VALUE AND USE
SPECIES: Melilotus officinalis | Yellow Sweetclover 



WOOD PRODUCTS VALUE : 
NO-ENTRY


IMPORTANCE TO LIVESTOCK AND WILDLIFE : 
Eaten by most herbivores including elk, deer (all species), pronghorn,
and domestic livestock, yellow sweetclover is an important range,
forage, hay, and pasture species [20,62,64,66].  Yellow sweetclover will
comprise up to 35 percent of pronghorn diet [5].  Mule deer diet
consists of up to 77 percent yellow sweetclover in summer and early fall
[16,20,44,45,49].  Kufeld [39] and Mackie [44] rated sweetclover as
highly valuable for Rocky Mountain elk in summer and fall.

Yellow sweetclover is important to birds as cover and food, and is
planted with grass seed to improve sage grouse and prairie chicken
habitat [2,36,48,58,61].  It is considered important nesting habitat for
dabbling ducks (mallard, gadwall, blue-winged teal) in hayland and
seeded fields [12,41].  Cropland adjustment program areas (fields left
fallow for wildlife habitat) in North Dakota containing yellow
sweetclover as a principal species with wheatgrasses (Agropyron spp.) or
brome grasses (Bromus spp.) and alfalfa (Medicago sativa) provide
habitat for pheasants, sharp-tailed grouse, greater prairie chickens,
American bitterns, marsh hawks (northern harriers), short-eared owls,
and many species of passerine birds [19,36,67].

A problem with yellow sweetclover as a hay crop is sweetclover bleeding
disease.  Coumarin, which is present is sweetclover and gives its bitter
taste, breaks down to dicoumarol when sweetclover becomes moldy.
Dicoumarol is a powerful anticoagulant and causes hemorrhage in cattle
(it is not as harmful to sheep or horses), and can result in death.
Sweetclover bleeding disease can be avoided by proper curing of
sweetclover hay and/or by interspersing the feeding of moldy hay with
other materials, as it takes several weeks of feeding moldy hay to cause
the disease.  Cultivars with reduced coumarin content are available
[9,64].  Bloat can also be caused by yellow sweetclover but occurs less
frequently than with alfalfa (Medicago sativa) or clover (Trifolium
spp.) [44,64].


PALATABILITY : 
Yellow sweetclover has a bitter taste, making it less palatable to
cattle than other legumes.  It is more palatable in early spring and
summer, becoming woody in late summer and fall [62,64].

Palatability of yellow sweetclover for elk and deer is rated high in
spring and summer, and for pronghorn is rated medium in summer [60].

Palatability of yellow sweetclover in several western states has been
rated as follows [17]:

                UT      CO      WY      MT      ND
Cattle         fair    good    good    good    good
Sheep          fair    good    good    good    good
Horses         fair    fair    good    good    good


NUTRITIONAL VALUE : 
Yellow sweetclover makes palatable and nutritious hay when properly
cured.  Protein content and digestible protein of yellow sweetclover hay
was reported as follows [48]:

crude protein                   15.0 %
digestible protein-cattle       10.2 %
                   goats        10.8 %
                   horses       10.5 %
                   rabbits      10.4 %
                   sheep        10.6 %


COVER VALUE : 
Yellow sweetclover provides good cover for small mammals and birds
[12,19,36,41].  Wildlife cover values for several western states are as
follows [17]:

                         UT      CO      WY      MT      ND
Elk                     ----    poor    ----    poor    ----
Mule deer               fair    ----    poor    good    good
White-tailed deer       ----    ----    poor    ----    good
Pronghorn               fair    ----    poor    good    good
Upland game birds       good    good    good    good    good
Waterfowl               fair    ----    good    ----    good
Small nongame birds     good    good    good    good    good
Small mammals           good    good    good    good    good


VALUE FOR REHABILITATION OF DISTURBED SITES : 
Yellow sweetclover grows rapidly and is easy to establish, therefore it
is widely used in grass and forb seed mixtures for stabilization of
disturbed sites such as road cuts, mining disturbances and mine spoils
[1,14,30,55] after any type of burn [10,15,23,31,37], and for
rehabilitation of overgrazed rangeland [42,50,62].


OTHER USES AND VALUES : 
Yellow sweetclover is often planted in grass/forb seed mixtures on range
sites, including pinyon (Pinus edulis)-juniper (Juniperus spp.)
communities, to improve forage production [13,35,58,62], and for soil
improvement, to increase available soil nitrogen and to improve
drainage, aerate the soil, and increase water absorption in heavy clay
soils [62,64].

Yellow sweetclover is considered an excellent source of nectar for honey
production and also an excellent source of pollen [62].

Yellow sweetclover is used medicinally as a source of an anticoagulant
(dicoumarol and derivatives) used to reduce postsurgical blood clots
[62].


MANAGEMENT CONSIDERATIONS : 
Use of yellow sweetclover as an agricultural species has declined in
part due to its tendency to "volunteer" for years after planting and to
its weediness in colonizing disturbed sites.  It is considered a noxious
weed in some areas; its ability to colonize undisturbed habitat is
related to the amount of disturbed area (including roads) adjacent to
habitat and the amount of light penetrating to the understory [26].
Additional factors contributing to the decline in its use include:
stand establishment problems due to sweetclover weevil (Sitona
cylindricollis), bleeding disease, a decrease in rotation systems of
cropping, and the availability of inexpensive nitrogen fertilizers
[62,69].

Control:  In an effort to restore native prairie, invading yellow
sweetclover is controlled with a combination of brush-hogging,
herbicides, and prescribed fire [8]. Yellow sweetclover is sensitive to
2,4-D, dicamba, tordon, aflon, nevuron, and dalapon.  It is more
difficult to kill with 2,4-D in the second year [67].


Establishment:  To provide habitat for dabbling duck nesting, it is
necessary to establish vigorous stands with the tallest, densest cover
form possible.  This can be achieved through a combination of prescribed
fire and planned grazing for native seedings, but mechanical tillage,
with reseeding every 2 years, is best to maintain introduced grasses and
legumes [19].  Prairie grouse habitat can be developed on cultivated
land by planting yellow sweetclover and leaving it undisturbed until
stand vigor declines, and then restoring it by tillage and replanting or
by prescribed fires [36].

If yellow sweetclover is to be used to convert sage range to grassland,
there needs to be a minimum of 11 inches (30 cm) of annual
precipitation.  It should be seeded in grass mixtures at a rate of 1 to
2 pounds of yellow sweetclover seed per acre (2.2 kg/ha) [35].  Love and
Jones [42] recommend a grazing rotation that includes no grazing the
first year; light grazing the second; grazing early in the third year
then removal of stock; a prescribed fire the fourth year, keeping stock
off; then a repeat of the cycle, with the fifth year as the second.
Removal of tops during the critical growth period in September reduces
root growth and top growth the following year.  No grazing or mowing
should be done during this time [62,67].  Nitrogen fertilizers are not
needed if sweetclover is inoculated with Rhizobium bacteria at seeding;
it does respond to phosphorous, potassium, and sulfur fertizilation
[64].

Elliot [22] found that yellow sweetclover does not affect seedling
survival of ponderosa pine and can be used as part of soil stabilization
seeding mixtures.

Rietveld [56] noted that the bunchgrasses contain a substance toxic to
germination of sweetclover, and that sweetclover roots contain
substances allelopathic to crested wheatgrass (Agropyron cristatum),
Russian wildrye (Psathyrostachys juncea), intermediate wheatgrass
(Thinipyrum intermedium), smooth brome (Bromus inermis), and timothy
(Phleum pratense).

Diseases and Pests:  Some diseases of yellow sweetclover include root
rot (Phytophthora cactorum), brown root rot (Plenodomus meloliti),
common leaf spot (Pseudopeziza meliloti), and gray stem canker
(Ascochyta caulicola).  The 'Yukon' cultivar is resistant to brown root
rot and gray stem canker.  Common leaf spot is controlled by cutting
before defoliation becomes severe, and gray stem canker can be
controlled through crop rotation and cutting fields cleanly [62,64].

The primary pest of yellow sweetclover is the sweetclover weevil (Sitona
cylindricollis).  To avoid infestation, new stands should not be planted
adjacent to established stands.  Cultivars that are more resistant to
sweetclover weevil are available [62].  Other serious insect pests
include grasshoppers and cutworms, which can be controlled with poisoned
baits [69].

Related categories for Species: Melilotus officinalis | Yellow Sweetclover