More info for the terms: competition, cool-season, cover, forbs, litter, prescribed fire, presence, selection, shrubs, warm-season
Alfalfa is the most highly valued and widely planted legume. Before
planting, however, managers should take into account the grazing
management plan for the range unit. Seeded species can do more
harm than good, and alfalfa may not always be the most appropriate
legume [46,97]. There is a general trend for preferring native species
for rangeland over introduced species where feasible. It is often the
case that assembly of native seed mixtures is more expensive than
commercially available seed. There are, however, some companies that
are starting to make native legumes available [96,97].
The choice of alfalfa for plantings should depend on climatic and
edaphic conditions favorable to alfalfa establishment. A minimum of 10
to 12 inches (28-38 cm) of precipitation is needed, at least half of it
not snow. Alfalfa is the only exotic legume recommended for planting in
southwestern Saskatchewan and southeastern Alberta [56]. It appears to
be limited by high elevations [109]. Alfalfa performance and
persistence is quite variable and is dependent on a number of factors,
not all of them predictable [42]. Seedings of alfalfa mixtures in
southeastern Oregon have persisted for 17 years or more, and as long or
longer in other western states [60,99]. The weather factors following
seeding are considered to be highly important in determining successful
establishment. A severe frost following germination is lethal [50].
Grazing management is also influential in establishment and persistence.
'Nomad' alfalfa normally forms seed, so grazing prescriptions that are
designed to favor trampling of seed (thus scarifying it and making a
firm seedbed) may improve persistence [60]. A general trend in western
rangeland seedings is that initial establishment and productivity are
usually good to excellent and drop off as the stand matures [95]. In
southern Oregon, a 1972 aerial seeding of 'Nomad' alfafa in stands of
crested wheatgrass was "spotty" by 1975 and still lower by 1986. In a
pinyon-juniper type in central Utah, initial coverage of alfalfa on a
chained and seeded rangeland was excellent but declined slightly from
1982 to 1985 [21]. Creeping rooted cultivars are longer lived than
other strains on sites with 12.6 to 15 inches (32-38 cm) precipitation
[51]. The value of alfalfa is such that even a small amount contributes
to forage quality and productivity [49].
Since it is difficult to choose seed mixtures that are perfectly adapted
to particular conditions and produce a specified composition of species,
mixtures of a wide variety of seeds are preferred in most cases [21].
The choice of the grass species to be seeded with alfalfa has an effect
on alfalfa persistence. 'Whitmar' bluebunch wheatgrass
(Pseudoroegenaria spicata) allowed more alfalfa to coexist than did
'Greenar' bluebunch wheatgrass or 'Nordan' crested wheatgrass (Agropyron
cristatum) [60].
In the western juniper (Juniperus occidentalis) zone of central Oregon,
a range planting study failed to establish alfalfa. The area receives
11 to 15 inches (28-38 cm) precipitation and has shallow clayey loam
soil. The author concluded that the inclusion of seeds of grasses,
forbs, and shrubs other than crested wheatgrass and Siberian wheatgrass
(Agropyron sibiricum) is "questionable" for the western juniper zone
[69]. It is probable that the planting conditions may have been too dry
for good establishment or that deer or rodents may have damaged the seed
and/or seedlings too heavily. There are other reports of range seeding
failures and plantings that did not have productivity results as high as
expected; these also may have failed to take into account initial
planting conditions or may have failed for more obscure reasons
(competition, rodent predation on seeds or roots etc.) [14,23,60,102].
For rangeland improvement in aspen (Populus spp.) parklands in
Saskatchewan, smooth brome (Bromus inermis) is planted with alfalfa.
Areas that have been chained and seeded are susceptible to regrowth of
aspen and prickly rose (Rosa acicularis) suckers. Application of
herbicides to control aspen and prickly rose have a detrimental effect
on alfalfa. Alfalfa is sensitive to picloram, 2,4,-D and 2,4,5-T, and
is killed at levels applied to control woody species [7]. It may
therefore be only beneficial to include alfalfa in such plantings when a
mix of 2,4-D and picloram is applied 5 to 10 years after the forage
stand is seeded [8]. In a study to control woody reinvaders (aspen and
snowberry [Symphoricarpos occidentalis]) in burned and seeded aspen
parkland, it was found that early season, short-duration heavy grazing
severely reduced competition from woody suckers. Newly germinated
forage seedlings survived better and resulted in a more rapid
establishment of forages than under either late-season, short-duration
heavy grazing or no grazing [4].
Establishment: Alfalfa establishes best with a firm seedbed, and
drilling is the preferred method of seeding in most areas
[42,53,91,110]. Recommended planting depth is 1/4 to 1/2 inch (1 mm-
2 mm) [53]. Seed germination is inhibited by the presence of pine and
juniper litter over buried seed. In pinyon-juniper types, germination
may be enhanced by broadcast seeding rather than drilling [34,89]. No
added nitrogen is needed if the seed is inoculated with Rhizobium
bacteria. However, phosphorus, potassium, and sulfur should be
supplemented if the soil is deficient in these nutrients [110,114]. The
acid intolerance of alfalfa may be overcome by the addition of calcium
and nitrogen fertilizers, which counteracted the effects of low pH under
laboratory conditions [115].
Some recommended seeding rates (certified pure live seed) are as
follows:
For pure stands 15 - 20 lbs per acre (17-22 kg/ha) [50]
9 lbs per acre (10 kg/ha) [110]
10-15 lbs per acre(12.5-22 kg/ha) [53]
For mixed stands 1-2 lbs per acre (1.25-2.5 kg/ha) [53,111]
2.5 lbs per acre (2.8 kg/ha) [99]
Viable seed is bright olive green [111].
No significant effect on yield was detected between applications where
all seeds were mixed and seeded, and applications where alfalfa was
seeded alternately with crested wheatgrass [101].
The preference of deer mice for alfalfa seed has contribute seeding
failures in Nevada; deer and rodents probably contributed to seeding
failures in northeastern Washington and on a subalpine grassland study
in north-central Washington [32,35,109]. In a study of the combined and
individual effects of deer, rabbit, and rodent use of alfalfa, deer use
was found to have a greater negative impact than rabbit use. Rabbit
damage is usually minimal, except in peak rabbit population years [95].
The soil-loosening effect of alfalfa roots may increase rodent burrowing
activity, which can contribute to postestablishment failures [45].
Seeding dates vary with location. In South Dakota, late summer seedings
are more successful than spring seedings. Sowing can take place later
farther south; near the Gulf of Mexico, alfalfa can be sown as late as
October, and in the Southwest, plantings can be made as late as
December. North and east of Nebraska, spring sowing is usually best
with a companion grain crop [50]. If the management goal is to provide
a seasonally balanced grassland, it is important to delay seeding to
favor warm-season species. If planted too early, the tendency is to
establish a stand dominated by cool-season species [84].
Planting methods and further management considerations are detailed in
Horton 1989 [53], Hull and others 1958 [55], Love and Jones 1952 [73],
and in:
1. U.S. Department of Agriculture, Forest Service, Intermountain Forest and
Range Experiment Station. 1979. User guide to vegetation. Gen. Tech.
Rep. INT-64. Ogden, UT.
2. U.S. Department of Agriculture, Forest Service, Intermountain Forest and
Range Experiment Station. 1979. User guide to soils. Gen. Tech. Rep.
INT-68. Ogden, UT.
For postfire regeneration projects in Alberta, where much of the organic
matter is destroyed by fire, alfalfa seeded with wheatgrasses, red
fescue, brome grasses, and clovers is more successful in spring
plantings than fall plantings [2]. The concern has been raised that
seeding introduced species such as alfalfa can suppress native
vegetation. In degraded big sagebrush (Artemisia tridentata) habitat
types, cheatgrass (Bromus tectorum) is an invading species that is
reduced by moderate to severe wildfires. Since the native perennial
grass seed bank in these areas is depauperate, postfire seeding of
introduced species after such wildfires can greatly reduce the acreage
invaded by cheatgrass. These seedings appear to prevent revegetation by
species native to the area, so managers must be able to judge which
areas are likely to be invaded by cheatgrass after fire (which can be
partially predicted by the amount of unburned organic litter remaining
after a fire) and seed those, leaving other areas to natural
regeneration [128].
Livestock use: Rangeland use of alfalfa carries the risk of bloat in
cattle, horses, and sheep. This risk can be reduced by planting
perennial grasses to cover at least half of the site [50,110,114].
Bloat risk is also reduced by delaying grazing until after flowering is
completed [110].
Alfalfa does not persist on moderately to heavily grazed rangelands
unless there are well-timed rest periods [53]. A short period of
intense grazing during May and June is considered more favorable
management for alfalfa than a long period of summer grazing [97].
Alfalfa tolerates rotational grazing; stands will weaken rapidly if
grazed continuously [50]. Hafenrichter [46] recommends a rotation
deferred system in bunchgrass areas. Grazing should not be closer than
4 to 6 inches (10-15 cm). Alfalfa is sensitive to depletion of root
reserves in the fall and should not be grazed heavily at this time
[110]. Frequent, intense clipping decreases lateral shoot spread [95].
The longevity of alfalfa in some semiarid environments appears related
to the degree of utilization--persistence is enhanced when only lightly
used [99]. Some cultivars are more tolerant of grazing than others. A
prostrate growth form is associated with persistence under grazing [20].
For example, under close grazing, 'Nomad' alfalfa assumes a prostrate
form, which increases its tolerance to grazing [60].
Methods for hay production are detailed in [46,50,70,110,130,131].
Insect pests: The pea aphid (Acyrthosiphon pisum) causes stunted,
wilted plants and reduces cold hardiness. The alfalfa weevil (Hypera
postica) is the most important pest in the United States and Ontario.
It can defoliate both first and second cuttings of hay, reducing hay
yield up to 50 percent and also reducing hay quality. Alfalfa curculio
(Sitona scissifrons), a weevil that attacks leaf edges, is not a problem
in established stands but can destroy seedling fields. Lygus plant bugs
(Lygus spp.) mostly damage seed production. The alfalfa looper
(Autographa californica) is not a serious problem except where local
outbreaks can cause severe damage. Grasshoppers (Melanoplus spp.,
Camnula spp.) consume all plant parts and can be extremely destructive
in dry years [110].
Control of insect pests: The pea aphid, alfalfa weevil, and alfalfa
looper are subject to biological control; chemical control is also
recommended for the pea aphid, alfalfa weevil, alfalfa curculio, lygus
plant bugs on seed crops; outbreaks of alfalfa looper; and for
grasshoppers [110].
Diseases: Most diseases of alfalfa become more severe with the age of
the stand; most stands are free of disease the first year, with the
exception of alfalfa sickness. Disease can be established by the second
year, and by the fourth year, it is often uneconomical to maintain the
stand. Stands can be kept healthy by such management practices as
adequate fertilizer and water. Varieties should be chosen that are
resistent to diseases common to the area.
Leaf and stem diseases include common leaf spot, yellow leaf blotch,
black stem, downy mildew, and verticillium wilt. Crown and root
diseases include winter crown rot crown bud rot, bacterial wilt, alfalfa
sickness, and brown root rot [110].
Control: Burning in the spring before growth begins prevents crop
injury by the burn and reduces the amount of infected leaves. Crown and
root diseases are mitigated with adequate fertilizer and by allowing
plants to recover in the spring before cutting or grazing. Adequate
late summer growth builds up winter reserves and reduces disease
susceptibility [110].
Wildlife use: Sharp-tailed and sage grouse habitat can be developed in
North Dakota by planting brome grass and alfalfa and left undisturbed
until stand vigor declines. Vigor can then be restored by mechanical
disturbance, reseeding, or burning, with prescribed burning considered
the least disruptive to grouse [62,63]. For wildlife habitat
(particularly dabbling ducks) in the northern prairie pothole region, it
is recommended that native grasses be planted on sites that receive 20
inches (51 cm) or more annual precipitation, and that introduced grasses
and legumes (particularly alfalfa) be used in the drier areas. It is
considered better for duck nesting if fields of 40 acres (25 ha) or more
are established near or adjacent to wetland types of habitat [30].
Removal of cover by mowing affects the distribution of breeding ducks
but probably does not decrease the overall breeding population.
However, residual growth is an important component of selection of nest
sites for many species of ducks, and therefore nesting would be
increased by allowing some areas to go unmowed in the latter part of the
season [75].
Gray partridge nesting in North Dakota can be encouraged in alfalfa
stands that are adjacent to cereal crops (especially on roadsides and
field edges). These stands are best if left unmowed so that heights of
9 to 12 inches (23-30 cm) are achieved. Programs to leave unmowed
strips along the crop side of fields and roadsides could greatly
increase potential nest sites for gray partridge [11].
Upland sandpipers in North Dakota have experienced population declines,
largely due to past hunging and loss of habitat. Many acres of suitable
habitat have been converted to grasses and legumes, notably alfalfa and
sweetclover. Alfalfa fields are usually too tall for upland sandpipers,
which prefer cover heights between 6 and 12 inches (15 and 30 cm).
Alfalfa is not recommended for upland sandpiper habitat and therefore a
management goal to increase habitat for upland sandpipers would include
conversion of alfalfa fields to native vegetation where appropriate
[62].
Management for pronghorn includes the maintenance of rangeland in seral
stages such that grasses and forbs dominate, with a low (15-20 percent)
shrub cover [127]. This was accomplished historically by periodic
wildfire, and today can be accomplished by prescribed fire or by
chaining and drill-seeding big sagebrush communities dominated by tall
shrubs. Recommended seed mixtures contain approximately six species
each of grasses, forbs, and shrubs [127]. Including alfalfa in the seed
mixtures is highly recommended for a number of habitat types. This
technique is considered very successful for pronghorn habitat
improvement in southeastern Oregon [59,61]. After at least 6 years,
alfalfa constituted 10 percent of the vegetation on most planted sites
[127].
Cultivars: For nonirrigated land, 'Ranger' alfalfa is a hardy,
wilt-resistent variety. It is widely adapted throughout the northern
and central United States. 'Ladak' alfalfa produces a large first crop
but is very slow to recover recovery after cutting. It has some
resistance to wilt and leaf diseases. It is most valued in cold, dry
climates. 'Vernal' alfalfa is a variety developed in Wisconsin and has
excelled 'Ranger' in both yield and stand persistence. 'Nomad' alfalfa
is a creeping or pasture-type which persists under intensive and
continuous grazing. It has rather wide adaptation throughout the
Northwest and elsewhere under dry and cold conditions. 'Rambler'
alfalfa is also a creeping variety that spreads by true underground
roots. It is adapted to the prairie provinces of Canada and northern
areas in the United States [111,122].
A more complete list of cultivars and their availability can be found
in :
1. U.S. Department of Agriculture, Agric. Handb. 177
2. Barnes, D. K.; Smith, D. L. 1984 Review and description of alfalfa
varieties. In: Report of the Alfalfa Improvement Conference.
Washington, DC: U.S. Department of Agriculture, Agricultural Research
Service: 115-118.
