PASTURE FORAGE PRODUCTION: INTEGRATION OF IMPROVED PASTURE SPECIES INTO SOUTH TEXAS LIVESTOCK PRODUCTION SYSTEMS
William R. Ocumpaugh and Oscar Rodriguez
Texas A&M Univ. Agric. Res. Sta., Beeville, TX and G. E. Pogue Seed Co. Inc., Kenedy, TX.
This manuscript will concentrate on introduced forage grasses and legumes for use in the hyperthermic soils region of Texas (soil temperature of more than 68 F at 20 inches), which is generally south of Hwy. 90 from Del Rio to San Antonio to just north of Victoria, TX. This encompasses the land resource area known as the South Texas Plains or Rio Grande Plains and part of the land resource area known as the Gulf Prairies or Coastal Prairies. The total land area is about 23 million acres, most of which is used for grazing by domestic livestock and wildlife. Average rainfall ranges from less than 18 inches on the west to more than 40 inches on the east, with large monthly and annual variations. Droughts are common. Irrigation is not used on a large percentage of land, but some irrigated land is used for strategic grazing on some ranches. Elevation ranges from sea level on the east to about 1000 ft on the west. The soils in this region range from poorly to moderately well drained cracking clays in the Victoria area, to shifting sands along the Laguna Madre, to silty clay loams in the central part of the region, interspersed with large areas of caliche outcrops. Some of the best soils are farmed with traditional crops, particularly along the eastern and northern part of the region. It is common to have as much variation in soil characteristics within a field or pasture as within a farm/ranch or county. Soil pH is generally above 7, but you can find a field where the pH will be below 6. Saline areas are significant in some areas and species adapted to saline soils should be used on these sites. Much of the area has adequate K2O for pasture species, with a more restricted area having adequate to high levels of P2O5. Grasses often do not respond to additional P2O5, but to grow legumes, additional P2O5 is usually a must. Most areas require a source of N to optimize yields in the wetter years. Micronutrient deficiencies are observed with some forages, with the only practical solution being to plant a species that has an adaptive mechanism for the plant to take up limited amounts from the soil (Wei et al. 1997).
When considering a species to plant you need to consider all of these environmental characteristics. Some forages have specific soils restrictions. Some have fairly definitive rainfall requirements for both establishment and then for long term persistence. Most species also have some restriction on how much cold temperature they might withstand and survive. Likewise, many will not tolerate the duration of our high temperatures.
By far, the greatest risk in growing a forage is the ability to establish and maintain an adequate stand of the desired species (Table 1) (Rouquette 1996). Many of the forage species are difficult to establish from seed or sprigs, and when improperly managed can be lost in one growing season. This risk is as great or greater here as in any other part of Texas. Hence, there is a high price to pay for improper species selection, as well as mismanagement. One of the most often asked questions that we get is related to some "wonder species" that someone has read about that is easy to establish and will persist forever . . . but most often that is in some other region of the state, in some other state, or in some far off land like New Zealand.
Table 1. Estimates of risk ratings for vigor and sustainability of introduced forages for the South Texas areas.
These places likely have these "wonder species", but they are only wonder species for the region similar to where they were developed, and 999 out of 1000 times will not work in South Texas. Producers need to consult a reputable seed supplier in the region, their County Agent, an NRCS specialist, or one of the State or Federal Researchers in the region for an independent evaluation before planting any substantial acreage of any species or variety not commonly grown in the region.
The Forage Researchers in Texas spend years evaluating a new forage plant (and discard hundreds, perhaps thousands) before we will recommend one to the producers. Unfortunately, some of these prove to be of limited usefulness, because of our limited ability to test them in all environments. An additional concern we have is a producer who wants to plant only one species. Sometimes, the choices are few, but we have seen cases of a species that has been widely planted in a region become susceptible to a pest or pathogen and the impact on the forage base is devastating. If only one species is well adapted, then you should at least consider planting more than one variety.
In South Texas, introduced forage species make up from 0 to 100% of the land area on an individual ranch. Some are used exclusively for hay and some exclusively for grazing and all possible combinations thereof. For some producers, these introduced species are annuals planted each fall or spring, but most common are perennial warm-season grasses. One or more varieties of buffelgrass, bermudagrass, kleingrass, Old World bluestem, Wilman lovegrass, and rhodesgrass will make up the majority of the land area planted to introduced species. The most commonly planted annual grasses would be oats, ryegrass, and sorghums.
Legumes are not planted on a large number of acres, but nevertheless, there are some old and new legumes that are used by a lesser number of producers who are willing to go the extra mile to impose the management to make them work. The list of legumes that will work in South Texas includes both perennials and annuals. There are a few acres of alfalfa grown along the Rio Grande River in rotation with vegetables. There are a small number of producers growing warm-season perennial legumes like leucaena, bundleflower, and lablab for wildlife food plots or other specialty uses. Winter annual legumes have a longer history of use and include things like Hubam sweetclover and true clovers. There are a limited number of acres of other species used for grazing and wildlife food plots in the region. There is another family of legumes that are common enough in the region that many people think they are natives. These are the annual medics . . . annual relatives of alfalfa. One of the most common of these annual medics is burr medic (also called burr clover) (Ocumpaugh et al. 1997). This group of plants is not native to Texas, but is well enough adapted that it has become naturalized and can be found along roadsides, in lawns, and pastures in spite of the management imposed. We think annual medics will enjoy widespread acceptance once we learn more about where each species will best work.
Buffelgrass (Cenchrus ciliaris) is the most widely grown warm-season perennial grass in the South Texas region due to its excellent drought tolerance, forage production, and proven adaptability to the semiarid areas (Holt, 1985; Hanselka 1988; Dickson 1978; Edye 1975). Buffelgrass was reintroduced into South Texas by the Soil Conservation District office in San Antonio, TX in the late 1940's after an unsuccessful attempt into the northern part of the state in 1917. ‘Common' buffelgrass (T-4464) occupies between 4 and 5 million acres or 99% of the acreage planted to this grass in the region. With the discovery by Mr. Pat Higgins in the late 1960's of an unusual plant of this grass that Dr. E. C. Bashaw (USDA-ARS) later identified as a sexual clone, a new era of buffelgrass breeding arose. In the mid 1970's the Texas Agricultural Experiment Station (TAES) released ‘Higgins', an apomictic selection from the sexual clone, followed by ‘Nueces' and ‘Llano', the first hybrid buffelgrass varieties ever released. The hybrid varieties proved to out yield Common by more than 30% in forage production, but the low seed production and seed quality of these new hybrids discouraged seed companies to the point that currently there is no certified Nueces or Llano buffelgrass seed produced in the state. These hybrid varieties do not occupy more than 1 to 3% of the total acreage.
Current buffelgrass varieties are well adapted to most soils (except the sandy soils along the coast) in the southern two-thirds of this region. The advantage buffelgrass has in the semiarid region cannot be capitalized on if one cannot get a good stand. Buffelgrass is difficult to plant due to the nature of the seed; it is lightweight, fluffy with long awns or bristles and bridges up in standard seed metering devices. Recently, a dehulling process has been perfected that allows the caryopsis to be removed from the involucre ("Pogue Process", G. E. Pogue Seed Co. Kenedy, TX). This process allows for a more precise metering of seed, including aerial application, more precise planting using standard seed drills, and usually much improved stands compared to awned seed. By removing the involucre, seed dormancy is removed, resulting in up to 90% germination. Hanselka et al. (1996) reported that dehulled seed resulted in 800 to 1000 lb/acre advantage in forage because of earlier establishment, increased vigor, and higher stand densities.
All buffelgrass varieties reproduce by apomixis, where the embryo of the seed develops from an unreduced vegetative (somatic) cell in the ovule of the female and receives no genetic material from the male (Bashaw and Hanna 1990), resulting in plants that are identical to their maternal origin, or in other words, varietal clones. The apomixis trait is both an asset and a liability. It is an asset in that once we find a plant with good agronomic characteristics we can save the seed from it and it always breeds true, producing a very uniform variety. The liability is that the crossing of plants with good traits is not a one-step process since the use of the sexual clone is indispensable. Another proven crossing procedure is the fertilization of unreduced gametes, a procedure that is possible in some varieties (Bashaw and Hignight 1990). Also, this "clone" approach imposes a restriction on the genetic variability within a variety. A reduced genetic base on any widely used crop represents a threat, leaving pests and pathogens the opportunity of producing a single mutation to become virulent. Once virulent, the pathogen is capable of attacking all plants since all are equally susceptible. As expected, such an event has occurred in buffelgrass, and currently we are faced with an epidemic of buffelgrass blight caused by the heterothallic ascomycete fungus Magnaporte grisea (anamorph Pyricularia grisea), reducing the quality and production of buffelgrass forage and seed (Rodriguez et al. 1998). The disease was observed in Mexico and South Texas as early as 1990 but it was confused with drought conditions. Pyricularia grisea is a highly variable pathogen and differential responses have been found to occur in South African and Australian varieties (Table 2), (Rodriguez 1998). Preliminary molecular fingerprint analysis has revealed up to 15% variation within locations sampled and 50% variation between locations and years in this pathogen (Rodriguez 1998). The widespread use of a monoculture of Common buffelgrass (10 to 11 million acres between South Texas and Mexico) and the alternate cycles of buffelgrass blight epidemics and severe drought conditions are devastating to pastures. Cattle producers have reported severe stand loss of buffelgrass in South Texas. As a result of this problem, public and private research efforts are underway. In the near future, blends of several disease resistant strains and hybrids will be released to better manage buffelgrass blight (Rodriguez 1998).
Bermudagrass (Cynodon dactylon) is the most widely grown introduced warm-season grass in the Southeast, and perhaps in Texas, but it occupies a small total acreage in South Texas. Bermudagrass is a favorite of many cattlemen for hay. Likewise, most wildlife managers would prefer some other species. Bermudagrass is well adapted to the wetter part of the region, but requires large amounts of N fertilizer to be productive. This problem can be somewhat, if not completely, alleviated by growing winter annual legumes with bermudagrass (Ocumpaugh 1990). Bermudagrass can take heavier grazing pressure and survive than any other grass grown in the region. Often overgrazed bermudagrass becomes very weedy, and a herbicide is required to restore the pasture to its productive potential. Bermudagrass does not tolerate shade, so productivity is severely depressed when weeds are allowed to dominate. There is a long list of available varieties, but for South Texas, ‘Coastal' is the most widely used. We have evaluated most of the varieties and one real improvement over Coastal is ‘Tifton 85'. It was selected for improved quality and yield, and we have found it to be as drought tolerant, if not more tolerant, than Coastal. The disadvantage to Tifton 85 has been the price of the sprigs (released in 1991) and it is somewhat more difficult to establish. ‘Jiggs', a private release in 1989, seems to have some advantage in the heavy clay soils in the Victoria area; however, it is also susceptible to some leaf diseases. ‘NK-37' has the advantage that it is seed propagated; however, the seed is not cheap and some seed sold as NK-37 is contaminated with common bermudagrass. ‘Tifton 68' was released in 1984 and is the highest quality bermudagrass available. The weakness of Tifton 68 is that it has no rhizomes and has very poor winter survival in the northern part of the region. Tifton 68 should be considered for irrigated, intensively managed pastures along the Rio Grande.
Table 2. Reaction of commercial and experimental varieties and hybrids to buffelgrass blight in 1997.
Kleingrass (Panicum coloratum) is well adapted for the northern third of the region and is widely used in the 25 to 40 inch rainfall area almost all the way to the Red River. Two varieties are available, with the main difference being seed size. ‘Selection 75' was formally released in 1969, but was available for at least 10 years before that. ‘Verde', released in 1982, was selected for larger seed to aid in improved establishment and to be more useful as a game bird food. The advantage to establishment has not been large. Research on issues related to improved stand establishment have or are currently being addressed by ARS and TAES scientists. The approach has been to address dormancy problems (Young, et al. 1993) as well as crown node placement (Elbersen et al. 1998; Ocumpaugh et al. 1995). Kleingrass is more productive than bermudagrass when the two are not fertilized, or when low rates of N fertilizer are utilized. Kleingrass seems to grow a bit longer into the autumn than bermudagrass, and some years it greens-up sooner in the spring. Frosted kleingrass is more palatable than frosted bermudagrass. Being a bunchgrass, it is compatible with winter annual legumes like annual medics. Kleingrass responds to a drought by going dormant, providing limited grazing. Kleingrass may require more irrigation water to be productive in mid-summer than buffelgrass or bermudagrass. A thin stand of kleingrass can be encouraged to thicken by light-to-moderate cultivation.
Old World Bluestem is the common name of a number of species and even genera of plants that were introduced from the Middle East, southern Asia, and Africa. The majority of the varieties that perform well in South Texas belong to Dichanthium annulatum (‘Kleberg', ‘PMT-587' and ‘Pretoria 90') and D. aristatum (‘Gordo' and ‘Medio'). Other varieties that are also called Old World Bluestem belong to the genus Bothriochloa (Ocumpaugh 1993). The one new variety ‘WW-BDahl', released in 1994, is a B. bladhii and its adaptation in South Texas is still being determined. Those varieties belonging to Bothricochloa caucasia (Caucasian bluestem) and B. ischaemum (‘King Ranch', ‘Plains', ‘WW-Iron Master', and ‘WW-Spar') do not perform well in South Texas (Ocumpaugh 1993). These plants are very stemy and do not produce the quantity or quality of forage when grown in South Texas that they do when grown in areas north of this region. Seed production and seed harvest is generally difficult with many of these varieties because of the indeterminate flowering habit. In fact, commercial seed of Pretoria 90 is no longer produced in Texas. Pretoria 90 is less winter hardy than other Dichanthium varieties and is only reliable in the southern third of the region. Gordo and Medio are best adapted to heavy soils which may experience periodic flooding. Kleberg and PMT-587 perform well on sandy clay loam and clay loam sites in the 25 plus inch rainfall areas of South Texas.
Rhodesgrass (Chloris gayana) is a seed propagated warm-season perennial grass with limited winter hardiness in the northern half of the region. The plant also spreads by stolens to fill in open spaces. ‘Bell', released in 1966, is used to vegetate saline sites in South Texas. Rhodesgrass is somewhat unpalatable, so is not well suited to mixtures, but if livestock are not given a choice, they will consume it and perform well.
Wilman Lovegrass (Eragrostis superba) is a short-lived perennial warm-season grass that has excellent establishment characteristics. It is particularly well adapted to sandy soils in the area receiving less than 30 inches of annual rainfall. ‘Polar', released in 1972, is the only variety. It is often planted in mixtures with kleingrass to enhance early stand establishment. Since it is a short-lived perennial, it must be allowed to produce seed to perpetuate the stand. Unlike many of the other lovegrasses, Wilman lovegrass is quite palatable.
Blue panic (Panicum antidotale) is a robust short-lived warm-season perennial grass that is used in planting mixtures with other grasses. Blue panic has a large seed and establishes easily, but do not expect it to persist. Common seed is available for those interested in including it in a mixture.
Forage sorghum (and sudangrass) (Sorghum bicolor) are summer annual grasses often planted for hay and sometimes for grazing. In our opinion, there is a lot of money wasted growing forage sorghums as a regular practice. These plants are an alternative to not having forage planted on a piece of ground, but it is expensive to grow, it is difficult to make even moderate quality hay, it stores poorly in round bales, and in 2 years out of 5 it has either nitrate or prussic acid poisoning problems. Most hay is made when the plant is overripe, either by poor management or due to weather complications. There are too many varieties to try to list them. There is one relatively new innovation in forage sorghums, and that is the development of varieties which are photoperiod sensitive. This prevents flowering if planted after daylength reaches 12 hr and 20 min, but does not prevent maturation of the tissue; so even though the plant does not flower, it can still be of poor quality if you let it grow too long before you utilize it. These plant types are well adapted to intensive grazing programs, because unlike most varieties they will regrow better after defoliation, providing that you do not let the plant get too big before you initiate grazing (or cut it for hay).
Sorghum almum (S. almum) is a natural hybrid between S. bicolor and S. halepense (Johnsongrass) which has perennial and rhizomatous characteristics like Johnsongrass, but does not have sufficient winter hardiness to perennate in most of the region. The seed shatters readily, making it a good food source for game birds. A lot of sorghum almum seed is sold each year for use by livestock and wild game managers.
Pearlmillet (Pennistum americanum) is another summer annual grass that resembles the forage sorghum in growth habit, but has not proven to have any real yield or quality advantage over dryland forage sorghums in this region. Pearlmillet is more sensitive to cold stress during germination and early seedling growth than are the sorghums. Temperatures in the 40 to 50 F range can kill pearlmillet seedlings (Fribourg 1995). By not being a member of the sorghum family, pearlmillets do not have problems with prussic acid poisoning. Like in the forage sorghums, the photoperiod sensitive trait has recently been incorporated into pearlmillet varieties.
Oats (Avena sativa) are the most widely used winter annual grass in the region. Oats are most productive when grown on land that is cultivated well in advance of seeding time. The oat seed is well adapted to this environment, as it will emerge from deep planting and the husk prevents the seed from trying to germinate when there is inadequate moisture in the soil to keep the seedling alive for several days. The list of varieties available is long, but leaf and stem rust attaches all but the best and limits the productivity of most varieties (Bryn et al. 1989a). ‘Coronado' is the one variety that has lasted longer than most in the region, but this last year it seemed to show more rust than usual, so perhaps it is on its way out. ‘TAMO 397', released within the last year, performed well in planting throughout the region this last winter. Oats can be planted in September or October to provide early winter grazing. They are more productive than wheat in the early part of the season, but we generally suggest that producers overseed oat plantings with 10 to 15 lbs/A of a good ryegrass variety to extend the spring grazing period and ensure against winter-killed oats in those periodically severe cold winters (Ocumpaugh 1988). Oats should be planted 1.5 to 3 inches deep depending on the soil texture, soil moisture, and time of the year, but ryegrass should not be planted more than 3/4 to 1 inch deep, so you cannot mix the seed. Oats are widely used in dryland plantings, but are more productive in irrigated sites, especially if mixed with ryegrass.
Ryegrass (Lolium multiflorum), or more correctly annual ryegrass, is one of the most widely used winter annual grasses in the USA. It has only been in the last decade or so that the value of ryegrass in South Texas has been realized. Our experience at the Research Station at Beeville has been that ryegrass will out yield oats or wheat in 8 out of 10 years (Bryn et al. 1989a&b). The advantage to ryegrass over oats comes later in the growth cycle; that is, oats will usually out yield ryegrass in the first harvest, because oats comes up quicker than ryegrass. Ryegrass is best used on cultivated land, its potential as an overseed crop on perennial warm-season grasses is limited to the high rainfall areas, and then will only work in South Texas with some cultivation of the perennial grass at planting time. The reason overseeding ryegrass on perennial grasses does not work here without cultivation is direct competition with the warm-season perennial grass for water, light, and most of all nitrogen. If you apply enough nitrogen to stimulate the ryegrass, the perennial grass will try to grow and become even more competitive. There are subtle differences among varieties, and most are limited in yield by lack of rainfall and nitrogen fertilizer. The list of varieties is too long to list, but in South Texas, there are differences among varieties for disease resistence and for winter growth. Disease resistence is a must. Varieties that are advertised as having good winter hardiness will yield less in midwinter, because the winter hardiness is associated with reduced winter growth. We recommend you use a variety that has been tested and evaluated under South Texas conditions. ‘Gulf' ryegrass will grow here, but one of our concerns is that almost none of the ryegrass seed sold is certified; hence, there is little quality control. We have thought for years that Gulf ryegrass is not always the same from year-to-year; hence, you get different results from year-to-year. If you are going to use ryegrass in intensively managed (and particularly in irrigated) grazing systems, we suggest that you pay the extra 3 or 5 dollars a bag and purchase a known product.
Wheat (Triticum aestivum) is a winter annual grain crop that is also used for forage. We have found little advantage to wheat as a forage crop in South Texas (Ocumpaugh 1988). The potential to graze wheat in the winter and harvest grain in the spring has not proven to be reliable in South Texas. Wheat does have a bit more winter hardiness than oats, but overseeding ryegrass on oats will provide more grazing.
Triticale (X Triticosecale) is a hybrid between wheat and rye (Secale cereale) and was developed to provide an improvement in forage characteristics over either of the parents. The current varieties have shown little merit in South Texas as they were developed for the central USA. Another weakness of triticale is that the seeds will try to germinate when there is insufficient soil moisture to support seedling growth and development. Hence, seeds can germinate and die unless the field is irrigated or you wait to plant after a good rain.
Alfalfa (Medicago sativa) is a perennial cool-season legume that is planted on limited acreage in the Rio Grande Valley area under irrigation. It is used for hay or dehydrated for export. Non-dormant varieties developed for use in southern California and other similar locations should work equally well in the area. Cotton root rot is one of the limiting factors for the longevity of stands. Expect 2 to 3 years of production before significant cotton root rot damage. Irrigation is essential for good production.
Sweetclover (Melilotus alba) is another legume that has a long history of use in South Texas. The variety ‘Hubam' is produced and sold by a number of farmers and seed producers in Texas. This plant grows best with oats and other winter annual grasses, as it does not produce a good natural reseeded stand without cultivation. Hubam is a tall growing, stemy plant that often produces more dry matter than is utilized by the grazing animal. Hubam is not highly palatable, so you often see a lot of skeleton left in the field.
Clovers (Trifolium sp.) have a very limited use in South Texas. None reseed well, and many are susceptible to iron-deficiency chlorosis (Gildersleeve and Ocumpaugh 1988 and 1989). Red clover (T. pratense) is used to a limited degree in the Victoria, TX area for hay. Red clover is resistant to iron-deficiency chlorosis. The variety ‘Cherokee' was developed in Florida for winter growth and has shown the greatest promise. Berseem clover (T. alexandrum) has the greatest growth potential of any clover we can grow in South Texas, but also has the least drought tolerance. We recommend berseem for irrigated areas and other high rainfall or flood prone areas of South Texas. Varieties that perform well include ‘Bigbee', ‘Multicut', and ‘Burton'. Berseem can also be used to extend the productive life of an alfalfa stand by overseeding a thinned or cotton root rot-weakened stand. This overseeding should be done in the fall and will extend the productive life through the following spring. Subterranean clover or subclover (T. subterraneum) has a long list of varieties, but only a short list of varieties are resistant to iron-deficiency chlorosis (Gildersleeve and Ocumpaugh 1989). The varieties that we recommend include ‘Clare' and ‘Koala'. These subclovers are well adapted to the areas that receive at least 28 inches of rainfall, usually produce sufficient seed even under grazing, but the seed usually does not persist until the next growing season. Crimson clover (T. incarnatum) has great seedling vigor, and even though it is not highly resistant to iron-deficiency chlorosis, it usually grows quite well. We believe one place crimson clover has is to use it in blends. Seed prices are often lower than competing legumes and it provides a means of reducing the seed cost per acre by blending crimson with other better adapted, but more costly, species (Ocumpaugh et al. 1996). We have planted a number of varieties, including ‘Dixie', ‘Tibbee', and ‘Flame', over the years and most have worked well. Ball clover (T. nigrescens) is relatively new to our testing program. Only common seed (no named variety) is available. The seed size is very small. At this point, we are suggesting producers try ball clover only on a small scale in South Texas. Arrowleaf clover (T. vesiculosum) has been used for several years in the higher rainfall part of this region, but all varieties are susceptible to iron-deficiency chlorosis (Gildersleeve and Ocumpaugh 1988) as well as a number of diseases. Arrowleaf has a weak seedling and is difficult to inoculate (Ocumpaugh and Smith 1991), thus we are no longer recommending it.
Annual Medics (Medicago sp.) are annual relatives of alfalfa, and all that we have tried are resistant to iron-deficiency chlorosis. This genus has a large number of species, several of which have potential for use in South Texas (Ocumpaugh 1987; Ocumpaugh et al. 1997 and 1998). We have more than 15 years experience with some of these species, and they grow well in mixtures with perennial warm-season grasses. Barrel medic (M. truncatula) has at least two varieties developed in Australia that have performed well in the region for several years. ‘Jemalong' is an old variety and we are currently recommending it for areas south of Austin, TX. ‘Parabinga' is a newer variety that matures earlier than Jemalong but is more frost sensitive. We currently believe Parabinga will work best in areas south of Beeville, and because it matures earlier, should be better adapted to the lower rainfall areas of the region. Most other varieties do not have sufficient frost tolerance to be reliable in the northern part of the region. Burr medic (M. polymopha) is also known as burr clover. This plant was introduced into Texas more than 75 years ago and has become naturalized. It can be found from the Rio Grande to nearly Dallas, TX. We have been evaluating a selection collected at the Research Station at Beeville, TX for several years now and hope to release a cultivar in 1998. This selection has consistently produced 4000 lbs/A of dry matter in the 30-inch rainfall zone, reseeds extremely well, and spreads to adjacent pastures. This selection has a very high level of hard seededness. Limited amounts of Certified seed should be available in 1998. Black medic (M. lupulina) is also adapted to at least part of the region. No commercial varieties have shown any promise, but a naturalized selection, collected at the Research Station at Beeville, is currently under a seed increase for expanded evaluation. Black medic bares its fruit in a single-seeded pod; hence, it can easily be consumed by game birds. In 1998, we harvested a naturalized stand of a M. minima, or small burr medic, from a pasture near Devine, TX. We think it will be a legume for the drier regions. We plan to continue the pursuit of additional naturalized annual medics.
Bundleflower (Desmanthus sp.) is a warm-season perennial legume native to South Texas and to a large part of the Americas. In 1993, the Research Station at Beeville started an evaluation program of the USA and Australian PI (Plant Introduction) collections. Australia had also released three varieties of prostrate bundleflower (D. virgatus, ‘Uman', ‘Bayamo', and ‘Marc') in that same year. We evaluated these varieties and part of the PI collection and identified four lines that are currently under testing throughout South Texas. Of the Australian varieties, Bayamo looked best at Beeville, but not as good as the four lines identified from the collection (Grichar et al. 1998). Uman may well work further south in the state, as it flowered too late to produce seed in Beeville. Freeze tolerance on Uman was marginal at Beeville. Our lines produce an abundance of seed and the seedlings have excellent vigor. Our lines have sufficient winter hardiness to grow and produce seed throughout the hyperthermic region. ‘Sabine' Illinois bundleflower (D. illinoensis) is not adapted to South Texas.
Leucaena (Leucaena sp.) is another warm-season perennial legume that is native to South Texas and the Americas. The best variety seems to be ‘K-636'. The biggest weakness of this group of plants appears to be poor seedling vigor. A number of producer fields have been established by transplanting seedlings. The plant has its greatest potential use in wildlife food plots.
Lablab (Lablab purpueus) is a perennial warm-season legume that lacks winter hardiness even in deep South Texas, but is being sold and used for wildlife food plots. It is very drought tolerant and can emerge from deep planting. The plant is so palatable that wildlife managers find that they have to fence the deer out each year during the establishment phase. It must be planted each year. The variety ‘Tecomate' is currently the only variety being sold in Texas.
Cowpeas (Vigna unguiculata) are summer annual legumes that are best known as a vegetable crop. They are large-seeded and are widely adapted in Texas. There are several varieties, but ‘Iron and Clay' have proven to be most versatile as a forage.
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