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Pearl millet weed management systems for Georgia and Florida

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Title:
Pearl millet weed management systems for Georgia and Florida
Series Title:
Research report (North Florida Research and Education Center (Quincy, Fla.))
Creator:
Dowler, Clyde C
Teare, I. D ( Iwan Dale ), 1931-
Wright, D. L ( David L )
North Florida Research and Education Center (Quincy, Fla.)
Place of Publication:
Quincy Fla
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North Florida Research and Education Center
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English
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16 leaves : ; 28 cm.

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Subjects / Keywords:
Pearl millet ( lcsh )
Weeds -- Control ( lcsh )
City of Quincy ( flego )
Millet ( jstor )
Pearls ( jstor )
Herbicides ( jstor )
Genre:
bibliography ( marcgt )

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Bibliography:
Includes bibliographical references.
General Note:
Caption title.
Statement of Responsibility:
Clyde C. Dowler, David L. Wright and I. D. Teare.

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University of Florida
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All applicable rights reserved by the source institution and holding location.
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71188182 ( OCLC )

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/ 0,0-



NFREC Research Report 94-14

Iarst' o! Science
9/ / 1 PEARL MILLET WEED MANAGEMENT SYSTEMS FOR

GEORGIA AND FLORIDA 0 199
Clyde C. Dowler, David L. Wright and I.D. Teare i 00frid

ABSTRACT
Pearl millet is a potentially-productive, high-quality grain being developed
for the Southeastern United States. Published research on weed management
systems for pearl millet is virtually nonexistent. During the past several
years, field and greenhouse experiments have been conducted by the University of
Florida and USDA-ARS to evaluate herbicide and cultural practices, which would

effectively and economically control weeds, specifically annual grasses, in pearl
millet. Atrazine applied as early post-emergence was the most effective single
herbicide controlling a broad spectrum of weeds in pearl millet. Combinations

of Atrazine with Prowl and Ramrod or Ramrod with 2,4-D generally controlled grass
and broadleaf weeds and did not seriously injure pearl millet. Dual caused
moderate to severe pearl millet injuries and reduced yield. Conventional, no-
till, or stale seedbed preparation generally did not affect level of weed control
or pearl millet production. Cultural practices such as plant population and row
spacing can increase effectiveness of weed control systems in pearl millet.

Presently, there are no federally registered herbicides treatments for pearl
millet grown as grain. Utilizing no-till or stale seedbed techniques that use

Gramoxone Extra to kill existing vegetation before pearl millet emerges is an
effective, economical, and legal procedure.


C.C. Dowler; USDA ARS, Coastal Plain Exp. Stn., Tifton, GA 31793: D.L. Wright and

I.D. Teare. North Fla. Res. and Educ. Ctr., Quincy, FL 32351.










INTRODUCTION

Pearl Millet [Pennisetum glaucum (L.)] is a potentially-productive, high-

quality grain or silage crop (Burton et al., 1986 and Kumar et al., 1983). It

can be grown under relatively low-input management conditions with reduced

fertilizer and water application.

With the development of pearl millet as a potential grain crop for the

Southeastern U.S. there is an urgent need to develop weed management systems that

will result in improved quality and quantity of the grain produced. Presently,

there are only two herbicides, Banvel and 2,4-D, that are registered for use on

millet. There is no federally approved registration for these herbicides on

pearl millet as a grain crop. Banvel is registered under a special, local needs

(24C) permit in several western states for use on millet. The labeling of 2,4-D

suggest its use for forage crops, which would include millet. Therefore, the

registered use of these herbicides on pearl millet as a grain crop is unclear.

Weed pressures and diversity in the southeastern U.S. require development of

effective and efficient weed management systems for pearl millet. In addition

to a wide range of broadleaf weeds, annual grasses such as Texas panicum,

crabgrass, and crowfootgrass present major production problems for pearl millet.

Published research data on use of herbicides on pearl millet for grain is

virtually non-existent. The herbicides imazethapyr and nicosulfuron reduced

pearl millet grain yield 60 and 100 percent, respectively, compared to an

untreated check (Wright et al., 1993). Specific effects of herbicide stress on

pearl millet have only been reported in relation to head length (Pudelko, et al.,

1993).

The potential narrow herbicide selectivity range between annual grass weeds

and pearl millet presents a major problem in developing weed management systems.

Research in Florida and Georgia, during the past few years, has emphasized

systems that will selectively control annual grasses in pearl millet. The

objectives of developing weed management systems are to: 1) selectively control

annual grasses and broadleaf weeds in pearl millet; 2) develop low cost weed

control programs; 3) prevent potential injury and yield reduction from weed










management systems; and 4) provide efficacy data for potential registration of

herbicides or herbicide combinations for use in pearl millet.



METHODS AND MATERIALS

Weed control experiments in pearl millet were conducted under both

greenhouse and field conditions from 1988-1994. Pearl millet hybrid seed

HGM100, developed by the pearl millet breeding program of the USDA-ARS, Coastal

Plain Experiment Station, was used in all experiments.

The experiments were conducted on a Norfolk sandy loam or Tifton loamy sand

(fine, loamy, siliceous, thermic Typic Kandiudults) located at the North Florida

Research and Education Center, Quincy, Florida, and the Coastal Plain Experiment

Station, Tifton, Georgia, respectively.

Weed species varied from year to year, but included Texas panicum,

crabgrass, crowfootgrass, smallflower morningglory, morningglory spp., Palmer

amaranth, cocklebur, carpetweed, purple nutsedge, and yellow nutsedge. Crop

injury and weed control efficacy was determined by visual observation of each

plot with 0 = no effect and 100 = complete kill. Bird damage was devastating to

experimental plots, but yield on some experiments were measured in two ways: 1)

predicting grain yield by regression analysis from head lengths as reported by

Pudelko, et al., 1993 or 2) bagging of 10 heads/plot after pollination, allowing

the grain to mature and dry, weighing the threshed grain, and then converting the

yield data to lb/A based on the number of heads/acre.

In Florida, the no-till systems were established on land that had been

fallowed for one year. The experimental area was mowed and treated with

Gramoxone Extra to kill existing vegetation before planting pearl millet. In

Georgia, stale seedbed systems were established by preparing a conventional

seedbed and then delaying planting of pearl millet 10-14 days. This allowed the

first flush of weeds to emerge, which were killed by applying Gramoxone Extra at

planting.

Pearl millet was planted 0.75 to 1.0 inch deep in either 18 or 36 inch rows.

Herbicides were applied with a conventional boom sprayer, applying 20 gal/A at









approximately 30 PSI. Where necessary, a nonionic surfactant or crop oil

concentrate was used with post-emergence herbicides.

The herbicides used in these experiments are listed in Table 1.

The experiments were either a split plot or randomized complete block design

with three or four replications. Results were subjected to analysis of variance

and means were separated using Fisher's Least Significant Difference Test, at the

0.05 level of probability.



RESULTS AND DISCUSSION
Florida

Weed control for individual herbicide treatments was similar in till and

no-till systems in 1993 and 1994 (Tables 2, 3, 4, and 5). In 1993, the level of

control of both grass and broadleaf weeds was good to excellent (83-100 percent).

Treatments that included Atrazine controlled 95-100 percent of all broadleaf

weeds. The addition of a crop oil concentrate increased the activity of Atrazine

on grasses when compared to Atrazine alone. Herbicide combinations of Dual,

Ramrod, and Prowl with 2,4-D or atrazine did not significantly improve weed

control over Atrazine applied alone in 1993. In 1994, herbicide combinations of

Ramrod and Prowl generally improved grass control compared to Atrazine applied

alone. However, the level of broadleaf weed control was not improved by

herbicide combinations compared to Atrazine alone.

Treatments that included Dual or Ramrod caused moderate to severe pearl

millet injury in 1993. The data in Tables 2 and 3 show that Dual injured pearl

millet more than Ramrod. Herbicide treatments that included Prowl also caused

moderate injury to pearl millet. The injury ratings were recorded approximately

two to three weeks after herbicide treatment. As the growing season progressed,

pearl millet recovered from this herbicide injury as reflected in yield data in

Tables 2 and 3. Severe herbicide injury, caused by Dual, resulted in reduced

pearl millet yield, but the early pearl millet injury recorded in excess of 95

percent did recover and produced some grain in both conventional and no-till

systems. These data would indicate that herbicides in the same chemical family










as Dual should not be considered for use in pearl millet. The silage yield data

in 1994, reflected the same general trend in yield response to herbicides as the

1993 grain yield. The herbicide treatments applied to pearl millet in 1994

caused slight to moderate injury to pearl millet shortly after treatment, but the

crop completely recovered later in the growing season (data not shown). When

compared to yield data for the handweeded check, Dual, Atrazine at 2 Ibs/A,

Ramrod + 2,4-D at 2.25 + 0.45 lbs/A, and Prowl + Atrazine at 0.75 + 1.0 lb/A

reduced pearl millet silage yield (Table 4). In the 1994 no-till system, most

of the herbicide treatments resulted in significant reduction in pearl millet

silage yield, as compared to the handweeded check (Table 5).


Georgia

Control of grasses such as Texas panicum was a major concern for developing

weed control systems in pearl millet. Preliminary experiments in greenhouse and

under field conditions were directed to controlling grasses in pearl millet.

Previous experience in grain sorghum and corn indicated an early post-emergence

applications of Atrazine and/or Prowl would control seedling (1-2 leaf) Texas

panicum. Greenhouse experiments confirm that Atrazine or Atrazine + Prowl would

control seedling grasses, but could also significantly injure pearl millet. At

rates and timing normally used in field corn or grain sorghum, Atrazine in excess

of 1 lb/A to 2-3 leaf pearl millet caused moderate to severe injury, but

suppressed Texas panicum emerging or in the 1-2 leaf stage. Application of

Atrazine at 1 lb/A to 4-leaf pearl millet did not cause significant injury, but

did not control Texas panicum beyond the 1-2 leaf stage. Several greenhouse

experiments involving rates and timing of application with Atrazine in various

combinations confirmed these results (data not shown). In 1991, two field

demonstration plots treated early postemergence with Atrazine at 1 lb/A confirmed

greenhouse experiments (Table 6).

The growth habit of pearl millet dictated that cultural aspects of weed

management needed to be evaluated. This include plant population, row spacing,

and the concept of stale seedbed preparation. Preliminary greenhouse experiments









indicated that delaying pearl millet planting 10-14 days after seedbed

preparation and killing the existing vegetation at planting would be feasible.

In 1992, a field demonstration plot of pearl millet was planted in 18 and

36 inch row spacing and then treated with paraquat at 0.5 lb/A within 48 hours

of planting. Weed control observations, 14-21 days after planting, showed

overall weed control at 95%, which included weeds such as Texas panicum,

crabgrass, Smallflower morningglory, and Palmer amaranth.

At approximately 21 days after planting, canopy closure (overlapping the row

middles) of pearl millet planted in 18 inch rows occurred and provided shade and

competition for weeds for the remainder of the growing season. Pearl millet

planted in 36 inch rows required about 4 weeks after planting for canopy closure,

which provided an opportunity for some weeds to emerge and grow in the row

middles. The use of stale seedbed techniques utilizing Gramoxone Extra was very

effective and economical as a weed management program in pearl millet. A second

demonstration plot, in 1992, indicated that pearl millet planted in a stale

seedbed and treated with Gramoxone Extra at 0.25 lb/A at planting, followed by

Atrazine at 0.75 lb/A as an early post-emergence treatment was also very

effective in controlling a broad spectrum of annual weeds and that 18 inch row

spacing provided more shade and competition to weeds than 36 inch row spacing.

In 1993 and 1994, experiments evaluated selected post-emergence herbicide

treatments on pearl millet grown in conventional and stale seedbed (Tables 7, 8,

9 and 10). In 1993, the control of all weeds generally ranged from good to

excellent. Some treatments caused slight to moderate injury to pearl millet, but

pearl millet recovered by maturity. A direct comparison between conventional and

stale seedbed results could not be made because these were separate experiments,

but the data in Tables 7 and 8 indicate very little difference in the level of

weed control between seedbed preparation and specific herbicide treatments.

Yield data were not collected in 1993 because of severe bird damage.

In 1994, data in Tables 9 and 10 indicate a much higher level of weed

control in stale seedbed than in the conventional seedbed. Again, statistical

comparison could not be made because these are separate experiments. But, the










control of Smallflower morningglory and Palmer amaranth was much higher and more

consistent in the stale seedbed experiment. The type of seedbed preparation did

not appear to affect pearl millet yield (Tables 9 and 10). There was a general

trend for better weed control for pearl millet planted in 18 inch rows as

compared to pearl millet planted in 36 inch rows. Pearl millet canopy planted

in 18 inch rows closed (overlapped the row middles) about 7-10 days earlier than

pearl millet planted in 36 inch rows, which would provide greater competition to

the weeds present.

It was also observed in border areas outside the experimental plots that

weed control in the stale seedbed experiment was much higher than in the

conventional seedbed experiment.



REFERENCES
Burton, G. W., A. T. Primo, and R. S. Lowrey. 1986. Effect of clipping
frequency and maturity on the yield and quality of four pearl millets.
Crop Sci. 26:79-81.
Hanna, W. W. 1991. Pearl millet A potentially new crop for the U.S. In
Abstr. of Tech. Papers, No. 18, Southern Branch ASA, 2-6 Feb 1991, Ft.
Worth, TX.
Kumar, K. A., S. C. Gupta, and D. J. Andrews. 1983. Relationship between
nutritional quality characters and grain yield in pearl millet. Crop Sci.
23:232-234.
Pudelko, J. A., D. L. Wright, and I. D. Teare. 1993. A method for salvaging
bird damaged pearl millet research. Fla. Agric. Exp. Stn. Res. Rep. No.
NF 93-12:1-11.
Wright, D. L., I. D. Teare, F. M. Rhoads, and R. K. Sprenkel. 1993. Pearl
millet production in a no-tillage system. p. 152-159. In P. Bollich
(Ed.) 1993 Southern Cons. Tillage Conf. for Sustainable Agric.
June 15-17, Monroe, LA. SB 93-1.


TABLE 1. Herbicides evaluated on pearl millet in Florida and Georgia


Common Name Trade Name
atrazine Atrazine
bromoxynil Buctril
metolachlor Dual
paraquat Gramoxone Extra
pendimathalin Prowl
propachlor Ramrod
2,4-D Weedar-64





TA 2. Activity of selected herbicide treatments or arl millet and weeds in conventional seedbed.
Quincy, 1993


Percent Control


Treatment

Atrazinel

Atrazine
Atrazine"

Atrazine'
Dual + 2,4-D

Dual + 2,4-D
Dual + 2,4-D

Ramrod + 2,4-D

Ramrod + 2,4-D
Prowl + 2,4-D
Prowl + 2,4-D

Dual + Atrazine'
Dual + Atrazine*

Ramrod + Atrazine*
Ramrod + Atrazine*
Prowl + Atrazine'
Prowl + Atrazine"

Hand weed check

Non-treated

Non-treated

Ramrod

Prowl + Atrazine*
Prowl

Prowl + Atrazine*

LSD (0.05)


'Crop oil concentrate at 1 qt/A.


Rate
lb/A

1.5

2.0
1.5
2.0
1.0 + 0.5

1.5 + 0.5
2.0 + 0.5

3.0 + 0.5
4.5 + 0.5

0.5 + 0.5
0.75 + 0.5

1.0 + 1.0
1.5 + 1.0
3.0 + 1.0
4.5 + 1.0

0.5 + 1.0
0.75 + 1.0


Grass

83

88

94
95
88

99

100

94
90
100
95

100
100
99

99

95
93

100

0

0

94


99


Broadleaf

98

98

98

98
88

85
88

85

95
98
95

100
100
100
99
100

98

100
0

0

100


100


5


Percent
injury

9

15
25

20
81

95
96

33

43

21
16

95

100
64
59

13
25

0

0

0

0


0


8


Yield
lb/A

3016

2954

2675
2405
2435

1553

1506

3128

3202
3073

2806

1353
1612
2901
2544

2970
2877

2575
2754

2563
2909


2561


311


4.5

0.5 + 1.0'
0.5

0.5 + 0.5'





Al treatments of Atrazine applied postemergence.

TA 3. Activity of selected herbicide treatments on earl millet and weeds in a no-till system.

Quincy, FL 1993


Percent Control
Rate Percent Yield
Treatment lb/A Grass Broadleaf injury lb/A

Atrazine' 1.5 94 100 7 2720
Atrazine 2.0 90 100 11 2819
Atrazine* 1.5 95 99 17 2641
Atrazine* 2.0 94 100 25 3087
Dual + 2,4-D 1.0 + 0.5 98 93 83 1971
Dual + 2,4-D 1.5 + 0.5 89 96 96 1199
Dual + 2,4-D 2.0 + 0.5 98 90 97 509
Ramrod + 2,4-D 3.0 + 0.5 98 85 45 2173
Ramrod + 2,4-D 4.5 + 0.5 94 83 44 1823
Prowl + 2,4-D 0.5 + 0.5 95 97 16 3066
Prowl + 2,4-D 0.75 + 0.5 98 100 13 3382
Dual + Atrazine* 1.0 + 1.0 98 99 89 1892
Dual + Atrazine* 1.5 + 1.0 100 97 97 1001
Ramrod + Atrazine* 3.0 + 1.0 98 97 31 2103
Ramrod + Atrazine* 4.5 + 1.0 98 100 76 2319
Prowl + Atrazine* 0.5 + 1.0 99 97 10 2348
Prowl + Atrazine* 0.75 + 1.0 100 97 14 2678
Hand weed check 100 100 0 2807
Non-treated 0 0 0 2785
Non-treated 0 0 0 2799
LSD (0.05) 7 5 7 322

*Crop oil concentrate at 1 qt/A.
'All treatments of Atrazine applied postemergence.

TABLE 4. Activity of selected herbicide treatments on pearl millet and weeds in conventional seedbed.





Quincy, FL 1994


Percent Control


*Crop oil concentrate at 1 qt/A.

'All treatments of Atrazine applied postemergence.

2Silage consisted of 35% dry matter.


Treatment

Atrazine'

Atrazine

Atrazine'

Atrazine*

Ramrod + 2,4-D

Ramrod + 2,4-D

Prowl + 2,4-D

Prowl + 2,4-D

Ramrod + Atrazine*

Ramrod + Atrazine*

Prowl + Atrazine*

Prowl + Atrazine"

Dual

Hand weed check

Non-treated

LSD (0.05)


Rate
lb/A

1.5
2.0

1.0

1.5

1.5 + 0.5

2.25 + 0.5

0.5 + 0.5

0.75 + 0.5

1.5 + 1.0
2.25 + 1.0

0.5 + 1.0

0.75 + 1.0

1.0


Grass

59

30

47

42

70

43

67

85

69

43

79
46

27
100

0

32


Broadleaf

88

85

87

82

80

73

83

89

78
69

86

78

34

100

0

21


silage yield2
T/A

36

24

49

40

49

36

46

51

43

45

54

37

15

53

33

17





TABLE 5. Activity of selected herbicide treatments on pearl millet and weeds in a no-till system.

Quincy, FL 1994


Percent Weed Control
Rate Silage yield2
Treatment lb/A Grass Broadleaf T/A

Atrazine' 1.5 8 5 59

Atrazine 2.0 17 86 57
Atrazine* 1.0 57 87 41

Atrazine* 1.5 44 88 40

Ramrod + 2,4-D 1.5 + 0.5 73 81 60
Ramrod + 2,4-D 2.25 + 0.5 46 77 51
Prowl + 2,4-D 0.5 + 0.5 73 82 57
Prowl + 2,4-D 0.75 + 0.5 85 86 62
Ramrod + Atrazine' 1.5 + 1.0 85 89 52

Ramrod + Atrazine' 2.25 + 1.0 54 65 32
Prowl + Atrazine* 0.5 + 1.0 85 87 56

Prowl + Atrazine* 0.75 + 1.0 59 82 21
Dual 1.0 40 36 17

Hand weed check 100 100 77
Non-treated 0 0 52

LSD (0.05) 32 21 17

*Crop oil concentrate at 1 qt/A.

'All treatments of Atrazine applied postemergence.

2Silage consisted of 35% dry matter.












TABLE 6. Effect of atrazine on weed control and pearl millet yield. Tifton, GA 1991


Row Spacing
Spacing in Row Texas Crowfoot- Crab- Florida Florida Palmer Planting Date
(in.) (in.) panicum grass grass beggarweed pusley amaranth 5-24 6-14


------------------- % Control' --------------------- -- Yield, lb/A2 --

36 3 80 95 95 95 95 95 3,020 3,334 ab

36 6 2,943 2,889 b

18 3 90 95 100 100 100 100 2,942 2,975 b

18 6 2,745 3,636 a

NS


as determined by DMRT at


'Atrazine applied at 1 lb/A to 2-leaf pearl millet.

Data within column followed by the same letter are not significantly different
P = 0.05.












TABLE 7. Effect of postemergence herbicide treatments to weeds in pearl millet on conventional seedbed.

Tifton, GA 1993


---- Treatment --- --------------- % Weed Control-----------------
Rate Row Spacing Weed Crowfoot- Texas Palmer Wild
Herbicide lb/A (in.) control grass panicum amaranth radish


Atrazine 0.75 36 98 97 100 100 100

Atrazine 0.75 18 100 100 100 100 100

Buctril 0.38 36 94 93 97 95 100

Buctril 0.38 18 98 100 100 97 100

Buctril 0.38 36 98 97 100 98 100
Atrazine 0.75

Buctril 0.38 18 100 100 100 100 100
Atrazine 0.75

2,4-D 0.5 36 95 90 97 98 100

2,4-D 0.5 18 98 93 99 99 100


'Weed control data collected two weeks after application.












TABLE 8. Effect of postemergence herbicide treatments to weeds in pearl millet on stale seedbed'.

Tifton, GA 1993


----- Treatment ------ --------------- % Weed Control -----------------
Rate Row Spacing Weed Crowfoot- Texas Palmer Wild Injury
Herbicide lb/A (in.) control grass panicum amaranth radish %


Atrazine 0.75 36 96 93 100 100 100 5

Atrazine 1.0 18 97 95 97 100 100 7

Buctril 0.38 36 95 93 100 87 100 6

Buctril 0.38 18 97 95 100 100 100 0

Buctril 0.38 36 97 97 97 100 100 13
Atrazine 0.75

Buctril 0.38 18 97 95 100 100 100 27
Atrazine 0.75

2,4-D 0.5 36 96 95 95 100 100 0

2,4-D 0.5 18 90 70 93 100 100 7


'All plots treated with paraquat at 0.5 lb/A

2Weed control data collected two weeks after


after planting.

application.









TABLE 9. Effect of postemergence herbicide treatments to weeds in pearl millet on conventional seedbed.
Tifton, GA 1994



---- Treatment --- ------------ % Weed Control-----------------
Rate Row Spacing Crowfoot- carpet- Smallflower Palmer Yield
Herbicide Ib/A (in.) grass weed morningglory amaranth Nutsedge Ib/A


Atrazine 0.75 18 0 100 17 47 97 2,174

Atrazine 0.75 36 0 100 30 40 100 1,829

Atrazine 1.0 18 10 100 27 60 100 2,702

Atrazine 1.0 36 0 100 17 47 100 2,183

Buctril 0.38 18 0 100 10 57 100 2,350

Buctril 0.38 36 0 100 17 7 100 2,033

Buctril 0.38 18 3 100 67 80 100 2,486
Atrazine 0.75

Buctril 0.38 36 3 100 20 73 100 2,102
Atrazine 0.75

2,4-D 0.5 18 3 100 17 40 100 2,111

2,4-D 0.5 36 0 100 0 27 100 2,079

NS






TABLE 10. Effect of postemergence herbicide treatments to weeds in pearl millet on stale seedbed'.

Tifton, GA 1994


----- Treatment ----- % Weed Control-----------------------
Rate Row Spacing Crowfoot- Crab- Carpet- Smallflower Palmer Yield
Herbicide Ib/A (in.) grass grass weed morningglory amaranth Nutsedge lb/A


Atrazine 0.75 36 3 78 83 93 100 100 2,340

Atrazine 0.75 18 7 73 100 90 100 100 2,491

Atrazine 1.0 36 7 93 100 93 100 100 2,266

Atrazine 1.0 18 3 77 100 100 100 100 2,412

Buctril 0.38 36 3 63 100 80 100 100 1,970

Buctril 0.38 18 0 40 100 75 100 100 1,985

Buctril 0.38 36 5 85 100 90 100 100 2,334
Atrazine 0.75

Buctril 0.38 18 10 87 100 83 100 100 2,777
Atrazine 0.75

2,4-D 0.5 36 0 27 90 57 100 100 2,757

2,4-D 0.5 18 0 43 93 83 100 100 2,372

NS



'All plots treated with paraquat at 0.5 lb/A after planting.