:> ION BULLETIN 526 April, 1983

>5io.„ BIO SCI

/lo

526

LIBRARY

SOD SEEDING OF FORAGES
II. Vegetation Control

by
G.W. Mueller-Warrant, D.W. Koch, and J.R. Mitchell

NEW HAMPSHIRE

AGRICULTURAL EXPERIMENT STATION

UNIVERSITY OF NEW HAMPSHIRE

DURHAM, NEW HAMPSHIRE 03824

ISSN: 0077-8338

Urtlversity of New Hampshire Library

• ION BULLETIN 526 April, 1983

H^h BIO SCI

'""' LIBRARY

SOD SEEDING OF FORAGES
II. Vegetation Control

by
G.W. Mueller- Warrant, D.W. Koch, and J.R. Mitchell

NEW HAMPSHIRE

AGRICULTURAL EXPERIMENT STATION

UNIVERSITY OF NEW HAMPSHIRE

DURHAM, NEW HAMPSHIRE 03824

ISSN: 0077-8338
Urilversity of New Hampshire Library

ACKNOWLEDGEMENTS

The authors wish to thank Stephen Bunker, Kingman Farm Superintendent,
for his assistance in conducting the trials and Monsanto Co., Chevron
Chemical Co., and Rhom and Haas Co. for supplying herbicides used in the
trials.

Special thanks are due to Ralph Booth, Green Dream Farm, Lee;
Richard Bros., Green Gold Farm, Suncook; Dave Osborne, Pittsfield; Robert
Yeaton, Epson; and Sam Johnson, Northwood, N.H., for providing land and for
their cooperation in conducting the trials.

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opzn to att peA40Ki4 without fizgcuid to fiact, colon., ncvbional onJ.Q-in on. &z\.
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Employ HA.

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3 ^tDDD DDLlfi M7T7

ABSTRACT

One of the most important management decisions in planning a
sod seeding is the method of controlling vegetation. This report
highlights the results of a number of no-till seedings of alfalfa
into sod at several locations in southern New Hampshire from 1977
to 1980. Various herbicides, application dates, and rates were
studied in relation to seeding dates. Only fields with soil sufficiently
fertile for alfalfa production were selected for renovation.

Most consistent and effective control of grasses and broadleaf
weeds was achieved with spring application of glyphosate. A glyphosate
treatment in early May was superior to an application in mid-late May,
measured in terms of seedling density and first harvest forage and
alfalfa yield. Fall treatment with glyphosate gave adequate sod
control when vegetation was green and actively growing at time of
treatment. Pronamide was useful in controlling perennial grasses and
was most effective when three lbs/acre or more were applied in the
fall. It did not control broadleaf weeds . Treatment with pronamide
in the fall, followed by paraquat at time of seeding, improved
alfalfa establishment over that from either herbicide alone. Paraquat
provided adequate suppression of vegetation only with split fall and
spring or split application in the spring.

Existing (old) alfalfa was more easily controlled with glyphosate
when it was 10-12 inches in height (mid-May) than earlier. When seeding
was within a few days after treatment, establishment generally improved
with glyphosate rate up to 2.0 lbs/acre; 1.33 lbs/acre was adequate if
applied at least two to three weeks before sod seeding.

Delaying application of glyphosate until near seeding time
resulted in decreased seedling density and decreased alfalfa yields,
in most cases. Alfalfa was most adversely affected by seeding immediately
after herbicide treatment on moderately well-drained and poorly
drained soils. On extremely well-drained (sandy) soils, alfalfa seeded
soon after treatment with glyphosate established as well as when treated
earlier.

KEY WORDS: No Till seeding. Reduced tillage. Alfalfa establishment,
Glyphosate, Pronamide, Paraquat, 2,4-D, Seeding date,
Quackgrass control.

Table of Contents

Page

INTRODUCTION 1

LITERATURE REVIEW 2

MATERIALS AND METHODS 4

RESULTS AND DISCUSSION 6

Control of grasses 6

Control of existing alfalfa 9

Control of broadleaf weeds 11

Timing of herbicide treatment in 12
relation to seeding

CONCLUSIONS 16

REFERENCES 17

11

SOD SEEDING OF FORAGES. II. VEGETATION CONTROL
G. W. Mueller-Warrant, D. W. Koch, and J. R. Mitchell-

INTRODUCTION
With the recent development of new herbicides and no-tillage
seeding equipment there is an opportunity for timely introduction of
legumes in order to sustain high productivity of hay land and pastures.
Alfalfa is the most productive legume in the Northeast when grown on
soils which are well drained and highly fertile. It is often used as
a comparatively inexpensive source of home-grown protein for dairy
animals. While alfalfa is a relatively long-lived crop, periodic
renovation of stands is necessary to maintain maximum yields and
quality. Much of the land in forage production in the Northeast is
rocky and/or steep. Difficulties in renovating and delayed re-
seeding lead to alfalfa thinning and grass domination of the stand.

One alternative to complete renovation is application of nitrogen;
however, the currently high cost of nitrogen and the relative
unresponsiveness of weedy grasses limit the value of this method. There
is a need for reliable methods of introducing legumes without tillage.

— Formerly Graduate Research Assistant, Associate Professor, and Associate
professor, respectively. Plant Science Department, University of New
Hampshire, Durham, N.H. 03824. Senior author is now Assistant Professor,
South Central Kansas Experimental Field, Route 2, Hutchinson, KS 67501.

LITERATURE REVIEW

Van Keuren and Triplett (21) noted that it is necessary to
reduce grass competition with herbicides during no-till establish-
ment of alfalfa seedlings. Other researchers have made successful
no-till seedings of alfalfa without herbicides, but have found it
necessary to reduce grass competition by repeated clipping of the
grass just above the legume seedlings (19).

Paraquat at 0.25 to 0.5 lbs/acre has been widely used to desic-
cate and destroy emerged vegetation prior to no-till seeding of
many crops (20). Paraquat is most effective on sods dominated by the
less vigorous species, such as Kentucky bluegrass, timothy, and red
fescue (22) ,

Grasses can be controlled with pronamide at rates of 2 to 3
lbs/acre. Pronamide is absorbed entirely through the root system
and is subject to chemical degradation in the soil at temperatures
above 50F (16) . It is therefore most effective if applied in late
fall and moved into the soil by rainfall before the ground freezes.

Glyphosate provides nearly complete kill of most herbaceous
perennial species at rates of 1.0 to 3.0 lbs/acre when applied to
the foliage and translocated throughout the plant during periods of
active growth (1,17). Quackgrass in the spring is not adequately con-
trolled by glyphosate until the three- to four-leaf stage (6 inches) ,
when the quackgrass shoot directs most of its carbohydrates to the
rhizomes. Under these conditions glyphosate will destroy the regener-
ative potential of rhizome nodes (15). Previous research (3,10,18)
has shown some advantage in delaying seeding as much as one month
following glyphosate application. Delayed seeding, compared to

seeding immediately after treatment, was associated with: (1) more

2
alfalfa seedlings per ft , (2) faster development of alfalfa seedlings,

(3) greater alfalfa yield at the first harvest, and (4) greater density

of alfalfa plants the year after seeding. Following the application of

glyphosate, Moshier and Penner (9) noticed injury to seedlings when the
decaying vegetation collapsed onto them. Both Moshier and Penner (9)
and Campbell (3) found negative effects of glyphosate on establishment
of sod-seeded alfalfa when application rate increased beyond 2.0 lbs/acre
and when treatment and seeding dates were in close proximity. They
felt that emerging alfalfa seedlings might be absorbing glyphosate
through contact with treated litter on the soil surface. However,
glyphosate applied at rates as high as 60 lbs/acre to the soil has not
been found toxic to plants (1) .

Successful establishment of alfalfa is favored by a minimum of
competition from weeds or companion small grains during the late
spring and early summer, especially if moisture is limiting (11) . Taylor
et al. (19) found that minimum-tillage seedings in the spring were
more often successful than late-summer seedings, which were superior to
mid-summer seedings.

METHODS AND MATERIALS

Sod seedings of 'Saranac' alfalfa at 12 lbs/acre were made
in 1977-79 at the locations shown in Table 1. In 1978 and in 1979
a John Deere Powrtill seeder was used to seed into vegetation mowed
to a 2-inch stubble height after herbicide treatment. A Tye Pasture
Pleaser seeder was used for the 1979 seedings in vegetation left in place
after herbicide treatment. Herbicides evaluated included pronamide
[3,5-dichloro (N-1, l-dimeyhyl-2-propnyl benzamide], paraquat
(l,l'-dimethyl-4,4'-bipyridinium ion), glyphosate [N- (phosphonomethyl)
glycine], and 2 , A-dichlorophenoxy acetic acid. Carbofuran (2, 3-dihydro-
2,2'-dimethyl-7-benzofuranyl methyl carbamate) was broadcast at 1.0 lb/acre
to all seedings soon after alfalfa seedling emergence. All treatments
were replicated from 3 to 5 times.

All fields renovated had previously been seeded conventionally to
alfalfa. Stands had eventually become dominated by various cool-
season grasses. All sites had pH values between 5.7 and 6.4 and med-
ium to very high levels of available phosphorus (Table 1) . Phosphorus
was surface applied prior to no-till seeding to raise the soil test
response of the surface 4 inches to very high levels. Potassium was
applied in accordance with expected crop removal the year following
seeding.

Seedlings were counted 3 to 7 weeks after seeding in randomly

2
chosen 1 ft areas within each plot. Swaths 3 ft wide across each

plot were harvested and weighed, and subsampled in order to determine

percentage dry matter. Species composition of forage was determined

by hand separation of subsamples in 1977, and was visually estimated

for all harvests taken from 1978 to 1980. Percentage ground cover by

alfalfa was visually estimated at three to four weeks after harvest

during the year following seeding.

Mention of a commercially available product is for the benefit of the
reader and does not imply endorsement by the New Hampshire Agricultural
Experimental Station.

Table 1. Descriptions of fields used in no-till alfalfa studies.

Species present prior

Soil to treatment, %

Location Cooperator Series pH P ALF QG SBG OR TI KBG BW

Madbury Univ. N.H. Charlton 6.2 VH

Lee R. Booth Hollis 5.7 H

Pembroke Richard Bros . Merrimac 6.1 VH

Lee Univ. N.H. Charlton 6.4 L-M 45

Epsom R. Yeaton Hinckley 6.2 H

Pittsfield D. Osborne Paxton 6.6 H

Northwood S. Johnson Paxton 6.1 M

ALF = alfalfa, QG = quackgrass, SBG = smooth bromegrass, OR = orchardgrass,
Tl = timothy, KBG = Kentucky blue grass, and BW = broadleaf weeds. Sward
composition was judged in the fall of the year in which treatments were
initiated.

L,M,H,VH denote low, medium, high and very high levels, respectively, of

0

90

0

0

0

5

5

0

5

0

65

0

10

20

65

20

0

0

0

0

15

45

25

25

0

0

5

0

20

20

60

0

0

0

0

0

5

10

25

20

25

10

0

15

10

0

20

15

35

soil available phosphorus (P)

RESULTS AND DISCUSSION

Control of grasses

As shown in Table 1, all stands except the one at Pembroke, were
dominated by grasses. Quackgrass, bromegrass, and orchardgrass were the
most aggressive species present. At all locations at least one of these
species was present in significant amounts when the experiments were initiated.

The response to fall-applied glyphosate at various rates is shown
in Table 2. Good control of grasses was obtained when glyphosate was
applied at 1.0 to 3.0 lbs/acre to green growth at least five inches high.

At Northwood, dry weather in late summer-early fall of 1978, in
combination with the low soil fertility, caused the grasses to be
yellow and brown in color in September and October. Grasses in this
condition were unaffected by glyphosate, even at the highest rate used.
At Epsom, the field had been closely grazed in September of 1978.
Glyphosate at 2.5 lbs/acre was needed for 50% control of grasses on
October 23, whereas on November 13, when the grass had reached 4-5
inches, only 1.1 lbs/acre of glyphosate was needed for comparable grass
control. This is evidence that previous management and soil conditions
can affect response to glyphosate.

The rate of fall-applied glyphosate necessary to provide good
control of grasses varied with site and year, probably due to differ-
ences in translocation of the herbicide from the leaves into the root
system, which would be influenced by amount of leaf area present and
the photosynthetic activity of leaves. Control of healthy cool-season
grasses has been reported to improve slightly when glyphosate was applied
immediately following a light frost (4) .

The effectiveness of pronaraide was influenced more by rate of
application than by condition of grasses at time of treatment (Table 3).
This is expected since pronamide enters plants through the roots only (16).
Pronamide at 3.0 lbs/acre was needed to adequately control vigorous

Table 2, Grass control and alfalfa establishment from fall-applied
glyphosate at seven locations.

Grass

Rate

i of

Grass

Alfalfa content.

condition

glyphosate

control

first

harvest

It

)s/acre

%

0.6

to

1.0

62

62

Yellow-green

I to

1.2

to

1.6

65

62

green, more

than

1.9

to

2.3

85

73

5 inches growth

2.5

to

3.1

82

69

0.6

to

1.0

1

24

Green with

less

1.2

to

1.6

0

29

than 4 inches

1.9

to

2.3

25

44

growth

2.5

to

3.1

58

57

Yellow to

0.6

to

1.0

0

2

1.2

to

1.6

4

3

brown

1.9

to

2.3

3

8

2.5

to

3.1

10

12

^Seedings were made on April 25 and May 3 at Epsom. Grass was extremely
short when treated in the fall due to grazing in September.

Sod at Northwood was subject to late summer drought. Seeding made on
May 28.

grasses such as quackgrass, bromegrass, and orchardgrass . The addition
of paraquat at time of seeding to pronamide treatment the previous fall
was a reliable method for establishing alfalfa although, in some
instances, it was slightly less satisfactory than spring-applied gly-
phosate.

Glyphosate applied in the spring generally controlled grasses
better than when applied in the fall at equal rates (Tables 2 and 4).
Control of grasses improved, at all locations, with increases in glyphosate
rates from 0.7 to 1.3 lbs/acre (Table 4). At some locations, grass con-
rol improved with increases in glyphosate rates from 1.3 to 2.0

Table 3. Grass control and alfalfa establishment with pronamide and

1 . a
paraquat at seven locations.

Treatment

Herbicide

Rate

Grass
control

Alfalfa content,
first harvest

Pronamide

Pronamide

Pronamide

Pronamide
+Paraquat

lbs/acre

1.0

2.0 - 2.2

3.0 - 3.3

2.0 - 2.2
0.25 - 0.50

33
64
86

86

38
59
71

78

Grasses were yellow-green to green and at least 5 inches high when
treated. Ten seedings were made at five different locations.

Table 4. Responses to spring-applied herbicides at seven locations,

Treatment

Herbicide

Rate

Grass percentage. Alfalfa percentage,
first harvest spring following seeding

Avg.

Range

Ave.

Range

Glyphosate

Glyphosate

Glyphosate

Glyphosate

Paraquat

Split paraquat

Pronamide (fall)
+ Paraquat (spring)

lbs/acre
0.7 to 1.0
1.3 to 1.5

2.0

2.7

0.5

0.25 + 0.25

2.0
0.25

42

28 -

56

24

9 -

38

12

5 -

20

18

7 -

29

70

55 -

84

54

39 -

69

17

7-26

57

45 -

68

68

57 -

79

82

73 -

91

73

65 -

80

54

35 -

72

47

34 -

60

73

64 - 82

lbs/acre. Even 0.7 lbs/acre was often sufficient to cause injury to
nearly all grass topgrowth. However, considerable regeneration from
underground growing points occurred at rates under 1.0 lbs/acre. The
somewhat better grass control obtained with 2.0 lbs/acre of glyphosate
generally did not improve alfalfa establishment over that from rates
of 1.3 to 1.5 lbs/acre, although it did slightly increase the ratio of

alfalfa to grass in the stand. Substantial variation with location
occurred in response to spring-applied herbicides (Table 4) . Grass
percentage of forage at the first harvest varied by a factor of
four times with glyphosate rates between 1.3 and 1.5 lbs/acre.

Successful establishment of alfalfa was more consistently obtained
with glyphosate than with paraquat. On average, paraquat resulted in
establishment of an alfalfa percentage similar to that from 0.7 lbs/
acre of glyphosate (Table 4) . Split application of paraquat was more
effective than single application on quackgrass and orchardgrass.
Paraquat was also effective as a followup treatment of plants recovering
from pronamide treatment, or to temporarily suppress, without sacrificing
desirable species such as alfalfa.

Control of existing alfalfa

At Pembroke, where there was a relatively dense stand of alfalfa,
an attempt was made to maintain existing (old) alfalfa plants, yet enhance
establishment of new alfalfa seedlings by reducing grass and weed pressure,
Pronamide, applied in the fall, killed grasses and left old alfalfa
plants unharmed, but few new alfalfa plants established (Table 5) .
Treating with 2,4-D, followed with pronamide, injured or killed much
of the old alfalfa, as well as controlling grasses, but relatively
little alfalfa was established. Glyphosate applied November 16 had
a similar effect. At that time alfalfa had gone dormant, as indicated
by drooping stems and yellow and white leaves. Glyphosate applied
November 1, however, controlled nearly all of the old alfalfa. It
was the only treatment with a significant amount of newly established
alfalfa and with which alfalfa stands were improved over those initially
present.

At Lee (University of New Hampshire) fall-applied glyphosate did not
affect the existing alfalfa, which appeared to be dormant at time of
treatment (Table 6). Old alfalfa at Lee survived treatment with 0.7 lbs/
acre of glyphosate on May 2. Higher rates of glyphosate were required to
control old alfalfa on May 2 than on May 16. Apparently, translocation
patterns were more favorable, at this location, in mid-May.

10

Table 5. Control of existing alfalfa with fall-applied herbicides
and establishment of new alfalfa with spring sod seeding
at Pembroke.^

Treatment

Alfalfa
first

percentage,
harvest

Alfalfa
ground

Herbicide

Date

Rate

Old

New

cover, 1980

lbs/acre

%

Glyphosate

Nov.

1

2.0

10 c

47 a

79 a

Glyphosate

Nov.

16

2.0

52 b

10 b

54 b

Pronamide

Nov.

16

2.0

85 a

1 c

46 b

2,4-D +

Pronamide

Nov.
Nov.

1
16

1.4
2.0

A3 b

9 b

45 b

^eans followed by the same letter within a column for a single location
do not differ at the 5% level.

Table 6. Control of existing alfalfa with herbicides and establishment
of new alfalfa with spring sod seeding at Lee (University of
New Hampshire).^

Treatment

Alfalfa
first

percent
harvest

;age,

7

Alfalfa
ground

Herbicide

Date Rate

Old

Nev

cover, 1980

lb

s/acre

%

Glyphosate

Oct. 28

2.0

84

a

10

C

50 cde

Pronamide

Nov. 17

3.0

81

a

8

C

58 bed

Glyphosate

May 2

0.7

28

c

35

b

48 de

Glyphosate

May 2

1.3

4

d

81

a

60 be

Glyphosate

May 16

0.7

0

e

45

b

43 e

Glyphosate
+ Glyphosate

Oct. 28

May 2

1.3
0.7

56

b

37

b

64 ab

Glyphosate
+ Glyphosate

Oct. 28
May 16

1.3
0.7

2

de

91

a

79 a

Means followed by the same letter within a column do not differ at the
5% level.

11

Control of Broadleaf Weeds

At locations with perennial broadleaf weeds, 2,4-D and/or dicamba
(3, 6-dichloro-o^-anisic acid) was applied early in the fall preceding
the planned no-till seeding.

Broadleaf weed control from these herbicides was usually very
satisfactory, however, at Northwood, where dandelions were abundant,
2,4-D + dicamba applied in the fall before seeding failed to provide
control due to weed dormancy at time of treatment. This was probably
induced by the cool, dry weather and the relatively low soil fertility.
These herbicides can also be applied in the spring, allowing 3 to 4 weeks
for deactivation in the soil before seeding. While application of 2,4-D
one day after seeding gave better control of dandelions than did
application of paraquat, 2,4-D was excessively toxic to alfalfa
seedlings (Table 7) .

At Pitts field, the judgment that the number of broadleaf weeds
were insufficient to justify application of 2,4-D in the fall proved to
be in error. On plots treated in the fall with grass-killing herbicides,
such as pronamide and glyphosate, dense growth of perennial broadleaf
weeds occurred. Glyphosate, applied in the spring, however, gave excellent
control of these weeds.

Table 7. Effects of spring-applied 2,4-D and paraquat on a 1979 sod
seeding of alfalfa at Northwood, N.H.

Alfalfa Dandelion Alfalfa yield.

Herbicide seedling yield, spring following

density Oct. 22 seeding

2

No. /ft lbs/acre ■ tons/acre

Paraquat 6.7 304 0.96

2,4-D 2.7 232 0.49

LSD (.05) 2.0 62 0.32

12

Timing of herbicide treatment in relation to seeding

Glyphosate applied in early May and followed by a mid to late-May
seeding resulted in highest seedling densities and alfalfa yields in
1979 (Tables 8 and 9). Treatment just prior to seeding in late May was
much less suitable. In all seedings made from 1977 to 1980 treatment
early in May with seeding delayed 2-3 weeks resulted in higher yields
of alfalfa the first harvest than did treatment later in May with the
same seeding date (Table 9) . First harvest yields of seedings made in
1979 were lower than those in 1977 due to a virtual lack of rainfall
from early June through July. The best alfalfa ground cover ratings
were obtained with the combination of early treatment and mid-to late-
May seeding (Table 10). By the second year, however, there was little
difference among treatment date/seeding date combinations in alfalfa
yield. These results are in agreement with previous research results,
which indicate that there is an advantage to delayed seeding following
glyphosate application (3,10,18).

Table 8. Effects of glyphosate application and seeding dates on alfalfa
seedling density at four locations.

Glyphosate Seeding Alfalfa seedling density by location

applications date Madbury Lee Pittsfield Northwood

Fall Early May

Fall Mid- late May

Early May Early May

Early May Mid- late May

Mid- late May Mid- late May

Means followed by the same letter within a column do not differ at the
5% level.

Seedling counts were made one month after seeding and are averaged over
glyphosate rates of 1.3, 2.0, and 2.7 lbs/acre, except at Madbury, which
received only 2.0 lbs/acre.

no.

Vft^

X

6.3 be

12.7 b

X

X

14.2 a

16.4 a

4.5 b

29.0 a

4.2 c

8.6 c

X

27.9 a

12.4 a

15.7 a

6.1 a

15.6 b

8.2 b

14.2 ab

2.2 c

13

Table 9. Effect of seeding date In relation to glyphosate application
on first-harvest yield of alfalfa at four locations.

Glyphosate Seeding Alfalfa yield by location

application date Madbury Lee Pittsfield Northwood

tons/acre

Fall Early May x 0.17 cd 0.41 be x

Fall Mid- late May x 0.10 d 0.30 c 0.00 c

Early May Early May 1.10 a 0.26 b 0.38 be x

Early May Mid- late May 0.90 a 0.39 a 0.54 a 0.16 a

Mid- late May Mid- late May 0.64 b 0.22 be 0.44 b 0.06 b

"Means followed by the same letter within a column do not differ at the
5% level.

Alfalfa yields are for the first harvest and are averaged over glyphosate
rates of 1.3, 2,0, and 2.7 lbs/acre, except at Madbury, which received
only 2.0 lbs/acre.

Table 10. Effect of seeding date in relation to glyphosate application
on ground cover ratings of alfalfa at four locations.

Glyphosate

Seeding
date

Alf,

alfa

ground

cover by location

application

Madbury

Lee

Pittsfield

Northwood

- % ground

Fall

Early May

X

53 be

69 b

X

Fall

Mid- late May

X

49 c

69 b

5 c

Early May

Early May

100 a

48 c

93 b

X

Early May

Mid- late May

95 ab

67 a

86 a

43 a

Mid- late May

Mid- late May

80 b

62 ab

82 ab

14 b

r^eans followed by the same letter within a column do not differ at the 5% level

Ratings of alfalfa ground cover were made three to four weeks following harvest
during the seeding year and are averaged over glyphosate rates of 1.3, 2.0,
and 2.7 lbs/acre, except at Madbury, which received only 2.0 lbs/acre.

14

Fall application of glyphosate generally resulted in similar or
higher seedling densities than those from spring treatments (Table 8) .
With fall-applied herbicides, establishment and first-harvest yields
were usually better with an earlier, compared with a later, spring
seeding date (Tables 8-10). This was due, in part, to the effects of
competition from the surviving species on alfalfa seedlings. Seed-
lings would obviously be smaller and more vulnerable to competition
if seeded later in the spring since the surviving weeds will begin
spring growth without regard to the date the alfalfa was seeded. Fall-
applied glyphosate with a followup application in late May, 1980,
produced a stand better than that from any other treatment at Lee
(79% ground cover rating, vs. 67% gound cover for the next best treat-
ment). Baird, et al. (1) reported superior control of quackgrass when a
given amount of glyphosate was split-applied between the fall and spring,
rather than in one application.

The advantage of delaying seeding following spring treatment must
be weighed against the likelihood that later seedings will encounter
summer dry periods, having had less time for seedlings to develop
root systems. An advantage of sod seeding, however, is that once
the sod is killed and left in place, moisture is effectively conserved,
in contrast to conventionally prepared seedbeds. This may allow for later
spring planting with sod seeding, compared with conventional seeding. Also,
by delaying spring seeding, surviving fall treatment and early germinating
annual weeds can be more effectively controlled. Early seeding in the
spring, made possible by fall application of herbicides would likely be
most beneficial on sandy, droughty soils.

Comparative results of an August and a late spring no-till seeding
in 1977 are shovm in Table 11. The August seeding in 1977 received less
than 0.4 inches of rainfall during the first two weeks after seeding,
in contrast to 1.7 inches for the June 4 seeding. Under conditions as
dry as those encountered by the August seeding, the value of glyphosate
in preventing moisture depletion by the sod is clearly evident. However,

15

since treating with glyphosate on May 30 and waiting until August to seed
would sacrifice forage production during the seeding year, such a program
seems impractical.

Table 11. Comparison of August and late spring no-till seeding of alfalfa
into dense quackgrass.

Treatment

Seeding

Herbicide Date date

Alfalfa content. Seasonal yields Alfalfa

standing
spring harvest Forage Alfalfa rating

Paraquat Aug. 8 Aug. 9

Glyphosate May 30 Aug. 9

Paraquat June 3 June 4

Glyphosate May 30 June 4

%

3 d

49 b

27 c

97 a

— tons/acre —
1.6 c 0.1 c
2.9 b 1.8 b
2.4 b 1.3 b
4.0 a 3.9 a

% optimum

3 d

67 b

47 c

93 a

'lleans followed by the same letter within a column do not differ at the
5% level.

Total for the year following establishment .

'Based on visual ratings by two observers on alfalfa ground cover and vigor
two weeks following last seasonal harvest.

16

CONCLUSIONS

1. Suppression of such vigorous grasses as quackgrass, brome grass, and
orchardgrass was vital to successful establishment of no-till alfalfa.

2. Spring application of glyphosate consistently controlled existing vege-
tation, while fall application produced variable results.

3. Other successful methods for suppressing vegetation included: (a) split
application of paraquat fall and spring or split application in the
spring; (b) fall application of pronamide followed at time of seeding

by paraquat or a low rate of glyphosate; and (c) fall application of
glyphosate to green, healthy-looking vegetation.

4. Increased seedling numbers and increased yield of alfalfa at first
harvest were achieved by killing vegetation two or more weeks in
advance of seeding, compared with treatment just before seeding,
especially on moderately well-drained and poorly-drained soils.

5. The optimum rates of glyphosate were: (1) approximately 1.33 lbs/acre
in early May for delayed seeding; (2) 2.0 lbs/acre immediately before
seeding; and (3) 1.5 to 2.0 lbs/acre in the fall for early spring
seeding.

6. Fall application of glyphosate at 1.0 to 1.5 lbs/acre resulted in a
well decomposed sod at time of spring seeding. Following this ap-
plication with a treatment of 0.5 to 1.0 lbs/acre glyphosate just
prior to seeding in mid- late May (when shoots of surviving grass
plants were emerged) improved stands of alfalfa.

17

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18

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