Proc. 57th Southern Pasture and Forage Crop Improvement Conference, Athens, GA April 23-25, 2002
Red, White, Crimson, and Other Southern Clovers:
Where Have They Gone and Why?
K.H. Quesenberry
clover@mail.ifas.ufl.edu
Introduction
The true clovers are members of the genus Trifolium, one of the most important genera in the legume family. The genus includes approximately 230 species found naturally on all the world’s continents except Australia, although several have been naturalized there. Depending on one’s classification, only about 8 to 14 species are of significant use as sown pasture crops around the world. This paper will attempt to summarize the current status of cultivars and cultivar improvement efforts in the USA Southern Region and discuss some of the factors contributing to the current status. The focus will be on the two major perennial clover species, red (T. pratense L.) and white (T. repens L.) clover, with some attention to crimson (T. incarnatum L.), and less emphasis on arrowleaf (T. vesiculosum Savi.), rose (T. hirtum All.) and ball (T. nigrescens Viv.) clover.
The use of perennial and annual clovers in the USA has declined dramatically from highs in the early part of the 20th century. As an example, red clover was estimated to be planted on as much as 35 million acres in the period 1909 to 1920, but declined to around 15 million acres in 1957, and to an estimated 10 million acres in 1995 (Taylor and Quesenberry, 1996). As economic conditions change and the price of commercial N fertilizer increases proportional to the rising price of crude oil, the use of clovers may warrant review and reconsideration. Clovers have economic value in production agriculture primarily in three forms: 1) biological nitrogen fixed by well nodulated clover species; (2) high quality clover hay for sale (or on-farm use); and (3) increased beef production per animal unit resulting from improved protein content in diets of animals grazing clovers.
Value of Clovers
Clovers for Nitrogen Fixation. Estimates of the amount of N fixed by perennial clovers are in the range of 100 to 300 kg ha-1 yr-1. Reports include: red clover – 77 to 260 kg N ha-1 yr-1 (Heichel et al., 1985) and white clover 62 to 332 kg N ha-1 yr-1 (Crush, 1987). Current prices of N in the form of NH4NO3 are in the range of $225 to 250 t-1 or about $0.34 to 0.38 lb-1 N. Assuming an intermediate level of N2-fixation of 150 lb acre-1 yr-1 and a cost of $0.35 lb-1 N, the value of N fixed annually by the estimated 10 million acres of red clover in the United States would be $525 million.
Clovers for Hay. Dry matter yield estimates for red and white clover are variable depending on many factors including cultivar, location, and weather pattern in a given year. Typical yields in the USA are in the range of 6,000 to 9,000 lbs acre-1(Pederson and Brink, 1991). The selling price of high quality legume hay is generally most influenced by supply and demand and also by purchaser preferences. Assuming yields of 8,000 lbs acre-1 and a selling price of $160 ton-1 for good quality red clover hay, the value of hay if all the 10 million USA acres of red clover were harvested for hay could be as high as $6.4 billion.
Clovers for Animal Production. The effects of enhanced crude protein content of the animal diet provided by the inclusion of clovers in a grass-clover grazed pasture are well known. Benefits to beef cattle accrue in both improved calving percentage (Koger, et al., 1970) and improved weight gain of growing calves (Petritz, et al., 1980). In general, research has shown beef average daily gains on grass clover mixtures equivalent to those on grass alone fertilized with 120 to 150 lbs N acre-1 (Hoveland, et al., 1991). Other extensive research has documented that inclusion of clover in the sward of endophyte infected fescue pastures will ameliorate the toxic effect of the ergovaline alkaloids produced by the endophyte (McMurphy, et al., 1990).
Having documented the value of clovers, however, the use of clovers must be weighed against alternatives for providing the need addressed in each of the above categories. For example, the value of a clover crop for biological N2-fixation to add N to the soil for a companion grass or in crop rotations for a grain crop, must be weighed against the use of commercial N fertilizer for these same purposes. Sometimes the use of clover can be viewed as an increased cost with associated risk. The current low level of use of clovers would suggest that farmers in the southeast USA have determined that economics often favor alternatives to growing clovers.
Major Perennial Clovers: Who Is Doing What in the SE USA?
Red Clover. In the southeast USA [Zone B (Taylor and Smith, 1995)] successful operators have used red clover in combination with crimson clover (T. incarnatum L.) and annual ryegrass (Lolium multiflorum Lam.) to extend the production season from as early as January into late June or July in the southern parts of this region. The adaptation to soils with somewhat lower pH than where alfalfa can be grown and tolerance of a wider range of soil moisture conditions, makes red clover a desirable choice for a forage legume on many sites.
Major red clover breeding programs in the southeast USA since the 1980s have been located in Kentucky and Florida, although more recently work is being conducted in Georgia and Alabama. Selection for reduced winter dormancy response has improved the production potential of red clover in the lower south. For example, the cultivar ‘Marathon’, bred at Madison, Wisconsin (Smith, 1994) is generally among the poorest yielding when grown at Gainesville, Florida. A primary yield advantage of ‘Cherokee’ [developed at Gainesville, FL (Quesenberry, et al., 1993)] at southern latitudes is increased early season yield due to reduced spring dormancy (earlier spring growth) compared to cultivars developed in Kentucky, Indiana, or Wisconsin. Conversely, although Cherokee may yield well in the seeding year in Kentucky it does not go dormant in the fall early enough and may initiate regrowth too soon in the spring resulting in winter killing and poor yields in the second year.
Root-knot nematodes have been identified as limiting factors to clover production on the sandy soils of the lower Coastal Planins of the southeast USA. Cherokee, was selected for intermediate tolerance to root-knot nematodes (RKN) (Quesenberry, et al., 1989). A new cultivar, developed at Florida and tested as FLMR7, has enhanced resistance to RKN, and was recently approved for release by the Florida agricultural Experiment Station. The Kentucky program has recently released ‘Freedom!’, a red clover that has no pubescence (non-glandular trichomes or hairs), and was developed to permit faster drying and to reduce dustiness of hay. Freedom! is a medium red clover adapted to the central region of the United States. The Georgia program has focused on selection of red clover for persistence under grazing defoliation and Dr. Bouton will be discussing his program at this meeting. Work at Alabama with red clover was summarized in the proceeding of the 2001 meeting (Mosjidis, 2001).
White Clover. There are two principal types of white clover grown in commercial agriculture, intermediate types, sometimes called Dutch white clover, and the large types, sometimes called Ladino white clover or Ladino clover. The intermediate types are typical of many pasture ecotypes with abundant flowering in spring, shorter growth habit, and a higher stolon density than large types. Intermediate types are generally less winter dormant, and thus flower earlier and more profusely than large types. ‘Osceola’, developed in Florida, retains the large type growth habit, but has increased flowering and has been a successful cultivar throughout the southeast USA for much of the1990s (Baltensperger, et al., 1984).
Research programs working with white clover in the southeast USA are currently located at Florida, Georgia, and Texas. The change in emphasis of the USDA-ARS program at Mississippi during the 1990s resulted in a significant reduction in research with white clover in the region. The Georgia program has shown that intermediate ecotypes selected from long term grazed pastures have higher stolon density and are much more persistent in grazed swards than either the current large type cultivars or presently available intermediate cultivars (Hoveland and Bouton, 2000). Hybrids of Georgia ecotypes and large (Ladino) types were the most persistent in both tall fescue and bermudagrass [Cynodon dactylon (L.) Pers.] sods. Cultivars from this research are moving toward commercial status and Dr. Bouton will provide more details in his presentation. Recent white clover research at Florida has focused on selection for RKN resistance in an Osceola type. Research at Texas has focused on development of an early flowering white clover (replacement for La S-1).
In contrast to red clover, the dormancy response of white clover does not seem to be as great a factor in stand persistence, although, as previously mentioned, it does influence flowering density and subsequent reseeding potential. For example, Osceola has been successfully grown in most white clover growing areas of the USA, well north of its latitude of development.
Major Annual Clovers: Who Is Doing What in the SE USA?
Crimson clover. Research with crimson clover in the southeast USA is currently being conducted primarily at Alabama, Florida, and Texas. The change in emphasis of the USDA-ARS program at Mississippi also resulted in a significant reduction in research with crimson clover in the region. The Alabama program, which was recently summarized in these proceedings (Mosjidis, 2001), has released an early maturing type, ‘AU Sunrise’ (Mosjidis, et al., 2000). The Texas program has selected for late flowering and has a potential cultivar in testing for release. At Florida, five cycles for production and vigor on well drained sandy soils with high disease and nematode pressure have been conducted. The base germplasm for this selection program was a diverse collection of USA and European cultivars and local ecotypes including ‘Flame’ (Baltensperger, et al., 1987). Seed of an experimental population is currently available for regional testing.
Arrowleaf clover. Although some germplasm testing of arrowleaf clover has been conducted at several locations, only the program at Overton, TX has been actively engaged in breeding arrowleaf clover in recent years. Dr, G. R. Smith indicates that a new arrowleaf clover cultivar, ‘Apache’, with better resistance to bean yellow mosaic virus (BYMV) disease and higher forage yields than ‘Yuchi’ has been released. It was developed from Yuchi, ‘Meechee’, and ‘Amclo’ germplasm through restricted recurrent phenotypic selection for tolerance to BYMV. Seed of Apache should be available to producers in fall 2002. A continuing limitation of arrowleaf clover on light sandy soils is susceptibility to RKN and to date no sources of resistance have been identified.
Ball Clover. No research is known to have been conducted with this species in the SE USA in recent years. A long term reseeding population was collected in north Florida in 2000 and 2001, and preliminary evaluations are underway to identify superior plants in this population for potential development of an improved cultivar.
Clovers in the Southeast USA: Why the Reduction in Use?
Although several southeast USA breeding programs with clovers have been closed in the past two decades, it is evident from the above review that elite cultivars of the most important species are still being developed. It is also evident that substantial research is available to document the value of clovers for various applications. The question then becomes, why aren’t producers utilizing these plants to a greater extent.
I believe that the answer to this lies in the classic chicken vs. egg debate! In this case it is which comes first, the demand for clovers or the production and marketing of new cultivars of clovers. From the perspective of the breeders that I talk to, a major point of potential failure of new cultivars occurs after release, ie. in production and marketing. Most state agricultural experiment stations are currently willing to enter into exclusive licensing and production agreements for cultivars today. The problem with the clovers appears to be that of identifying a company that has good seed production and processing capabilities in the Pacific Northwest and a strong and diverse sales, advertising and marketing organization in the Southeast. New cultivars can flounder and fail for lack of either production or marketing. There is a feeling among breeders that aggressive marketing is needed to cultivate the demand for new cultivars, but the culture of “buy the cheapest seed available”, usually does not reward the those who are willing to invest in advertising. Consolidation of programs and enhanced pre-development arrangements between commercial companies and university breeders will likely be required for continuation of improved clover cultivar development programs in the southeastern USA.
Reference
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