Eleusine coracana, known as finger or African millet, is the only species of economic importance in the tribe Chlorideae. Finger millet has been grown predominantly in India and Africa, both for grain and forage. In contrast to most millet, it requires mild weather and a considerable amount of rainfall to mature (Haq 1989). The tribe Paniceae is the largest tribe of the Poaceae, containing 71 genera with approximately 1400 species distributed mainly in tropical and also temperate regions (Roshevits 1980). Economically important cultivated millets in the tribe Paniceae are: pearl millet (Pennisetum americanum L.) (Andrews et al. 1993) foxtail millet (Setaria italica L. Beauv.), proso millet (Panicum miliaceum L.), and Japanese millet (Echinochloa frumentaceae L.).
The genus Panicum is one of the largest genera of the grasses, including more than 400 species distributed primarily in the tropics and subtropics and also warmer parts of temperate zones (Roshevits 1980). Within this large genus, two species are of economic importance; proso millet and to a lesser extent little millet (P. miliare L.). The genus Panicum is poorly represented in drier tropics, apart from a few more or less xerophytic species (Cobley 1976).
Proso, an ancient Slav name used in Russia and Poland (Candolle 1964), has also been called common millet, hog millet, broom corn, yellow hog,hershey, and white millet. Although the origin of proso millet has not been ascertained, it is one of the first cultivated cereal grasses, most likely prior to wheat. Proso millet has been known for many thousands of years in Eastern Asia including China, India, and Russia. The cultivation of proso is more generally thought to come from central and eastern Asia and spread to India, Russia, the Middle East, and Europe (Roshevits 1980). Proso is still extensively cultivated in India, China, Russia, in the Middle East including Iran, Iraq, Syria, and Turkey, and also in Afghanistan and Romania (Martin et al. 1976). According to Matz (1986), however, proso is probably a native of Egypt and Arabia and has been cultivated in Asia Minor and southern Europe since prehistoric times. Candolle (1964) also states that Egypto-Arabian origin of proso millet is very probable.
The genus Setaria is widely distributed in warm and temperate areas. Foxtail millet is the most economically valuable of the genus. Foxtail millet is one of the world's oldest cultivated crops. Its planting has been mentioned in Chinese records as early as 2700 BC (Vinall 1924). S. italica was the most important plant food in the neolithic culture in China, and its domestication and cultivation was the earliest identifiable manifestation of this culture, the beginning of which has been estimated at over 4,000 years ago (Chang 1968). In Russia, foxtail millet has been cultivated since ancient times and there is evidence that it was grown as long as 1,500 years ago (Movsisyants, 1950). Malm and Rachi (1968) thoroughly reviewed the domestication of foxtail millets and the taxonomy. They report the use of subspecies by Scholz (1960) based on papillae on the epidermal cells of the glumes (moharia) and no papillae (maximas). Perhaps of more practical value was the breakout by Coleman (1939) based on head type and seed color.
The proso plant is considered a short-day plant and usually an erect annual, 30 to 100 cm tall with few tillers and an adventitious root system. However, Anderson (1994) showed that 'Cope' proso millet development can be related to temperature by using growing degree days (GDD). For proso, he used a base temperature of 10°C. He showed that 'Cope' began tillering at 430 GDD and initiated flowering at 750 GDD. This relationship needs to be confirmed for other cultivars.
Proso stems and leaves are covered with slight hairs. The leaves may be up to 30 cm long with a short ligule but no auricles (Cobley 1976). The stem is terminated by a drooping panicle 10 to 45 cm long that may be open or compact (Hulse et al. 1980). Proso (2n = 36) is considered a self-pollinated crop, but natural cross-pollination may exceed 10% (Popov 1946). Proso seeds are smaller than pearl millet and grain sorghum, generally oval in shape and about 3 mm long and 2 mm wide (Cardenas et al. 1983). The seeds vary in color as white cream, yellow, orange, red, black to brown. Growth and development characteristics of proso millet were explained in detail by Cardenas et al. (1983). They distinguished three phases; vegetative, reproductive, and ripening, which may be further sub-divided into physiologically distinct stages. The vegetative phase covers the period from germination to panicle initiation, depending on the cultivar used and climate in the area, may be completed 16 to 20 days after planting. An increase in number of leaves, tiller buds, and plant height are characteristics of this phase. The period, about 20 to 25 days, from panicle differentiation to flowering of the main culm is the reproduction phase. This phase initiates when the panicle primordium is greater than 0.5 mm. Rapid elongation of stem internodes and an increase in leaf area accompanied by more tillers are noticed in this phase. The ripening phase starts at flowering or blooming and continues to the end of physiological maturity, which covers a period of 20 to 30 days. Throughout this period, the plant actively accumulates dry matter, particularly in the grains. Rodriques et al. (1990) studied the dry matter accumulation pattern of two cultivars of proso millet with optimum nutrient and water availability. From anthesis to maturity, dry matter accumulated at a rate of 0.5 mg/ha-day. Panicles at maturity accounted for 55% of the total plant dry matter, which is higher than for wheat and grain sorghum. The authors concluded that since proso accumulates higher dry matter in the reproductive parts compared to wheat, maize, and sorghum, it may be advantageous to grow proso in dry and short growing seasons. Physiological maturity proceeds from top to bottom of the panicle. The ripening of the seed is not uniform throughout the panicle and delay in harvesting may cause losses due to shattering (Theisen et al. 1978; Baltensperger et al. 1995a). The grains from the main panicle reach maximum dry weight and a small dark layer at the hilar region of the seed is formed. At maturity, the grain generally includes about 20% or less moisture.
Proso plants generally mature between 60-90 days after planting and can be grown successfully in poor soil and hot dry weather. Proso is an easy crop to grow and it seems to be better adapted than most crops to primitive agricultural practices. Under high-input conditions, however, it may be a poor choice because of low response to high fertility and abundant water (Baltensperger et al. 1995a).
Proso millet requires very little water, possibly the lowest water requirement of any cereal, and converts water most efficiently to dry matter/grain (Theisen et al. 1978; Hulse et al. 1980). According to Arnon (1972), this is not because of its drought-resistance but because of its short growing season. Proso has a very low transpiration ratio, which may be attributed in part to the C4 photosynthetic mechanism (Martin et al. 1976). The low straw grain ratio of proso also contributes to its water use efficiency and adaptation to moisture-limited areas. Proso is very shallow rooted and does not grow well under water stress, nor under excess moisture. Plants seem to tolerate more cold than most other C4 crops, especially sorghum, but will not tolerate frosts. Moderately warm weather is necessary for germination of the seed and growth of the plant. Proso germinates well at temperatures of 10deg. to 45°C, but does not germinate at 5° or 50°C. The highest rate of germinations is between 35° and 40°C (Theisen et al. 1978).
The feed value of proso has been studied with several classes of livestock. Luis et al. (1982a, b), investigated both broiler and turkey diets with proso. The turkey poults were significantly heavier at the end of the 28 day feeding period with proso than those on either corn or sorghum diets. Broilers fed balanced diets of the three cereals were not significantly different in gains. When proso was evaluated in layer diets it was concluded that "proso millet, either ground or whole, is an excellent ingredient for layer diets" (Luis et al. 1982c). Kies et al. (1975) investigated various millet mixes in human diets and discussed their potential. The feed value of proso millet for cattle and swine is generally considered to equal that of grain sorghum or milo and maize when less than 50% of the maize in the ration is replaced (Table 2).
Growth and development of foxtail millet is well described by Malm and Rachie (1971). A progressive shortening of the vegetative period occurs with later plantings, and stem elongation is determined by the length of the vegetative period. Stem elongation was hastened by late sowing and was retarded by early sowing. The transition from vegetative growth into inflorescence takes place very rapidly. In the lower third of the cone of growth, initial humps of secondary axes appear following enlarged growth of the growing point, with the middle and upper parts still undifferentiated. Later, secondary axes differentiate up to the very top into points of growth. The inflorescence of foxtail millet has a main stalk with shortened side branches bearings spikes and bristles. The first flowers of foxtail millet may open when three fourths of the panicle emerges from the sheath, or as many as five days after full emergence. Flowering proceeds from the top of the head downward in each of the panicle branches. A large head may take 8 to 16 days to compete flowering. A single floret may remain open about 30 min, and about 80 min are required for the complete blooming process, which is hastened by high temperatures and low humidity (Malm and Rachie 1971). The world's foxtail millet crop is grown largely in China, India, Russia, and the United States. Foxtail millet is by far the most important millet species in China and is grown in Hopei, Horank, and Shansi provinces to a large extent and in most northern areas of China (Anderson and Martin 1949). Foxtail millet grows in mountainous as well as plains regions. It provided approximately 17% of the total food consumed in China (Malm and Rachie 1971). Werth (1937) considered China or central Asia to be the center of origin of the cultivated varieties. Many related species, with 2n levels as multiples of the 18 found in foxtail, occur in China. In Russia foxtail cultivars are grown up to 50°N. Foxtail millet is grown primarily for hay in the United States. The primary area is the Northern and Western Great Plains or High Plains, including Colorado, Kansas, Nebraska, Wyoming, South Dakota, and North Dakota. It has been grown at elevations over 1500 m in New Mexico. Seed supplies for hay production are grown in the more southern portion of this region including Texas. The seed can yield as much as proso but foxtail millet seeds are generally much smaller than proso millet seeds. Foxtail millet has about 500,000 seeds/kg, or more than twice that of proso (Wietgrefe 1990). Foxtail millet and proso millet both grow from a height of 0.5 to 2 m, but make little or no regrowth once they are cut. They are generally cut for hay during the early heading stage. Research on forage quality shows foxtail is similar in quality to other C4 annual grasses. It is finer-stemmed and easier to cure than pearl millet or forage sorghum (Baltensperger 1992). Malm and Rachie (1971) give tables of the relative feed value of foxtail millet and discuss its use as a human food and on animal performance. A small amount of foxtail millet is grown and hand picked for millet sprays for the caged bird seed industry (Wietgrefe 1989).
Proso breeding in the United States has been conducted at primarily two locations: the USDA program at Akron, Colorado, which was discontinued when Dr. Greg Heinz left in the late 1980s, and the Univ. of Nebraska program at the Panhandle Research and Extension Center. Dr. Lenis Nelson developed crossing techniques for proso at this location and produced the first cultivar from a hand-made cross ('Rise'), in 1984 (Nelson 1984a, b). Since that time, several cultivars have been released from this program that are currently grown on the majority of U.S. millet hectorage (Nelson 1990a; Baltensperger et al. 1995a, b). Recent work has emphasized the development of increased seed size (Kara 1992). A wider choice of proso cultivars is available today than ever before in the U.S., but most of the high yield, white seed, strong straw types have `Dawn' as one parent in their pedigree, so germplasm base may be narrower than expected. Nearly all proso grown in the major production areas is white-seeded. Red-seeded proso has some demand, but probably is best grown away from the usual production areas and with a contract or specific market identified. A yearly update of cultivars can be found in the Nebraska Cooperative Extension Publication, EC 107, (Nebraska Proso and Sunflower Variety Tests). The average proso yield in Nebraska is approximately 2 t/ha (Baltensperger et al. 1994).
Three cultivars (Sunrise, Huntsman, and Earlybird) were released in 1994 and 1995. 'Sunrise' is a joint release of the Univ. of Nebraska and USDA (Baltensperger et al. 1994). It is large, white-seeded, with excellent yield potential, intermediate in maturity, excellent lodging tolerance, and is expected to replace 'Sunup' in most growing areas. 'Huntsman' is also a joint release of the University of Nebraska and USDA. It is a large, white-seeded cultivar with excellent yield potential, late in maturity, excellent lodging tolerance, and is expected to replace 'Cope' in most growing areas. 'Huntsman' is shorter than 'Cope' (Baltensperger et al. 1995c). 'Earlybird' was released by the University of Nebraska. It is a large, white-seed cultivar with excellent yield potential. It is early in maturity, has excellent lodging tolerance, and is expected to replace 'Dawn' and 'Rise' in most growing areas (Baltensperger et al. 1995b). 'Sunup' is a 1989 release from Nebraska (Nelson 1990b). It is a white-seeded cultivar similar to 'Dawn' and 'Rise'. 'Sunup' is as lodging resistant as 'Dawn' and 'Rise' and is larger seeded than 'Rise'. It is less susceptible to seed shattering than the common proso cultivars. 'Sunup' has replaced 'Rise' as the most commonly grown cultivar in the United States. The newer releases are all larger seeded, but have a similar panicle type. Several other distinct types of proso are available. 'Panhandle' from Nebraska, 'Minco' from Minnesota, and 'Abarr' from Colorado are all similar to the original common white (Baltensperger et al. 1995a). Although these cultivars differ slightly in height, yielding ability, and maturity, they have white seed and are readily marketed though normal channels in the proso growing areas. They all have fairly open panicles and suffer from lodging and seed shattering.
A second type with acceptable white seed is 'Minsum', which was developed in Minnesota as an early maturing cultivar with a very loose panicle type. Colorado State Univ. developed a tall, late maturing cultivar, 'Cope', that has acceptable white seed. Due to its maturity, 'Cope' is likely best adapted to relatively longer growing seasons. University of Nebraska released 'Dawn', a very short, very early cultivar with a tight panicle. It has a superior white grain, but is inferior agronomically because of its height (Nelson 1976). Because of its earliness, shatter resistance, seed size, and lodging tolerance it has been used extensively as a parent in breeding programs.
If red seed is desired, the two choices are 'Cerise', an early maturing cultivar from Nebraska, or 'Red Leonard', a tall, late maturing cultivar from Colorado. 'Red Leonard' has superior yield if planted early. Both have smaller seed size and are less acceptable as a feed due to a higher tannin content. Bird seed manufacturers use small amounts of red proso to improve eye appeal of the final product.
Proso and foxtail millet usually follow in the spring after wheat has been harvested. Both may be planted late as catch crops to replace winter wheat that has been destroyed due to winterkilling, blowing, or hail. Hail storms usually occur after May 15. An attempt is made to plant as soon as the soil is dry enough. Three problems prevail under these circumstances. First, wheat has taken a considerable amount of moisture from the soil profile; second, decaying wheat residue interferes with proso growth; and third, residual herbicide from the wheat crop may persist and injure the millet. Generally, in a wheat-fallow rotation it is more desirable to plant millet into fallow intended for wheat planting in the fall and to utilize the hailed wheat land for fall winter wheat planting. In yield studies conducted in the Nebraska Panhandle, proso yields were more than doubled by using available fallow ground for seeding compared with planting into hailed-out wheat land. The increase of more than 1,000 kg/ha would increase gross returns more than $120/ha using a price of $0.12/kg. The advantage of using the fallow ground is the soil moisture at planting. The danger with this strategy is that hailed wheat land may not store sufficient moisture to provide successful seeding of winter wheat in the fall (Baltensperger et al. 1995a).
The millets can also replace summer crops late in the season when they have poor germination or are destroyed due to early drought, late spring frost, hail, or insects, providing a good chance of obtaining a crop. In moisture-limited areas of the central Great Plains, proso is often well adapted to winter wheat-proso-fallow rotation and gives an extra cash crop every three years. Shanahan et al. (1988) compared three different crop rotations; millet-millet, winter wheat-millet, and fallow-millet for the productivity and water use of proso in the central Great Plains. Over the 5-year period of study, the wheat-millet and fallow-millet out yielded the millet-millet 50% and 116% in grain yield, respectively. Lyon and Baltensperger (1995) and Higgins et al. (1994) showed the value of including millet in a rotation with winter wheat for the control of winter-annual grass weeds.
Several methods of seedbed preparation, as outlined by Baltensperger et al. (1995a) are available to farmers growing proso millet. Work by Nelson and Fenster (1983) and Anderson (1990) show that management within a technique is probably more important than the technique. No-till systems were becoming dominant in the High Plains prior to proso being dropped from the atrazine label. The dropping of the highly tolerant crop from the label is representative of the problems in working with minor crops. Atrazine at the use rates found in proso (less than 0.5 kg/ha) is seldom an environmental problem in dryland areas with more than 20 m to the water table. Alternative strategies to grow no-till proso require several applications of alternative herbicides. The loss of atrazine labeling in proso has increased management demands and the cost of proso production (Baltensperger et al. 1995a).
In general, proso and foxtail millet do not respond consistently to the addition of nitrogen fertilizer. If a full year of fallow precedes the millet, fertilizer is not generally recommended except on the poorest soils (soil test with less than 25 ppm in upper 0.5 m). But, when proso follows wheat, it is generally recommended that 45 kg/ha of nitrogen be applied (Baltensperger et al. 1995a). Chadhari and Rai (1982) suggest that 40 kg N, 20 kg P and 20 kg K/ha used for obtaining a good crop of proso under irrigated conditions in India. Higher rates typically lead to lodging. Proso currently has an upper yield plateau around 5 t/ha because of a lack of straw strength. Yield limits may be higher in more tropically adapted foxtail millets.
Proso millet has a very long planting period and it is often used for replacing dead winter crops or unsuccessful early spring crops. If good weed control is practiced, taking better advantage of spring rains, the earlier dates will produce better yields. In western Nebraska, proso can produce a seed crop when planted as early as May 15 or as late as July 5. Nelson (1990a), using three different cultivars of proso, evaluated influence of planting date on grain yield and other agronomic traits of proso millet at six-year location sites in western Nebraska. The results indicated that planting date of May 15 and June 1 were optimal for grain yield. Foxtail millet cultivars are more variable in maturity than available proso cultivars and some will not mature if planted after June 15 ('White Wonder', 'Golden German' and others), but since most are grown for hay, the practical planting window may be extended to July 15 and still produce a good hay crop.
It is generally accepted that narrow rows (<30cm) are beneficial in reducing weed competition and increasing yield (Nelson 1977; Agdag 1995). The equipment used to plant millet is usually dictated by the equipment available for other crops. The most common drill is one used for winter wheat, usually a deep furrow or hoe-opener type. This is not the most desirable type since it is difficult to maintain a shallow depth with it. When a hoe drill is used, the rate is set high (17 kg/ha) and the depth is quite shallow. The packerwheels can be very beneficial if planting into a loose seedbed, but that combination is most susceptible to crusting from a heavy rainstorm (Baltensperger et al. 1995). The most desirable drill for planting proso where stubble is not a problem is double-disk drill. It can place the seed into a shallow slot and firm the soil around it. It leaves very little furrow to wash in and crust in the event of a heavy rainstorm. The final drill type is one designed for no-till wheat. Regardless of the type of equipment used, it is necessary to have the seed firmly packed and covered with 1 to 2 cm of soil. Nebraska studies showed that choice of drills did not greatly affect yield if a good job of seeding was accomplished (Nelson 1990a).
Ripening is not uniform throughout the panicle in proso. Frequently the seeds in the upper portion of the panicle are ripe while the lower seeds are still green (Matz 1986). A delay in harvesting until the grain has dried sufficiently for threshing will cause considerable losses due to shattering. It is generally recommended that swathing be done when most of the panicle has lost its green color. Threshing can the be delayed until the grain is below 13% moisture (Baltensperger et al. 1995a). Foxtail heads ripen more uniformly and are less subject to shatter, but frequently have tillers that are significantly different in maturity. Foliage is still green at maturity so it is generally swathed prior to combining
The primary limitation on foxtail millet production in the High Plains is not actually a serious problem for foxtail millet itself. It is that it serves as a carrier for both the wheat curl mite, Eriophyes tullipae Keifer, the carrier for wheat streak mosaic virus and the virus itself. While adapted cultivars of foxtail are not seriously impacted by the disease, the crop serves as an over-summering host and adjacent wheat fields are frequently severely impacted. Recent research by Marcon (1994) has identified germplasm with much higher levels of resistance that may help to expand the utilization of foxtail millet in the region. Proso has been immune to this disease and is the primary reason it is utilized on a larger scale. However, one of the weeds in many proso fields is green foxtail Setaria viridis which can cause the same problems in wheat fields adjacent to proso fields. Management can be utilized to reduce the severity of the problem by harvesting the proso early enough that no living material is present for at least 2 weeks prior to wheat planting.
The International Sorghum and Millet Project has specifically excluded research on these two species. As a result, even though foxtail and proso millet have been more significant in U.S. agriculture and are a significant food source for millions of people, much less research has occurred on them during the past ten years than on pearl millet in the United States. The politics of minor crops continues to be a significant factor to overcome in their development, but the potential remains high for both foxtail and proso millet.
|Paniceae||Setaria italica||Foxtail millet, Italian millet, German millet, Hay millet|
|Panicum miliaceum||Proso millet, Common millet, Hershey millet, Hog millet, White millet, Broomcorn millet|
|Brachiaria ramosum||Brown top millet|
|Digitaria exilis||Fonio millet|
|Echinochloa colonum||Shama millet|
|Frumentaceae||Japanese millet, Barnyard millet|
|Paspalum scrobiculatum||Kodo millet|
|Pennisetum americanum||Pearl millet|
|Chlorideae||Eleusine coracana||Finger millet|
|Feed||Crude protein (%)||Net energy for maintenance (Mcal)||Net energy for gain (Mcal)||Total digestible nutrients (%)|
|Maize, dry rolled||10.0||102||70||90|
|Sorghum, dry rolled||10.0||93||64||84|
|Wheat, hard dry rolled||12.5||99||68||88|
Fig. 1. Nebraska maize, sorghum, and millet price comparisons 1981-1995. Prices shown are $/tonne.