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Krall, J., R.W. Groose, and J. Sobels. 1996. Winter survival of Austrian winter pea and annual medic on the western high plains. p. 237-240. In: J. Janick (ed.), Progress in new crops. ASHS Press, Alexandria, VA.

Winter Survival of Austrian Winter Pea and Annual Medic on the Western High Plains

James Krall, Robin W. Groose, and Jonathan Sobels

    1. Annual Medics
    2. Austrian Winter Pea
  4. Table 1
  5. Table 2
  6. Table 3

Hard red winter wheat (HRWW) is the most commonly grown non-irrigated crop in eastern Wyoming. Approximately 81,000 ha of HRWW are grown annually in a wheat fallow system (Wyo. Agr. Stat. Serv. 1995). The predominance of HRWW is due largely to climatic patterns of this region. The latitude (41 to 43° N) and altitude (1220 to 1830 m) result in a mean frost-free period of 128 days. Mean annual precipitation is 390 mm with 66% occurring between the months of April and August. This can result in mid-winter conditions of infrequent snow cover and below freezing temperatures.

Current HRWW production utilizes primarily native organic N which is depleted as N is mineralized and soil organic matter is lost (Schuman et al. 1994). N applied as commercial fertilizer is also used which adds to production costs and public concern about environmental pollution.

In some regions of the world annual legumes have replaced fallow in cereal agroecosystems. Self-regenerating pastures of annual medics (Medicago spp.) grown in rotation with wheat contribute to sustainable agriculture in the cereal/pasture zone of southern Australia by providing organic N, conserving and building soil, and providing a break from cereal pests and diseases.

This wheat/sheep system is a short-term annual system of pasturing in a 330 to 450 mm annual precipitation zone which occupies as much as 30 million hectares (Crawford et al. 1989). The legumes naturally regenerate annually from seed. They are prostrate in growth habit, making them relatively easy to manage in the wheat crop. Pasture phases are short term (1 to 3 years) followed by wheat. Soil nitrogen and water-stable soil aggregates increased with each pasture phase and decreased with each wheat phase (Reeves 1987); however, in the integrated system both nitrogen and water-stable aggregates are maintained above the previous continuous cropping levels.

Pest control benefits that result from crop rotation can also have a significant economic and environmental impact. For example, in Australia, cereal cyst nematode (Heterodera avenae Woll.) can be a serious problem. Rotation to annual grass-free legume pasture can effectively control this pest as well as the disease, take-all (Gaeumannomyces graminis var. tritici Walker) (Tow and Schultz 1991). On the Great Plains 2- or 3-years rotations with legumes will result in control of Cephalosporium stripe [Cephalosporium gramineum Nis. & Ika. (syn. Hymenula cerealis Ell. & Ev.)] (Wiese 1977). Additionally, winter annual grass weeds such as downy brome (Bromus tectorum L.) can be effectively managed in legume rotations.

In northern Idaho, fall-planted Austrian winter pea [AWP, Pisum sativum spp. arvense (L.) Poir] has also been shown to have the potential to improve soil quality, producing in excess of 10 t ha-1 of organic matter (Auld et al. 1982). On the Western High Plains, winter annual legumes could play a similar role in rotation with wheat by partially replacing the typical 14 month fallow period if materials can be identified with sufficient cold-tolerance to survive the harsh winters of this region. The objective was to determine winter survival potential of cultivars and/or experimental lines of annual medic and Austrian winter pea on the Western High Plains.


Replicated field trials at various locations in southeastern Wyoming were conducted starting in 1992 beginning with AWP. Field trials contained 3 to 4 replications. Plots were 1.5 by 7.6 m, except for the 1994/95 medic trial which were 15 by 60 cm microplots. Trials were established during Aug.-Sept. To assess winter survival, stand counts were made in Nov. and again in Apr. Means were calculated and are presented in plants/m2.


Annual Medics

Commercial Australian annual medic cultivars failed the winters of 1993/94 and 1994/95 (Table 1 and 2). Experimental lines with potential cold tolerance were established in fall 1994 along with commercial cultivars. On Apr. 1, 1995 survival was as follows: M. polymorpha cv. Santiago (0%), M. polymorpha line SC03077 (3%), M. truncatula cv. Paraggio (3%), M. truncatula line SCO7078 (5%), M. rigidula line SCO3075 (55%), and (80%) for the control M. sativa cv. Ladak, a very winter hardy alfalfa (Abernethy and Thiel 1985). Plants of M. rigidula flowered beginning Apr. 28 and produced mature seed pods by July 6.

Our results indicate that M. rigidula offers the greatest potential for winter survival of all the annual medics evaluated in this region. Our study confirms results of Abd El Moneim and Cocks (1986) and Cocks and Ehrman (1987) at the International Center for Agricultural Research in the Dry Areas, Allepo, Syria. These researchers found that in two severe winters (1983 and 1984), Medicago rigidula exhibited more cold tolerance than other annual Medicago spp.

Recently M. rigidula has been differentiated into the two species M. rigidula (L.) All. and a new species, M. rigiduloides E. Small. (Small et al. 1990; Small 1990). Subsequently, research at the South Australian Research and Development Institute (R.W. Groose, R. Ballard, N. Charman, A.W.H. Lake, unpublished results) has demonstrated that the two species have very different Rhizobium requirements. Commercial strains of Rhizobium recommended for various annual medic species in South Australia effectively nodulated M. rigidula lines but failed utterly with lines of M. rigiduloides. Conversely, some experimental Rhizobium strains effectively nodulated M. rigiduloides but were only weakly effective with M. rigidula.

Lines of M. rigidula and M. rigiduloides from high elevations and the northern limits of the ranges of these species in Europe and Asia have been selected and used as parents in a breeding program to produce winter-hardy medics adapted to the Western High Plains that will combine enhanced cold-tolerance, optimum Rhizobium specificity, reduced pod spininess and high productivity.

Austrian Winter Pea

Mean winter survival of AWP cv. Melrose across 15 location-years was 63% (Table 3). Survival of AWP cv. Common across 5 location-years was 86%. These findings compare favorably to those reported for Moscow, Idaho and Bozeman, Montana (Auld et al. 1983). Our findings indicate that commercial sources of AWP should contain good winterhardiness potential for the Western High Plains. A screening program is under way with hopes of identifying lines with even greater winter survival potential.


Table 1. Fall and spring plant populations of commercial Australian annual medic cultivars along with alfalfa in Wyoming 1993/94, values are means based on four locations.

Population (plants/m2)
Genotype Fall Spring
M. littoralis cv. Harbinger AR (strand medic) 15 0
M. truncatula cv. Caliph (barrel medic) 44 0
M. truncatula cv. Paraggio (barrel medic) 9 0
M. sativa cv. Ladakz (alfalfa) 28 11
M. scutellata cv. Sava (snail medic) 16 0
zVery winter hardy.

Table 2. Fall and spring plant populations of experimental lines and commercial Australian annual medic cultivars along with alfalfa in Wyoming 1994/95.

Population (plants/m2)
Genotype Fall Spring
M. polymorpha cv. Santiago (burr medic) 260 0
M. polymorpha SC03077 (burr medic) 260 7
M. rigidula SCO3075 260 143
M. sativa cv. Ladakz (alfalfa) 260 208
M. truncatula cv. Paraggio (barrel medic) 260 7
M. truncatula SCO7078 (barrel medic) 260 14
zVery winter hardy.

Table 3. Location, year, fall and spring populations of Melrose Austrian winter peas planted in Wyoming.

Population (plants/m2)
Location Year Fall Spring
Archer 1990/91 28 4
Torrington 1990/91 13 7
Archer 1992/93 108 68
Chugwater 1992/93 104 96
Hawk Springs 1992/93 116 56
Pine Bluffs 1992/93 144 40
Torrington 1992/93 60 52
Chugwater 1993/94 69 52
Hawk Springs 1993/94 62 45
Pine Bluffs 1993/94 71 19
Chugwater 1994/95 62 (56)z 51 (48)
Hawk Springs 1994/95 67 (61) 54 (58)
Pine Bluffs 1994/95 65 (57) 49 (46)
Torrington 1994/95 60 (57) 55 (49)
Archer 1994/95 22 (20) 17 (16)
Mean 70 (50) 44 (43)
zParenthetical values are for 'Common' Austrian winter pea.

Last update June 9, 1997 aw