The common name is rye (Hitchcock, 1971; Munz, 1973; McLeod, 1982) or cereal rye (McLeod, 1982). The use of the latter name reduces confusion with ryegrasses (Lolium spp.).

Secale cereale L. (Hitchcock, 1971).

There are relatively few varieties of cereal rye available (Stoskopf, 1985); 28 varieties were listed in the Southern Seedsmen's Association Directory and Buyers' Guide, 1990-91 (Bugg, pers. comm.). Although cereal rye is usually regarded as a winter crop, spring-sown varieties are available (Stoskopf, 1985). Drought tolerance among varieties varies, with diploid varieties more tolerant than those that are tetraploid (Starzycki, 1976).

The inflorescences and seed are as follows: Spikelets usually 2-flowered, solitary, placed flatwise against the rachis, the rachilla disarticulating above the glumes and produced beyond the upper floret as minute stipe; glumes narrow, rigid, acuminate or subulate-pointed; lemmas broader, sharply keeled, 5 nerved, ciliate on the keel and exposed margins, tapering into a long awn (Hitchcock, 1971).

 

According to Stoskopf (1985), the lemma and palea that enclose the floret are free-threshing, and the lemma often bears barbs on the keel and often has an awn of intermediate length. The rye kernel is longer and more slender than that of wheat. Cereal rye seed may germinate in storage or even while still in the ear (Starzycki, 1976). Seed will germinate at temperatures as low as 3-5 C, but optimal range is 25-31 C (Starzycki, 1976).

Hitchcock (1971) described cereal rye as an erect annual grass with flat blades and dense spikes; habit resembles that of wheat, but usually taller, the spike longer and more slender, somewhat nodding. Munz (1973) described the species as a tufted annual 1-1.5 m tall, blue green, blades to ca. 12 mm broad, long pointed, spike slender, 7-15 cm long.

According to Stoskopf (1985), cereal rye plants are taller than those of wheat and tiller less. The flag leaf is smaller and less important in photosynthesis; leaves have a bluish color.

Cereal rye is grown in the cool temperate zones or at high altitudes (Bushuk, 1976). It is the most winter hardy of all small cereal grains (Miller, 1984; Stoskopf, 1985) enduring all but the most severe climates (Johnny's Selected Seeds, 1983). Its cold tolerance exceeds that of wheat, including the most hardy winter wheat varieties (Stoskopf, 1985), and it is seldom injured by cold weather (McLeod, 1982). Starzycki (1976) stated that 3-5 degrees C or higher is required to germinate, with the optimal range being 25-31 degrees.

In the Northeast, it can be established when seeded as late as October 1 (Schonbeck, 1988). Minimal temperatures for germinating cereal rye seed have been variously given as 3 to 5, 0.6, and 1 to 2 degrees C; optimal range has been given as 25 to 31 and 13 to 18 degrees C. According to Stoskopf (1985), for vegetative growth to occur, a minimum temperature of 4 degrees C is required. Once well established, cereal rye can withstand temperatures as low as -35 degrees C (-31 degrees F). The structure of the rye plant enables it to capture and hold protective snow cover, which enhances winter-hardiness. Cereal rye is a long-day plant and flowering is induced by 14 hours of daylight accompanied by temperatures of 5 to 10 degrees C (Stoskopf, 1985).

Because it grows better in cooler weather, cereal rye can be incorporated earlier in the spring (McLeod, 1982). In summary, cereal rye is one of the best crops where fertility is low and winter temperatures are extreme (McLeod, 1982).

Vegetative growth for cereal rye requires a temperature of at least 4 degrees C Stoskopf, 1985).

Cereal rye is thought to be native to the mountains of southwestern Asia (Hitchcock, 1971; Munz, 1973) and to have been derived from Secale montanum Guss., a perennial grass native to that area (Hitchcock, 1971). Cereal rye has a wide range of adaptability; no other winter cereal can be grown as far north (McLeod, 1982). It shows the widest geographic distribution of all cereal crops (Bushuk, 1976): production is possible throughout the temperate and subtropical zones, within the Arctic Circle, and in southern Chile. In the Himalayan mountains, cereal rye can be grown at 4,300 m (14,400 ft) elevation (Stoskopf, 1985). Its wide range of adaptation is due to its great winter hardiness and tolerance of marginal soils: it can be grown in soils too acidic for wheat (Stoskopf, 1985). Evans and Scoles (1976) said that the extensive root system of cereal rye enables it to be the most drought-tolerant cereal crop, and its maturation date can alter based on moisture availability. Cereal rye is more drought tolerant than oat (Miller, 1984).

Cereal rye grows best with ample moisture, but in general it does better in low rainfall regions than do legumes (McLeod, 1982), and it can outyield other cereals on droughty, sandy, infertile soils (Stoskopf, 1985). Its extensive root system enables it to be the most drought-tolerant cereal crop, and its maturation date can alter based on moisture availability (Evans and Scoles, 1976). Maturation date of cereal rye varies according to soil moisture, but vegetative growth stops once reproduction begins (Stoskopf, 1985). The structure of the rye plant enables it to capture and hold protective snow cover, which enhances winter-hardiness (Stoskopf, 1985); this snow retention might also be expected to enhance water availability. Drought tolerance among cereal rye varieties varies: diploid varieties are more tolerant than are those that are tetraploid (Starzycki, 1976). Cereal rye is more drought tolerant than oat (Miller, 1984), and Starzycki (1976) indicated that cereal rye requires 20-30% less water than wheat per unit of dry matter formation, but this point has not been tested scientifically, according to Stoskopf (1985).

Cereal rye is one of the best cover crops where fertility is low and winter temperatures are extreme (McLeod, 1982); it has a low requirement for lime (McLeod, 1982); and can outyield other cereals on droughty, sandy, infertile soils (Stoskopf, 1985).

Guerrero et al. (1967) found that cereal rye grown on acid, unproductive grassland soils (Wilder Variant Series and Sixmile Series) showed increased yield in response to P addition but did not respond as much to liming. Past research cited by these authors indicated aluminum tolerance in cereal rye.

Cereal rye is well known to tolerate acid soil (McLeod, 1982). The range of best suitability is pH 5.0-7.0, but tolerance is between 4.5 and 8.0 (Stoskopf, 1985). Cereal rye has the widest range of adaptation of all cereals because of its great winter hardiness and tolerance of marginal soils, and it can be grown in soils too acidic for wheat (Evans and Scoles, 1976).

According to McLeod (1982), cereal rye grows best on well drained loam or clay loam soils, but even heavy clays, light sands, and infertile or poorly drained soils are feasible. It will grow on soils too poor to produce other grains or clover (McLeod, 1982). In general, it is tolerant of different soil types (Johnny's Selected Seeds, 1983; Miller, 1984); does well on loamy or sandy soil (Brinton, 1989); will give good yields on poor, sandy soils (Bushuk, 1976.); and does better than oat on sandy soil (Miller, 1984). Cereal rye can outyield other cereals on droughty, sandy, infertile soils (Stoskopf, 1985).

Given the ability of cereal rye to grow during cold weather when deciduous orchard trees are leafless, shade tolerance is seldom an issue (Bugg, pers. comm.).

No specific information was available on salinity tolerance of cereal rye, but this is not typically listed as one of its virtues, by contrast with the situation for barley (Bugg, pers. comm.).

Cereal rye is a common weed in the intermountain area of California along dry lakes and road edges of alkaline areas (Fred Thomas, pers. comm.)

Cereal rye is susceptible to glyphosate (Bugg, pers. comm., Bugg et al., 1991) and to paraquat (Laub and Luna, 1991).

Cereal rye is an annual grass (Hitchcock, 1971; McLeod, 1982). In the Northeast, it can be established when seeded as late as October 1 (Schonbeck, 1988). Minimal temperatures for germinating cereal rye seed have been variously given as 3 to 5, 0.6, and 1 to 2 degrees C; optimal range has been given as 25 to 31 and 13 to 18 degrees C (Stoskopf, 1985). Starzycki (1976) stated that 3-5 degrees C or higher is required to germinate, with the optimal range being 25-31 degrees. According to Stoskopf (1985), for vegetative growth to occur, a minimum temperature of 4 degrees C is required. Once well established, cereal rye can withstand temperatures as low as -35 degrees C (-31 degrees F) (Stoskopf, 1985). The structure of the rye plant enables it to capture and hold protective snow cover, which enhances winter-hardiness (Stoskopf, 1985). Cereal rye is a long-day plant and flowering is induced by 14 hours of daylight accompanied by temperatures of 5 to 10 degrees C (Stoskopf, 1985). Cereal rye is largely cross-pollinated; most plants are self sterile (Stoskopf, 1985).

Maturation date of cereal rye varies according to soil moisture, but vegetative growth stops once reproduction begins (Stoskopf, 1985). Cereal rye plants are taller than wheat and tiller less; the flag leaf is smaller and less important in photosynthesis (Stoskopf, 1985).

Based on the account by Gawronska and Nalborczyk (1989), cereal rye has the longest stems of all cultivated small grains, and these provide most of the photosynthetic area. During grain formation, stems with sheaths account for 60-80% of the total plant area. At grain set, 15-20% of the photosynthetic area is provided by leaf blades, which is much lower than for maize, wheat, and oat. Stems and sheaths have lower rates of photosynthesis and export of assimilates than do leaves. For winter rye, photosynthetic area decreases rapidly after grain set, and does not achieve a plateau near the maximum, as seen with other grains. These features were consistent across the six cultivars assessed. Taken together, these factors suggest that winter rye grain formation occurs under unfavorable physiological conditions for yielding.

In the autumn, cereal rye grows more rapidly than wheat, oat, or various other annual grasses (Knight, 1985), and it produces more fall and early spring growth than oat (Miller, 1984). Because it grows better in cooler weather, cereal rye can be incorporated earlier in the spring (McLeod, 1982). Although cereal rye is usually regarded as a winter crop, spring-sown varieties are available (Stoskopf, 1985).

Suggested seeding rates are: 60 to 90 lbs/acre (Miller et al., 1989); 90-112 kg/ha (80-100 lb/a) (Miller, 1984); 90 to 160 lb/acre for green manure (McLeod, 1982); 112 lbs/acre (Johnny's Selected Seeds, 1983); 120-200 lb/a (Brinton, 1989.); and 56 lbs/acre when sown with clover (Johnny's Selected Seeds, 1983). According to Stoskopf (1985), cereal rye is normally seeded at 112 kg/ha but when seeded late the rate should be increased up to 336 kg/ha to achieve rapid and complete vegetational cover and reduce erosion; to minimize erosion, a leaf area index of 1.0 [complete cover] may be necessary.

Recommended seeding depths include: 3/4 inches (McLeod, 1982); 1 inch (Johnny's Selected Seeds, 1983); 0.4 to 1.2 inches (Brinton, 1989); and 2.5 to 5.0 cm (1-2 in.) (Miller, 1984).

In general, drill into prepared seedbed or broadcast and disk lightly or cultipack to cover (Bugg, pers. comm.). Cereal rye can be seeded into Bermuda grass sod in pecan orchards during early to late autumn by mowing the sod closely and seeding with a no-till drill. Alternatively, seed can be broadcast and the sod disked lightly (Bugg, R.L, pers. comm.).

Scott and Burt (1985) describe studies in New York state where rye or wheat can be seeded in late summer or early autumn. If late seeding is needed, rye will perform better because it shows better growth during cold weather. Cover crops evaluated after overseeding into corn of 6-18" high were medium red clover, mammoth red clover, alfalfa, yellow sweetclover, alsike clover, birdsfoot trefoil, Canada field peas, Austrian winter peas, cowpeas, perennial or annual ryegrass, medium red clover + ryegrass, or medium red clover + rye. Of these, alfalfa, medium red clover, yellow sweetclover, hairy vetch, ryegrass, and medium red clover + ryegrass have performed well. Species tested following overseeding while corn is tasseling through silking included rye, perennial or annual ryegrass, buckwheat, medium red clover, and hairy vetch. Rye was the only crop that consistently performed well under these conditions. In practice, rye used in this context would be seeded aerially.

Cereal rye can be seeded very late in the fall (Brinton, 1989); it requires temperatures of 3-5 degrees centigrade or higher to germinate, with the optimal range being 25-31 degrees. (Starzycki, 1976). In the Northeast, it can be established when seeded as late as October 1 (Schonbeck, 1988). This presumably means that in most of California, it can be established when seeded in December (Bugg., pers. comm.).

Cereal rye is not a legume and requires no inoculation with rhizobia (Bugg, pers. comm.).

Seed is readily available. The Southern Seedsmen's Association (1992) listed 28 suppliers of cv 'Elbon' and 19 of cv 'Wrens Abruzzi.'

Rye is a long-day plant: flowering is induced by 14 hours of daylight when this is accompanied by temperatures of 5-10 C (55-65 F) (Stoskopf, 1985). According to Stoskopf's (1985) review, shortened daylength can cause rye plants to remain vegetative for up to seven years.

Cereal rye is a long-day plant and flowering is induced by 14 hours of daylight accompanied by temperatures of 5 to 10 degrees C (Stoskopf, 1985). Munz (1973) stated that in California flowering occurs from May-August, which suggests that seed maturation would occur from May-September. Cereal rye matures earlier than oat (Miller, 1984). Maturation date can alter based on moisture availability, but vegetative growth stops once reproduction begins (Stoskopf, 1985). Evans and Scoles (1976) said that the extensive root system of cereal rye enables it to be the most drought-tolerant cereal crop, and its maturation date can alter based on moisture availability.

Worldwide mean grain production in 1972 was about 1.77 Mg/ha (Bushuk, 1976).

The seed remains viable for a relatively long time (McLeod, 1982), but seed may germinate in storage (Bushuk, 1976).

Cereal rye is an erect annual grass (Hitchcock, 1971). Based on the account by Gawronska and Nalborczyk (1989), it has the longest stems of all cultivated small grains, and these provide most of the photosynthetic area. During grain formation, stems with sheaths account for 60-80% of the total plant area. At grain set, 15-20% of the photosynthetic area is provided by leaf blades; this area is much lower than for maize, wheat, and oat. Stems and sheaths have lower rates of photosynthesis and export of assimilates than do leaves. For winter rye, photosynthetic area decreases rapidly after grain set, and does not maintain a plateau near the maximum, as seen with other grains. These features were consistent across the six cultivars assessed. Taken together, these factors suggest that winter rye grain formation occurs under unfavorable physiological conditions for yielding.

According to Stoskopf (1985), average height of cereal rye is 147 cm, and range is from 139 to 154. Heights of winter rye varieties (in cm) were as follows: 'Dankowske Zlote', 144.8; 'Dankowskie Nowe', 137.4; 'Pancerne', 144.0; 'Kustro', 134.2; 'Wojcieszyckie', 161.2; and 'Viatka', 188.9 (Gawronska and Nalborczyk, 1989b). Cv 'Wintergrazer' is shorter than cv. 'Wrens Abruzzi' (which attains a height of over 72") (Bugg, pers. comm.). Cv 'Merced' reached a height of 148.6+/-7.6 cm, mean +/- S.E.M., (58.5 +/- 2. inches) in Mendocino County, California (Bugg et al., 1996).

Cereal rye has the best-developed root system among annual cereal crops (Starzycki, 1976) as with other grasses, the system is fibrous, with no defined taproot (Bugg, pers. comm.). The extensive root system enables it to be the most drought-tolerant cereal crop (Evans and Scoles, 1976) and makes it among the best green manures for improving soil structure (Pears et al., 1989).

Cheng and Coleman (1990) conducted a field/laboratory study in Georgia and found that decomposition of incorporated 14C-labelled cereal rye residue was accelerated through having cereal rye plants growing in the soil. This was believed to be due to the rhizosphere microbial complex.

Sheng and Hunt (1991) compared shoot and root dry weight and soil moisture during progressive growth stages for 'Columbus' wheat, 'TZ' triticale and 'Gazelle' cereal rye in both greenhouse, pot and field studies. The cereal rye cultivar had significantly greater root dry weight in the pot studies, but wheat showed greater root mass from depths of 22.5 to 52.5 cm in the field studies. Root growth was greatest from the seedling to flag leaf for all three cereals. In the field study, soil water depletion was significantly greater for triticale than the other cereals for 60-65 cm depth.

Triticale Trical cv. 102 shows unusually vigorous and deep root growth during winter and early spring. (Chuck Cambra, pers. comm. 1997).

From data presented by Jackson et al. (1993b), for mid-November-planted cover crops in March, approximate values for N contained in root systems obtained by subtraction were as follows in kg N/ha:

Jackson et al. (1993b) stated that, for mid-November-planted cover crops in March, root biomass figures in kg/ha were:

 

 

Jackson et al. (1993b) stated that, for mid-November-planted cover crops in March, root length measurements yielded the following figures during March (m/m2):

 

Wyland et al. (1996) during winter in Salinas, CA, grew tansy phacelia (cv. 'Phaci') and cereal rye (cv. 'Merced') both preceded and followed by broccoli; control plots were fallow. There were three replications. Plots were managed by th reduced-tillage "Sundance System." Both cover crops were tilled under in mid-April and broccoli was planted in late April. Both phacelia and cereal rye cover crops developed extensive fibrous root systems reaching depths of 75cm.

Kutschera (1960) reported that cereal rye generally roots to a depth of 90-230 cm.

Cereal rye grows rapidly and vigorously during fall and spring, and performs well under cold conditions and with poor soil (Stoskopf, 1985).

Cereal rye can become a weed through volunteering (Stoskopf, 1985) and sometimes escapes in waste places and fields in California (Munz, 1973).

Cereal rye is a common weed in the intermountain area of California because it will volunteer and grow with only 5 or 6 inches of precipitation. Dick Jacobs, CSU Chico Crops Coordinator, reported that the 15% of common rye included in Lohse Mill Beneficial Blend was still a problem three years later (1997, pers. comm.).

Cereal rye may be grazed or mowed in late fall without diminishing the grain yield (Starzycki, 1976). In late April or early May in North Carolina, mowing with a rotary mower can be used to kill cereal rye (cv 'Abruzzi') (Laub and Luna, 1991).

Schonbeck (1988) mentioned that cereal rye can regrow following tillage, particularly if tilled under when 8 inches or less in height. There is less difficulty when rye is incorporated after it has attained a height of 12 inches, though one grower disputed this.

Cereal rye has been shown to be allelopathic towards other plants, but some of the suppressive effects may relate to tie-up of soil nitrogen by decomposing rye residues. If rye is incorporated while under 16 inches in height and the tissue is still sweet to the taste, this sort of tie-up can supposedly be minimized (Schonbeck, 1988).

Cereal rye can inhibit germination or growth of vegetable crops sown after rye is incorporated (Schonbeck, 1988).

Grain of cereal rye can be harvested like wheat (presumably with combines), but the large amount of straw makes harvest less efficent (Stoskopf, 1985).

In late April or early May in North Carolina, mowing with a rotary mower (bush hog) can be used to kill cereal rye (cv 'Abruzzi') (Laub and Luna, 1991).

Grain of cereal rye can be harvested like wheat (presumably with combines) (Stoskopf, 1985).

Thorough incorporation of rye cover is essential to prevent regrowth of cereal rye cover crops (Richard Smith, pers. comm.).

Cereal rye can serve as grain, hay, pasture, cover crop and green manure (McLeod, 1982). It is a good pioneer crop for sterile soils (Bushuk, 1976). When used as a cover crop, it is grown for erosion control, to add organic matter, to enhance soil life, and for weed suppression (Johnny's Selected Seeds, 1983). It may also stabilize and prevent leaching of excess soil or manure nitrogen (Schonbeck, 1988). Cereal rye is useful for preventing wind or water erosion (Miller, 1984); it has been used to protect soil from wind erosion in Australia (Bushuk, 1976) and, with its tall stature, may be of some value in providing windbreaks (Schonbeck, 1988).

Cereal rye is a good green manure because it produces large quantities of organic matter but should be used only in rotation with row crops because other grain crops are graded down in the market if they contain rye seed (McLeod, 1982). On the other hand, it can inhibit germination or growth of vegetable crops sown after rye is incorporated (Schonbeck, 1988). Winter cover crops of rye are often seen (Gershuny and Smillie, 1986), and it has performed well when overseeded into field corn, sweet corn, or brassica crops in the Northeast (Schonbeck, 1988) and in pecan orchards in southern Georgia (Bugg, pers. comm.).

Cereal rye can be sown with legumes or other grasses (Miller, 1984). For example, berseem clover can be grown in combination with white clover, oat, or rye (Duke, 1981). Johnny's Selected Seeds (1983) suggested that cereal rye be seeded at 56 lbs/acre when sown with clover. Cv 'Wrens Abruzzi' was dominant when sown in a mixture with six other cover crops (Bugg, pers. comm.).

Cereal rye is often sown along with vetches, for which it provides structural support. Hairy vetch (20 lb/a) and cereal rye (70 lb/a) can be grown in biculture in the winter, then managed no-till by mowing (rather than herbicides) and the residue manipulated to suppress weeds yet allow development of a crop of corn. Surface-feeding Lumbricidae (earthworms) are apparently responsible for ensuring efficient availability of nitrogen to the economic crop. This system has been perfected for Virginia, and may prove useful elsewhere, with some modifications (Luna and Rutherford, 1989).

Cereal rye/hairy vetch biculture also appears useful in southern Georgian pecan orchards, where it can provide a seasonal sequence of aphid prey to lady beetles: first bird cherry - oat aphid (Rhopalosiphum padi) on rye, and pea aphid (Acyrthosiphon pisum) later on the vetch (Bugg et al., 1991).

Cereal rye has performed well when overseeded into field corn, sweet corn, or brassica crops (Schonbeck, 1988).

Rye produces several compounds that inhibit crops and weeds. The most active compounds are two hydroxamic acids and their breakdown products (Chase et al., 1991).

Inclusion of barley, oat, or rye in a mix of cover crops along with vetches and bell beans appears to reduce infestation by common fiddleneck (Amsinckia intermedia) (Bugg, 1990).

Cereal rye can be drilled into pre-existing stands of perennial legumes. In Poplar Ridge, N.Y., cereal rye did especially well when drilled into red clover and white clover. Second year stands competed more than first year stands with cereal rye. In particular, birdsfoot trefoil interfered little the first year, but substantially the second (White and Scott, 1991).

White and Scott (1991) in New York found that yield of cereal rye was less affected by living mulch of white clover, 'Ladino' clover, or red clover than of crown vetch, birdsfoot trefoil or alfalfa.

Ranells and Wagger (1997b) conducted a replicated field trial on N-dynamics of the following monocultural and bicultural cover crops: (1) cereal rye; (2) crimson clover; (3) hairy vetch; (4) cereal rye/crimson clover; and (5) cereal rye/hairy vetch. Cereal rye grown without legume (in monoculture) contained 11.2 and 11.1 (two years of data) kgN/ha when grown with low residual soil N (prior corn fertilized using 150 kgN/ha). The corresponding values for cereal rye grown with crimson clover were 12.3 and 12.3 and with hairy vetch, 19.9 ad 15.3 kgN/ha. With high residual N (300 kgN/ha) applied to preceding corn crop), results were qualitatively similar, with statistically significant differences obtained in 1993 as follows: rye (11.3 kgN/ha) < rye (with crimson clover-18.2 kgN/ha) < rye (with hairy vetch-26.5 kgN/ha). These results occurred while the corresponding figures for cereal rye biomass in Mg/ha were 5.73 > 3.26 > 2.27. Cereal rye monocultures reduced residual soil N by 62 and 37% in 1993 and 1994. Bicultures with cereal rye and legumes reduced residual soil N by 44 and 15% for the same years. Taken together, these values strongly suggest transfer of N from legumes to associated cereal rye, because the cereal rye was sown at lower densities and attained equal or lower biomass in biculture, yet accumulated higher total N than in cereal rye monocultures.

Cereal rye produces large amounts of organic matter (McLeod, 1982); in Hopland, Mendocino County, California, cv 'Merced' produced an above-ground dry biomass of 9.9+/-1.8 Mg/ha (Mean +/- S.E.M.) (Bugg et al., 1996). This was less than 'U.C.475' barley or 'California Red' oat (but not significantly less), despite Miller's (1984) statement that oat does not produce as much dry matter as barley, rye, or wheat. Biomass yields are not always great: in a three year field trial in Georgia, cereal rye biomass averaged only 4.03 Mg/ha (Hargrove. 1986), and Brinton (1989) mentioned only 1,100-1,300 lb/a of dry biomass. Per-plant biomass ranges from 25.8 ('Viatka') to 35.1 g ('Dankowske Zlote'), according to Gawronska and Nalborczyk (1989). Cereal rye produces more fall and early spring growth than oat (Miller, 1984).

Jackson et al. (1993b) stated that, for mid-November-planted cover crops in March, above-ground biomass figures in kg/ha were:

 

In North Carolina, Ranells and Wagger (1997) reported a replicated trial on recovery of potassium nitrate labeled with 10 atom % N-15 by monocultures of cereal rye and crimson clover and a biculture of the two. Above-ground dry matter production through time was as follows (data given for two successive years).

Above-ground N accumulation through time was as follows (data given for two successive years):

Above-ground C:N ratios through time were as follows (data given for two successive years).

 

Wyland et al. (1996) during winter in Salinas, CA, grew tansy phacelia (cv. 'Phaci') and cereal rye (cv. 'Merced') both preceded and followed by broccoli; control plots were fallow. There were three replications. Plots were managed by th reduced-tillage "Sundance System." Both cover crops were tilled under in mid-April and broccoli was planted in late April. For phacelia, biomass production was 3,640 +/- 283.8 kg/ha and N content 106 +/- 10.4 kg/ha. The corresponding values for cereal rye were 3,727 +/- 1.29.2 kg/ha and 136 +/- 9.5 kg/ha.

Cereal rye may stabilize and prevent leaching of excess soil or manure nitrogen (Schonbeck, 1988). Benkenstein et al. (1990) reported that point placements of labeled ammonium sulfate and sodium nitrate at depths of 40, 60, and 80 cm under growing cereal rye plants resulted in the arrest of some 72% of the nitrate evolving from the 40 cm placement, and 18% from the 80 cm depth. Mean N content of three year field trial in Georgia was 38 kg/ha (Hargrove, 1986), whereas Brinton (1989.) listed a mean nitrogen content of 7-14 lb/a.

Schonbeck (1988) noted that cereal rye has been shown to be allelopathic towards other plants, but some of the suppressive effects may relate to tie-up of soil nitrogen by decomposing rye residues. If rye is incorporated while under 16 inches in height and the tissue is still sweet to the taste, this sort of tie-up can supposedly be minimized.

McCracken et al. (1989) documented first-year residual effects of nitrogen fertilization and cover crops of hairy vetch and rye in corn. Control plots used corn stover alone. One year after discontinuing the practice, the residual effect of N-fertilization was to increase N uptake by corn by 20.4 kg/ha over that seen with corn residue alone. With hairy vetch, uptake by corn was higher by 28.0 kg/ha. Holdover effects of rye cover cropping were small and inconsistent.

Ranells and Wagger (1996) found that, based on linear correlation coefficients, initial C:N ratio was a consistently significant predictor of N release by cover crop residues (cereal rye, crimson clover, hairy vetch, and bicultures of cereal rye/crimson clover and cereal rye/hairy vetch). By contrast, Lignin:Nitrogen ratio was not a reliable predictor of N release, although this has been the case in prior studies.

In a replicated field study, Ranells and Wagger (1997a) explored N-recovery by cereal rye and crimson clover monocultures, bicultures of these two plants, and a weedy fallow on the coastal plain of North Carolina. 15N-labelled potassium nitrate fertilizer was applied to microplots 1 week after sowing cover crops (sowing in early October) in a Norfolk loamy sand. Rooting depth was 25 cm in December, 70 cm in March, and 90 cm in April. Percent recovery of fertilizer N by various cover crop regimes was as follows:

Significance tests (Fisher's plsd) indicated the following ranking for efficiency of fertilizer N recovery: cereal rye > cereal rye/crimson clover > crimson clover = resident winter-annual weeds.

Ranells and Wagger (1996) conducted field trials on the North Carolina coastal plain concerning monocultures of crimson clover, hairy vetch, and cereal rye, and bicultures of crimson clover/cereal rye and hairy vetch/cereal rye managed without tillage. The greatest N-content occurred with hairy vetch monocultures (154 kg N/ha) and the least with cereal rye (41 kg N/ha). The rates of N-release were in this order: hairy vetch > crimson clover = hairy vetch/cereal rye > crimson clover/cereal rye = cereal rye. For cereal rye grown in monoculture, the C:N ratio was 40:1, whereas when cereal rye was grown in biculture with hairy vetch, the C:N ratio was 28:1. Thus, cereal rye grown with hairy vetch has less likelihood of immobilizing N during decomposition. Mean values obtained for this two-year study were as follows:

In this tillage experiment, growth stages were as follows, on April 19 or 20.

In the warm, rainy first year of the study, 90% of the N in the hairy vetch monoculture had been released by the 8th week of the study; 71% of the N had been released for the cereal rye monoculture.

Quemada and Cabrera (1995a) reported the following:

These data for residues left on the soil surface reflect the slower breakdown of stems, and the immobilization of N caused by application of materials with high C/N ratios.

Quemada and Cabrera (1995a) also evaluated the relative allocation of carbon to soluble compounds, cellulose, hemicellulose, and lignin, which have profoundly differing rates of decomposition, with the foregoing list given in descending order of rate of breakdown. For all three plant species mentioned, stems had much higher concentrations of lignin than did leaves.

Using the CERES-N submodel, Quemada and Cabrera (1995b) further explored the release of N from no-till cover crop residues, deriving decay rate constants from breakdown rates for stems, leaves, and mixtures of both. The constants that best fitted the data were 0.14-day for cellulose; decay rate for lignin was assumed to be 0.00095-day. That is, each day, more than 10% of the soluble carbohydrate pool degrades to CO2, about 0.34% of the cellulose pool degrades, and less than 0.1% of the lignin.

Quemada and Cabrera (1995b) in Georgia used the CERES-N model to predict conditions for leaves or stems or 50:50 by dry weight mixtures of crimson clover, cereal rye, oat, and wheat harvested at maturity. All crop residue was cut into 1-cm pieces and placed atop sandy loam soil that had previously been managed without tillage. Incubation was in acrylic plastic cylinders at 35° and 98% RH, for 160 days. The study was replicated three times. Observed N-mineralization was slower than previously reported for incorporated residues:

Humus native to the soil was estimated to mineralize N at 0.00042/day.

Reported C/N ratios were:

Ranells and Wagger (1992) in the North Carolina Piedmont reported that N release rate from crimson clover residues managed without tillage was dependent on the growth stage at which the plant was killed (using glyphosate [Round Up®] herbicide). After 16 weeks of decomposition, %N release and total cumulative N release for crimson clover residues were as follows (means of two years):

 

Ranells and Wagger (1997b) conducted a replicated field trial on N-dynamics of the following monocultural and bicultural cover crops: (1) cereal rye; (2) crimson clover; (3) hairy vetch; (4) cereal rye/crimson clover; and (5) cereal rye/hairy vetch. Cereal rye grown without legume (in monoculture) contained 11.2 and 11.1 (two years of data) kgN/ha when grown with low residual soil N (prior corn fertilized using 150 kgN/ha). The corresponding values for cereal rye grown with crimson clover were 12.3 and 12.3 and with hairy vetch, 19.9 ad 15.3 kgN/ha. With high residual N (300 kgN/ha) applied to preceding corn crop), results were qualitatively similar, with statistically significant differences obtained in 1993 as follows: rye (11.3 kgN/ha) < rye (with crimson clover-18.2 kgN/ha) < rye (with hairy vetch-26.5 kgN/ha). These results occurred while the corresponding figures for cereal rye biomass in Mg/ha were 5.73 > 3.26 > 2.27. Cereal rye monocultures reduced residual soil N by 62 and 37% in 1993 and 1994. Bicultures with cereal rye and legumes reduced residual soil N by 44 and 15% for the same years. Taken together, these values strongly suggest transfer of N from legumes to associated cereal rye, because the cereal rye was sown at lower densities and attained equal or lower biomass in biculture, yet accumulated higher total N than in cereal rye monocultures.

In replicated studies in Salinas, CA, Jackson et al. (1993b) reported that November-planted cover crops had attained the following total-plant N content (kg N/ha) figures by March; approximate above-ground N contents were read from a graph and are given parenthetically:

From data presented by Jackson et al. (1993b), for mid-November-planted cover crops in March, approximate values for N contained in root systems obtained by subtraction were as follows in kg N/ha:

 

In Salinas, CA, Wyland et al. (1995) found that a cover crop of cereal rye (cv 'Merced') grown (preceding crisphead lettuce) from December 16 through April 8 was senescing, had produced a biomass of 2,820 kg/ha, contained 39.5 kg N/ha, and had a C:N ratio of 29:1. This cover crop was difficult to incorporate by disking, and led to N immobilization in the soil and deficiencies to the following lettuce crop.

In North Carolina, Ranells and Wagger (1997) reported a replicated trial on recovery of potassium nitrate labeled with 10 atom % N-15 by monocultures of cereal rye and crimson clover and a biculture of the two. Above-ground dry matter production through time was as follows (data given for two successive years).

Above-ground N accumulation through time was as follows (data given for two successive years):

Above-ground C:N ratios through time were as follows (data given for two successive years).

 

Quemada and Cabrera (1995a) in Georgia found that chemical composition of various winter-annual plants varied in their chemical composition and in their decomposition rates when managed without tillage. In addition, leaves consistently varied from stems in having greater C/N ratios and lignin and cellulose contents (the latter two expressed as g/kg of plant material). Based on CO2 emissions and N mineralized, stems decomposed more slowly than leaves for crimson clover, cereal rye, wheat, and oat.

Cereal rye mean phosphorus content is 2-3 lb/a, and mean potassium content is 10-11 lb/a based on biomass estimates of only 1,100-1,300 lb/a of dry biomass according to Brinton (1989).

Eckert (1991) found that in no-till managed corn and soybean production (Ohio), a cereal rye cover crop increased concentrations of exchangeable K near the soil surface (0-5 cm, 3 of 4 comparisons), but otherwise had little effect on soil chemical attributes.

Ranells and Wagger (1996) cited Van Soest (1964) as a reference for the statement that lignin linkages in non-leguminous plants are usually more resistant to decomposition than those of legumes. Ranells and Wagger observed that, based on field trials in North Carolina, lignin concentrations were significantly greater for hairy vetch (84g/kg) than for cereal rye (27g/kg) or crimson clover (46g/kg) (Least Significant Difference=11).

Cereal rye is useful for preventing wind or water erosion (Miller, 1984); if disked under, it improves infiltration by irrigation water (Williams, 1966).

Wyland et al. (1996) during winter in Salinas, CA, grew tansy phacelia (cv. 'Phaci') and cereal rye (cv. 'Merced') both preceded and followed by broccoli; control plots were fallow. There were three replications. Plots were managed by th reduced-tillage "Sundance System." Both cover crops were tilled under in mid-April and broccoli was planted in late April. Cover-cropped soil showed lower soil moisture than control from mid- to late March.

Werenfels et al. (1963) conducted unreplicated field observations in long-term cover crop plots that had been established in 1924 and managed consistently until 1961 in an apricot orchard on a Yolo loam soil in Davis, California. The researchers suggested that infiltration rates (ring infiltrometers) were in descending order: alfalfa (Medicago sativa) > 'Hubam' white sweetclover (Melilotus alba) > sour clover (Melilotus indicus) > cereal rye (Secale cereale) > clean cultivation. The researchers stated that the alfalfa and white sweetclover alleviated a plow pan, but that cereal rye did not. Unfortunately, the unreplicated nature of the study severely limits interpretation.

Cereal rye is useful for preventing wind or water erosion. (Miller, 1984); it may be of some value in providing windbreaks for vegetable crops (Schonbeck, 1988).

Young (1922) conducted 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.

Cereal rye as a cover crop is grown for erosion control, to add organic matter, to enhance soil life, and for weed suppression (Johnny's Selected Seeds, 1983). It may stabilize and prevent leaching of excess soil or manure nitrogen (Schonbeck, 1988); has an extensive root system that makes it among the best green manures for improving soil structure (Pears et al., 1989); and is a better soil renovator than oat (McLeod, 1982). Cereal rye is useful for preventing wind or water erosion (Miller, 1984) and has been used to protect soil from wind erosion in Australia (Bushuk, 1976); if disked under, it improves infiltration by irrigation water (Williams, 1966).

Cereal rye is normally seeded at 112 kg/ha, but when it is seeded late, the rate should be increased up to 336 kg/ha to achieve rapid and complete vegetational cover and reduce erosion. To minimize erosion, a leaf area index of 1.0 (complete cover) may be necessary (Stoskopf, 1985).

No-till hairy vetch preceding corn showed significantly-higher soil organic matter than either rye or fallow (Frye and Blevins, 1989).

Zhang and Hendrix (1995) in Georgia conducted laboratory microcosm studies on carbon flow as affected by the epigeic earthworm Lumbricus rubellus and the endogeic earthworm Aporrectodea caliginosa vs. microcosms lacking earthworms. Sorghum leaf litter was labeled with 13C, whereas cereal rye fine roots and root exudates were labeled with 14C. the sorghum leaves were placed on the microcosm soil surfaces; cereal rye portions were included in the soil. Mason jars containing 500g of the 14C-labeled soil served as microcosms. There were three treatments, each replicated 5 times: (1) 14C soil and 13C litter; (2) 14C soil and 13C litter and 4 adult L. rubellus; and (3) 14C soil and 13C litter and 4 adult A. caliginosa. After 37 days of incubation at 18° C, destructive sampling terminated the experiment. Key findings included: (1) Earthworms decreased translocation of soil C into leaf litter, possibly by reducing fungal hyphal connections; (2) the epigeic earthworm (L. rubellus) preferentially ingested 13C litter, whereas the endogeic A. caliginosa fed preferentially on the 14C-labeled soil. The former increased surface litter loss by ~15% and the latter by ~11% vis a vis the control microcosms.

Ranells and Wagger (1997b) conducted a replicated field trial on N-dynamics of the following monocultural and bicultural cover crops: (1) cereal rye; (2) crimson clover; (3) hairy vetch; (4) cereal rye/crimson clover; and (5) cereal rye/hairy vetch. Cereal rye grown without legume (in monoculture) contained 11.2 and 11.1 (two years of data) kgN/ha when grown with low residual soil N (prior corn fertilized using 150 kgN/ha). The corresponding values for cereal rye grown with crimson clover were 12.3 and 12.3 and with hairy vetch, 19.9 ad 15.3 kgN/ha. With high residual N (300 kgN/ha) applied to preceding corn crop), results were qualitatively similar, with statistically significant differences obtained in 1993 as follows: rye (11.3 kgN/ha) < rye (with crimson clover-18.2 kgN/ha) < rye (with hairy vetch-26.5 kgN/ha). These results occurred while the corresponding figures for cereal rye biomass in Mg/ha were 5.73 > 3.26 > 2.27. Cereal rye monocultures reduced residual soil N by 62 and 37% in 1993 and 1994. Bicultures with cereal rye and legumes reduced residual soil N by 44 and 15% for the same years. Taken together, these values strongly suggest transfer of N from legumes to associated cereal rye, because the cereal rye was sown at lower densities and attained equal or lower biomass in biculture, yet accumulated higher total N than in cereal rye monocultures.

Wyland et al. (1996) during winter in Salinas, CA, grew tansy phacelia (cv. 'Phaci') and cereal rye (cv. 'Merced') both preceded and followed by broccoli; control plots were fallow. There were three replications. Plots were managed by th reduced-tillage "Sundance System." Both cover crops were tilled under in mid-April and broccoli was planted in late April. Phacelia led to significantly higher soil microbial biomass C and N than cereal rye or control on several dates in late March and early April. Cover-cropped soil showed lower soil moisture than control from mid- to late March.

Werenfels et al. (1963) conducted unreplicated field observations in long-term cover crop plots that had been established in 1924 and managed consistently until 1961 in an apricot orchard on a Yolo loam soil in Davis, California. The researchers suggested that infiltration rates (ring infiltrometers) were in descending order: alfalfa (Medicago sativa) > 'Hubam' white sweetclover (Melilotus alba) > sour clover (Melilotus indicus) > cereal rye (Secale cereale) > clean cultivation. The researchers stated that the alfalfa and white sweetclover alleviated a plow pan, but that cereal rye did not. Unfortunately, the unreplicated nature of the study severely limits interpretation.

Cereal rye grain and straw have relatively low quality as livestock feed (Bushuk, 1976.).

No specific information on cereal rye effects on workers is available. Cereal rye, with its tall stature, might be expected to inhibit foot traffic in cover cropped fields or orchards (Bugg, pers. comm.). It can interfere with sprinkler irrigation by blocking the emitters (George Kresa, pers. comm.).

Bugg et al. (1991) used "dying mulches" of cool-season cover crops in efforts to enhance biological control of insect pests on succeeding spring plantings of cantaloupe (Cucumis melo L. var. reticulatus Seringe). Eight cover-crop regimes were tested in a replicated trial. Cereal rye was particularly poor habitat for Geocoris punctipes, an important generalist predator in vegetable and field crops. Especially good habitat was provided by 'Mt. Barker' subterranean clover.

Bugg et al. (1990) evaluated 20 cover-cropping regimes and associated insects, and found that convergent lady beetle (Hippodamia convergens Guerin-Meneville]) and seven-spotted lady beetle (Coccinella septempunctata [L.]) first were found in substantial numbers on rye (which harbored bird cherry - oat aphid [Rhopalosiphum padi {L}]), then on crimson clover and lentil, later on subterranean clover, still later on narrow-leafed lupin, then on hairy vetch, and lastly on mustard and collard.

Haley and Hogue (1990) assessed influence of type of ground cover on apple aphid, Aphis pomi DeGeer (Homoptera: Aphididae), and its predators in a young apple orchard, four ground cover regimes were compared: (1) fall cereal rye (Secale cereale), herbicided in spring and summer; (2) a mixture of white clover (Trifolium repens) and grass; (3) herbicided tree-row strips and grassed-in alleys; and (4) woven black-plastic strips in the tree row and grassed alleys. The trial was initiated at the beginning of the second year of the orchard. Few aphidophagous insects of interest (e.g., the predatory mirids Deraeocoris brevis and Campylomma verbasci, the predatory midge Aphidoletes aphidimyza, lady beetles, hover flies, or lacewings), were found in the ground covers. In the first year of the study, leaf nitrogen and aphid and predator densities were lower on trees with the white clover-grass mixture. These differences did not occur the second year. Terminal growth was particularly depressed for apple trees with understories of white clover and grass.

Bugg et al. (1991) in southern Georgia, found that in mature pecan orchards under minimal or commercial management, cool-season understory cover crops of hairy vetch, Vicia villosa Roth, and rye, Secale cereale (L.), sustained significantly higher densities of aphidophagous lady beetles than did unmown resident vegetation or mowed grasses and weeds. In cover-cropped understories, mean densities of aphidophagous coccinellids were nearly 6 X greater than in unmown resident vegetation and approximately 87 X greater than in mown grasses and weeds. During late winter and spring, rye harbored abundant bird cherry - oat aphid, Rhopalosiphum padi L., whereas hairy vetch sustained pea aphid, Acyrthosiphon pisum (Harris); blue alfalfa aphid, A. kondoi Shinji; and thrips, Frankliniella spp. The following aphidophagous lady beetles were adundant in cover-cropped understories: (1) convergent lady beetle, Hippodamia convergens Guerin-Meneville; (2) Olla v-nigrum (Mulsant); and (3) seven-spotted lady beetle, Coccinella septempunctata L. In the orchard under minimal management, there was evidence that the rye/vetch mixture led to enhanced densities of convergent lady beetle in the pecan trees. No other effects on coccinellids were seen, and there was no evidence of improved biological control of pecan aphids.

In the minimal-management orchard, lady beetles occurred on rye in substantial densities from early April through early May. By contrast, attendance on hairy vetch extended from early April until early June for H. convergens and C. septempunctata. On the other hand, by early May, O. v-nigrum had had almost entirely left the understory and entered the pecan canopy. From mid April through early May, O. v-nigrum was mainly associated with pecan catkins, which contained abundant thrips (mainly Frankliniella tritici [Fitch] and F. bispinosa [Morgan]). In the commercial orchard, convergent lady beetle occurred predominantly on rye from early April through early May, and thereafter was found mostly on hairy vetch. Olla v-nigrum relied almost exclusively on rye through early May, by which time many of the beetles had dispersed to the pecan catkins, as in the Tifton study. Seven-spotted lady beetle relied substantially on rye from late April until mid May, and from early through late May on hairy vetch. Coccinellid larvae appeared to concentrate almost exclusively on the bird cherry - oat aphid on rye, from early May through early June (Bugg et al., 1991b).

Wyland et al. (1996) during winter in Salinas, CA, grew tansy phacelia (cv. 'Phaci') and cereal rye (cv. 'Merced') both preceded and followed by broccoli; control plots were fallow. There were three replications. Plots were managed by th reduced-tillage "Sundance System." Both cover crops were tilled under in mid-April and broccoli was planted in late April. Phacelia led to significantly higher densities of bulb mite (Rhizoglyphus echinopus) on the soil surface than did either cereal rye or bare plots, during broccoli growth.

Starzycki (1976) wrote that cereal rye may be attacked by Ditylenchus dipsaci Kuehn, Anguina tritici (Steinbuch), and Heterodera avenae. Carrot, wheat, potato, turnip, lupin, serradella, sainfoin, alfalfa, and white mustard can be grown preceding cereal rye to reduce D. dipsaci. Clean seed and crop rotation reduces A. tritici. Use of leguminous and root crops in rotation reduces H. avenae.

On a sandy soil in Florida, McSorley and Dickson (1989) found that cereal rye as a cover crop led to increased densities of Belonolaimus longicaudatus; for 5 other plant-parasitic nematodes assessed, cover cropping led to mainenance or a slight decline in pre-existing densities.

Cereal rye harbored particularly low densities of root lesion nematode (Pratylynchus penetrans) in an orchard in Ontario, Canada (Marks and Townsend, 1973).

In northern peninsular Florida (Live Oak, Gainseville) McSorley (1994) found that winter cover cropping with cereal rye (cv. 'Vita Maze' or 'Wrens Abruzzi') nearly maintained the densities of the plant-parasitic nematode Meloidogyne arenaria, unlike crimson clover, which is highly susceptible to this nematode and leads to its build-up.

Starzycki (1976) reported that cereal rye is afflicted by the following fungi: powdery mildew (Erysiphe graminis DC), ergot of rye (Claviceps purpurea (Fr.) Tul., take-all of wheat (Gaeumannomyces graminis Arx et Olivier - - Opiobolus graminis Sacc.), stalk smut (Urocystis occulta [Wallr.] Rab.), stem rust (Puccinia graminis Pers., f. secalis), brown leaf rust (Puccinia dispersa Erikss.) yellow rust (Puccinia striformis West - - Puccinia glumarum Erikss et Henn.), eyespot (Cercosporella herpotrichoides Fron.), snow mold (Fusarium nivale (Fr.) Ces.), fusariosis of rye spikes (Fusarium spp.), spot blotch (Helminthosporium sativum [Pam] King et Bakke [Bipolaris sorokiniana {Sacc. in Sorok} Shoemaker]), black mold (Cladosporium herbarium [Pers.]), Antracnose (Colletotrichum graminicola [Ces.] Wils.), septoria leaf blotch (Septoria secalis [Rob.]), and leaf blotch of rye (Rhynchosporium secalis [Oudem.] I.I. Davies). Viral diseases of cereal rye include barley yellow dwarf, wheat dwarf, soil-borne mosaic, and oat blue dwarf (Starzycki, 1976).

Cereal rye can itself become a weed through volunteering (Stoskopf, 1985), yet it is noted as a good rotational crop because it suppresses weeds (Bushuk , 1976). In the Northeast, it has been noted for suppressing lambsquarters and pigweed, but not wild mustard (Schonbeck, 1988).

Rye produces several compounds that inhibit crops and weeds. The most active compounds are two hydroxamic acids and their breakdown products (Chase et al., 1991). Perez and Ormeno-Nunez (1991) reported that hydroxamic acids are exuded by the roots of growing cereal rye plants and can inhibit root growth of wild oat (Avena fatua L.). Exudates of wheat roots contained no hydroxamic acids and showed no such inhibitory effects. Residues of tillering plants and rye crop residues contain much lower amounts of allelopathic compounds (various phenolic acids) than do seedlings (Wocjcik-Wojtkowiak et al., 1990).

Some suppressive effects of cereal rye may relate to tie-up of soil nitrogen by decomposing rye residues. If rye is incorporated while under 16 inches in height and the tissue is still sweet to the taste, this sort of tie-up can supposedly be minimized (Schonbeck, 1988).

Smeda and Putnam (1988) studied cover crops of cereal rye (cv 'Wheeler'), wheat (Triticum aestivum L. 'Yorkstar') and barley (Hordeum vulgare L. cv 'Barsoy') grown amid 2-year-old stands of strawberry (Frageria X ananassa Duchesne Rosaceae; cv 'Midway' or 'Guardian'). There were also control plots with no cover crops seeded. The cover crops were planted in mid September and killed during early or late May, with applications of the graminicidal herbicide fluazifop-butyl. All cover crops showed better weed suppression than the control, but the only significant differences among cover crops indicated that barley was inferior to rye or winter wheat. There were no significant differences among treatments in yield of strawberries.

Inclusion of barley, oat, or rye in a mix of cover crops along with vetches and bell beans appears to reduce infestation by common fiddleneck (Amsinckia intermedia) (Bugg, 1990).

In plots seeded to 'Merced' cereal rye in Mendocino County, California, above-ground dry biomass of weeds during mid May was 0.03+/-0.03 Mg/ha, Mean +/- S.E.M., which is only 0.63% of the weed biomass in unseeded control plots. Dominant weeds were annual ryegrass, rattail fescue, common chickweed, and scarlet pimpernel. Vegetational cover data by the cereal rye was 96.3+/-2.4 % Vegetational Cover (Mean +/- S.E.M.) (Bugg et al., 1996).

Sun and Corke (1992) described the weedy rye believed to be a hybrid of S. cereale spp. cereale and its wild perennial progenitor Secale montanum. The weedy rye populations occur in mixed stands in mesic or xeric sites of the mountains of Northern California and Southern Oregon. 50 years generations (yrs.) have apparently occurred in California.

Perez and Ormeno-Nunez (1993) reported on laboratory and field observations in Chile concerning the root exudation of hydroxamic acids by the cereal rye cultivar 'Forrajero-Baer'. In an unreplicated field trial, the plot with the cereal rye cultivar reduced total weed biomass below the values observed for one plot of wheat cv. 'Nabo' or one of forage oat (Avena strigosa). Qualitatively similar results were obtained for reduction of the weed wild oat (Avena fatua). Petri dish tests of wild oat seeds showed reduced growth of radicles and coleoptiles at concentrations of 0.25mm for three hydroxamic acids.

Cereal rye is a common weed in the intermountain area of California because it will volunteer and grow with only 5 or 6 inches of precipitation. Dick Jacobs, CSU Chico Crops Coordinator, reported that the 15% of common rye included in Lohse Mill Beneficial Blend was still a problem three years later (1997, pers. comm.).