This form has been termed field pea (Duke, 1981; McLeod, 1982) and Austrian winter pea (Munoz & Graves, 1988), but it is completely interfertile with other forms of Pisum sativum, and is therefore sometimes grouped with common pea or garden pea (Duke, 1981).

Pisum sativum L., or Pisum sativum L. ssp. arvense (L.) Poir. (Duke, 1981).

The most common varieties of field peas used in California are Austrian winter pea and its derivatives. Two strains, the 'Early Austrian' and the 'Dixie Wonder,' are selections of the Austrian winter pea and differ only in that they mature earlier (Miller et al., 1989).

'Austrian Winter' has been largely replaced by the field pea varieties 'Melrose' and 'Glacier' (Hoveland and Townsend, 1985). 'Melrose' was selected from progeny of a cross between common Austrian winter pea and powdery mildew resistant 'Perfection,' a spring pea (Auld et al., 1979).

'Century' variety of field pea performed well in trispecific mixes (pea - barley - white mustard) even with high soil nitrogen. The smaller 'Alaska' pea did well in such mixtures with high water and low nitrogen (Liebman, 1989).

Seeds are globose or angled, smooth or wrinkled, exalbuminous, whitish, gray, green, or brown; 100 seeds weigh 15-25 g (Duke, 1981). The seeds are larger than those of common vetch and are almost spherical; they are pale green to brown, covered with numerous specks of a darker coloring; black seed scar is relatively small (Goar, 1934).

Cv 'Melrose' has a chocolate-brown seed coat (Auld et al., 1979).

Germination of pea is cryptocotylar; optimum temperature for germination is 24 degrees C (Duke, 1981). Emergence of pea seedlings was unaffected by soil crust formation, by contrast with the situation for narrow-leafed lupin (Lupinus angustifolius) and medics (Medicago spp.), which were severely damaged (White and Robson, 1989b).

Field pea is an annual herb, bushy or climbing, glabrous, usually glaucous; stems are weak, round, and slender (Duke, 1981). The plant is very viny, with weak, small stems (though larger and more succulent than those of vetches) and requires a supporting crop, such as oat or rye, in order to ascend (Goar, 1934). Flowers are white, pink, or purple (Duke, 1981) and are borne singly or in pairs on long stems; usually two leaflets and a tendril constitute the leaf (Goar, 1934).

Cv 'Melrose' has purple flowers which occur indeterminately in early June above the 16th node; two to three pods form per peduncle. At maturity, length of vines may exceed 5 feet. Root nodules are abundant (Auld et al., 1979).

At maturity, pea (cv 'Early Dun') contained 34% of its total dry matter and 56% of its total N (90 kg/ha) in the seed, 60 kg/ha in the stubble, and 6-8% of the N fixed (less than 15 kg N/ha) in the root system (Herdina and Silsbury, 1990).

Common pea tolerates mean annual temperatures of 5.0-27.5 degrees C, with the mean of 137 cases being 12.9. Germination can occur at 4.5 C, but optimal temperature for germination is 24 degrees C. Higher temperatures may accelerate germination but increase seedling susceptibility to soilborne pathogens (Duke, 1981).

Field pea grows in the winter where the climate is mild or in the spring where the winters are too severe for growth. The plant requires cool, moist growing conditions and can withstand heavy frost; however, it succumbs quickly to heat, especially if combined with humidity (McLeod, 1982). Cold resistance is due to winter dormancy (Madson, 1951; Miller et al., 1989). Cv 'Melrose' shows excellent winter hardiness (Auld et al., 1979).

Common pea ranges from the Boreal Moist to Wet through the Tropical Very Dry Forest Zone (Duke, 1981). Field pea is especially adapted to the interior valleys and to the foothills sections of California (Goar, 1934). Munz (1971) listed field pea as an occasional escape from cultivation in California.

Common pea tolerates annual precipitation of from 0.9 to 27.8 dm with a mean of 137 cases of 9.2 (Duke, 1981). Field pea requires cool, moist growing conditions (McLeod, 1982) and shows a 20-inch irrigation requirement (less any rainfall) (Munoz & Graves, 1988).

A study by Mohler and Liebman (1987) indicated that high-density plantings of barley were better at suppressing weeds than were intercropped barley and field pea. Weed suppression appeared to be due to competition for soil moisture. Weed populations were not reduced, but weed biomass was.

A trial by Liebman (1989) indicated that 'Century' variety of field pea performed well in trispecific mixes (pea - barley - white mustard) even with high soil nitrogen. The smaller 'Alaska' pea did well in such mixtures with high water and low nitrogen.

Common pea, requires moderately fertile soil, and is relatively unresponsive to fertilizers but often does benefit from added P or K (Duke, 1981). This species does well on calcareous soils (McLeod, 1982).

Lupins suffer iron deficiency when grown on calcareous soils, much more so than does field pea. However, this is not due to to a lesser ability to acidify the root zone or to an incapacity to reduce Fe3+, as shown with studies of field pea, Lupinus anugustifolius and L. cosentinii in solution culture (White and Robson, 1989).

'Century' variety of field pea performed well in trispecific mixes (pea - barley - white mustard) even with high soil nitrogen. The smaller 'Alaska' pea did well in such mixtures with high water and low nitrogen (Liebman, 1989).

Common pea grows in soil pH ranging from 4.2-8.3, with a mean of 122 cases of 6.3; optimal range is variously given as 5.5-6.5, 5.5-6.8, and 6.00-7.50 (Duke, 1981). According to Munoz & Graves (1988), field pea tolerates basic to acid soil conditions.

Lupins suffer iron deficiency when grown on calcareous soils, much more so than does field pea. However, this is not due to to a lesser ability to acidify the root zone or to an incapacity to reduce Fe3+, as shown with studies of field pea, Lupinus anugustifolius and L. cosentinii in solution culture (White and Robson, 1989).

Common pea grows well on a wide range of soil types, but is intolerant of waterlogging (Goar, 1934; Duke, 1981; McLeod, 1982). Loam to clay soils are suitable (Munoz & Graves, 1988), and field pea will produce on any soil that will produce oat (McLeod, 1982). Sand can predispose for drought problems because field pea roots are shallow (McLeod, 1982).

Loam to Heavy Soils - Adapted to large range of soil types (Madson, 1951).

Lupins suffer iron deficiency when grown on calcareous soils, much more so than does field pea. However, this is not due to to a lesser ability to acidify the root zone or to an incapacity to reduce Fe3+, as shown with studies of field pea, Lupinus anugustifolius and L. cosentinii in solution culture (White and Robson, 1989).

White and Robson (1990) conducted studies on field pea and narrow-leaf lupin (Lupinus angustifolius) grown in nutrient solution at various Fe III EDDHA concentrations, with bicarbonate (HCO3) used in half the cases, to induce iron deficiency. Fe deficiency led to rapid distortion and brown discoloration of lupin roots, followed by resumption of apparently normal, though slower, growth. Pea was less affected than lupin in terms of plant growth and tissue concentration of Fe III.

Field pea has been successfully used as part of cover crop mixtures in walnut (West Sacramento, California) and citrus (Porterville) orchard understories; the former are densely shaded from April through November; the latter are evergreen and afford moderate shade throughout the year (Bugg, pers. comm.). In light of field pea's intolerance of hot weather (Duke, 1981), some shade is probably beneficial if autumn or spring weather turns hot (Bugg, pers. comm.).

Duke (1981) wrote that peas show little salinity tolerance, with yields declining with EC=3-5 mmhos. Pisum sativum, cv 'DMR 11' and 'Bonneville' were sown in plots with differing soil salinities. The 'DMR 11' pea showed 100% germination up to salinities of ECe 9 dS/m, but 'Bonneville' had 100% germination only up to 6.0 dS.m. At ECe 12 dS/m, germination was 34 and 16% for 'DMR 11' and 'Bonneville'. 'DMR 11' and 'Bonneville' varieties of pea were deemed moderately tolerant and moderately sensitive to salinity (Dua et al., 1989).

Lemerle and Hinkley (1991) found that the field pea cultivars 'Alma', 'Dunn' and 'Maitland' were tolerant of the herbicides Metribuzin and MCPA. Cultivars 'Alma' and 'Dundale' were tolerant of Terbutryne and MCPA. 'Dunn', 'Maitland' and 'Wirreza' were tolerant of Diuron. 'Alma', 'Dinkum', and 'Maitland' tolerated pyridate 1:35 kg/ha.

'Austrian Winter' pea is a winter annual in the South and a summer annual in the North (Miller, 1984). It is a winter annual in most of California but can be grown during the summer in cool coastal areas (Bugg, pers. comm.). Like most other winter-hardy annuals, it grows little during cold weather but rapidly during spring (Goar, 1934). Because of the winter dormancy, most growth is made too late for field pea to be of use as a cover crop (Miller et al., 1989).

The literature review by Buttery and Gibson (1990) indicated that N-fixation by pea reaches a maximum before or at flowering and drops during pod formation, whereas in faba bean substantial fixation continues up to plant maturity.

Seeding rates are given as 70 to 90 lb/acre (Madson, 1951; McLeod, 1982; Miller et al., 1989), 80-120 lb/acre (Miller, 1988), and 100-150 lb/acre (Munoz & Graves, 1988).

According to Auld et al. (1979), seeding rate should be 75 lbs/acre on September 15. Increase seeding rate one lb for every day seeding is delayed. In rough seed beds, increase seeding rates an additional 15 to 25 lbs/acre.

If broadcast seeded, field pea plants will fall down and rot if the crop is not sown thickly or with a nurse crop (McLeod, 1982).

Recommended seeding depths are 2.5-7.5 cm (1-3 inches) (Duke, 1981), 1-1/2 inches (McLeod, 1982), and 1.5 to 2.5 inches according to moisture conditions (Goar, 1934).

According to Duke (1981), seed should be sown 5-7.5 cm apart, at a depth of 2.5-7.5 cm., with rows separated by 0.6-0.9 m; field pea is often intercropped with cereals. Especially on pre-irrigated land, seed should be drilled sufficiently deep to contact moist soil, 2 in. or more in depth, if necessary. Delayed plantings should be made closer to the surface (Madson, 1951).

Seeding should be in early fall according to Munoz & Graves (1988) and, in October-November, according to Madson (1951). 'Melrose' should be sown during early to mid-September to obtain highest yields.

According to Auld et al. (1979), early fall seeding increases winter survivability and leads to larger plants better able to compensate for pea leaf weevil attack the following spring. Early fall-seeded peas flower earlier, avoiding hot weather that can decrease seed production. Early seeding also reduces soil erosion

Pea should be inoculated with Rhizobium leguminosarum (Nitragin Inoculant Type "C") (Nitragin Company, Inc., No Date), which is the same type as used for various vetches (Vicia spp.) (Munoz & Graves, 1988). Inoculation is essential for good growth (McLeod, 1982).

The high price, combined with the large amount of seed required to plant an acre, makes seeding expensive (Miller et al., 1989).

The Southern Seedsmen's Association 1990-1991 Directory and Buyers' Guide listed 37 distributors of field pea seed. Austrian Winter Pea has been grown in California for seed, some for sale in the southern states (Miller et al., 1989).

Field pea flowers in from 32-55 days (Duke, 1981).

Field pea matures seed from 20-30 days after bloom or 52-75 days after planting (Duke, 1981).

Common pea seed yields average 1,725 kg/ha in the U.S.A. (Duke, 1981). Heat is disastrous to seed production and, when grown on fertile soils, rank vegetative growth may occur but few pods (McLeod, 1982). Cv 'Melrose' yielded between 1,800 and 2,000 lbs/acre, outyielding other varieties in 9 of 10 trials conducted at University of Idaho from 1973 to 1979 (Auld et al., 1979).

Seed of field pea remains viable for a relatively short time (McLeod, 1982). Immerse seeds in boiling water for two minutes to kill pea bug (Abstractor's note: presumably this indicates pea weevil, Bruchus pisorum - - R.L. Bugg); this brief exposure will not harm the seed (McLeod, 1982).

Field pea is an annual herb (Duke, 1981); growth habit is low and viny (Miller, 1988); the small, weak stems will not permit upright growth without a supporting crop, such as oat or rye (Goar, 1934).

Spring sown 'Austrian Winter' pea attain a height of about 0.45 m in coastal Massachusetts (Bugg and Ellis, 1990). In Hopland, Mendocino County, California, height of fall-sown cv 'Austrian Winter' was 66.68+/-4.32 cm (Mean +/- S.E.M.) (Bugg et al., unpublished data).

Field pea is shallow rooted and, therefore, subject to drought on sandy soils (McLeod, 1982).

An experiment with pea grown using a split-root procedure suggested that at the time of harvest 22-46% of the below-ground N had been shed into the rhizosphere (root zone). Because this N "rhizodeposition" has not previously been assessed for annual legumes, nitrogen fixation may be underestimated by about 10% (Swatsky and Soper, 1991).

At maturity, pea (cv 'Early Dun') contained 34% of its total dry matter and 56% of its total N (90 kg/ha) in the seed, 60 kg/ha in the stubble, and 6-8% of the N fixed (less than 15 kg N/ha) in the root system (Herdina and Silsbury, 1990).

The following is based on Duke's (1981) account. Soil preparation prior to seeding is important, including the creation of a smooth surface, so that planting depth is uniform. Interseeding field pea and cereal grains is common. During hot weather, field pea germination is rapid, but seedlings may die from pathogens.

Avoid creating waterlogged conditions, because field pea does not tolerate these (Duke, 1981).

Field pea does not regrow well after mowing or grazing (Munoz & Graves, 1988).

Field pea should be turned under at flowering (Munoz & Graves, 1988).

Pods are harvested when yellow but not open (Duke, 1981).

Normal seed drills, mowers, and tillage implements are appropriate for field peas.

Field pea can be used for forage, hay, silage, grain and green manure (McLeod, 1982). Hay is of very good quality, but pea is more succulent than vetches and more difficult to cure. For hay production in California, 'Austrian Winter' was the best variety, according to Goar (1934).

When grown for hay, silage, or green manure, vetches and peas are often interseeded with cereals which will support the legumes. Oat is most commonly used, but rye, wheat, or barley are occasionally preferred by the growers (Goar, 1934). Pea (cv 'Trapper') can successfully twine on intercrops of rape, mustard, and oat, but not so well on flax. Successful twining reduces lodging of the pea (Cowell et al., 1989).

In two of five experimental sites, percentage of nitrogen obtained by fixation was greater when legumes were intercropped with non-legumes. However, total nitrogen fixed was almost always less with intercropping (significantly so at two sites). Transfer of nitrogen from legume to non-legume was apparently minimal, based on N-15 enrichment experiments (Cowell et al., 1989).

A long-vined variety of field pea ('Century') was better than a short- vined variety ('Alaska') at suppressing mustard growth by shading. 'Century' also showed a greater yield (Liebman and Robichaux, 1990).

Various legumes in the tribe Vicieae (pea, lentil, and vetches) contain Beta-(3-isoxazolinonyl) alanine, which is released into soil as a root exudate, and apparently is an allelopathic compound. This chemical can cause reduced growth in seedlings of various grasses and of lettuce. Pea was only slightly affected. (Schenk and Werner, 1991).

Intercropped barley and field pea were no better at suppressing weed mustards (Brassica kaber) and white mustard (B. hirta) than was a dense monoculture of barley. The main mechanisms of weed suppression were shading (especially by the pea) and competition for nitrogen (especially by the barley) (Liebman and Robichaux, 1990).

High-density plantings of barley were better at suppressing weeds than were intercropped barley and field pea. Weed suppression appeared to be due to competition for soil moisture. Weed populations were not reduced, but weed biomass was (Mohler and Liebman, 1987).

'Century' variety of field pea performed well in trispecific mixes (pea - barley - white mustard) even with high soil nitrogen. The smaller 'Alaska' pea did well in such mixtures with high water and low nitrogen (Liebman, 1989).

Vetch or Austrian winter pea is good in mixtures with oat in California because they reach the ideal stage of maturity at the same time (Goar, 1934). Pea and oat are one of the best mixtures for hay, and oat is the best nurse crop for field pea (McLeod, 1982).

Monocultures of oat (Avena sativa, cv 'Mulga') or triticale yielded more dry matter and digestible organic matter than did bicultures involving common vetch (Vicia sativa) or pea (Pisum sativum). Yields of mixtures did exceed those of monocultures of the relevant legumes. Digestibility and crude protein content were highest in mixtures of peas and triticale. There appears little incentive for farmers to grow mixtures of annual legumes and small-grained cereals for forage production (Droushiotis, 1989).

Dry matter yields (Mg/ha) obtained in individual studies were given as: 5.6, 1.7, 1.8 (Smith et al., 1987); above-ground dry biomasses of Austrian winter pea straw were 8.0 and 8.5 Mg/ha in separate trials in Idaho (Mahler and Auld, 1989). Mid-May above-ground harvest of 'Austrian Winter' in Hopland, Mendocino County, California yielded 6.9+/-0.7 Mg/ha, Mean +/-S.E.M. (Bugg et al., unpublished data); with associated weeds included, the corresponding figures were 7.2+/-0.7 Mg/ha.

Field pea is later to start putting on biomass and fixing N in spring than some other legumes (Stivers & Shennan, pers. comm.) but can produce as well if permitted to grow until May (Miller et al. 1989).

At maturity, pea (Cv 'Early Dun') contained 34% of its total dry matter and 56% of its total N (90 kg/ha) in the seed, 60 kg/ha in the stubble, and 6-8% of the N fixed (less than 15 kg N/ha) in the root system (Herdina and Silsbury, 1990).

Above-ground nitrogen contents of Austrian winter pea were 128 and 203 kg/ha in separate trials in Idaho (Mahler and Auld, 1989). N content can range from 100-200 lb/acre, according to Munoz & Graves (1988). Stivers & Shennan (pers. comm.) estimated 150 lb N/ac by late March. Based on the mean N proportion of 0.01994 obtained from the data of Mahler and Auld (1989), the biomass yields of 5.6, 1.7, 1.8 reported by Smith et al. (1987) translate as 111.67, 33.90, and 17.33 kg N/ha; reports of a mean above-ground biomass of 6.9+/-0.7 Mg/ha (Mean +/-S.E.M.) translate to 137.41 +/- 14.84 kg N/ha (Bugg et al., unpublished data).

For the field pea cv 'Early Dun,' N fixation began 20 days after sowing and stopped when seed began to fill. At maturity, 34% of the total dry matter and 56% of the total N (90 kg/ha) was contained in the seed, 60 kg/ha in the stubble, and 6-8% of the N fixed (less than 15 kg N/ha) in the root system (Herdina and Silsbury, 1990).

The literature review indicates that N-fixation by pea reaches a maximum before or at flowering and drops during pod formation, whereas in faba bean substantial fixation continues up to plant maturity (Buttery and Gibson, 1990).

An experiment with pea grown using a split-root procedure suggested that at the time of harvest, 22-46% of the below-ground N had been shed into the rhizosphere (root zone). Because this N "rhizodeposition" has not previously been assessed for annual legumes, nitrogen fixation may be underestimated by about 10% (Swatsky and Soper, 1991).

In Idaho, according to Mahler and Auld, (1989), it was more efficient to harvest Austrian winter peas for seed than to use them for green manure. A seed pea-winter wheat-spring barley rotation was the most efficient. Despite the harvesting of the seeds, Austrian winter pea residues led to the equivalent of 75 kg/ha of nitrogen available to the following crop, as compared to 94 kg/ha following peas used for green manure and 68 kg/ha following summer fallow. The nitrogen yields from summer fallow are not sustainable because they result from gradual decomposition of a finite supply of soil organic matter.

In an experiment on rotational cash crops ("break crops") for wheat farmers, fertilizer N requirements were increased by 10 kg/ha following winter oat; decreased by 30 kg/ha following winter rape, winter peas, spring faba beans, or cultivated fallow; and decreased by 40 kg/ha following spring peas (McEwen et al., 1989).

On a sandy soil in New Delhi, India, return of field pea stover (crop minus the seeds) to the soil increased the amount of N available to subsequent maize by 16.2 kg/ha (Seth and Balyan, 1989).

Simon (1991) in the Czech Republic evaluated N fixation in hydroponically grown pea cultivars that had been newly developed, along with various isolates of Rhizobium leguminosarum Pea cultivar HM2377 with rhizobial strain 120 was the most promising combination, with total nitrogenase activity much higher than any other grouping. Shoot biomass was also highest for the HM2377/120 combination. The established pea cultivar Bohatyr obtained high shoot biomass best with rhizobial strains 117 and 128C30.

Lupins suffer iron deficiency when grown on calcareous soils, much more so than does field pea. However, this is not due to to a lesser ability to acidify the root zone or to an incapacity to reduce Fe3+, as shown with studies of field pea, Lupinus anugustifolius and L. cosentinii in solution culture (White and Robson, 1989a).

An experiment with pea grown using a split-root procedure suggested that at the time of harvest 22-46% of the below-ground N had been shed into the rhizosphere (root zone). Because this N "rhizodeposition" has not previously been assessed for annual legumes, nitrogen fixation may be underestimated by about 10% (Swatsky and Soper, 1991).

Dried peas are eaten by livestock (Duke, 1981).

In coastal Massachusetts, spring-planted 'Austrian Winter' pea harbored pea aphid and the associated predators Toxomerus spp. (syrphid flies) and seven-spotted lady beetle, Coccinella septempunctata. At various times during July and early August, 'Austrian Winter' pea/rye and Canadian field pea/rye harbored relatively high densities of aphids (pea aphid, corn leaf aphid, and English grain aphid, pooled). Whole-plot visual inspection showed that 'Austrian Winter' pea exhibited the highest densities of aphidophaga on July 8th and 11th (Bugg and Ellis, 1990).

Infestation by pea aphid (Acyrthosiphon pisum) can actually stimulate pea production on nodes (Badenhausser et al., 1991).

Cv 'Melrose' can tolerate only limited populations of pea leaf weevil (Auld et al., 1979).

Flowers of field pea attract bees (Munoz & Graves, 1988).

Grafton-Cardwell et al. (unpublished manuscript) found that pollen of bell bean, 'Austrian Winter' field pea, and New Zealand white clover sustained longevity and fecundity of the predatory mite Euseius tularensis (Acari: Phytoseiidae) as well as the standard diet of iceplant pollen. By contrast, reduced fecundity was observed for common vetch, woollypod vetch, and crimson clover, and E. tularensis did not survive more than one generation when fed pollen of rose clover or red clover. Inoculation with E. tularensis in early spring led to build-up of the mite by late spring in a cover crop of bell bean, field pea, and woollypod vetch. Most of the mites were found on the bell bean component of the mix. When the cover crop was mowed and the mowings placed in young citrus trees, significantly increased densities of the predatory mite were observed on the citrus foliage.

Pisum sativum is subject to attack by 39 species of plant-parasitic nematodes (Duke, 1981).

Duke (1981) presented a lengthy list of pathogens afflicting common pea.

According to Auld et al. (1979), field pea is susceptible to Fusarium Wilt Race 1, sclerotinia white mold, and powdery mildew. These diseases can cause serious losses under some conditions. Ascochyta is one of the most serious diseases of Austrian winter peas. This fungus in the form of foliar blight can destroy leaf and stem tissue or it can attack the root and underground stem of the pea as a foot rot. Melrose has better tolerance to this disease than other cultivars.

Winter oat, winter rape, winter pea, and spring faba bean as break crops greatly reduced the incidence of take-all of wheat (Gaeumannomyces graminis) (McEwen et al., 1989).

Koike et al. (1996), in Salinas, CA, conducted greenhouse and field studies testing tansy phacelia, oil seed radish, barley, 'Lana' woollypod vetch, purple vetch, fava (faba) bean, and 'Austrian Winter' field pea for host status vis a vis the fungal pathogen Sclorotinia minor, and for effect on incidence of the associated lettuce drop disease on following crops of lettuce. Phacelia ('Anglia'), 'Lana' woollypod vetch, purple vetch, and 'Austrian Winter' field pea were identified as major hosts in lab and field trials. An additional field trial in a commercial lettuce field, high incidence of lettuce drop was observed in one of two years following tansy phacelia, but was consistently low following cereal rye.

When field pea grows vigorously, it outcompetes and helps to reduce weeds, according to McLeod (1982). By contrast, Miller, (1988) wrote that field pea is a poor competitor in areas with abundant winter weed growth.

Various legumes in the tribe Vicieae (peas, lentils, and vetches) contain Beta-(3-isoxazolinonyl) alanine, which is released into soil as a root exudate, and apparently is an allelopathic compound. This chemical can cause reduced growth in seedlings of various grasses and of lettuce. Pea was only slightly affected (Schenk and Werner, 1991).

A long-vined variety of field pea ('Century') was better than a short-vined variety ('Alaska') at suppressing mustard growth by shading. 'Century' also showed a greater yield (Liebman and Robichaux, 1990). 'Century' variety of field pea also performed well in trispecific mixes (pea - barley - white mustard) even with high soil nitrogen. The smaller 'Alaska' pea did well in such mixtures with high water and low nitrogen (Liebman, 1989).

Intercropped barley and field pea were no better at suppressing weed mustards (Brassica kaber) and white mustard (B. hirta) than was a dense monoculture of barley. The main mechanisms of weed suppression were shading (especially by the pea) and competition for nitrogen (especially by the barley) (Liebman and Robichaux, 1990).

High-density plantings of barley were better at suppressing weeds than were intercropped barley and field pea. Weed suppression appeared to be due to competition for soil moisture. Weed populations were not reduced, but biomass was (Mohler and Liebman, 1987).

In Mendocino County, California, weed above-ground dry biomass (dry) in vineyard plots seeded to 'Austrian Winter' pea was 0.312+/-0.258 Mg/ha, Mean +/- S.E.M. This is 6.35% of the weed biomass in control plots. Dominant winter annual weeds were chickweed, shepherdspurse, rattail fescue, and darnel (Bugg et al., unpublished data). The 'Austrian Winter' field pea provided 96.25+/-3.75 % Vegetational Cover (Mean +/- S.E.M.) by early May (Bugg et al., unpublished data).

Appears highly palatable to, and easily damaged by, rabbits and ground squirrels (Bugg, pers. comm.).