Purple Vetch (Munoz & Graves, 1988).

Vicia benghalensis L.; Vicia atropurpurea Desf. has been deemed a synonym (Munz, 1973; Duke, 1981).

'Certified': this is a composite of purple vetch germplasm in California, with no characters distinguishing it from other forms of purple vetch (Williams, 1964).

The plump, hairy pods, from 1 to 1.5 inches in length, contain from four to five seeds of a solid velvety black, with a prominent white scar at the point of attachment to the pod (McKee, 1922). The scar is termed a hilum or eye (Madson, 1951). The hilum encircles 1/5 of the seed (Hermann, 1960).

Seed are compressed subglobose, the subquadrate, 4 to 5 mm. in diameter (Hermann, 1960), and, according to McKee (1922), about the same size as common vetch seed, i.e., practically the size of wheat. According to Goar (1934), seed are slightly smaller than common vetch seeds and fairly uniform in shape and size.

The plant is densely pubescent or pilose when young (Duke, 1981).

Munz (1973) describes purple vetch as a soft pubescent annual attaining a height of 3-8 dm. Duke (1981) called the plant a straggling, climbing, or trailing annual or shortlived perennial. Madson (1951) remarked on the vigorous viny growth and the marked hairiness or pubescence. Purple vetch produces a compact raceme or cluster of purple flowers borne on a long stem, or peduncle, arising from the axis of the leaf. Leaves are compound, made up of several pairs of leaflets, but without a terminal leaflet.

Hermann (1960) described purple vetch as softly white-hairy; stems weak, angular, and striate, 1 to 2 m. long; leaves all bearing prominent, branched tendrils; leaflets 10 to 16, oval to oblong, 2 to 3 cm. long, usually blunt but mucronate; stipules rather large, semisagittate, dentate; flowers 2 to 12, large (13 to 18 mm.), in a rather close, secund raceme, all opening at the same time; calyx not, or only slightly, gibbous at the base, the teeth prolonged, subulate, the lower 3 to 4 mm., the upper 2 to 3 mm. long; corolla narrow, whitish at the base, dark purple above, the blade of the standard much shorter than the claw; pod narrowly oblong, broad, 25 to 35 mm. by 8 to 12 mm., pubescent.

By Goar's (1934) description, the leaf has seven to nine pairs of leaflets, and is long, oval, and terminated by a tendril. The leaflets, and to a lesser extent the stems, are covered with numerous fine hairs, which give the plant as a whole a silvery-grayish appearance. Unlike common vetch, the flowers of this variety are borne in showy clusters of twenty or more purple flowers, which hang more or less to one side of the flower stem.

McKee's (1922) description follows: The length of the stems is usually from 3 to 6 feet. From seven to nine pairs of leaflets, terminated with a tendril, constitute the leaf. The leaflets are long, oval, and covered with down, giving the plant a silvery gray cast. Twenty or more amaranth-purple flowers are borne in numerous conspicuous clusters. The plump, hairy pods, from 1 to 1.5 inches in length, contain from four to five seeds.

Purple vetch is among the least hardy of the cultivated vetches; it overwinters in the milder parts of California, but cannot endure winters in the Cotton Belt, except in southern Georgia and Alabama (Duke, 1981). McKee (1922) stated that purple vetch is winter hardy in all the milder parts of California and Arizona and that only in the mountains will the crop winter kill. McKee (1922) regarded purple vetch as a little less winter hardy than common vetch but as otherwise having similar climatic requirements. Goar (1934) concurred, calling purple vetch less winter-hardy than common vetch and not likely to survive temperatures lower than 15 F. above zero. McKee (1922) recounted that in severe winters in western Oregon, purple vetch was injured more than common vetch, but never entirely winterkilled. Snow protection and the amount of moisture in the soil may affect overwintering; Mckee (1922) stated that under average conditions, purple vetch will stand a temperature of about 15 F. above zero with little or no injury. McLeod (1982) stated that purple vetch is injured at 10-15 degrees F with fluctuating temperatures. Madson (1951) ascribed to it moderate resistance to cold, stating that it withstood temperatures of 20 F, but that it would be injured by prolonged periods at this temperature. However, Goar (1934) also remarked that purple vetch makes more growth during the cool weather of winter than any other standard variety. Madson (1951) wrote that Purple vetch usually makes more growth during the winter and early spring than most other vetches. Peaceful Valley (1988) reported consistent, high yields where temperatures do not drop below 20 degrees F. Miller (1988) termed purple vetch "resistant to frost," and later stated that it does well in all sections where winter temperatures do not fall below 20 F (Miller et al., 1989). Williams, 1964 stated that 'Certified' purple vetch suffered no damage from temperatures of 21 F in 1963.

Purple vetch is assigned to the Mediterranean Center of Diversity, ranging from the Warm Temperate Dry to Moist through the Subtropical Moist Forest Life Zone. The species is native to the Mediterranean region of southern Europe from Azores east from Portugal; it is an escape in Kenya (Duke, 1981).

Munz (1973) reported that purple vetch is naturalized in the San Francisco Bay Area. Robert L. Bugg (pers. comm.) observed in mid-June 1992 that purple vetch volunteers in roadcuts and pastures on the campus at University of California at Santa Cruz. In general, it succeeds best near the coast (Goar, 1934). 'Certified' is adapted to valley and foothill sites up to 3,000 foot elevation in California, and its area of adaptation probably include western Oregon, western Washington, southern Georgia and Alabama (Williams, 1964).

Purple vetch tolerates annual precipitation of from 3.1-16.6 dm; the mean of 8 cases was 8.5. The species requires moderate soil moisture, and is drought intolerant (Duke, 1981). Munoz & Graves (1988) stated that purple vetch requires 20 inches of water.

According to Goar (1934), if rainfall is late, vetch should be irrigated about October 1. In the Sacramento and San Joaquin valleys, the crop will mature without additional irrigation if soils have good moisture-holding capacity. April irrigation may be needed in lieu of spring rains. On light soils, three to five irrigations may be needed. Both near the coast and in the foothills, good yields are usually produced with normal rainfall (Goar, 1934).

Duke's (1981) account mentions that purple vetch is tolerant of acid soil; that in western Oregon, gypsum is often applied at 85-167 kg/ha; that P and K may be applied in the Southeast; and that N fertilizers are seldom used. Purple vetch has a low requirement for lime (McLeod, 1982), tolerates low fertility soils, but fixes maximum N on fertile, phosphorus-rich soils (Peaceful Valley, 1988). Purple vetch grows best if well supplied with calcium, sulfur, boron, phosphorus (Cantisano, pers. comm.).

McKee (1922) reported that purple vetch requires about the same amounts of lime and gypsum as common vetch receives in the South and in western Oregon and Washington. In experiments at Corvallis, Oregon, lime or gypsum addition caused only a slight increase of seed or hay. Well-drained soils of western Oregon and western Washington require little lime; other soils may benefit from lime: 1 to 2 tons per acre is recommended. Gypsum can benefit most soils: 75 - 100 lbs/acre should be applied.

Purple vetch tolerates soil pH of 4.8-8.2, with a mean of 7 cases of 6.7; it is said to tolerate high pH (Duke, 1981). By contrast, Munoz & Graves (1988) stated that it is suited to neutral to acid soil. Peaceful Valley (1988) stated that the species tolerates low pH.

Purple vetch is said to show more growth, hardiness and N fixation on neutral soils (Cantisano, pers. comm.).

Purple vetch tolerates most types of soil, but does best on rich loams (Duke, 1981). Munoz & Graves (1988) stated that it is suited to loam to clay soil. According to McLeod (1982), purple vetch grows best on well-drained loam or clay loam soils, but does fairly well on sandy or gravelly soils (McLeod, 1982). Loam soils are recommended by Madson (1951).

Goar (1934) remarked that like common vetch, purple vetch is adapted to a wide range of soil conditions, doing best on fine-textured clay and clay-loam soils, but tolerating sandy loams and somewhat gravelly soils. Soil should be well drained.

McKee (1922) stressed the importance of good drainage, and he wrote that purple vetch does best in heavy loams or clay loams but has done fairly well on sandy and gravelly soils. In western Oregon, purple vetch sometimes did better on poorly drained land than common vetch, but good crops were not produced.

Purple vetch is moderately shade tolerant, showing better growth in full sun (Cantisano, pers. comm.). It is commonly used in mixture with common vetch, hairy vetch, field pea, and oat in orchard cover crops (Bugg, pers. comm.).

Purple vetch was termed an annual by Munz (1973) and McKee (1922). By contrast, Hermann (1960) stated that it is an annual or biennial, and rarely perennial. Duke (1981) termed purple vetch a straggling, climbing, or trailing annual or short-lived perennial herb. It is fall-sown in the Southeast and on the Pacific Coast, but spring sown in the northern states Duke (1981).

Like common vetch, purple vetch should be fall-planted (Goar, 1934), after which it grows vigorously from January through May (Cantisano, pers. comm.).

Seeding rates have been suggested: 56-67 pounds/acre as green manure in vegetable system (Munoz & Graves, 1988), 25-50 pounds/acre in rotation with cereal (Munoz & Graves, 1988), 50-60 pounds/acre (McLeod, 1982), 30-60 pounds/acre (Miller, 1988), 40-80 pounds/acre (Peaceful Valley, 1988), 52 pounds per acre (Finch & Sharp, 1983), 50 to 65 lbs/acre (Madson, 1951), 50 to 65 lbs/acre (Miller et al. 1989), 60 to 80 lbs/acre (McKee, 1922), 56-67 kg/ha (Duke, 1981), 40 lbs/acre in mixture with grain (grain sown at half the monocultural rate) (McKee, 1922).

56 lbs/acre are required to plant 12 vetch seeds per square foot, or 522,720 seeds per acre (Goar, 1934).

Suggested seeding depths include 1/4 to 3/4 inches (Cantisano, pers. comm.), 3/4 inches (McLeod, 1982), 1.5 to 2.5 inches depending on soil moisture (Goar, 1934), and 2 inches or more (Madson, 1951). When planting is delayed until late in the season, seed should be planted closer to the surface (Madson, 1951). Duke (1981) suggested a seeding depth of 10 cm (about 4 inches), which seems extremely deep in light of the seed size and the other recommendations quoted above (Bugg, pers. comm.).

Seed should by drilled deep enough to contact moist soil and can be planted 2 in. or more in depth. Late seedings should be at lesser depths (Madson, 1951).

Purple vetch seed can be broadcast or drilled; it can be overseeded into existing stands of rice, corn, etc. (Cantisano, pers. comm.). Drilling leads to better germination and less winterkilling than does broadcasting seed (McKee, 1922). Drilling ensures more uniform depth of seeding, and better germination and stand (Goar, 1934).

According toGoar (1934) seedbed for vetches should be firm and well prepared. Lacking irrigation, summer-fallowed land should be worked lightly after the first rains in the fall to destroys the first weeds and create seed bed.

If rainfall is late, pre-irrigation about October 1, followed by disking or spring-tooth harrowing and rolling, floating, or otherwise smoothing the surface. Seed vetch by October 15 (Goar, 1934).

Purple vetch is fall-sown in the Southeast and on the Pacific Coast, but spring sown in the northern states Duke (1981). In other words, sow in fall where mild winters prevail and in spring where winters are severe (McLeod, 1982).

In California, suggested planting dates include early fall (Goar, 1934; Munoz & Graves, 1988), and October-November (because delayed seeding may result in cold soils and poor stands) (Madson, 1951).

Cantisano (pers. comm.) remarked that in much of California, purple vetch can be planted as late as December, but maximum growth will result from September or October seeding.

McKee (1922) stated that seeding dates vary regionally and according to the purpose of the crop. In western Oregon and Washington, purple vetch should be fall sown immediately after the first rains, or in February or March. April seedings suffice where spring comes late, but if rain ceases early, late plantings may yield poorly. Seed during fall in California west of the Sierra Nevada, in southern Nevada, and in the southwestern half of Arizona. For green manuring with irrigation, plant from mid-August to mid-September. For hay in California without irrigation, sow on fallow land in the fall before the winter rains.

Goar (1934) suggested fall (October or November) seeding in the interior valleys. For both pasture and hay, seeding should be no later than October 20. In coastal and foothill areas, delays are tolerable. In Marin and Alameda counties, December to January 1 plantings have succeeded. Lacking irrigation, delay seeding until rains begin. If land has been summer-fallowed and weeds are not a serious threat, seeding may be done in the "dust," as was successful at Ahwahnee.

Inoculant type "C" is used with purple vetch (Nitragin Co.) (Burton and Martinez, 1980; Munoz & Graves, 1988).

Inoculation of purple vetch is mandatory on most soils, and it costs about $2.00 per 100 pounds of seed (Cantisano, pers. comm.).

Cantisano (pers. comm.) remarked that seed availability for purple vetch is excellent in most years but was low in 1988 due to drought. Seed is produced under dryland conditions. Purple vetch needs spring rains for seed development.

According to Munz (1973), flowering is from May through June. However, precise flowering dates depend on planting dates. Purple vetch begins flowering in March or April in most sites (Cantisano, pers. comm.).

Vetches mature in late spring or early summer (Duke, 1981). Purple vetch matures in four to eight months, depending on climate and annual rainfall (Cantisano, pers. comm.).

Yields of vetches vary from 25-30 bu/ha, with 50-67 bu/ha the maximum (Duke, 1981). Purple vetch yeilds vary: 10 bushels is low; 30 to 35 bu/a is near maximum; 12 to 20 bu/a is near the mean, or about the same as common vetch. In experimental plots at Corvallis, Oregon, yields ranged from 0 to 50 bushels per acre. Total failure occurred during 1914-1915 due to the winterkilling of fall plantings. In tests from 1915-1920, 80 and 100 pounds of seed sown per acre, yielded 21.8 and 24.5 bu/a of seed. In commercial plantings in western Oregon, western Washington, and northwestern California the yields have ranged from 0 to 30 bushels per acre, with winterkilling causing the failures (McKee, 1922).

Seed yields depend on spring rainfall. Purple vetch seed is difficult to harvest due to viny growth, but this can be done with grain combines with minor modifications (Cantisano, pers. comm.).

For seed crops, light grazing in the spring reduces excessive vine growth, making harvesting easier. Sheep do less trampling damage than other livestock (McKee, 1922).

Purple vetch is a straggling, climbing or trailing annual or short-lived perennial herb, with stems 20-80 cm long. Purple vetch is viny and succulent, often producing a matted carpet two feet deep by springtime (Miller, 1988).

Purple vetch has much the same habit of growth as common vetch (McKee, 1922). The species has been termed the most vigorous vetch (Peaceful Valley, 1988), and is said to have moderate to heavy density of growth (Madson, 1951). The species will grow upright when mixed with grain/grasses to support viny growth (Cantisano, pers. comm.).

Height estimates vary: 30-80 cm in height (11.8-31.5 inches) (Munz, 1973); 18 to 24 inches in monoculture (45.7 cm - 61.0 cm), but up to 36 inches (91.44 cm) when allowed to grow up grain/grass stems (Cantisano, pers. comm.); 57.15+/-4.46 cm, Mean +/- S.E.M. (22.5 +/- 1.8 inches) in monculture, Hopland, Mendocino County, California (Bugg et al., unpublished data). The stems attain 3 to 6 feet in length or more (Goar, 1934).

Purple vetch has thick roots to a depth of one foot, and lesser roots to three feet or deeper (Cantisano, pers. comm.).

Cantisano (pers. comm.) stated that establishment of purple vetch is easy if seed is sown when the ground is still warm in fall. Establishment is slow when it is planted in winter, and the species shows fairly low vigor until after winter solstice.

Purple vetch seed remains viable for a relatively long time (McLeod, 1982).

Purple vetch has been variously said to tolerate mowing and grazing (Peaceful Valley, 1988) and to not respond favorably to mowing (Munoz & Graves, 1988). It has been called difficult to mow due to its viney growth (McLeod, 1982) and not difficult to mow with a flail mower/chopper (Cantisano, pers. comm.).

Purple vetch should be turned under at flowering in vegetable systems or in rotation with cereal when seeding the latter (Munoz & Graves, 1988).

Purple vetch is easier to incorporate if mowed first (Peaceful Valley, 1988), and the residue breaks down easily after disking (Finch & Sharp, 1983).

When overseeded into rice, rice yields are greater when the vetch is turned under 4 to 6 inches than when it is placed shallower. Reducing the time interval between turning under the vetch and flooding and sowing the rice also increases yields, if nitrification is rapid during the preflooding period. Properly incorporated vetch is equivalent to ammonium nitrogen in increasing rice yields (Williams and Finrock, 1963).

Purple vetch should be cut for hay between full bloom and formation of the first pods (McKee, 1922). Goar (1934) recommended that it is best for hay when cut in full bloom. Vetch leaves dry much faster than the stems, so hay should be handled rapidly in the field to minimize loss of leaves (Goar, 1934). One day in the swath usually suffices, then the hay is put in shocks to complete curing (Goar, 1934).

McKee (1922) wrote that when purple vetch is grown for seed, it should be cut soon after the lower pods are ripe. Upper pods mature earlier, so seed load will be maximal. Later cutting causes pods to drop; earlier cutting increases the proportion of immature seed. Purple vetch shatters less readily than common vetch, but the likelihood increases when seed are overripe; also pods drop without bursting. The guiding principle in harvesting vetch seed is to handle the crop as quickly and as little as possible.

Duke stated that purple vetch should be harvested when 75-90% of the pods are mature. Combine harvesting is practical.

According to Bugg (pers. comm.), vetch is easier to mow with a flail than with rotary or sickle-bar mowers. Incorporation with a light disk can be difficult because of binding. Power spaders and rototillers are effective at incorporation; the former can be used on tall cover crops when soils are somewhat moist.

Purple vetch has been used for forage, cover crops, and green manures (McLeod, 1982). It has been used as a green manure in vegetable systems (Munoz & Graves, 1988), in rotation with cereal crops (e.g., rice) (Munoz & Graves, 1988), and for cover in Californian citrus (McLeod, 1982). It is rated excellent for hay, green chop or forage when mixed with red or white oat (Peaceful Valley, 1988).

McKee (1922) stated that purple vetch is especially valuable compared to other winter annual legumes (including other vetches). In Californian orchards, purple vetch has shown heavier growth than field pea, common vetch, fenugreek, bur clover, and sourclover, all of which have been used extensively. Purple vetch gives superior early growth, so can be incorporated earlier in spring. This is important in southwestern citrus groves, where green manures should be turned under by mid-February or the first of March. The total biomass production of purple vetch is seldom equaled.

Purple vetch is equal to common or hairy vetch for pasture, serving for all kinds of stock. Where mild climates permit early fall seeding, it can provide pasturage in the fall and the following spring (McKee, 1922).

Purple vetch hay quality had not been formally assessed by the early twenties (McKee, 1922). In preliminary feeding tests, livestock ate purple-vetch hay as readily as common-vetch hay, and chemical analyses suggested feeding value similar to that of common vetch. The hairiness of purple vetch exceeds that of common vetch but is less than that of pubescent forms of hairy vetch; the latter has been much used for hay with no bad results, so the feature is probably inconsequential (McKee, 1922). Duke (1981) stated that the protein content of purple vetch ranges from 10-20%, depending on developmental stage.

Murphy et al. (1976) stated that vetches are useful as a source of spring feed, but that they serve best as summer dry forage, or as a seed source for upland game birds. Ground seed is used for poultry food (Duke, 1981).

When grown for hay, silage, or soiling, the vetches and peas are usually mixed with seeds of one of the cereals, which will support the legume. Oat is most commonly used, although rye, wheat, or barley are occasionally preferred by the growers (Goar, 1934). Oat is especially suitable as an intercrop for vetch, because oat seed is more easily separable from vetch seed than are barley, cereal rye, or wheat (Duke, 1981).

By the account of Schenk and Werner (1991), 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.

Vetch or Austrian winter pea is good in mixtures with oat in California because they mature at the same time (Goar, 1934).

When seeding with grain for hay purposes, seed about 40 lbs of purple vetch seed per acre and about half the amount of grain used when seeding grain alone (McKee, 1922).

Vetch is best for hay when cut in full bloom. Oat makes good hay if cut when the grain is in the soft-dough stage. When common, purple, or hairy vetch or Austrian Winter pea is used in combination with Kanota oat, legumes and oat usually mature at the same time. For this reason, vetch and oat make a very good combination (Goar, 1934).

In California, mixtures of hairy vetch, purple vetch, common vetch, field pea, and oat are often used in cover cropping. Bell bean and 'Lana' woolypod vetch can also be included (Bugg, pers. comm.).

Goar (1934) stated that purple vetch does best near the coast, where it outyields common vetch, and that it grows more during the winter than any other standard variety. In past trials, purple vetch produced yields (presumably fresh weight) of 12 to 15 tons of green matter per acre at Davis and well over 20 tons in the Imperial Valley (Madson, 1951).

McKee (1922) reported hay yields (presumably dry weight) of 1.5 to 3.5 tons per acre, with the mean being about 2.5 tons.

Bugg et al. (unpublished data) reported that purple vetch was seeded during October, 1990, and biomass harvested May 15-16, 1991, in a replicated study (r=4) at Blue Heron Vineyard, Fetzer Vineyards, Hopland, Mendocino County, California. Dry above-ground biomass for purple vetch was 10.117+/-0.535 Mg/ha (Mean +/- S.E.M.). This was the highest absolute yield obtained for any of the 19 legumes assessed, but was only significantly greater than biennial sweetclovers, strawberry clover, and mixed ladino and strawberry clovers. Biomass of purple vetch plus weeds was 10.834+/-0.810 (Mg/ha, Mean +/- S.E.M.).

Nitrogen contents for purple vetch have been variously presented as 50-200 pounds/acre N in vegetable/green manure system (Munoz & Graves, 1988), 50-100 pounds/acre in rotation with cereal (lower seeding rate) (Munoz & Graves, 1988), up to 300 pounds of N per acre between October and the end of April in northern California (Miller, 1988), the equivalent of 80 lbs/acre of fertilizer nitrogen when followed by sugar beets in trails at Davis and Santa Maria (Miller et al., 1989), and in unirrigated pasture, about 53 lb/a of nitrogen (Holland et al., 1969). In a vineyard study in Hopland, Mendocino County, California, purple vetch showed a mean biomass yield of 10.117, which based on 10-20% protein containing 6.25% N projects to above-ground N content of 63.23-126.46 kg N/ha.

Like many other legumes, purple vetch fixes more N when soil N is restricted, but P, S, and Ca are readily available (Cantisano, pers. comm.).

Available N from purple vetch can be estimated by multiplying harvested fresh weight of cover crop from a sixteen square feet (4 x 4 ft.) sample plot by 16 (result is in lbs of N/acre) (Miller et al., 1989).

Purple vetch cover reduces soil temperature slightly and increases humidity (Cantisano, pers. comm.).

Young (1922) reported an unreplicated study upon which have been based many subsequent generalizations about cover-crop effect on temperatures in citrus groves. A 6-acre grove was divided into 2, 3-acre sections. A cover crop of sourclover (Melilotus indica, 30 lb/a) mixed with rye (Secale cereale, 10 lb/a) and some purple vetch (Vicia benghalensis) was established. Locations of two temperature stations were assigned based on similarity of low temperatures when dense cover crops were present in both sections. On January 18, 1922, the northern half of the orchard was ploughed, but the cover crop in the southern half was left intact. Conditions were wet during this study. Temperature measurements were made for 16 nights of frost, including the exceptionally-cold spell from Januay 19-23, which included the coldest weather in southern California since 1913. Sheltered thermometers showed that 10 inches above the ground, the cover-cropped plot was, on average, approximately 2 degrees F colder than the clean-cultivated plot during the night. The only effect at 5 feet above ground was to decrease the rate of temperature rise during the morning. Unsheltered thermometers showed that depression of minimum temperatures was about 2.4 degrees F at 7 inches above the ground, and 0.4 degrees F at 24 inches above the ground. At times when air temperatures were falling rapidly, the temperature at 7 inches could be as much as 11 degrees colder in the cover-cropped plot. The results suggest that cover crops do increase the risk of frost, but only to a slight extent.

Young (1925) also conducted another unreplicated study, a followup on the previous unreplicated study about cover-crop effect on temperatures in citrus groves (Young 1922). The results conform in large measure with those of the prior study. A 10-acre grove of navel and Valencia oranges was divided into 2, 5-acre sections. A cover crop was established of purple vetch (Vicia benghalensis), Broad Windsor horse bean (Vicia faba) and many tall weeds. Conditions were dry during this study. Locations of two temperature stations were assigned near the center of each plot when dense cover crops were present in both sections. On January 4, 1924, the eastern half of the orchard was ploughed, but the cover crop in the western half was left intact. Temperature measurements were then made for 24 nights of frost. Sheltered thermometers showed that 10 inches above the ground, the cover-cropped plot was, on average, approximately 1.3 degrees F colder than the clean-cultivated plot during the night. The difference at 5 feet above ground was 0.5 degrees. The results again suggest that cover crops do increase the risk of frost, but only to a slight extent.

Purple vetch gives fair erosion control when plant is well established or in areas of natural reseeding. Control is better when purple vetch is mixed with grasses and grains (Cantisano, pers. comm.).

Livestock will avoid purple vetch when it is green but will readily eat it when it is dry. (Fred Thomas, pers. comm.)

Purple vetch shows no adverse effects except attraction of honeybees when in flower. A vetch cover crop makes the ground firmer for winter/rainy field work (Cantisano, pers. comm.).

Vetch cover crops can impede walking through orchards, so can reduce access for winter activities (Bugg, pers. comm.).

Flowers of purple vetch are attractive to bees (Munoz & Graves, 1988), and purple vetch is rated a good honey plant (Peaceful Valley, 1988).

Cantisano (pers. comm.) said that purple vetch attracts many species of beneficial insects: Nabis, Orius, assassin bugs, Hippodamia lady beetles, lacewings, and others, and that it is an excellent beneficial insectary. However, it lacks the extrafloral nectaries that bell bean, bigflower vetch, and common vetch possess; this presumably makes purple vetch less attractive to parasitic wasps, lacewings, ants, and lady beetles; lygus bugs are also less likely to be abundant (Bugg, pers. comm.). Purple vetch is later maturing than several other species of vetch so might be expected to harbor beneficial insects later.

Flexner et al. (1990) found that, in southern Oregonian pear orchards, certain understory weeds can harbor high densities of twospotted spider mite, Tetranychus urticae Koch (Acari: Tetranychidae). This mite is mainly a secondary pest and a creature of pesticide-disrupted or stressed agroecosystems. Among the plant species suitable for use as cover crops, vetch appeared particularly prone to outbreaks of the mite. Use of herbicides led to increased movement by mites into trees.

McKee (1922) noted that although aphids have caused serious damage to purple-vetch, more damage is typically done to field pea, common vetch, and other leguminous crops. This can lead to seed and biomass yield reductions.

Duke (1981) reported that purple vetch harbors the following plant-parasitic nematodes: Heterodera glycines (original reference, Riggs, 1962), H. goettingiana (original reference, Oostenbrink, 1951), H. schachtii (original reference, Raski, 1952), H. trifolii (original reference, Oostenbrink, 1951), and Pratylenchus vulnus (original reference, Jensen, 1953).

H. goettingiana is not important in California. (Oostenbrink, 1951), nor is Heterodera glycines (Riggs, 1962).

Meloidogyne javanica and Xiphinema americanum have been found associated with this cover crop in vineyards, but greenhouse testing is needed for confirmation (McKenry, pers. comm.).

Purple vetch may increase the potential for foliar disease in orchards if allowed to grow over two feet tall during spring (Cantisano, pers. comm.).

Purple vetch, with its viny habit, will grow up most grasses, weeds or other plants in the mix. It has been termed good for smothering winter weeds (Peaceful Valley, 1988), and excellent for controlling star thistle in pastures (pers. comm.).

In plots seeded to purple vetch during late October, 1990, in Hopland, Mendocino County, California harvest on May 15-16, 1991, showed that weed above-ground biomass (dry) was 0.717+/-0.566 Mg/ha, Mean +/- S.E.M., which was 14.6% of the weed biomass in control plots (Bugg et al., unpublished data). Dominant winter annual weeds were chickweed, shepherd's purse, rattail fescue, and annual ryegrass. In early May vegetational cover was 95.00+/-2.04 % (Mean +/- S.E.M.) by purple vetch (Bugg et al., unpublished data).

As reported by Schenk and Werner (1991), 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.

Purple vetch harbors voles, gophers, and their predators (Cantisano, pers. comm.).