L'; e

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of4

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CONTENTS
EXPERIMENTAL PROCEDURE RESULTS ...............................

Page 5 5 5 10 14
18

...................................................

Cool-Season Weeds........................................... Warm-Season Weeds (1977) ............................... Warm-Season Weeds (1980) ...............................
DISCUSSION ............................................. ..............

SUMMARY

AND CONCLUSIONS....................................

19 20

LITERATURE CITED..................................................

FIRST PRINTING 4M, MARCH 1986

Informnation contained herein is available to all without regard to race, color, sex, or national origin.

Forage Nutritive Quality of
Weeds in Alabama
C. S. Hoveland, G. A. Buchanan, S. C. Bosworth, and I. J. Bailey1

WEEDS

ARE OFTEN PRESENT in pasture, hay, and

silage grown in the Southeastern United States. While it is generally recognized that weeds effectively compete with cultivated forages for moisture, fertility, and light, the contribution of many weed species to overall forage productivity and quality is not well known. In England, weed species were found to differ considerably in forage quality (1). Many weed species in Minnesota had digestibility and crude protein values equal or superior to oats (A-ena sativa) (5), but mineral content differed greatly among species. Palatability of many weed species to livestock was high and similar to that of oats. Animal gains on grass-weed mixtures can be equal to gains on a pure stand of cultivated grasses (9). As grazing pressure increases in a pasture, selectivity by animals is decreased; thus, more weeds, regardless of quality and palatability, are consumed (7). In south Alabama, beef calf gains were higher on annual winter weeds in late winter on Coastal bermudagrass (Cynodon dactylon) pasture than later when the forage was strictly bermudagrass (3). The nutritive value of common weed species in Alabama has not been previously reported. This publication summarizes the results of several experiments where the nutritive value was determined in weed species grown in nurseries at Auburn (shown in cover illustration) and harvested at different stages of maturity.
l Respectively,.former Professor of Agronomy and Soils (now Professor, Agronomy Department, University of Georgia, Athens); Professor of Agronomy and Soils; and former graduate students of Agronomy and Soils.

4

ALABAMA

AGRICULTURAL EXPERIMENT STATION

TABLE 1. WEED AND FORAGE SPECIES ANALYZED FOR NUTRITIONAL VALUE

Common name Cool-season species

Botanical name

Forbs Carolina geranium ........................................... Geranium caro/inianumn Cutleaf evening primrose...................................QOenotheralaciniata Henbit......................................................... Lamium amnp/exieau/e Virginia pepperweed.............................. Lepidium z irginicumn Cur......y...dock........................................ Rumnex erispus Grass weeds Virginia wildrye.............................................. Elymus zvirginicus Wild oats ...................................................... Aiena fatua Cheat .......................................................... Bromus seca/inus
Little barley...................................................

Hordeumn pusi//um

Cultivated forages Wrens Abruzzi rye........................................... Kentucky 31 tall fescue ..................................... ladino clover .......................................... Hairy vetch ...................................................

Regal

Secale cereale Festuca arundinacea Trfo/rum repens Vicia zi//osa

Warm-season species Forbs Sicklepod...................................................... Cassia obtusifo/ia Coffee senna.................................................. Cassia occidenta/is Hemp sesbania ............................................... Sesbania exalata Tall morningglory.......................................... Ipomaea purpurea
Ivyleaf morninggory........................................ Ipomoea zederacea

C ypressvine morningglury.................................. Ipomoea quazooclit Florida beggarweed.......................................... Desmodiumn tortuasum Prickly sida ................................................... Sida spinosa Common purslane ........................................... Partul/acaa/eracea Bur gherkin................................................... Cucumis anguria Redroot pig weed............................................. Ama ranthus ret raftexus J imsonweed................................................... Datura stramoniumn Maypop passionflower....................................... Pass iora incarnata Common ragweed ........................................... Ambrasia artemnisiJo/ia Common cocklebur.......................................... Xanthium strumnariumn Pennsylvania smartweed .................................... Palygan um pensylva nieu m Bristly starbur ................................................ Acanthaospermnum hispiduin Rough goldenrod............................................ Sa/idaga rugasa Balloonvine ................................................... Ca rdiaspermum ha/icacabumn
Mexicantea

....................... .........................

Chenopodium aznbrosioides

Common pokeweed.......................................... Blue vervain .................................................. Florida pusley ................................................ Citronmelon.................................................. Common lambsquarters .................................... Horsenettle ................................................... Grass weeds Fall panicum.................................................. Texas panicum...............................................

Phyloaara amerirana Verbena hastata Riehardiasea bra Citru//us lanatus Chenapadiuin a/bum Soaanu m ea ro/inense

Panieumn diehatomj/lorumn Panjeum texanumn Yellow foxtail ................................................ /uteseeus Large crabgrass .............................................. Digitariasanguina/is Crowfootgrass................................................ Daety/oeteniuin aegyptiu in Goosegrass.................................................... Eleusine indira Field sandbur................................................. Cenchrus ineertus Cultivated forages Millex 23 pearlmillet ........................................ Pennisetumn amerieanum Coastal bermudagrass ....................................... GCynodan dacty/on

Setaria

FORAGE NUTRITIVE QUALITY OF WEEDS

5

EXPERIMENTAL PROCEDURE Forage nutritional status was determined from samples collected from cool- and warm-season weed and cultivated forage species planted in a field at Auburn, Alabama, in Cowarts sandy loam, table 1. Plots were 5 x 5 feet with four replications, with sufficient space between plots to allow optimum growth of the species. The soil was limed and fertilized according to soil test recommendations for forage species. All nonlegume species were fertilized with 15 pounds nitrogen per acre at planting and 35 pounds nitrogen at three times during the growing season. Irrigation was applied to maintain vigorous growth during periods of low rainfall. Forage was hand harvested from each plot for nutritional analyses at vegetative, flowering, and fruiting stages for two experiments. In some instances, forage was collected at only one or two stages of maturity. Nutritive quality was determined by in vitro dry matter digestibility (8), crude protein by macroKjeldahl N x 6.25, phosphorus by chlorostannous-reduced molydophosphoric acid blue color in sulfuric acid (4), and calcium, magnesium, and potassium by atomic absorptionemission spectrophotometry. RESULTS Digestibility is one of the best indicators of forage quality. Digestibility values of 60 percent or higher are considered good and should be satisfactory for growing cattle, while values of 50 percent or less are unsatisfactory, even for lactating beef cows. Crude protein levels of 11 percent or more are adequate for growing animals, whereas levels of 9 percent are needed for lactating beef cows. Phosphorus and magnesium levels of 0.2 percent, calcium levels of 0.3 percent, and potassium levels of 0.5-0.8 percent are required for beef cattle (6). Cool-Season Weeds Digestibility Digestibility of the cool-season species was generally high at the vegetative stage of maturity, table 2. With the exception of cutleaf evening primrose and curly dock, digestibility was similar to or higher than that for rye and ladino clover, which are regarded as high quality forage plants. Digestibility of

6
TABLE

ALABAMA AGRICULTURAL EXPERIMENT STATION 2.
PERCENTAGE IN VITRO DRY MATTER DIGESTIBILITY (IVDMD) OF COOL-SEASON WEED AND FORAGE SPECIES AT THREE STAGES OF MATURITY

IVDMD
Species

Vegetative Pet.

Flower/boot Pct. 70 d B 69 d A bc A 72 cd B 54 e B 74 cd B 69 d B 78 bc A

Fruit/head Pct. 68 d B 52 B 75 cA 63 def C 51 gB 60 f C 61 efC 62 ef B

Forbs 78 b A* Carolina geranium ............. 72 c A Cutleaf evening primrose....... -78 H enbit ..................................... Virginia pepperweed...........86 a A 73 cA Curly dock ............................... Grass weeds Virginia wildrye ................ W ild oats .............................. Cheat ................................. Little barley .......................... 80 75 81 82 bA bc ab A ab A

Cultivated forages 70 cd B 81 ab A 79 b A Rye ........................................ 67 de B 73 cd A 78 bA Tall fescue ............................ 83 aA 85 aA 81 ab A Ladino clover ...................... 77 bA 77 bc A 80 bA Hairy vetch ........................... lower case letter are not *Any two means within a column followed by the same significantly different at the 5 percent level as determined by Duncan's multiple range test. Any two means within a line followed by the same upper case letter are not significantly different at the 5 percent level as determined by Duncan's multiple range test.

TABLE

3.

PERCENTAGE CRUDE PROTEIN OF COOL-SEASON WEED AND FORAGE SPECIES AT THREE STAGES OF MATURITY

Species

Vegetative Pct. 18.7 19.6 31.9 29.9 23.1 23.2 23.4 23.6 27.9 22.1 27.2 30.0 e A* de A aA ab A cd A cd cd A c A b A cde A b A ab A

Crude protein Flower/boot Pct. 13.8 14.1 20.1 25.8 19.1 gh B gh B de A ab B def B

Fruit/head Pct. 10.6 11.3 16.2 17.1 16.1 fg C ef C c A c C cd C

Forbs Carolina geranium .................. Cutleaf evening primrose ....... Henbit ..................................... Virginia pepperweed .......... Curly dock ............................... Grass weeds Virginia wildrye ...................... W ild oats ............................. Cheat ...................................... Little barley ............................ Cultivated forages Rye ......................................... Tall fescue .............................. Ladino clover ......................... Hairy vetch .............................

18.8 def B 17.6 ef B 17.6 ef B 24.2 16.5 22.1 28.7 bc B fg B cd B a A

6.8 h C 13.8 gh C 13.8 de C 13.4 12.5 23.2 26.2 de C ef C b C a A

*Any two means within a column followed by the same lower case letter are not significantly different at the 5 percent level as determined by Duncan's multiple range test. Any two means within a line followed by the same upper case letter are not significantly different at the 5 percent level as determined by Duncan's multiple range test.

FORAGE NUTRITIVE QUALITY OF WEEDS

7

most weed species declined faster than cultivated forages. The digestibility of grass weeds was similar to rye and tall fescue at the vegetative stage; however, digestibility of grass weeds was lower than rye at the oldest stage of maturity. Henbit and Carolina geranium maintained high digestibility at the oldest stage of maturity. Although there is a tendency for digestibility of some cool-season weeds to decline with maturity, the nutritive quality would generally be equal or superior to bermudagrass in early spring when it is most digestible, averaging 55 to 58 percent.
Crude Protein

At the vegetative stage of maturity, all weed species and cultivated forages were more than adequate to provide the protein requirement of 11 percent for a growing beef steer, table 3. Weed and cultivated forage species generally declined in percent crude protein as the plants matured. However, Virginia wildrye was the only weed that decreased enough in crude protein by the most mature stage that it would be inadequate for a growing steer or lactating beef cow. Crude
protein content of henbit and hairy vetch was not significantly

affected by maturity.
TABLE 4. PERCENTAGE CALCIUM OF COOL-SEASON WEED AND FORAGE SPECIES AT THREE STAGES OF MATURITY

Species

Calcium Vegetative
Pct.

Flower/boot
Pct.

Fruit/head
Pct.

Forbs Carolina geranium ................. 0.41 e C* Cutleaf evening primrose ....... 1.15 a B H enbit ..................................... Virginia pepperweed ............... 66 c A Curly dock ............................... 29 fgh B Grass weeds Virginia wildrye ..................... W ild oats ................................ Cheat ...................................... Little barley ............................ .22 .33 .31 .25 h A f fg A gh A

0.56 1.29 .69 .67 .49

d B a A c A c A dA

0.69 1.34 .57 .53 .52

c A a A dB d B dA

.20 f AB .33 e A .21 f B .29 .31 .80 .56 ef AB e A b AB dA

.15 g B .30 e A .20 fg B .26 .27 .87 .54 ef B ef A b A dA

Cultivated forages Rye ........................................ . 31 fg A Tall fescue .............................. .27 fgh A Ladino clover ....................... .. .75 b B Hairy vetch ............................. .55 d A

*Any two means within a column followed by the same lower case letter are not significantly different at the 5 percent level as determined by Duncan's multiple range test. Any two means within a line followed by the same upper case letter are not significantly different at the 5 percent level as determined by Duncan's multiple range test.

8

ALABAMA AGRICULTURAL EXPERIMENT STATION

TABLE 5. PERCENTAGE PHOSPHORUS OF COOL-SEASON WEED AND FORAGE SPECIES AT THREE STAGES OF MATURITY

SpeciesPhosphorus Vegetative Pet.

Flower/boot Pct.

Fruit/head Pct. 0.09 de B .14 abc B .17 a B .14 abc B .15 ab B .08 e B .12bcdC .12 cd C .12 cd C .15 ab A .12 bcd B .16 a B letter are not multiple range letter are not multiple range

Forbs Carolina geranium ................ 0.13 e A* 0.11 f B Cutleaf evening primrose ....... .16 de A .15 cd AB H enbit ..................................... ab A .20 Virginia pepperweed ............ .23 bA .19 b AB Curly dock ............................... .24 b A .14 def B Grass weeds Virginia wildrye ................. Wild oats ....... .................... Cheat .................................... Little barley .......................... Cultivated forages Rye ..................................... Tall fescue ........................... Ladino clover ....................... Hairy vetch ........................... .16 .32 .21 .17 de A a bc A de A .13 def A -.17 bc B .14 cde B .22 .14 .11 .18 a B cde A ef B bc B

.31 a A 19cdA .18 cd A .21 bc A

*Any two means within a column followed by the same lower case significantly different at the 5 percent level as determined by Duncan's test. Any two means within a line followed by the same upper case significantly different at the 5 percent level as determined by Duncan's test.

TABLE 6. PERCENTAGE MAGNESIUM OF COOL-SEASON WEED AND FORAGE SPECIES AT THREE STAGES OF MA'URITY

SpeciesMagnesium Vegetative Pct.

Flower/boot Pet. gh A bA aA d A cA

Fruit/head Pct. 0.10 .26 .33 .13 .24 f A b A aB e B cA

Forbs 0.10 e A* 0.09 Carolina geranium .................. .28 .27 a A Cutleaf evening primrose ....... .39 H enbit ..................................... .18 Virginia pepperweed ................ 18 bc A .24 .19 b B Curly dock ............................. Grass weeds Virginia wildrye ..................... W ild oats ................................ Cheat ...................................... Little barley ............................. .10 e A .11 e . 11 A .09 g A

e

.07 hi B -.08 hi B .06 i B .11 fg A .12fA .14 e C .13 efA

.05 g C .07 g C .07 g B .09 fA .12 eA .18 d A .13 eA

Cultivated forages . 11 e A Rye ........................................ Tall fescue ................................ 13d A .16 c B Ladino clover ......................... .13 d A Hairy vetch .............................

*Any two means within a column followed by the same lower case letter are not significantly different at the 5 percent level as determined by Duncan's multiple range test. Any two means within a line followed by the same upper case letter are not significantly different at the 5 percent level as determined by Duncan's multiple range test.

FORAGE NUTRITIVE QUALITY OF WEEDS

9

MiVineral Coztent

Cool-season weeds contained enough calcium to provide
adequate amounts for growing beef steers, table 4. Cutleaf

evening primrose contained high levels of calcium at all maturity stages, exceeding that of ladino clover. Only Virginia wildrye had a marginal level of calcium as required for beef cattle. Of the weed species, only Virginia pepperweed, curly dock, wild oats, and cheat had adequate phosphorus at the vegetative stage to meet the needs of a growing beef steer, table 5. At the flowering stage, henbit and Virginia pepperweed were the only ones with adequate phosphorus levels. Levels of phosphorus in both weed and forage species, except tall fescue, declined as plants matured. All weeds and cultivated forages
had phosphorus concentrations below adequate levels at the

oldest stage of maturity. Magnesium levels of less than 0.2 percent may cause grass tetany in lactating beef cows during late winter and spring. All of the cool-season grass weeds, cultivated forages, and
some of the cool-season forbs had magnesium concentrations

often associated with grass tetany, table 6. Weeds likely to
TABLE 7. PERCENTAGE POTASSIUM OF COOL-SEASON WEED AND FORAGE SPECIES AT THREE STAGES OF MATURITY

Potassium
Species

Vegetative Pct. 1.0 f AB* 1.2 ef A 1.4 cde A 2.2 b A 1.3 2.5 1.0 1.4 de A a f AB cde A

Flower/boot Pct. 1.2 1.2 1.0 1.3 2.0 de A d A e A d A a AB

Fruit/head Pct. 1.0 1.0 .9 1.0 1.9 d B d B de B d B a B

Forbs Carolina geranium .................. Cutleaf evening primrose ....... H enbit ..................................... Virginia pepperweed .............. Curly dock .............................. Grass weeds Virginia wildrye ..................... W ild oats ................................ Cheat ..................................... Little barley ............................ Cultivated forages Rye .......................................... Tall fescue .............................. Ladino clover .........................
Hairy vetch ............................

1.4 cd A 1.2 de A 1.4 cd A 1.6 bc B 1.7 b A 1.6 bc A
1.6 bc A

.6 e B 1.0 d B 1.2 cd B 1.4 bc B 1.4 bc B 1.6 ab A 1.6 b A

2.4 ab A 1.6 c A 1.4 cd B
1.3 de B

*Any two means within a column followed by the same lower case letter are not significantly different at the 5 percent level as determined by Duncan's multiple range test. Any two means within a line followed by the same upper case letter are not significantly different at the 5 percent level as determined by Duncan's multiple range test.

10

ALABAMA

AGRICULTURAL

EXPERIMENT

STATION

cause tetany included Carolina geranium, Virginia wildrye, wild oats, cheat, and little barley. Although the grass weeds were low in magnesium, all forbs except Carolina geranium and Virginia pepperweed had adequate or nearly adequate magnesium concentrations, particularly at later stages of growth. All weed and cultivated forage species had potassium levels well above the requirements for cattle, table 7. Wild oats and rye had the highest levels of potassium at the vegetative stage. Generally, potassium concentrations declined as plants matured. Warm-Season Weeds (1977) Digestibility At the vegetative state, all warm-season weeds except crowfootgrass were more digestible than pearlmillet or bermudagrass, table 8. All of the grass weeds and bermudagrass were
TABLE 8. PERCENTAGE IN VITRO DRY MA'TTER DIGESTIBILITY (IVDMD) OF WARM-SEASON WEED AND FORAGE SPECIES AT THREE STAGES OF MATURITY

IVDMD
Species

Vegetative
Pct.

Flower/boot
Pct.

Fruit/head
Pct.

Forbs Sicklepod ............................. Coffee senna ......................... Hemp sesbania .................... Tall morningglory.. .......... Ivyleaf morningglory .............. Cypressvine morningglory Florida beggarweed ........... Prickly sida .............................. Common purslane ................... Bur gherkin ............................. Redroot pigweed ..................... Jimsonweed .............................. Grass weeds Fall panicum ............. ............... Texas panicum ........................ Yellow foxtail ............ .............. Crabgrass ................................ Crowfootgrass ......................... Cultivated forages Pearlmillet .............................. Bermudagrass ......................... *Any two means within a significantly different at the test. Any two means within significantly different at the test.

84 a A* 81 abc A 70 cd A 82 ab A 80 abc A 80 abc A 74 abcd A 80 abc A -80 73 abcd A 72 abcd A 72 bcd A 74 abcd A 73 abcd A 79 abc A 67 de A 59e A 58 e A

76 ab B 75 abc A 66 bcd A -78 65 bcd B 70 abcd B a 75 abc A 71 abcd A 66 bcd A 63 62 66 72 54 cde B de B bcd B abcd B ef B

71 67 52 76

abc B bcd B gh B ab B a A 77 ab A 55 efg C 56 efg C
-

79 a A 64 cde B 56 defg B 54 52 57 63 43 efg C fghC defg C cdef C hi C

60 def A 51 f B

60 defg A 43 hi C

column followed by the same lower case letter are not 5 percent level according to Duncan's multiple range a line followed by the same upper case letter are not 5 percent level according to Duncan's multiple range

FORAGE

NUTRITIVE

QUALITY

OF

WEEDS

11

more digestible at the vegetative stage than at the flowering or fruiting state. Some forbs decreased in digestibility, particularly at the fruiting stage; however, the morningglories, bur gherkin, and pearlmillet remained unchanged at all stages. In contrast, bermudagrass declined sharply with maturity, similar to crowfootgrass, resulting in poor quality forage. Crude Protein Both weed and cultivated forage species had more than adequate crude protein at the vegetative stage to meet the requirements of growing beef steers, table 9. Most of the forbs were especially high in crude protein. Grass weeds were lower than most forbs but were comparable to both bermudagrass and pearlmillet at the vegetative stage. Concentrations of crude protein usually decreased when plants matured past the vegetative stage. At advanced maturTABLE 9. PERCENTAGE CRUDE PROTEIN OF WARM-SEASON WEED AND FORAGE SPECIES AT THREE STAGES OF MATURITY

Vegetative
Pct.

Crude protein Flower/boot
Pct.

Fruit/head
Pet.

Forbs Sicklepod .............................. 21.6 cd A* 16.5 fgh B Coffee senna ..................... Hemp sesbania ................. 31.2 a A Tall morningglory ... .20.1 de A Ivyleaf morningglor ............ 19.3 def A Cypressvine morningglory 20.3 de A Florida beggarweed ................. 21.9 cd A Prickly sida .............................. 17.2 efgh A Common purslane ................... Bur gherkin ............................. Redroot pigweed .. ............ 23.9 bc A Jimsonweed ..................... 25.1 b A Grass weeds Fall panicum .... ................ Texas panicum ... .............. Yellow foxtail ......................... Crabgrass ..... .................. Crowfootgrass ................... Cultivated forages Pearlmillet .. .................... Bermudagrass ......................... *Any two means within a significantly different at the test. Any two means within significantly different at the test. 19.0 defg A 15.7hA 17.5 efgh A 14.3 h A 15.5 h A 17.3 efgh A 15.9 gh A

13.6 c C 21.8 a A 13.9 c B -

16.9 17.7 19.3 17.3 17.4 20.7 9.1 10.5 11.5 8.1 7.9

b B b A ab b A b B a B de de de ef ef B B C B B

16.7 a B 15.2 abc B 11.2 def B 13.9 abcd B 11.0 defg B 13.2 bcde B 12.9 'cde C 12.3 cde B 14.2 abcd A 10.6 efgh C 16.5 ab C 7.2 8.4 14.3 6.4 8.5 hi B fghi C abcd B i B fghi B

6.0 f C 6.9 de C

8.3 fghi B 7.7 ghi B

column followed by the same lower case letter are not 5 percent level according to Duncan's multiple range a line followed by the same upper case letter are not 5 percent level according to Duncan's multiple range

12

ALABAMA

AGRICULTURAL

EXPERIMENT

STATION

ities, the grass weeds (except for yellow foxtail) generally had crude protein concentrations that would be inadequate for

growing steers, but the same was true for the cultivated forages. However, these crude protein levels would be adequate for maintenance of a dry pregnant cow. Forbs remained at a relatively high level of crude protein even at fruiting stage.
Mineral Content

Warm-season weed and cultivated forage species contained calcium concentrations above the requirements of cattle, table 10. Forbs were high in calcium, sometimes two to three times higher than some grass weed and cultivated grass species. Bur gherkin had an unusually high calcium concentration of 3.0 percent; other forbs ranged between 0.7 and 1.9 percent calcium. With the exception of crowfootgrass, the grass weeds had calcium levels similar to pearlmillet and bermudagrass.

TABLE 10. PERCENTAGE CALCIUM OF WARM-SEASON WEED AND FORAGE SPECIES AT THREE STAGES OF MATURITY

Calcium
Species

Vegetative Pct. 1.12 1.14 .96 1.02 .72 .98 1.88 1.04
-

Flower/boot Pct. 1.35 c A 1.24 cd A 1.02 def A -

Fruit/head Pct. 1.31 1.16 .92 .94 .76 .79 1.25 1.13
-

Forbs Sicklepod .............................. Coffee senna .......................... Hemp sesbania .................. Tall morningglory ............. Ivyleaf morningglory .............. Cypressvine morningglory Florida beggarweed ............ Prickly sida ............................ Common purslane .................. Bur gherkin ....................Redroot pigweed ..................... Jimsonweed .............................. Grass weeds Fall panicum ............................ Texas panicum ............... Yellow foxtail ........... ............... Crabgrass .............. .................. Crowfootgrass ......................... Cultivated forages Pearlmillet ............ ................... Bermudagrass .......................... *Any two means within a significantly different at the test. Any two means within significantly different at the test.

cd A* cd B d A dA e A d A aA d A

1.32 b C 1.26 cb A .33 .53 .41 .44 .71 gB fA fg A fg A e C

1.47 1.03 .90 3.01 1.80 1.06

c B def A ef a A b A de B

bc A cd AB ef A ef A fg A fg B bcd C cde A

2.96 a A 1.46 b B 1.01 def B .40 .54 .33 .39 .96 h A gh A h A h A ef A

.36 g AB .49g A .38 g A .42 A .80 f B .42 g AB .44 gA

.48 fg A 42gh A

.33 h B .40 hA

column followed by the same lower case letter are not 5 percent level according to Duncan's multiple range a line followed by the same upper case letter are not 5 percent level according to Duncan's multiple range

FORAGE

NUTRITIVE

QUALITY

OF

WEEDS

13
FORAGE

TABLE 11. PERCENTAGE PHOSPHORUS OF WARM-SEASON WEED AND SPECIES AT THREE STAGES OF MATURITY

SpeciesPhosphorus Vegetative Pct. Forbs Sicklepod .... ....................... Coffee senna ............................ Hemp sesbania ........................ Tall morningglory .............. Ivyleaf morningglory.............. Cypressvine morningglory Florida beggarweed ................. Prickly sida ............ .................. Common purslane ................... Bur gherkin ............................. Redroot pigweed .................. Jimsonweed .............................. Grass weeds Fall panicum ............................ Texas panicum ..................... Yellow foxtail ....................... Crabgrass .............................. Crowfootgrass ..................... Cultivated forages Pearlmillet ............................ Bermudagrass ....................... *Any two means within a significantly different at the test. Any two means within significantly different at the test. 0.13 g A* .14 gA .33 dA .15 fg A .16fg A .17 fg A .16fgA .13 g A .55 bA .39 cd A .36 .24 .31 .43 .34 cd A ef A de A c A d A

Flower/boot Pct. 0.09 eA .14 de A .16 de B .12 .16 .35 .27 .39 .22 .23 .17 .22 .25 .18

Fruit/head Pct. 0.11 .16 .11 .14 .22 .19 .18 .19 dA cd A d B cd A bc A bcd A cd A bcd A

e B cde A a b A aB bcd B bcd B cde A bcd B bc B bcde B

.23 bc A .42 a AB .37 a A .21 .20 .22 .17 .19 bcd B bcd A bc B cd C cd B

.69 a A .20 fg A

.25 bc B .15 de A

.21 bcd B .18 cd A

column followed by the same lower case letter are not 5 percent level according to Duncan's multiple range a line followed by the same upper case letter are not 5 percent level according to Duncan's multiple range

Calcium content of crowfootgrass increased while Florida beggarweed decreased with maturity. Many of the weed species were low in phosphorus and would be suboptimal for a high producing ruminant, table 11. Sicklepod, coffee senna, the morningglory species, Florida beggarweed, and prickly sida had suboptimal levels at the vegetative stage. Phosphorus concentrations in redroot pigweed, jimsonweed, and crabgrass were generally higher than many other weed species. Phosphorus concentration of pearlmillet was substantially higher than bermudagrass at the first two maturities. The majority of the forbs did not change substantially in phosphorus concentrations as plants matured. All warm-season weeds and cultivated grasses at all stages of maturity had magnesium concentrations adequate for cattle, table 12. Redroot pigweed and bur gherkin had the highest magnesium concentration at fruiting stage, 0.77 and 0.95, respectively.

14

ALABAMA AGRICULTURAL EXPERIMENT STATION
TABLE 12. PERCENTAGE MAGNESIUM OF WARM-SEASON WEED AND FORAGE SPECIES AT THREE STAGES OF MATURITY

SpeciesMagnesium Vegetative
Pct.

Flower/boot
Pct.

Fruit/head
Pct.

Forbs Sicklepod ............................. Coffee senna ......................... Hemp sesbania ........................ Tall morningglory ................... Ivyleaf morningglory.............. Cypressvine morningglory Florida beggarweed ............ Prickly sida .... .................... Common purslane ............... Bur gherkin ............................. Redroot pigweed ................ Jimsonweed ....................... Grass weeds Fall panicum ......................... Texas panicum ................. Yellow foxtail .................... Crabgrass .............................. Crowfootgrass ...................... Cultivated forages Pearlmillet .............................. Bermudagrass .......................... *Any two means within a significantly different at the test. Any two means within significantly different at the test.

0.35 .32 34 35 .30 .32 .31 .32 71

b A* bcd B bcd A bc A bcd A bcd A bcd A bcd B a B

0.32 efgh B .43 e A .29 fgh B .25 .39 1.25 73 .96 .58 .21 .35 .21 .33 .33

.66 aA
.31 .39 .22 .35 .38

gh B ef A a cB bA dA h B efg A b A efgh B efgh A

0.36 .40 .22 .36 .36 .31 .19 .35
-

de A d A gC deA de A ef A g C de AB

.95 a A .77 bB .57 cA .30 .38 .25 .39 .36 ef A d A fg A &A de A

bcd A b A d A b AB b A

.33 bcd A 23 cd A

.20 B .22 bA

.22 g B .22 g A

column followed by the same lower case letter are not 5 percent level according to Duncan's multiple range a line followed by the same upper case letter are not 5 percent level according to Duncan's multiple range

The majority of weed species were as high in potassium as bermudagrass, table 13, with yellow foxtail and pearlmillet highest at the vegetative stages (5.0 and 4.8 percent, respectively). Generally, potassium concentration decreased as plants matured.
Warm-Season Weeds (1980)

Digestibility Except for blue vervain and Pennsylvania smartweed, digestibility of all weed species at the vegetative stage was equal to or higher than that of pearlmillet, table 14. Generally, digestibility of most weeds declined sharply with maturity. Digestibility of maypop passionflower and Florida pusley remained high at fruiting, well above that of pearlmillet. Pennsylvania smartweed and blue vervain had extremely low digestibility values, indicating poor forage quality.

FORAGE

NUTRITIVE

QUALITY

OF

WEEDS

15

TABLE

13.

PERCENTAGE POTASSIUM OF WARM-SEASON WEED AND FORAGE SPECIES AT THREE STAGES OF MATURITY

Potassium Vegetative Pct. Forbs Sicklepod ................................. Coffee senna ........................ Hemp sesbania ..................... Tall morningglory .............. Ivyleaf morningglory ............. Cypressvine morningglory Florida beggarweed ............. Prickly sida ....................... Common purslane ................... Bur gherkin .................... Redroot pigweed ............... Jimsonweed ....................... Grass weeds .......... Fall panicum ........... Texas panicum ................. Yellow foxtail ....................... Crabgrass .............................. Crowfootgrass .................... Cultivated forages Pearlmillet .. .................. Bermudagrass ....................... 2.6 2.3 3.7 3.1 3.3 3.1 2.4 2.0
-

Flower/boot Pct. 1.7 h B 2.3 fg A 2.3 fg B
-

Fruit/head Pct. 1.6 1.8 1.4 2.7 2.3 2.4 1.6 1.9 gh B fgh A b C b A bcd B bcd B gh B fgh A

ef A* fg A bc A de A cd A de A fg A gA

3.7bcA 3.9 b A 3.5bcdA 3.5 bcd A 5.0 a A 4.0 b A 3.7- bc A 4.8 a A 2.3 fg A

1.6 h B 1.7 g B 3.8 ab 3.4 bcd A 3.5bcA 3.4 bcd A 2.6 3.1 4.1 3.2 2.7 f B de B a B cd B ef B

3.1 a A 3.1 aB 3.3 a A 2.4 bcde C 2.5 bcd C 3.3 a B 2.2 cdef C 2.1 def C 2.6 bc B 1.9 fgh B

3.0 de B 2.0 gh B

*Any two means within a column followed by the same lower case letter are not significantly different at the 5 percent level according to Duncan's multiple range test. Any two means within a line followed by the same upper case letter are not significantly different at the 5 percent level according to Duncan's multiple range test.

Crude Protein Crude protein values were lower in this experiment than in the previous one, indicating that nitrogen fertilization may have been inadequate because of heavy rains that caused excessive leaching. Even so, there were striking differences in crude protein contents of the weed species, table 14. Maypop passionflower, common ragweed, goosegrass, common pokeweed, Florida pusley, citronmelon, and horsenettle all had relatively high levels of crude protein at the vegetative stage. It is probable that the high crude protein value for horsenettle may not be protein but consists of nitrate since this species has been suspected to accumulate high levels of nitrates. With maturity, crude protein levels declined in most species, being especially low in Pennsylvania smartweed and common lambsquarters.

16

ALABAMA AGRICULTURAL EXPERIMENT STATION

TABLE 14. PERCENTAGE IN VITRO DRY MATTER DIGESTIBILITY (IVDMD) AND CRUDE PROTEIN OF WARM-SEASON WEED AND FORAGE SPECIES AT Two STAGES OF MATURITY, 1980

IVDMD

Crude protein

Species Forbs Florida pusley ............ Common cocklebur . Maypop passionflower .. Common pokeweed ...... Mexicantea .............. Citronmelon ............... Balloonvine ................ Common lambsquarters Common ragweed ......... Bristly starbur ............ Horsenettle ................ Goldenrod ............... Blue vervain ............. Pennsylvania smartweed Grass weeds Crabgrass ............... Goosegrass .............. Field sandbur ............ Cultivated forage Pearlmillet ...............

Vegetative
Pct.

Fruit/head
Pect.

Vegetative
Pct.

Fruit/head
Pct.

77 76 76 75 71 71 70 69 66 63 60 54 52 47

a A* ab A ab A abc A bcd A bcd A bcd A cde A def A efg A fg A hi A ij A j A

70 59 70 57 47 59 61 53 64 50 55 53 41 45

a B cd B a A de B g B cd B bcd B ef B bc A fg B def A ef A h B gh A

14.4cd A 10.6 ef A 23.6 a A 17.1 bc A 12.4 de A 19.2 bA 12.4 de A 8.9 fg A 16.5 bc A 10.1 ef A 24.6 a A 10.6 ef A 6.8 gA 8.9fg A 9.0 fg A 17.5 bA 10.3 ef A 10.0 ef A

9.5 cde B 7.4 efgh A 14.9 aB 12.3 b B 7.1 gh B 11.1 bc B 10.7 bcd A 6.3 hi B 10.6 bcd B 8.9cdefg A 12.6 b B 7.8 efgh A 9.5 cdef A 4.2 i A 10.3 bcd A 8.5 defg B 7.4 efgh B 9.5 cdef A

75 ab A 75 ab A 66 de A 59 gh A

66 ab B 53 ef B 56 de B 60 cd A

*Any two means within a column followed by the same lower case letter are not significantly different at the 5 percent level. Two means within a line for maturity date of IVDMD or crude protein followed by the same upper case letter are not significantly different at the 5 percent level.

Mineral Content Calcium content of all species was adequate for cattle nu-

trition, table 15. Florida pusley was much higher in calcium content than any other species. Many weed species contained inadequate phosphorus for cattle nutrition, table 15. Goosegrass, bristly starbur, crabgrass, common ragweed, common cocklebur, citronmelon, and field sandbur had the highest levels of phosphorus. Weeds having extremely low levels of phosphorus were Pennsylvania smartweed, goldenrod, common lambsquarters, mexicantea, common pokeweed, maypop passionflower, and Florida pusley. Magnesium concentration of all species was relatively high, table 15, with common lambsquarters rated very high. There was little change in magnesium concentration with maturity. Potassium concentration of all species was relatively high (adequate for animal nutrition), table 15. Common pokeweed

C)
TABLF 15. PFRCENTAGE CALCIUM, POTASSIUM, MAGNFSIUM, AND PHOSPHORUS OF WARM-SEASON Two STAGES OF MATURITY, 1980 WEFD AND FORAGE SPECIES AT

rn

z
c

Calcium SpeciesCaiPosuMVegetative Fruit/head PcI. Forbs Florida pusley ................. 2.28 a B* 1.98 b A Common cocklebur. Maypop passionflower .... 1.25 ef B Common pokeweed ........ .70 i A Mexicantea ................... 1.10 g A Citronmelon .................... 1.38 cde B Balloonvine ..................... .61 j A Common lambsquarters ..... 1.55 c A Common ragweed........1.45 cd A Bristly starbur ................. .76 hij B Horsenettle ..................... 93 gh A Goldenrod ....................... .94 gh A Blue vervain ....... 1.35 de A Pennsylvania smartweed....92 gh A Grass weeds Crabgrass................... .33 k A Goosegrass ................. .88 hi A Field sandbur .............. .29 h A Pct. 3.75 1.73 1.88 .61 .67 2.43 .71 .86 1.75 1.23 .76 1.15 1.48 .65 a A cd A c A ghij A ghijB b A ghi A g B cd A ef A gh A
fA

Potassium Vegetative Fruit/head Pct. 1.5 2.9 2.8 6.8 3.0 2.4 1.7 4.0 3.0 3.2 2.3 3.0 1.2 .6 g B cd A cde A aA cd A ef A g A bhA cd A cd A fA cd A g A g A Pct. 2.8 bcd A 2.1 efgh B 2.7 bcd A 3.0 ab B 2.1 fgh B 2.1 efgh A 1.8 hi A 2.0 fgh B 2.8 bcd A 3.0 bc A 2.4 cdef A 1.8 ghi B 1.4 lj A 1.1 j A 3.5 a A 2.4 bcdefg A 2.6 bcde A

MgeimPopou Vegetative Fruit/head Pct. 0.38 ghi A .65 bc A .41 fgh A .68bA .54deA .43 A .34 hlj A .79 a A .55 de A .45 f A .49 efA .31 i A .37 ghi A Pct. 0.58 ab A .50 bc A .46 cde A .67aA .38efghi A .45 cdef A .37 fghi A .47 cd B .52 bc A .44cdefgA
39defghA
.27jA

Vegetative Pct. 0.09 k A .22cdefA .14 hi A .13ijA .10 kA .30 bA .17 gh A .10jk A .21 def A .24 cdA
.19 efg A
.l0jkA

Fruit/head Pct. 0.13 d A .18 bc A .13 d A .08eA .06 eA .21 ab B .20 abc A .08 c A .17 cd A .19bcA
.13 d A

0
C

fg

rn
C,,

de A ghij B

.59 cd A
.30 ij A .49 ef A .26 jk A

.37eofghi A .47 cd A .38 efghi A .36 ghi A .32 hij A

.18 fA .10 jkA .22 cde A .25 c A .37 A

.08 e A
.7c .06 eA .19 bc A .16 cd A .26 a B

.43 ij A .68 ghij A .41lj A

3.6 bc A 2.9 cde A 3.1 cd A

Cultivated forage Pearlmillet ................. A .50 hij A 3.8 b A 2.1 efgh B .20 h A .29 ij A .24 cd A .19 bc A *Any two means within a column followed by the same lower case letter are not significantly different at the 5 percent level. Two means within a line for maturity of each mineral followed by the same upper case letter are not significantly different at the 5 percent level.

.66j

V

18

ALABAMA

AGRICULTURAL

EXPERIMENT

STATION

had an extremely high content of potassium, over 6 percent at the vegetative stage and 3 percent at fruiting.
DISCUSSION

Many of the cool-season weeds, particularly at an early stage of maturity, were found to have quality comparable to commonly grown cool-season cultivated forage species. Although the digestibility of cool-season weeds declines with maturity, the weed nutritive quality was generally superior to warmseason perennial grasses such as bermudagrass. Crude protein content of cool-season weeds was high and more than adequate for cattle. Cool-season weeds had adequate levels of calcium and potassium. Phosphorus and magnesium levels were low in most weed species and could be nutritionally deficient for cattle. Many warm-season weeds at the vegetative stage had a nutrient concentration comparable to that of cultivated forage grasses of the same season, such as Coastal bermudagrass and pearlmillet. Digestibility of most warm-season weeds sampled in these studies at the vegetative stage was superior to that of Coastal bermudagrass and equal to pearlmillet. Crabgrass, a highly palatable weed, had relatively high digestibility at all stages of maturity. Several weeds, such as Pennsylvania smartweed and blue vervain, were low in digestibility, indicating poor forage quality. Crude protein content of warm-season weed species at the vegetative stage was generally high and equal or superior to that of bermudagrass. However, crude protein content of grass weeds declined with maturity so they would be adequate only for maintenance of dry cows. Forbs maintained a relatively high crude protein level even at the fruiting stage. Pennsylvania smartweed had extremely low crude protein at fruiting stage. Calcium, magnesium, and potassium levels of warmseason weeds were relatively high. Phosphorus content of many warm season weeds was low and inadequate for cattle nutrition. Certain weeds can be useful forage plants in pastures. For example, palatable weeds such as crabgrass can be highly productive when adequately fertilized. However, other weeds have yield and palatability limitations. Such weeds as pokeweed, jimsonweed, and horsenettle may be mildly toxic (2), but a greater problem may be low palatability. Examples of unpalatable weeds are sicklepod, coffee senna, hemp sesbania,

FORAGE NUTRITIVE QUALITY OF WEEDS

19

prickly sida, jimsonweed, common ragweed, goldenrod, goosegrass, common pokeweed, horsenettle, and field sandbur. Intake of these unpalatable weeds by a grazing animal would be low; however, many of these weeds may be incorporated in hay or silage and be consumed by livestock. Many weed species can be desirable components of a pasture and are readily grazed by cattle desiring variety in their diet. Weeds probably contribute more to livestock nutrition than is generally recognized. The high nutritive quality of many weed species suggests that it may not always be desirable to eliminate them from pastures. SUMMARY AND CONCLUSIONS Warm- and cool-season weed species were grown in the field at Auburn, Alabama, and digestibility, crude protein, and mineral content compared with cultivated forage species. Cool-season weeds had high digestibility and crude protein at the vegetative stage, being comparable in quality to cultivated cool-season forage species. Even at more mature stages, nutritive quality of cool-season weeds was generally superior to bermudagrass. Cool-season weeds had adequate levels of calcium and potassium for beef cattle nutrition, but were often low in phosphorus and magnesium. Warm-season weeds generally were superior in digestibility to bermudagrass and most were equal to pearlmillet at the vegetative state. Crude protein content of warm-season weeds was comparable to bermudagrass at the vegetative stage but declined with maturity. Crabgrass maintained relatively high quality at all stages of maturity. Calcium, magnesium, and potassium levels of warm-season weeds were generally high. Phosphorus content of many warmseason weeds was low and inadequate for beef cattle.

LITERATURE CITED
(1) FAIRBAIRN, C.B. AND B. THOMAS. 1959. The Potential Nutritive Value

of Some Weeds Common to Northeastern England. 14:36-46.

J.

Brit. Grassi. Soc.

(2) FREEMAN, J.D. AND H.D. MOORE. 1974. Livestock-poisoning Vascular

Plants of Alabama. Ala. Agr. Exp. Sta. Bull. 460. J.A. McGUIRE, AND J.G. STARLING. 1977. Overseeding Winter Annual Forages on Coastal Bermudagrass Sods for Beef Cows and Calves. Ala. Agr. Exp. Sta. Bull. 496. (4)JACKSON, M.L. 1958. Soil Chemical Analysis. Prentice Hall, Inc., Englewood Cliffs, N.J. (5) MARTEN, G.C. AND R.N. ANDERSON. 1975. Forage Nutritive Value and Palatability of 12 Common Annual Weeds. Crop Sci. 15:821-827.
(3) HOVELAND, C.S., WB. ANTHONY,

(6) NATIONAL RESEARCH COUNCIL. 1976. Nutrient Requirements of Beef

Cattle. 5th ed. rev. National Academy of Science. Washington, D.C. (7) SPEDDING, C.R.W. 1966. Weeds and Animal Productivity. Proc. Br. Weed Control Conf. 8:854-860. (8) TILLEY, J.M. AND R.A. TERRY. 1963. A Two-Stage Technique for In Vitro Digestion of Forage Crops. J. Brit. Grassl. Soc. 18:104-111.
(9) TRIBE, D.E., J.G. GORDON, AND C.H. GIMINGHAM. 1952. The Nutritive

Value of Weeds and Coarse Herbage (Browse) for Young Cattle Grazing a Temporary Pasture. Emp. J. Exp. Agric. 20:240-248.