
did not influence weed yield at the first harvest. Alfalfa yields were also similar among
forages at the first harvest. Oat and weed competition during the initial growth were
extensive enough in all plots to prevent any differences among forages. Second harvest grass
growth was generally greater than at first harvest and more consistent among bromegrass,
orchardgrass, and timothy. Weed yields in the weedy alfalfa plots, initially seeded without
oat, comprised 40% of the total forage. The increase in the three grasses, in plots initially
seeded without oat, resulted in reduced weed content. In plots initially seeded with cat, weed
yields comprised up to 21% of the forage.

Wm. With one exception, including grass with alfalfa did not affect total,
alfalfa, grass, or weed yields at the first harvest of the seeding year (Table 2). Weed yields

accounted for up to 92 and 5% of total yields in forages seeded without and with oat. Seeded

48

without oat, bromegrass yields were greater than orchardgrass or Kentucky bluegrass yields.

At the second harvest, total and alfalfa yields were similar among forages in plots
seeded with cat. Without oat, total yields were greater in alfalfa-orchardgrass than the weedy
alfalfa while alfalfa yields were greater in the weedy alfalfa than in alfalfa-Kentucky
bluegrass. Kentucky bluegrass yields were lower than that of the other grasses. Weed yields
were not influenced by seeding with a forage grass. In forage initially established with or
without oat, weeds comprised up to 14 and 47% of the total yield.

Seeding alfalfa with forage grasses had no effect on total annual yields although the
addition of orchardgrass did provide enough added growth to increase total yields over the
weedy alfalfa at the second harvest. Kentucky bluegrass contributions to yield were
negligible at either harvest. Forage grasses did not provide enough growth at either harvest
to suppress weeds.

One year after seeding

W. At the first harvest in the year after seeding, total yields in mixtures
containing bromegrass, orchardgrass, and timothy were greater and alfalfa yields lower than
that of the weedy alfalfa or alfalfa-Kentucky bluegrass (Table 3). Weed yields in the
mixtures were similar to that of the weedy alfalfa. Although, the alfalfa-bromegrass was
higher in weed yield than the other mixtures. Among the grasses, orchardgrass yield was
greater than that of bromegrass and timothy which were in turn greater than Kentucky
bluegrass.

Second harvest total and alfalfa yields in alfalfa-timothy were lower than those of the

weedy alfalfa. Alfalfa yields in the weedy alfalfa were also greater than in the mixtures

49

containing orchardgrass, timothy, or Kentucky bluegrass. Orchardgrass yield was greater
than the other grasses. Weed yields in all mixtures were on average 57 kg ha" lower than
that of the weedy alfalfa.

Including grass with alfalfa did not influence third harvest total forage yields. Total
yields were lower in alfalfa-Kentucky bluegrass than in alfalfa-timothy. Yields of the
mixtures were similar to that of the weedy alfalfa. Alfalfa yields in mixtures with
orchardgrass or Kentucky bluegrass were lower than the other mixtures or the weedy alfalfa.
Orchardgrass yield was again superior to all grasses followed in descending order by
Kentucky bluegrass, bromegrass, and timothy. Weed yields were similar between the weedy
alfalfa and the mixtures but were 61 kg ha“ lower in alfalfa-orchardgrass than in alfalfa-
bromegrass.

At the fourth harvest, total forage and weed yields were similar among all forages.
Alfalfa yields were lower in the forage with orchardgrass or Kentucky bluegrass than in the
weedy alfalfa or alfalfa-timothy. Orchardgrass yield was greater than that of all other
grasses, Kentucky bluegrass yield was intermediate, and bromegrass and timothy lowest
yielding.

Including bromegrass with alfalfa provided greater total annual forage yields than the
weedy alfalfa or the alfalfa-Kentucky bluegrass. The alfalfa-Kentucky bluegrass was also

lower yielding than all other mixtures. Increased annual forage yield of mixtures over alfalfa
seeded alone are generally the result of greater yields at the initial spring harvest. With the
exception of Kentucky bluegrass, the grasses contributed 59 to 91% of the annual yields at

the first harvest. Kentucky bluegrass yield at the first harvest was 44% of the annual total.

50

The reduced percentage in spring and reductions in total growth of Kentucky bluegrass
relative to the other grasses contributed to the reduced annual yield.

Orchardgrass growth was superior to the other grasses at all harvests. The increased

growth of orchardgrass always reduced alfalfa yield compared to the weedy alfalfa and often
reduced alfalfa yield in comparison to the other mixtures. Including any grass with alfalfa
also reduced weed yield at one of the harvests. Differences in weed yields were also seen
between the alfalfa-bromegrass and the other mixtures. This may have been due primarily
to weedy grass contamination in the bromegrass seed. No consistent reduction in weed yield
was attributable to grass. Weed yields did not exceed 159 kg ha’l (3%) of the total yield at
any harvest.
Wm. Alfalfa seeded with bromegrass, orchardgrass, and timothy provided
greater first harvest total yields than the weedy alfalfa (Table 4). Alfalfa yields in the three
mixtures were lower than the weedy alfalfa or alfalfa-Kentucky bluegrass. Orchardgrass was
greatest, bromegrass and timothy intermediate, and Kentucky bluegrass lowest in yield.
Weed yields were not affected by seeding with a forage grass.

At the second through fourth harvests, total yields were similar among forages, alfalfa
yields were lower in alfalfa-orchardgrass than in all other forages, and orchardgrass yields
superior to the other grasses. In descending order, grass yields were orchardgrass, Kentucky
bluegrass, bromegrass and timothy. Weed yields at the second harvest were lower in all
mixtures than in the weedy alfalfa. Average reduction in weed yield was 17 kg ha". Weed
yields were not reduced by forage grasses in the remaining harvests. Although, weed yield

was lower in alfalfa-orchardgrass than alfalfa-Kentucky bluegrass at the final harvest.

51

Although mixtures were often greater in first harvest yields, the total annual yields
were similar for all forages. In the first harvest, alfalfa yields were reduced in alfalfa-
bromegrass, alfalfa-orchardgrass, and alfalfa-timothy, while total forage yields were
increased due to the addition of grass. Reduction in alfalfa yield by orchardgrass was
consistent at all harvests. Increased yields at the first harvest but not at subsequent harvests
is due to grass growth being greatest in spring. Yields of all grasses were greatest in spring
and accounted for over 54% of annual growth except for Kentucky bluegrass in which 38%
of annual yield was at the first harvest. Orchardgrass yield was consistently greater than that
of the other grasses at all harvests. Except for the first harvest, Kentucky bluegrass yields
were greater than bromegrass or timothy. Effects of grasses on weed growth were not
consistent with the trend in grass yields. All grasses reduced weed yields only at the second
harvest. The maximum reduction in weed yield was 21 kg ha". Weed content at any harvest
did not exceed 152 kg ha‘l (3.2%) of the total forage.

Two years after seeding

ng wegd pressure. Two years after seeding, the first harvest total yields of alfalfa-
orchardgrass were greater than all other forages (Table 5). Alfalfa yields in the alfalfa-
orchardgrass were lower than that of the weedy alfalfa or alfalfa-timothy. Orchardgrass yield
was superior to all grasses, Kentucky bluegrass yield intermediate, and bromegrass and
timothy lowest in yield at all harvests. Weed yields in the mixtures with orchardgrass or
Kentucky bluegrass were lower than the weedy alfalfa or the other mixtures. The average
reduction in weed yields from the weedy alfalfa was 127 kg ha“.

Second harvest total yields of alfalfa-Kentucky bluegrass were lower than that of the

52

weedy alfalfa or alfalfa-timothy. Forages with orchardgrass or Kentucky bluegrass were
lower in alfalfa yields than the others. Grasses did not reduce weed yields compared to the
weedy alfalfa. Alfalfa-orchardgrass was lower in weed yield than alfalfa-bromegrass.

In the third harvest, alfalfa-orchardgrass and alfalfa-Kentucky bluegrass total and
alfalfa yields were lower than that of the other forages. Weed yields in these two mixtures
were also lower than in the weedy alfalfa or alfalfa-bromegrass.

In the final harvest, total yields of alfalfa-Kentucky bluegrass were lower than that
of all other forages. Alfalfa yields in mixtures with orchardgrass or Kentucky bluegrass were
lower than in the other forages. Weed yield was lower in alfalfa-orchardgrass and alfalfa-
Kentucky bluegrass than in the weedy alfalfa or alfalfa-timothy.

Seeding grass with alfalfa did not increase total annual forage yields. Seeding alfalfa
with Kentucky bluegrass resulted in lower yields than that of the weedy alfalfa. Yields of
alfalfa-orchardgrass were superior to alfalfa-bromegrass and alfalfa-Kentucky bluegrass.
The greater annual yield was attributable mostly to greater first harvest yields of alfalfa-
orchardgrass.

Orchardgrass yield was superior to all grasses at all harvests. Kentucky bluegrass
was next highest in yields at all harvests. Both orchardgrass and Kentucky bluegrass growth
was greatest in the spring providing 53 and 42% of their annual yields at the spring growth.
Bromegrass and timothy yields were negligible at all harvests and were all but eliminated
from the stand. This was likely due to the harvest management. Rhykerd et al. (21, 23)
found that four annual cuts removed bromegrass and timothy apices before basal buds were

developed and bromegrass and timothy were eliminated from the stand by late in the third

53

year of the stand while orchardgrass persisted. The orchardgrass and Kentucky bluegrass
with alfalfa resulted in significant reductions in weed grth compared to the weedy alfalfa
at three of four harvests. Although significant, the greatest reduction in weed growth was
only 128 kg ha'l by the orchardgrass at the spring growth and 44 kg ha'I in regrowth. Total
weed content at any harvest did not exceed 140 kg ha" (3.7%) of any forage. Additionally,
seeding with orchardgrass consistently reduced alfalfa yields compared to the weedy alfalfa.
W. Two years after seeding, orchardgrass with alfalfa increased first
harvest total yield compared to that of the weedy alfalfa and the other mixtures (Table 6).
Subsequently, alfalfa yield in alfalfa-orchardgrass was lower than that of the weedy alfalfa
and also lower than that of alfalfa-bromegrass or alfalfa-timothy. Orchardgrass yield was
superior to the other grasses. Weed yields in alfalfa-orchardgrass and alfalfa-Kentucky
bluegrass were lower than in the weedy alfalfa or alfalfa-bromegrass. Weed content was
reduced an average of 176 kg ha'l by the two mixtures in comparison to the weedy alfalfa.

Second harvest total yields of mixtures were similar to the weedy alfalfa except for
alfalfa-Kentucky bluegrass which was lower than that of all other forages. Alfalfa yields in
alfalfa-orchardgrass and alfalfa-Kentucky bluegrass were lower than the other forages. Weed
yields were similar between the weedy alfalfa and the mixtures but lower in alfalfa-
orchardgrass than in alfalfa-bromegrass. Orchardgrass yields were greatest, Kentucky
bluegrass yields intermediate, and bromegrass and timothy yields lowest at harvests two
through four.

Third harvest total yield of alfalfa-Kentucky bluegrass was lower than all forages

except alfalfa-orchardgrass. Alfalfa yields were reduced by orchardgrass in comparison to

54

the weedy alfalfa or the mixtures. Weed yields were 37 to 67 kg ha‘1 lower in mixtures than
in the weedy alfalfa.

At the fourth harvest, total yields were similar among the forages while alfalfa yield
was lower in alfalfa-orchardgrass than the other forages. Weed yield was lower in mixtures
with orchardgrass, timothy, and Kentucky bluegrass than the one with bromegrass but not
different than that of the weedy alfalfa.

Reduction in total yield in the alfalfa-Kentucky bluegrass forage at individual
harvests resulted in a reduction in total annual yield compared to the other mixtures but not
to the weedy alfalfa. Including grass did not consistently affect total yields. Including
orchardgrass did provide greater spring yields but this did not affect annual totals. In two
of four harvests, the alfalfa-Kentucky bluegrass was lower in yield which lead to lower
annual yields. Alfalfa yields in alfalfa-orchardgrass were always lower than that of the
weedy alfalfa and often lower than in alfalfa-bromegrass or alfalfa-timothy. Yield of
bromegrass and timothy were minimal in all harvests. Orchardgrass and Kentucky bluegrass
yields were greatest at the first harvest. Including orchardgrass or Kentucky bluegrass
reduced weed content at the first and third harvests. The maximum reduction, occurring at
the first harvest, was 182 kg ha". The maximum weed content two years after seeding was
189 hg ha‘l (4.9%) in the weedy alfalfa at first harvest. In both experiments, weed content
was reduced at some but not all harvests. This is similar to results of Bendixen and Lanini
(1) where ryegrass and fescue seeded into established alfalfa reduced weed competition but

varied by harvest and year.

55
Forage Quality
Low weed pressure

Seeding grass with alfalfa had no effect on CP at the first harvest of the seeding year
(Table 7). In plots seeded without oat, ADF was similar among the forages. Acid detergent
fiber was greater in alfalfa-timothy than the weedy alfalfa or alfalfa-Kentucky bluegrass in
plots with oat. When seeded without oat, NDF of alfalfa-bromegrass was greater than that
of the weedy alfalfa, alfalfa-orchardgrass, and alfalfa-timothy. The increase in NDF of
alfalfa-bromegrass in plots seeded without oat over the other forages at the first harvest is
due to the bromegrass which accounted for 20% to the total forage. Alfalfa-orchardgrass and
alfalfa-timothy were greater in NDF than alfalfa-Kentucky bluegrass. Differences in forages
seeded with oat may be due to differences in the oat since alfalfa, grass, and weeds
contributed little to the total yield and were similar among the forages.

At the second harvest, CP was similar among forages regardless of the companion
and ADF and NDF similar among forages when seeded without oat. Acid detergent fiber
was greater in the weedy alfalfa than all mixtures except alfalfa-orchardgrass where initially
seeded with oat. Among the mixtures, alfalfa-orchardgrass was higher in ADF than alfalfa-
timothy and alfalfa-Kentucky bluegrass. Neutral detergent fiber was greater in alfalfa-
orchardgrass than the weedy alfalfa, alfalfa-timothy, and alfalfa-Kentucky bluegrass in plots
initially seeded with oat.

Reductions in ADF and NDF of alfalfa-timothy and alfalfa-Kentucky bluegrass over
the weedy alfalfa at the second harvest, when initially seeded with oat, could not be

explained by differences in weed or alfalfa content. Timothy or bromegrass may have been

56

lower in fiber than the other plants contributing to the reduced fiber content. Differences in
fiber content at the second harvest were not consistently in favor of the weedy alfalfa or the
mixtures. Also, differences in fiber content between the weedy alfalfa and mixtures did not
exceed 18 g kg'l . A difference this small may be of little relative importance. Without a
companion crop, grass contribution to the forage was not great enough to influence forage
quality at either harvest.

High weed pressure

Seeding with a forage grass had no effect on forage CP, ADF, or NDF at the first
harvest in the seeding year (Table 8). Crude protein was also unaffected at the second
harvest. In plots established without oat, ADF was greater in alfalfa-Kentucky bluegrass
than in the alfalfa-bromegrass or alfalfa-orchardgrass. When initially seeded with oat, ADF
was greater in alfalfa-bromegrass and alfalfa-Kentucky bluegrass than the weedy alfalfa and
forage quality was reduced. Neutral detergent fiber was higher and forage quality lower in
alfalfa-bromegrass than the weedy alfalfa in plots initially seeded with oat. Seeded without
cat, no differences in NDF were observed.

Including grass with alfalfa had no effect on any forage quality characteristic at the
first harvest but did affect fiber content at the second harvest. Greater ADF of alfalfa-
Kentucky bluegrass than of alfalfa-bromegrass or alfalfa-orchardgrass may have been due
to alfalfa and weed content. Alfalfa content was lower and weed content greater, although
not statistically significant, in the mixture containing Kentucky bluegrass than in the other
two mixtures. Differences in fiber content between mixtures and the weedy alfalfa could not

be explained by alfalfa, grass, or weed yield differences. Overall, few differences in forage

57

quality were evident as a result of including grass with alfalfa.

Plant density

Low weed pressure

At 6WAS, alfalfa density was not reduced by seeding with grass but alfalfa density
was greater in the mixture with bromegrass than the weedy alfalfa or the other forages when
seeded with cat (Table 9). A difference in alfalfa density in plots seeded with oat was not
expected. A reduction in alfalfa density in mixtures in comparison to the weedy alfalfa was
expected. Grass density in plots without oat were greatest for bromegrass and Kentucky
bluegrass, intermediate for orchardgrass, and lowest for timothy. High Kentucky bluegrass
density is due to high seeding rate and number of seeds per kilogram in relation to
orchardgrass or timothy. The seeding rates of bromegrass, orchardgrass, timothy, and
Kentucky bluegrass were approximately 100, 150, 1220, and 3260 seeds m2, respectively.
The high bromegrass density was unexpected since seeding rate was lower and seed size
greater than the other grasses. Seeded with oat, the only difference was that Kentucky
bluegrass density was greater than that of bromegrass. Grass density was usually lower in
plots seeded with oat than in those seeded without oat. Greater density of Kentucky
bluegrass did not lead to a greater grass yield. Greater bromegrass density may have been
the primary cause of greater yields at first harvest. Weed densities were similar among all
forages at 6WAS and at 4WAH. Addition of grasses to alfalfa, or differences among grasses,

were insufficient to reduce weed density in the seeding year.

58

Alfalfa plant density was not affected by seeding with grasses in the fall of the
seeding year or two years later in plots established in 1993 (Table 10). One year after
seeding, alfalfa density in alfalfa-Kentucky bluegrass was lower than in the weedy alfalfa or
alfalfa-timothy. In forages seeded in 1994, alfalfa density in fall of that year was greater in
alfalfa-bromegrass and alfalfa-timothy than in the weedy alfalfa. Density was also greater
in alfalfa-bromegrass than alfalfa-orchardgrass or alfalfa-Kentucky bluegrass. The following
year, mixtures with orchardgrass or Kentucky bluegrass were lower in alfalfa density than
the weedy alfalfa. There were no consistent differences in density among the mixtures.
While not always statistically different, alfalfa density in alfalfa-orchardgrass and alfalfa-
Kentucky bluegrass tended to be lower than in the other forages. Alfalfa density in alfalfa-
bromegrass and alfalfa-timothy were not expected to be greatly reduced since those grasses
were not maintained in the stands. Alfalfa density decreased in all forages as the stand aged.

In the fall two years after seeding, alfalfa with orchardgrass or Kentucky bluegrass
was lower in dandelion density compared to the weedy alfalfa or the other two mixtures
(Table 11). Dandelion densities in the weedy alfalfa, alfalfa-orchardgrass, and alfalfa-
Kentucky bluegrass were 7.3, 3.5, and 1.5 plants m2. Both grasses made large contributions
to yield and were effective at reducing dandelion density. Reduction in dandelion density
by bromegrass or timothy would not be expected since these two grasses were all but
eliminated from the stand.

High weed pressure
Alfalfa plant density at 6WAS was not influences by the grasses (Table 12).

Orchardgrass density was lower than the other grasses in plots established without oat.

59

Lower orchardgrass density is expected since seeding rate was lower. Kentucky bluegrass
density was greatest, timothy intermediate, and bromegrass and orchardgrass density lowest
when seeded with oat. This distribution of density parallels what may be expected given the
seeding rates of each grass. Unlike the experiment with low weed pressure, more differences
in grass density were seen in plots seeded with than without oat. Weed competition may
have been great enough to limit grass emergence or growth and thereby minimized
differences. Weed density was reduced by 59 and 57 plants m2 in mixtures containing
bromegrass or orchardgrass in comparison to the weedy alfalfa when seeded without oat.
This difference did not result in reduced weed yields at the first harvest. With oat, weed
density was greater in alfalfa-Kentucky bluegrass than in alfalfa-bromegrass. At 4WAH,
weed density in alfalfa-Kentucky bluegrass was greater than in alfalfa-timothy when seeded
without oat. With oat, no differences in weed density were seen among the forages.
Although differences in grass density were evident, including grasses with alfalfa most often
had no effect on alfalfa or weed density in the seeding year.

In the fall of the seeding year, alfalfa density was similar among the forages seeded
with or without grasses (Table 13). One year after seeding, the 1993 forages were also
similar in plant density. Alfalfa density one year after seeding was lower in alfalfa-
orchardgrass than in all other forages except alfalfa-Kentucky bluegrass in the 1994 seeding.
Two years after the 1993 establishment, alfalfa density in alfalfa-Kentucky bluegrass was
lower than that of the weedy alfalfa. One and two years after establishment, alfalfa density
in alfalfa-orchardgrass and alfalfa-Kentucky bluegrass tended to be lower (not always

significantly) than the weedy alfalfa. Alfalfa plants also appeared to be smaller (visual

6O

observations) in the alfalfa-Kentucky bluegrass mixture. Alfalfa density in alfalfa-
bromegrass and alfalfa-timothy was similar to the weedy alfalfa in both years.

Dandelion density was lower in alfalfa seeded with orchardgrass or Kentucky
bluegrass than in the weedy alfalfa (Table 11). Dandelion density in the weedy alfalfa,
alfalfa-orchardgrass, and alfalfa-Kentucky bluegrass were 11, 5.4, and 6.1 plants m2,
. respectively. No differences in density were observed among the mixtures. Where grasses
made significant contributions to forage yield, dandelion density was reduced. In these
experiments, orchardgrass and Kentucky bluegrass reduced the density of dandelion which
is a simple perennial. Similar results may be seen with other simple perennials. If a creeping
perennial such as quackgrass (Elytrigia repens L. Nevski) was the dominant weed invading

the stand, results might be different.

SUMMARY

In the seeding year, including forage grasses with alfalfa had no consistent effect on
total forage, alfalfa, and weed yields or plant densities. In a few instances, weed yields or
densities were reduced by seeding with a grass. Including forage grasses had no effect on
forage CP while a few differences in fiber content were seen in the seeding year. These
differences occurred primarily at the second harvest in plots initially established with oat.
In the following years, including grass generally resulted in greater forage yields at the first
harvest than that of the weedy alfalfa but this did not always result in greater annual totals.
Orchardgrass and Kentucky bluegrass provided significant yields in all harvests through the

second year after seeding (third year of the stand). Bromegrass and timothy contributed little

61

to yield after the first harvest in the second year of the stand. Increased orchardgrass and
Kentucky bluegrass yields often resulted in reduced alfalfa yields. Alfalfa-Kentucky
bluegrass forage yields were also often lower than the weedy alfalfa or the other mixtures by
the third year of the stand.

At times, alfalfa density was reduced by seeding with orchardgrass or Kentucky
bluegrass. These two grasses reduced weed content in one harvest in the second year of the
stand and in two or three harvests, depending on weed pressure, the following year.
Additionally, orchardgrass and Kentucky bluegrass reduced dandelion density in fall two
years after seeding. Forage grasses appeared to be more effective at reducing weed invasion
as the stand aged. This may be attributable to the amount of grass in the forage.
Orchardgrass and Kentucky bluegrass continued to grow and compete while bromegrass and
timothy were essentially eliminated from the stand by the four annual harvests. By the end
of the third growing season, weed content did not exceed 5% of the total dry matter in the
weedy alfalfa. It is likely that as the stand ages, forage grasses will become dominant and
weed content should be reduced in comparison to the alfalfa seeded alone. The producer
must determine the acceptability of weed versus grass content in the forage and the

subsequent effects on forage quality and yield.

LIST OF REFERENCES

10.

LIST OF REFERENCES

Bendixen, W.E., and WT. Lanini. 1994. Interplanting cereals and grasses into the
last year of an alfalfa stand. Proc. West. Soc. Weed Sci. 47:91-95.

Carlisle, R.J., V.H. Watson, and AW. Cole. 1980. Canopy and chemistry of pasture
weeds. Weed Sci. 28:139-141.

Casler, M.D., and RP. Walgenbach. 1990. Ground cover potential of forage grass
cultivars mixed with alfalfa at divergent locations. Crop Sci. 30:825-831.

Doll, J .D. 1984. Effects of common dandelion on alfalfa drying time and yield.
Proc. North Cent. Weed Control Conf. vol. 39:113—114.

Dutt, T.E., R.G. Harvey, and RS. Fawcett. 1982. Feed quality of hay containing
perennial broadleaf weeds. Agron. J. 74:673-676.

Dutt, T.E., R.G. Harvey, RS. Fawcett, N.A. Jorgensen, H.J. Larsen, and DA.
Schlough. 1979. Forage quality and animal performance as influenced by
quackgrass (Agropyron repens) control in alfalfa (Medicago sativa) with pronamide.

Weed Sci. 27:127-132.

Fawcett, R.S., R.G. Harvey, D.A. Schlough, and LR. Block. 1978. Quackgrass
(Agropyron repens) control in established alfalfa (Medicago sativa) with pronamide.
Weed Sci. 26:193-198.

Hall, M.S., W.S. Curran, E.L. Werner, and LE. Marshall. 1995. Evaluation of weed
control practices during spring and summer alfalfa establishment. J. Prod. Agric.
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Jung, GA, and BS. Baker. 1985. Orchardgrass. In Forages. The science of
grassland agriculture. 4th ed. M.E. Heath, RF. Barnes, and D.S. Metcalfe .(eds.),
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Kapusta, G., and CF. Strieker. 1975. Selective control of downy brome in alfalfa.
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62

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63

Legere, A., and J.M. Deschenes. 1991. Yield response of oats and alfalfa to
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147.

Lemieux, C., A.K. Watson, and J .M. Deschenes. 1987. Effect of barley, red clover
and weeds on yield and forage quality of timothy during establishment and
subsequent production years. Can. J. Plant Sci. 67:1019-1033.

Marten, G.C. and RN. Andersen. 1975. Forage nutritive value and palatability of
12 common annual weeds. Crop Sci. 15:821-827.

Marten, G.C., D.R. Buxton, and RF. Barnes. 1988. Feeding value (forage quality).
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D.K. Barnes, and RR. Hill, Jr. (eds). p. 463-491. American Society of Agronomy.
Madison, WI.

Marten, G.C., C.C. Sheaffer, and D.L. Wyse. 1987. Forage nutritive value and
palatability of perennial weeds. Agron. J. 79:980-986.

Meyer, D.W., and J .P. Bolger. 1983. Influence of plant density on alfalfa yield and
quality. p. 37-41. In Proc. Am. Forage Grassl. Counc., Eau Claire, WI 23-26
January. American Forage Grassland Council, Lexington, KY.

Moyer, J .R. 1985. Effect of weed control and a companion crop on alfalfa and
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Moyer, J.R. 1992. Alfalfa yields in establishment and subsequent yields after
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Moyer, J .R., and R. Hironaka. 1993. Digestible energy and protein content of some
annual weeds, alfalfa, bromegrass, and tame oats. Can. J. Plant Sci. 73: 1305-1308.

Peters, E.J. 1964. Pre-emergence, preplanting and postemergence herbicides for
alfalfa and birdsfoot trefoil. Agron. J. 56:415-419.

Rhykerd, C.L., C.H. Noller, J .E. Dillon, J .B. Ragland, B.W. Crowl, G.C. Naderman,
and D.L. Hill. 1967. Managing alfalfa-grass mixtures for yield and protein. Indiana
Ag. Exp. Sta. R. Bull. No. 839.

Reich, J .M., and Casler, MD. 1985. Genetic variation for response to advancing
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Rhykerd, C.L., C.H. Noller, J .E. Dillon, J .B. Ragland, B.W. Crowl, G.C. Naderman,
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SAS. 1994. Version 6.10. SAS Institute. Cary, NC.

Schmidt, J.R. 1991. Alternative methods of alfalfa establishment. MS. Thesis.
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Sheaffer, C.C., D.K. Barnes, and G.C. Marten. 1988. Companion crop vs. solo

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Sheaffer, CC, and D.L. Wyse. 1982. Common dandelion (Taraxacum oflicinale)
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Component contributions to dry matter and nitrogen harvests. Grass and Forage
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Wakefield, RC., and Nils Skaland. 1965. Effects of seeding rate and chemical weed
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65

Table 1. Component yields in the year of seeding (average of 1993 and 1994 seedings) with low weed
pressure.

 

 

 

 

 

Harvest Annual
Component Oat Alfalfa l 2 total
kg ha'1

Total Absent Weedy 3452 2685 6137
+ bromegrass 3447 2640 6087

+ orchardgrass 3381 2792 6173

+ timothy 3625 2840 6465

+ Kentucky bluegrass 3130 2850 5980

Present Weedy 63 57 2167 8524

+ bromegrass 6204 2205 8409

+ orchardgrass 6917 2204 9121

+ timothy 6621 2358 8979

+ Kentucky bluegrass 6639 2174 8813

Alfalfa Absent Weedy 1073 1558 -
+ bromegrass 917 1531 -

+ orchardgrass 925 1333 -

+ timothy 1006 1654 -

+ Kentucky bluegrass 764 1615 -

Present Weedy 1 04 1 769 -

+ bromegrass 166 1655 -

+ orchardgrass 104 171 1 -

+ timothy 78 17 19 -

+ Kentucky bluegrass 1 17 1788 -

 

' Means within a column and forage followed by the same letters are not significantly different (P<0.05).

Table l. (Cont’d).

66

 

 

 

 

 

Harvest Annual
Component Oat Alfalfa 1 2 total
kg ha‘1

Grass Absent Weedy - - -
+ bromegrass 703 a‘ 5633 -

+ orchardgrass 1 3 5b 715a -

+ timothy 261b 631a -

+ Kentucky bluegrass 38b 131b -

Present Weedy - - -

+ bromegrass 10 214ab -

+ orchardgrass 2 339a -

+ timothy 10 150ab -

+ Kentucky bluegrass 1 19b -

Weeds Absent Weedy 2379 1 127a -
+ bromegrass 1827 546b -

+ orchardgrass 2321 744b -

+ timothy 2358 555b -

+ Kentucky bluegrass 2328 1 104a -

Present Weedy 196 397ab -

+ bromegrass 68 335ab -

+ orchardgrass 1 1 1 153b -

+ timothy 178 488a -

+ Kentucky bluegrass 147 367ab -

 

‘ Means within a column and forage followed by the same letters are not significantly different (P<0.05).

67

Table 2. Component yields in the year of seeding (average of 1993 and 1994 seedings) with high weed
pressure.

 

 

 

 

 

Harvest Annual
Component Oat Alfalfa 1 2 total
kg ha“1

Total Absent Weedy 3 3 3 3 243 5b“ 5768
+ bromegrass 3404 2515ab 5919

+ orchardgrass 3020 2816a 5836

+ timothy 3446 2625ab 6071

+ Kentucky bluegrass 3467 2479ab 5945

Present Weedy 6407 1 9 1 7 83 24

+ bromegrass 6338 1993 8331

+ orchardgrass 5797 1996 7793

+ timothy 6287 2018 8305

+ Kentucky bluegrass 6442 1989 8431

Alfalfa Absent Weedy 23 8 1 600a -
+ bromegrass 266 1469ab -

+ orchardgrass 235 1359a) -

+ timothy 275 l477ab -

+ Kentucky bluegrass 243 1240b -

Present Weedy 68 l 700 -

+ bromegrass 62 1663 -

+ orchardgrass 85 1730 -

+ timothy 62 1673 -

+ Kentucky bluegrass 90 1733 -

 

‘ Means within a column and forage followed by the same letters are not significantly different (P<0.05).

68

Table 2. (Cont’d).

 

 

 

 

 

Harvest Annual
Component Oat Alfalfa 1 2 total
kg ha"

Grass Absent Weedy - - -
+ bromegrass 1 17a 279a -

+ orchardgrass 27b 244a -

+ timothy 46ab 224a -

+ Kentucky bluegrass 6b 26b -

Present Weedy - - -

+ bromegrass 14 56a -

+ orchardgrass 25 5 l a -

+ timothy l 1 58a -

+ Kentucky bluegrass 5 10b -

Weeds Absent Weedy 3 095 83 5 -
+ bromegrass 3021 767 -

+ orchardgrass 2758 1213 -

+ timothy 3 125 924 -

+ Kentucky bluegrass 3218 1213 -

Present Weedy 23 7 2 1 7 -

+ bromegrass 286 275 -

+ orchardgrass 287 215 -

+ timothy 333 287 -

+ Kentucky bluegrass 253 247 -

 

' Means within a column and forage followed by the same letters are not significantly different (P<0.05).

69

Table 3. Component yields one year after seeding (average of 1993 and 1994 seedings) with low weed
pressure.

 

 

 

 

 

Harvest Annual
Component Alfalfa 1 2 3 4 total
kg ha"
Total Weedy 4619b“ 3203a 2538ab 1492 1 1852bc
+ bromegrass 5193a 3165 ab 2614ab 1441 12413a
+ orchardgrass 5371a 3013ab 2424ab 1452 12260ab
+ timothy 5204a 2939b 2641 a 1484 12268ab
+ Kentucky bluegrass 4797b 3045ab 2370b 1390 1 16010
Alfalfa Weedy 4554a 3133a 2505a 1482a -
+ bromegrass 3693bc 293 9ab 2460a 1378ab -
+ orchardgrass 3351c 2388c 1944b 1 l49c -
+ timothy 3858b 2825b 2603a 1466a -
+ Kentucky bluegrass 42703 2726b 2149b 1257bc -
Grass Weedy - - - - -
+ bromegrass 1341b 206bc 92c 46c -
+ orchardgrass 1996a 614a 479a 302a -
+timothy 1317b 103C 18d 13c -
+ Kentucky bluegrass 492C 308b 196b l31b -
Weeds Weedy 6Sab 703 33ab 10 -
+ bromegrass 159a 20b 62a 17 -
+ orchardgrass 24b 1 1b 1b 1 -
+ timothy 29b 1 1b 20ab 5 -
+ Kentucky bluegrass 35b 1 lb 25 ab 2 -

 

'Means within a column and forage followed by the same letters are not significantly different (P<0.05). -

70

Table 4.« Component yields one year after seeding (average of 1993 and 1994 seedings) with high weed
pressure.

 

 

 

 

 

Harvest Annual
Component Alfalfa l 2 3 4 total
kg ha'1
Total Weedy 4701b’1 3095 2612 1697 12101
+ bromegrass 5091 a 3023 2706 1679 12499
+ orchardgrass 5144a 2979 2465 1666 12254
+ timothy 5068a 2975 2600 1703 12346
+ Kentucky bluegrass 4867ab 3065 2636 1637 12206
Alfalfa Weedy 4549a 3057a 2575a 1688a -
+ bromegrass 4087b 287 la 2605a 1655a -
+ orchardgrass 3750b 2476b 2036b 1387b -
+ timothy 4091b 2835a 25583 1689a -
+ Kentucky bluegrass 4523a 2813a 2506a 1545a -
Grass Weedy - - - - -
+ bromegrass 893b 132C 44c 16c -
+ orchardgrass 1361 3 486a 417a 276a -
+ timothy 914b 127C 220 9c -
+ Kentucky bluegrass 256C 233b 1 1 1b 72b -
Weeds Weedy l 52 34a 37 9ab -
+ bromegrass l 1 1 20b 57 8ab -
+ orchardgrass 33 17b 12 3b -
+ timothy 63 13b 20 6ab -
+ Kentucky bluegrass 88 19b 19 20a -

 

“Means within a column and forage followed by the same letters are not significantly different (P<0.05). ‘

71

Table 5. Component yields two years after seeding (1993 seeding only) with low weed pressure.

 

 

 

 

 

Harvest Annual
Component Alfalfa 1 2 3 4 total
kg ha"
Total Weedy 3814b‘ 28183 16313 945a 9208ab
+ bromegrass 3710b 2613ab 15713 938a 8832b
+ orchardgrass 4743a 2530ab 1425b 844a 95423
+ timothy 3894b 2789a 1607a 9483 9238ab
+ Kentucky bluegrass 4050b 2374b 1 l 1 10 654b 8189c
Alfalfa Weedy 3674a 2760a 1587a 934a -
+ bromegrass 35353b 2522a 1542a 929a -
+ orchardgrass 3172b 1876b 1027b 505b -
+ timothy 37553 27363 15793 9333 -
+ Kentucky bluegrass 3496ab 2076b 908b 399b -
Grass Weedy - - - - -
+ bromegrass 49c 60 3c 4c -
+ orchardgrass 1559a 6463 3983 3383 -
+ timothy 130 10 6c 5c -
+ Kentucky bluegrass 540b 292b 202b 254b -
Weeds Weedy 1403 583b 443 1 13 -
+ bromegrass 1263 853 263 53b -
+ orchardgrass 12b 8b 0b lb -
+ timothy 1263 523b 22ab 103 -
+ Kentucky bluegrass 14 b 6b 1b 1b -

 

‘ Means within a column and forage followed by the same letters are not significantly different (P<0.05).

72

Table 6. Component yields two years alter seeding (1993 seeding only) with high weed pressure.

 

 

 

 

 

Harvest Annual
Component Alfalfa 1 2 3 4 total
kg ha"
Total Weedy 3867b' 25193 20673 1337 97 903b
+ bromegrass 4003b 27423 21123 1380 102373
+ orchardgrass 46883 25223 2019ab 131 1 105403
+ timothy 3939b 27153 22253 1374 102533
+ Kentucky bluegrass 387 lb 2155b 1781b 1204 901 1b
Alfalfa Weedy 367 8ab 24363 20003 1 309a -
+ bromegrass 37843 25763 20703 13273 -
+ orchardgrass 2869c 1742b 1459b 890b -
+ timothy 3754ab 26293 22113 13633 -
+ Kentucky bluegrass 3299bc 1916b 15553 90% -
Grass Weedy - - - - -
+ bromegrass 59b 41c 120 9c -
+ orchardgrass 18123 7743 5603 4193 -
+ timothy 77b 23c 4c 1c -
+ Kentucky bluegrass 553b 208b 221b 294b -
Weeds Weedy 1893 83 ab 67a 28ab -
+ bromegrass 1603 1253 30b 44a -
+ orchardgrass 7b 6b 0b 2b -
+ timothy 1083b 63 ab 10b 10b -
+ Kentucky bluegrass 19b 3 lab 5b 1b -

 

‘ Means within a column and forage followed by the same letters are not significantly different (P<0.05).-

73

Table 7. Forage quality characteristics in the seeding year (average of 1993 and 1994 seedings) with low

 

 

 

 

 

 

weed pressure.
Harvest 1 Harvest 2
Oat
Characteristic Alfalfa absent present absent present
g kg"
CP' Weedy 145 95 182 218
+ bromegrass 137 96 187 212
+ orchardgrass 138 95 174 205
+ timothy 145 90 189 207
+ Kentucky bluegrass 135 90 182 217
ADF Weedy 272 34 lbc" 320 2993
+ bromegrass 288 347abc 316 290bc
+ orchardgrass 271 3523b 315 2973b
+ timothy 283 3563 316 281C
+ Kentucky bluegrass 283 337C 31 1 2820
NDF Weedy 436b 57 93b 466 418b
+ bromegrass 4753 5883b 480 4203b
+ orchardgrass 437b 5953 482 4293
+ timothy 444b 5933 477 4070
+ Kentucky bluegrass 4563b 570b 468 402C

 

' CP, crude protein; ADF, acid detergent fiber“, NDF, neutral detergent fiber.
b Means within a column and characteristic followed by the same letters are not significantly different

(P<0.05).

74

Table 8. Forage quality characteristics in the seeding year (average of 1993 and 1994 seedings) with high
weed pressure.

 

 

 

 

 

 

Harvest 1 Harvest 2
Oat
Characteristic Alfalfa absent present absent present
3 kg"
CP‘ Weedy 96 81 166 236
+ bromegrass 99 82 185 221
+ orchardgrass 97 80 186 236
+ timothy 100 83 1 76 232
+ Kentucky bluegrass 100 82 178 226
ADF Weedy 3 10 330 3103bb 262b
+ bromegrass 322 332 297b 2783
+ orchardgrass 316 334 298b 2693b
+ timothy 317 339 3073b 2743b
+ Kentucky bluegrass 318 332 3153 2813
NDF Weedy 505 566 474 388b
+ bromegrass 516 571 577 4133
+ orchardgrass 51 l 569 451 3963b
+ timothy 513 573 475 4023b
+ Kentucky bluegrass 523 570 483 4053b

 

' CP, crude protein; ADF, acid detergent fiber; NDF, neutral detergent fiber.
b Means within a column and characteristic followed by the same letters are not significantly different
(P<0.05).

75

Table 9. Plant density in the seeding year (average of 1993 and 1994 seedings) with low weed pressure.

 

 

 

 

 

6WAS‘ 4WAH
Oat Alfalfa Alfalfa Grass Weeds Weeds
plants In2
Absent Weedy 298 - 101 32
+ bromegrass 278 1293" 108 26
+ orchardgrass 262 87b 95 34
+ timothy 274 52c 95 28
+ Kentucky bluegrass 254 1353 89 31
Present Weedy 144b - 83 39
+ bromegrass 1933 23b 82 39
+ orchardgrass 157b 37ab 103 37
+ timothy 144b 523b 107 45
+ Kentucky bluegrass 156b 653 90 36

 

' 6WAS, 6 weeks after seeding; 4WAH, 4 weeks after first harvest.
b Means within 3 column and oat followed by the same letters are not significantly different (P<0.05).

Table 10. Alfalfa plant density in fall with low weed pressure.

 

Years after seeding

 

 

 

 

 

 

 

 

l 2
Seeding year
Alfalfa 1993 1994 1993 1994 1993
plants at2
Weedy 242 2020’’ 1453 1803 124
+ bromegrass 243 2573 1283b 1543b 1 15
+ orchardgrass 266 208bc 1363b l37b 100
+ timothy 240 2473b 1433 1693b 1 14
+ K. bluegrass 228 212bc 1 10b l34b 101

 

‘ Means within a column followed by the same letters are not significantly different (P<0.05).

76

Table l l. Dandelion density in fall two years after establishment (1993 seedings only).

 

Weed pressure

 

 

 

 

Forage Low High
Plants m2

Weedy alfalfa 7.33“ 1 1.03

Alfalfa + bromegrass 8.03 8.63b

Alfalfa + orchardgrass 3.5b 5.6b

Alfalfa + timothy 7.43 8.53b

Alfalfa + Kentucky bluegrass 1.5b 4.9b

 

' Means within a column followed by the same letters are not significantly different (P<0.05).

77

Table 12. Plant density in the seeding year (average of 1993 and 1994 seedings) with high weed pressure.

 

 

 

 

 

6WAS' 4WAH
Oat Alfalfa Alfalfa Grass Weeds Weeds
plants m2

Absent Weedy 231 - 253ab 46ab

+ bromegrass 264 783 194b 413b

+ orchardgrass 264 29b 196b 44ab

+ timothy 249 773 2243b 38b

+ Kentucky bluegrass 241 803 2273b 503
Present Weedy 276 - 1853b 52

+ bromegrass 255 38c 14% 51

+ orchardgrass 271 23c 1773b 49

+ timothy 283 70b 1783b 46

+ Kentucky bluegrass 238 913 2253 48

 

‘ 6WAS, 6 weeks after seeding; 4WAH, 4 weeks after first harvest.
b Means within a column and oat followed by the same letters are not significantly different (P<0.05).

Table 13. Alfalfa plant density in fall with high weed pressure.

 

 

 

 

 

 

 

 

 

Years after seeding
l 2

Seeding year

Alfalfa 1993 1994 1993 1994 1993
plants at2

Weedy 252 252 139 2023‘ 1283b
+ bromegrass 280 259 164 1983 1423
+ orchardgrass 256 265 150 158b 1 16bc
+ timothy 257 232 142 2053 122b
+ K. bluegrass 257 249 139 1813b 101c

 

“ Means within a column followed by the same letters are not significantly different (P<0.05).

CHAPTER THREE
Weed Invasion in Established Stands of Alfalfa Seeded
with Perennial Forage Grasses
ABSTRACT

Establishing alfalfa with perennial forage grasses may reduce weed invasion as the
stand ages. Data to support this potential advantage are not abundant. This study determined
the efi‘ect of seeding perennial forage grasses with alfalfa on weed and component yields and
on forage quality in established stands. Alfalfa was seeded alone (weedy alfalfa) and in
binary mixtures with bromegrass, orchardgrass, or timothy. Yields and forage quality were
determined at three annual harvests in the third and fourth years after seeding. Weed yields
in alfalfa seeded with orchardgrass were often lower than those in the weedy alfalfa.
Average weed content was 24, 17, 2, and 15% for the weedy alfalfa, alfalfa-bromegrass,
alfalfa-orchardgrass, and alfalfa-timothy, respectively. Seeding alfalfa with orchardgrass
increased first harvest and annual forage yields while reducing alfalfa yield. Crude protein
was reduced and acid detergent fiber and neutral detergent fiber increased by orchardgrass
primarily at the first harvest. Neutral detergent fiber was greater in alfalfa-orchardgrass than
in the weedy alfalfa at most harvests. Yields of orchardgrass ofien exceeded those of
bromegrass or timothy. There were no consistent differences among the weedy alfalfa and
the other mixtures in yields or quality. Of the perennial grasses seeded with alfalfa, only
orchardgrass consistently reduced weed invasion. The producer must determine the
acceptability of high weed or orchardgrass content in the forage and subsequent effects on

forage quality, yield, and stand life.

INTRODUCTION

Seeding perennial forage grasses with alfalfa (Medicago sativa L.) may help to
reduce weed invasion in subsequent years. Perennial forage grasses with alfalfa may also
be advantageous for reducing insect damage, soil and water conservation, and supplying a
consistent yield across a wide range of environments (5,16,35,54). Competition provided
by weeds may reduce alfalfa yields, stand persistence, and forage quality. Weed competition
can reduce alfalfa yield in the seeding year and in established stands (12,21,28,32,38,40,52).
Total forage yield, however, may not be affected (29) but the weeds may compose a large
proportion of the dry matter (28,48). Intense weed competition in the seeding year may
result in a stand failure (39).

Forage quality may or may not be reduced by the presence of weeds (9,10
l1,14,19,22,23,25,28,30,42). Generally, forage quality is affected most in the seeding year
and in old stands where weeds are more prevalent. The degree to which forage quality is
affected depends on the weed species present, maturity of the weed plants, and the proportion
of weeds in the forage (3,4,7,8, 10,25). Although similar in forage quality, weeds may be less
palatable (23) or potentially toxic to animals (4). This may be especially important for
producers growing hay for specialty markets. In addition, moisture content of weeds may
be greater than alfalfa and slow the drying rate (9) and weeds may provide seeds or

vegetative propagules that invade subsequent crops (24).

79

80

Weeds may be controlled in forages using chemical, mechanical, or cultural methods.
Herbicides have proven effective at controlling weeds (15, 1 8, 19,3 7,55) and are used
increasingly for weed control in pure alfalfa seedings (49). In established stands, herbicides
are not commonly used since the effect is often temporary and alfalfa yields and forage
quality may not be consistently increased (8,42). Tillage, alone or in combination with
herbicides, can be used prior to and at stand establishment to control weeds (1). Mechanical
control (clipping or mowing) requires accurate timing to reduce broadleaf competition and
minimize damage to alfalfa (20,26). Weed grasses may not be controlled since their growing
point is below the height of cutting. In established stands, mowing can be effective at
preventing seed production and decreasing infestation of certain perennial weeds (33).

Cultural methods of controlling weeds include prevention, altered planting time,
tillage, and using companion crops. Preventative measures such as using weed-free seed and
cleaning equipment between fields will limit weed introductions (33). Altering the seeding
date is also an effective method for controlling weeds. Seeding in early spring, in the North
Central region, results in heavy weed pressure primarily from the summer annuals such as
common lambsquarters (Chenopodium album L.), redroot pigweed (Amaranthus retroflexus
L.), and giant foxtail (Selaria faberi Hermm.) Seeding in late summer reduces summer
annual weed pressure but may increase winter annual weed pressure (13) or result in a failed
stand if soil moisture is not adequate (33). Producers may choose spring seeding in
preference to summer seeding to increase forage yields in the year of establishment. .

An annual or perennial crop may be seeded with the forage to suppress weed growth.

Annual companion crops, primarily small grains, are widely used in spring seedings of

81

alfalfa. An estimated 60% of alfalfa acreage planted in the north central and north eastern
USA was seeded with a companion crop (49). Oat (A vena sativa L.) is the most commonly
used companion crop (31,43,45). In addition, small grain companion crops may reduce soil
erosion, increase forage yield, and increase economic return.

Perennial forage grasses may reduce weed invasion in alfalfa. A reduction in weed
invasion or enhanced weed control has been given as a potential advantage of including a
forage grass (5) but little data is available to support this statement. In one study, seeding
annual ryegrass (Lolium spp.) or a fescue (Festuca spp.) into established alfalfa showed a
trend towards reducing weed competition (2). Willard (53) and Sollenberger et al. (46)
found that growing orchardgrass (Dactylis glomerata L.) with alfalfa was effective at
keeping weeds out of the stand. As alfalfa stands age, plant density decreases (27) thereby
allowing favorable conditions for weed growth. As alfalfa-grass stands age, the alfalfa plant
density decreases and grasses become dominant (44,50) which may reduce weed invasion.

Including grass in mixtures with alfalfa may reduce forage quality (34). Generally,
grasses mature faster than alfalfa and by harvest (bud to one-tenth bloom) may already be
in the flowering stage and quality will be reduced (49). The extent to which forage quality
is reduced is dependent on the specific harvest, grass species, and proportion of grass in the
forage. Including perennial grasses was shown to reduce forage quality primarily in spring
growth (47). Combinations of alfalfa with different species of grass resulted in differences
in forage quality among the combinations (41). Depending on the species and its specific
quality, the degree to which forage quality is changed results from the proportion of grass

in the stand. Earlier harvest of mixtures may be required to maintain high forage quality.

82

The potential for interseeded perennial forage grasses to reduce weed invasion has
been mentioned in numerous articles as a potential advantage. Data to support this
statement, however, are not abundant. Objectives of this research were to determine how
interseeding smooth bromegrass (Bromus inermis Leyss.), orchardgrass, or timothy (Phleum

pratense L.) with alfalfa affected weed content and component yields and forage quality.

MATERIALS AND METHODS

Field experiments were established in summer 1990 at the Michigan State University
Botany farm in East Lansing, Michigan on a Capac loam soil (fine-loamy, mixed, mesic
Aeric Ochraqualfs). Soil test data were used to determine fertilizer additions at seeding.
Fertilizer in the established stand was applied as needed based on soil tests.

Bentazon [3-(1-methylethyl)-(1H)-2,1,3-benzothiadiazin-4(3H)-one 2,2-dioxide] was
applied at 1.12 kg a.i. ha'l with crop oil at 0.38 1 ha‘1 in June prior to seeding to control
yellow nutsedge (C yperus esculentus L.). Glyphosate [N-(phosphonomethyl) glycine] was
applied at 1.68 kg at ha‘1 in early August prior to tillage to control quackgrass (Elytrigia
repens L. Nevski). Conventional tillage was used in seedbed preparation. Treatments were
seeded with a drill using 18 cm rows in mid-August in 9.9 by 13.7 m plots.

Treatments included alfalfa seeded alone (weedy alfalfa), and in binary mixtures with
bromegrass, orchardgrass, or timothy. ‘Big Ten’ alfalfa was seeded at 14.6 kg ha" in all
plots. ‘Common’ bromegrass, ‘Common’ orchardgrass, and ‘Common’ timothy were seeded
at 5.6, 1.1, and 4.5 kg ha", respectively. Experimental design was a randomized complete

block with four replications. Data were analyzed using PROC ANOVA of SAS (36) and

83

means separated with Duncans multiple range test. Differences were judged significant at
P<0.05.

In 1993 and 1994, plots were harvested three times annually at bud to one-tenth
bloom stage of alfalfa. Harvest dates in 1993 were 10 June, 26 July, and 8 September.
Harvest dates in 1994 were 1 June, 12 July, and 30 August. A 0.9 by 6.1 in strip was
collected with a flail harvester at each date and weighed. Approximately 500 g of fresh
forage was collected from the harvested sample and dried at 60°C for 72 h in a forced air
dryer to determine dry matter content. Forage yields were then calculated on a dry matter
basis. Following each harvest, remaining forage was removed with field equipment.

Two random samples were collected by hand from each plot. Samples were cut at
a height of 5 cm. One sample was hand separated into the following components: alfalfa,
perennial forage grass, broadleaf weeds, and grass weeds. Individual components were dried
and weighed to determine the specific components proportion of total forage. Percentages
of each component are included in Appendix Tables A9 and A10. The second sample was
dried and ground in a cyclone mill to pass a 2mm screen. This sample was analyzed in
duplicate for crude protein (CP), acid detergent fiber (ADF), and neutral detergent fiber
(NDF). Crude protein concentration was determined by using micro-Kjeldahl analysis to
measure total N and multiplying that number by 6.25. Fiber concentration was determined

by the modified sequential fiber analysis procedure of Van Soest et al. (51).

84

RESULTS
Component Yields

At the first harvest in 1993 and in annual totals, alfalfa-orchardgrass was greater in
forage yield than the weedy alfalfa (Table 1). No differences in total forage yield among
treatments were seen at the second or third harvests. Alfalfa yields in the mixtures
containing orchardgrass or timothy were lower than those of alfalfa-bromegrass or the weedy
alfalfa at the first harvest. In the second and third harvests, alfalfa yields in the alfalfa-
orchardgrass were lower than all other treatments. At all three harvests, yields of
orchardgrass were greater than bromegrass or timothy. Total weed content was lower in the
alfalfa-orchardgrass mixture at the first harvest and in all the mixtures at the third harvest
than in the the weedy alfalfa. At the second harvest, weed yields were not statistically
different.

In the spring harvest of 1994, mixtures with bromegrass or orchardgrass were greater
in total forage yield than the weedy alfalfa (Table 2). At the second harvest no mixtures
were greater in yield than the weedy alfalfa, but alfalfa-timothy was lower in forage yield
than all other treatments. In the third harvest alfalfa-bromegrass yielded more forage than
the weedy alfalfa. Mixtures of alfalfa with bromegrass or orchardgrass were higher in annual
forage yields than those of alfalfa-timothy or the weedy alfalfa.

Alfalfa yields were lower in mixtures containing orchardgrass or timothy than in the
weedy alfalfa in the spring harvest but not in the second harvest. At the third harvest, alfalfa
yield in the alfalfa-timothy was less than that in the alfalfa-bromegrass or the weedy alfalfa.

Orchardgrass yield was greater than that of timothy at all three harvests and greater than that

85

of bromegrass at the first and third harvests. Total weed yield was lower in the mixtures
containing orchardgrass than in the weedy alfalfa at the second and third harvests.

Total forage yields of alfalfa with orchardrass were greater than the weedy alfalfa at
the initial harvest and annually. Orchardgrass increased annual yields by an average 1657
kg ha". Average annual yield increases due to the orchardgrass were 16% which is close to
Chamblee and Collins (6) estimate of 10 to 15%. Alfalfa yields in the alfalfa-orchardgrass
were often lower than that of the weedy alfalfa. Alfalfa, as a percentage of total forage,
ranged from 26 to 68% in the alfalfa-orchardgrass. In all but one harvest, yields of
orchardgrass were greater than those of bromegrass or timothy. Orchardgrass percentage
was greater than the other grasses at all harvests and ranged from 30 to 73% of the total. As
alfalfa-grass stands age, the grass component tends to become dominant as shown by
orchardgrass. Jung and Baker (17) stated that orchardgrass is generally more tolerant of
environmental extremes than timothy but less so than bromegrass. Greater orchardgrass
growth also may be due to harvest schedule. In a three out system, the first harvest is taken
in early June and the orchardgrass has reached heading stage while bromegrass is in the boot
stage and timothy in the stem elongation stage (6). Harvest at this time can result in poor
regrowth because grasses have not reached maturity. Weed yields were often lower in the
alfalfa-orchardgrass than in the the weedy alfalfa (Tables 1 and 2). Weed dry matter was
found to decrease from 1.0 t ha" to 0.05 t ha‘l when orchardgrass was included with alfalfa
(46). Average weed content for the weedy alfalfa, alfalfa-bromegrass, alfalfa-orchardgrass,
and alfalfa-timothy were 24, 17, 2, and 15%, respectively. In Ohio, Sollenberger et al. (46)

found that weed content of alfalfa-orchardgrass did not exceed 0.2% of the stand while

86

alfalfa sown alone may contain over 50% weeds at the first harvest. Lack of significant
differences among weed yields in some harvests was due to high variability in the hand
separation samples. The hand samples were representative of the larger field since grass
dispersion was not uniform.

Forage Quality

The alfalfa-orchardgrass mixture was lower in CP, higher in ADF and NDF at the
first harvest, and higher in NDF at the second and third harvests than the weedy alfalfa in
1993 (Table 3). As a result, forage quality was often lower in the alfalfa-orchardgrass than
in the weedy alfalfa. Alfalfa-bromegrass was lower in CP and higher in NDF while alfalfa-
timothy was lower in CP than the weedy alfalfa at the first harvest only.

In 1994, all alfalfa-grass mixtures were lower in CP and higher in fiber content than
the weedy alfalfa at the first harvest (Table 4). Fiber content was also greater in the alfalfa-
orchardgrass than the weedy alfalfa at the third harvest.

The mixtures were often lower in forage quality than the weedy alfalfa at the first
harvest (Tables 3 and 4). The alfalfa-orchardgrass was also lower in quality, at times, in the
third harvest. Average grass content for each consecutive harvest was 48, 16, and 27%.
Forage quality reductions were due in part to the grass proportion of the total forage.
Average bromegrass, orchardgrass, and timothy content was 17, 54, and 22%. Given the

large orchardgrass content in the forage, the reduction in forage quality was not surprising.

87

SUMMARY

Seeding alfalfa with perennial forage grasses did not provide a consistent increase in
forage yield although total yield was increased by orchardgrass at the first harvest and
annually. Alfalfa yields were generally lower in the alfalfa-orchardgrass mixtures than in
other forages. Orchardgrass yields were often greater than those of bromegrass or timothy.
Including orchardgrass with alfalfa was effective at reducing weed content. Forage quality,
however, was also reduced by the orchardgrass. The effect of perennial grasses on weed
invasion depended on the grass species. Harvest management must favor a high level of
grass in the stand for effective reductions in weed content. The producer is faced with
determining if a forage with an average of 24% weeds is more or less desirable than one with

54% orchardgrass, potentially greater yields, and reduced quality.

LIST OF REFERENCES

10.

11.

LIST OF REFERENCES

Alfalfa management guide. 1991. U of Wisc. Ext. Coop. Ext. and Minn. E x t .
Service, U of Minn.

Bendixen, W.E., and WT. Lanini. 1994. Interplanting cereals and grasses into the
last year of an alfalfa stand. Proc. West. Soc. Weed Sci. 47:91-95.

Bosworth, S.C., C.S. Hoveland, and GA. Buchanan. 1985. Forage quality of
selected cool-season weed species. Weed Sci. 34:150-154.

Carlisle, RJ., V.H. Watson, and AW. Cole. 1980. Canopy and chemistry of pasture
weeds. Weed Sci. 28:139-141.

Casler, M.D., and RP. Walgenbach. 1990. Ground cover potential of forage grass
cultivars mixed with alfalfa at divergent locations. Crop Sci. 30:825-831.

Chamblee, D.S., and M. Collins. 1988. Relationships with other species in a
mixture. In Alfalfa and Alfalfa Improvement. Agronomy Monograph No. 29. AA.
Hanson (ed). p. 439-461. American Society of Agronomy. Madison, WI.

Cords, HP. 1973. Weeds and alfalfa hay quality. Weed Sci. 21 :400-401.

Cosgrove, DR, and M. Barrett. 1987 . Effects of weed control in established alfalfa
(Medicago sativa) on forage yield and quality. Weed Sci. 35:564-567.

Doll, JD. 1984. Effects of common dandelion on alfalfa drying time and yield.
Proc. North Cent. Weed Control Conf. vol. 39:113-114.

Dutt, T.E., R.G. Harvey, and RS. Fawcett. 1982. Feed quality of hay containing
perennial broadleaf weeds. Agron. J. 74:673-676.

Dutt, T.E., R.G. Harvey, RS. Fawcett, N.A. Jorgensen, H.J. Larsen, and DA.
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93

Table 1. Component yields three years after seeding (1993).

 

 

 

 

 

Harvest Annual
Component Alfalfa l 2 3 total
kg ha‘l
Total Weedy 4649b' 323 l 2786 10666b
+ bromegrass 50303b 3406 2586 110223b
+ orchardgrass 60453 3369 2759 121733
+ timothy 49783b 3323 2811 11112ab
Alfalfa Weedy 39933 29763 22023 -
+ bromegrass 37293 29173 21173 -
+ orchardgrass 1574c 1885b 1379b -
+ timothy 2896b 28443 23403 -
Grass Weedy - - - -
+ bromegrass 783c 13 lb 293b -
+ orchardgrass 44003 14833 13523 -
+ timothy 1797b 340b 305b -
Total weeds Weedy 6563 255 5843 -
+ bromegrass 5183b 358 176b -
+ orchardgrass 71b 1 28b -
+ timothy 2853b 139 l66b -

 

' Means within a column and component followed by the same letters are not significantly different

(P<0.05).

94

Table 2. Component yields four years after seeding (1994).

 

 

 

 

 

Harvest Annual
Component Alfalfa 1 2 3 total
kg ha"
Total Weedy 4528bll 347 13 2584bc 1 05 83b
+ bromegrass 60413 37723 31253 129383
+ orchardgrass 57873 35673 3036ab 123903
+ timothy 5356ab 2949b 2341c 10646b
Alfalfa Weedy 35403 2517 133 53 -
+ bromegrass 2474ab 2485 16083 -
+ orchardgrass 1540b 2410 12643b -
+ timothy 2074b 2337 709b -
Grass Weedy - - - -
+ bromegrass 2333b 6993 367b -
+ orchardgrass 42233 10683 16293 -
+ timothy 2557b 117b 535b -
Total weeds Weedy 988 9543 1249a -
+ bromegrass 1234 5883b 1150ab -
+ orchardgrass 24 89b 143b -
+ timothy 725 4953b 1097ab -

 

' Means within a column and component followed by the same letters are not significantly different

(P<0.05).

95

Table 3. Forage quality characteristics three years after seeding (1993).

 

 

 

 

 

Harvest
Characteristic Alfalfa l 2 3
g kg"
CP‘ Weedy 1983b 183 189
+ bromegrass 156b 181 199
+ orchardgrass 90c 170 174
+ timothy 158b 174 201
ADF Weedy 356b 332 318
+ bromegrass 368b 337 318
+ orchardgrass 4313 331 313
+ timothy 356b 326 318
NDF Weedy 476C 465b 47%
+ bromegrass 544b 475b 454b
+ orchardgrass 699a 5153 5203
+ timothy 53 lbc 470b 454b

 

‘ CP, crude protein; ADF, acid detergent fiber; NDF, neutral detergent fiber.
" Means within a column and characteristic followed by the same letters are not significantly different
(P<0.05).

96

Table 4. Forage quality characteristics four years after seeding (1994).

 

 

 

 

 

Harvest
Characteristic Alfalfa 1 2 3
g kg"
CP‘ Weedy 167ab 189 186
+ bromegrass 146b 181 186
+ orchardgrass 138b 180 172
+ timothy 138b 176 194
ADF Weedy 288C 295 247b
+ bromegrass 3483 318 2803b
+ orchardgrass 3523 325 3053
+ timothy 321b 302 2813b
NDF Weedy 391b 414 358b
+ bromegrass 5523 470 4423b
+ orchardgrass 5573 477 4983
+ timothy 5353 432 4323b

 

' CP, crude protein; ADF, acid detergent fiber; NDF, neutral detergent'fiber.

b Means within a column and characteristic followed by the same letters are not significantly different

(P<0.05).

APPENDIX

97

Table A 1. Soil fertility at seeding.

 

 

 

 

 

Low weed pressure High weed pressure

Characteristics 1993 1 994 1 993 1 994
kg ha"

Phosphorus 46 76 1 05 12 1
Potassium 224 170 3 14 367
Calcium 3405 3666 4527 4480
Magnesium 521 566 68 l 660
pH 7.5 7.5 7.1 7.4
Texture loam loam loam loam

 

Table A2. Fertilization information.

 

 

 

 

 

 

 

Low weed pressure High weed pressure
Fertilizer kg/ha 1993 seeding 1994 seeding 1993 seeding 1994 seeding
1993
0-14-42 448 10 May - - -
1994
0-0-60 392 11 April - 11 April - -
0-0-60 134 - 5 May 1 April 5 May
1995

 

 

0-14-42 392 1 April 1 April 1 April 1 April

98

Table A3. Component percentages in the seeding year (average of 1993 and 1994 seedings) with low weed
pressure.

 

 

 

 

 

 

 

Harvest
1 2
Oat
Component Alfalfa absent present absent present
% of total dry matter
Alfalfa Weed free 100 2.4 100 100
Weedy 31.7 1.7 60.2 81.2
+ bromegrass 27.6 2.4 58.6 75.2
+ orchardgrass 29.6 1.4 49.1 77.6
+ timothy 29.] 1.2 60.5 74.7
+ Kentucky bluegrass 25.2 1.7 57.4 83.1
Grass + bromegrass 21.5 0.2 21.1 9.4
+ orchardgrass 4.1 0.1 25.7 15.7
+ timothy 7.9 0.2 20.6 7.4
+ Kentucky bluegrass 1.2 0.0 4.5 0.9
Weeds Weedy 68.3 3.4 39.8 18.8
+ bromegrass 50.9 1.2 20.3 15.4
+ orchardgrass 66.3 1.7 25.2 6.7
+ timothy 63.0 2.9 18.9 17.9
+ Kentucky bluegrass 73.6 2.6 38.1 16.0

Oats Weed free - 97.6 - -
Weedy - 94,9 - -
+ bromegrass - 96.2 - -
+ orchardgrass - 96.8 - , -
+ timothy - 95.7 - -

+ Kentucky bluegrass - 95.7 - -

 

99

Table A4. Component percentages in the seeding year (average of 1993 and 1994 seedings) with high
weed pressure.

 

 

 

 

 

 

 

Harvest
1 2
Oat
Component Alfalfa absent present absent present
% of total dry matter
Alfalfa Weed free 100 1.5 100 100
Weedy 7.9 1.1 65.8 88.3
+ bromegrass 7.6 1.0 58.5 82.9
+ orchardgrass 8.5 1.5 51.4 87.3
+ timothy 7.7 1.0 57.4 83.1
+ Kentucky bluegrass 7.6 1.4 51.9 86.9
Grass + bromegrass 3.4 0.2 1 1.2 2.8
+ orchardgrass 0.9 0.4 9.5 2.6
+ timothy 1.5 0.2 8.5 2.9
+ Kentucky bluegrass 0.2 0.1 1.0 0.5
Weeds Weedy 92.1 3 .6 34.2 1 1.7
+ bromegrass 89.0 4.4 30.3 14.3
+ orchardgrass 90.6 4.8 39.1 10.1
+ timothy 90.8 4.7 34.1 14.0
+ Kentucky bluegrass 92.2 3.8 47.1 12.6

Oats Weed free - 98,5 - -
Weedy - 95,3 - -
+ bromegrass - 94,4 - -
+ orchardgrass - 93.3 - . -
+ timothy - 94,1 - -

+ Kentucky bluegrass - 94.7 - -

fl

100

Table A5. Component percentages in the year after seeding (average of 1993 and 1994 seedings) with low
weed pressure.

 

Harvest

 

Component Alfalfa l 2 3 4

 

 

 

% of total dry matter

Alfalfa Weedy 98.6 97.6 98.7 99.1
+ bromegrass 71.1 91.3 93.2 93.0
+ orchardgrass 62.8 77.7 75.4 72.7
+ timothy 74.1 94.9 98.1 98.0
+ Kentucky bluegrass 89.1 87.9 88.0 85.8
Grass + bromegrass 26.0 8.1 5.5 6.0
+ orchardgrass 36.7 21.9 24.5 27.3
+ timothy 25.3 4.7 1.3 1.5
+ Kentucky bluegrass 10.2 11.7 11.3 14.1
Weeds Weedy 1 .4 2.4 1 .3 0.9
+ bromegrass 2.9 0.6 1.3 0.9
+ orchardgrass 0.5 0.4 0.1 0.1
+ timothy 0.6 0.4 0.6 0.5

+ Kentucky bluegrass 0.7 0.4 0.7 0.1

101

Table A6. Component percentages in the year after seeding (average of 1993 and 1994 seedings) with high
weed pressure.

 

Harvest

 

Component Alfalfa 1 2 3 4

 

 

 

% of total dry matter

Alfalfa Weedy 96.7 98.6 98.5 99.3
+ bromegrass 80.3 94.7 95.8 98.0
+ orchardgrass 75.4 81.8 81.2 82.5
+ timothy 79.7 94.7 98.4 98.9
+ Kentucky bluegrass 92.5 90.5 94.3 93.5
Grass + bromegrass 17.1 4.6 2.4 1.6
+ orchardgrass 24.0 17.6 18.4 17.3
+ timothy 18.7 4.8 0.9 0.7
+ Kentucky bluegrass 5.8 8.8 5.1 5.5
Weeds Weedy 3.3 1 .4 1 .5 0.7
+ bromegrass 2.6 0.7 1.8 0.4
+ orchardgrass 0.6 0.6 0.4 0.2
+ timothy 1.6 0.5 0.7 0.4

+ Kentucky bluegrass 1.7 0.7 0.6 1.0

 

102

Table A7. Component percentages two years after seeding (1993 seeding only) with low weed pressure.

 

 

 

 

 

Harvest
Component Alfalfa 1 2 3 4
% of total dry matter

Alfalfa Weedy 96.2 97.7 97.1 98.7
+ bromegrass 95.3 96.8 98.1 98.8
+ orchardgrass 67.3 73.4 72.1 58.9
+ timothy 96.3 98.2 98.2 98.2
+ Kentucky bluegrass 86.5 87.4 81.8 61.4

Grass + bromegrass 1.3 0.2 0.2 0.5
+ orchardgrass 32.4 26.3 27.9 41.0
+ timothy 0.3 0.1 0.4 0.6
+ Kentucky bluegrass 13.2 12.4 18.1 38.5

Weeds Weedy 3.8 2.3 2.9 1.3
+ bromegrass 3.4 3.0 1.7 0.7
+ orchardgrass 0.3 0.3 0.0 0.1
+ timothy 3.4 1.7 1.4 1.2

+ Kentucky bluegrass 0.3 0.2 0.1 0.1

 

103

Table A8. Component percentages two years after seeding (1993 seeding only) with high weed pressure.

 

 

 

 

 

Harvest
Component Alfalfa 1 2 3 4
% of total dry matter

Alfalfa Weedy 95.1 96.6 96.7 98.0
+ bromegrass 94.6 94.2 98.0 96.4
+ orchardgrass 61.4 68.7 72.4 68.2
+ timothy 95.4 96.8 99.4 99.2
+ Kentucky bluegrass 85.2 88.9 87.5 75.4

Grass + bromegrass 1.4 1.4 0.6 0.6
+ orchardgrass 38.5 31.0 27.6 31.7
+ timothy 1.9 0.9 0.2 0.1
+ Kentucky bluegrass 14.3 9.7 12.4 24.5

Weeds Weedy 4.9 3.4 3.3 2.0
+ bromegrass 4.0 4.4 1.4 3.0
+ orchardgrass 0.1 0.3 0.0 0.1
+ timothy 2.7 2.3 0.4 0.7

+ Kentucky bluegrass 0.5 1.4 0.3 0.1

104

Table A9. Component percentages three years after seeding (1993).

 

 

 

 

 

Harvest
Component Alfalfa 1 2 3
% of total dry matter

Alfalfa Weedy 85.5 92.2 79.3
+ bromegrass 73.8 85.9 81.9
+ orchardgrass 25.9 56.9 50.0
+ timothy 58.5 85.4 83.1

Grass Weedy - - -
+ bromegrass 15.7 3.9 11.3
+ orchardgrass 72.7 43.0 48.9
+ timothy 35.8 10.4 10.9

Total weeds Weedy 14.5 7.8 20.7
+ bromegrass 10.5 10.2 6.8
+ orchardgrass 1.4 0.1 1.1
+ timothy 5.7 4.2 6.0

Broadleaves Weedy 9.4 2.8 4. 1
+ bromegrass 4.6 0.6 3.2
+ orchardgrass 0.5 0.0 0.8
+ timothy 4.8 3.1 2.0

Grass weeds Weedy 5.1 5.0 16.6
+ bromegrass 5.9 9.6 3.6
+ orchardgrass 0.9 0.1 0.3
+ timothy 0.9 1.1 4.0

 

105

Table A10. Component percentages four years after seeding (1994).

 

Harvest

 

Component Alfalfa 1 2 3

 

 

---------------—-- % of total dry matter

Alfalfa Weedy 76.9 72.2 51.3
+ bromegrass 40.5 65.1 51.8
+ orchardgrass 26.5 67.5 41.7
+ timothy 38.7 79.7 30.4
Grass Weedy - - -
+ bromegrass 39.9 18.2 1 1.6
+ orchardgrass 73.1 29.9 53.5
+ timothy 47.6 4.2 23.4
Total weeds Weedy 23.1 27.8 48.7
+ bromegrass 19.6 16.7 36.6
+ orchardgrass 0.4 2.6 4.8
+ timothy 13.7 16.1 46.2
Broadleaves Weedy 10.7 15 .7 21 .3
+ bromegrass 5.3 8.4 21.7
+ orchardgrass 0.3 1.6 3.4
+ timothy 13.7 8.3 21.3
Grass weeds Weedy 12.4 12.1 27.4
+ bromegrass 14.3 8.3 14.9
+ orchardgrass 0.1 1.0 1.4

+ timothy 0.0 7.8 24.9

 

- ‘ I!.-...""'!l.

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