Native Perennial Legumes: New Species for Grazing Systems

Native perennial legumes were once a vital component of Midwestern grassland ecosystems. We have evaluated the establishment of two native legumes, Illinois bundleflower and false indigo, in grazing systems on four farms in western and southeastern Minnesota. We have laid the foundation for plant breeding programs for both species using germplasm collected from the north central United States. We have seed of three source-identified populations of Illinois bundleflower and collected seed from our breeding nurseries in Fall, 2002, to initiate our plant breeding program.

Introduction:

Indigenous legumes were important components of the diverse Minnesota grassland and prairie ecosystems and present a unique opportunity to increase the diversity and profitability of modern agricultural systems. Although a number of the perennial indigenous legumes have potential as alternative grain and biomass fuel crops, the most expedient use of indigenous legumes will be as new forage species utilized in grazing systems.

Illinois bundleflower (Desmanthus illinoensis) is a prairie legume with a native range extending north to Minnesota and North Dakota, southwest to New Mexico, and southeast to Florida. The Land Institute of Salina, Kansas, has conducted research with this plant and considers it to have great potential as a perennial grain crop for human consumption. Illinois bundleflower does not begin to grow until early June, and is most productive during the month of July. The species will produce a deep taproot, flower, and set seed in the first year (Hellwinckel 1992). The plant is often most productive in lowland sites with moist soils, but does also occur on dry upland locations (Towne and Knapp 1996). It has been tested by the United States Department of Agriculture (USDA), and no toxic levels of oxalates, cyanides, nitrates, or alkaloids have been found in the seed or foliage (Kulakow et al. 1990). It has the ability to fix atmospheric nitrogen at rates similar to alfalfa or soybean (Kulakow et al. 1990). Seed yields in the central United States have been as high as 1513 lb/acre, with average yields of 1068 lb/acre; shattering is common, but plants with resistance to shattering have been discovered (Kulakow et al. 1990). Due to this heavy seed production, Illinois bundleflower will naturally reseed in a pasture (Dovel et al. 1990).

Illinois bundleflower establishment has been investigated. The first important step for successful establishment is seed scarification which increased germination from near zero to ninety percent (Carre and Cavigelli 1985). Dovel et al. (1990) studied the establishment of Illinois bundleflower in a Texas warm-season grass pasture, and its impact on rangeland production and quality. They found disking followed by broadcast seeding at 6 lb/acre to be an effective establishment method. Interseeding with Illinois bundleflower increased forage yield by 45 percent over unimproved pasture, and after four years the stand was still persistent, with Illinois bundleflower yielding over 2500 lbs/acre dry matter. Posler et al. (1993) also studied the potential for Illinois bundleflower as a forage species for mixture with warm season grasses in Kansas. They found that the plant drastically increased total forage yield, but slightly reduced in vitro dry matter digestibility as compared to grass alone. Most importantly, Illinois bundleflower in mixture with grass more than doubled the crude protein concentration in the mixture versus grass monoculture.

False indigo (Amorpha fruticosa) has been the investigated for its potential as a forage (Papachristou and Papanastasis 1994), and biomass energy crop (Roth, et al. 1984). This plant is a true shrub, producing woody stems that do not die back in winter. It is native to most of the continental United States, commonly occurring along rivers, streams, and lakes, but also in desert areas and on dry rocky outcroppings. We have observed it thriving in standing water and on extremely rocky prairie preserves in southwest Minnesota. False indigo is a warm-season legume.Its buds do not break dormancy in Minnesota until mid-May, but it grows rapidly during July and August (Lueschen 1997). It can grow about three feet in height per season, and at maturity has a square appearance with height and width of about ten feet. It forms a deep tap root system that is heavily nodulated by nitrogen-fixing bacteria (Allen and Allen 1981). False indigo has not been utilized in North America as a forage, but it has been used in Mediterranean countries.

Studies at the St. Paul research station have demonstrated the potential for rapid establishment of false indigo, with monocultured yields exceeding three tons of dry matter per acre in the second season (Lueschen 1996). Third year yield from plants that were harvested the preceding fall have exceeded seven tons of dry matter per acre, and contained 13.3 percent crude protein (Lueschen 1997). Plants harvested in the spring of the third year had crude protein concentrations over 20 percent (Lueschen 1997).

Grazing systems: The profitability and expansion of grazing systems is currently limited by several factors that may be overcome with the reintroduction of indigenous legumes. First, the productivity of our predominate, cool-season grass pastures in Minnesota is uneven with about two-thirds of the forage biomass being produced in the first one-third of the growing season. Several of the indigenous legumes including Illinois bundleflower (Desmanthis illlinoensis) and false indigo (Amorpha fruticosa) grow rapidly during the summer months and maintain high forage quality during the growing season when it is most needed by producers. Second, legumes have the ability to fix nitrogen which increases forage yield and quality of the pasture. The most commonly utilized legumes are often slow to establish and lack persistence. Illinois bundleflower and false indigo can establish rapidly, are productive in the seedling year, and are persistent. Third, farmers with low-lying or floodplain pastures cannot use current forage legumes because of high soil moisture and shade from vegetation. The legumes we are studying are found naturally in these types of environments and should be highly productive. The introduction of native legumes into these pastures should improve the profitability of the pastures and expand the use of controlled grazing along rivers resulting on a reduction in nonpoint source surface water contamination. Fourth, non-native legumes are incompatible with native warm-season grasses. Native legumes should be able to coexist and enhance warm-season grass pastures since they occur naturally in prairie ecosystems where warm-season grasses predominate. With eight million acres of warm-season grasses previously established through the Conservation Reserve program, the addition of native legumes into these grasslands will enhance the yield, quality and profitability of grazing and thus reduce the conversion back to cropland.

Allen, O.N., and E.K. Allen. 1981. The Leguminosae. Madison: University of Wisconsin. 42-43.

Carre, D., and M. Cavigelli. 1985. Effects of Density on Yield of Illinois Bundleflower (Desmanthus illinoinsis) and Wild Senna (Senna marilandica). The Land Report Research Supplement 2:7-9.

Dovel, R.L., M.A. Hussey, and E.C. Holt. 1990. Establishment and survival of Illinois bundleflower inter-seeded into an established kleingrass pasture. Journal of Range Management 43:153-156.

Hellwinckel, C. 1992. Comparison between stable and high seed yielding collections of Illinois
bundleflower (Desmanthus illinoensis). The Land Institute Research Report 12:20-25.

Kulakow, P.A., L.L. Benson, and J.G. Vail. 1990. Prospects for Domesticating Illinois Bundleflower. in J. Janik and J.E. Simon (ed.) Advances in New Crops. Portland: Timber Press. 168-171.

Lueschen, W.E. 1996. Unpublished data collected in 1996 from the native perennial legume nursery on the University of Minnesota Saint Paul Experiment Station. The nursery was established in 1995.

Lueschen, W.E. 1997. Unpublished data collected in 1997 from the native perennial legume nursery on the University of Minnesota Saint Paul Experiment Station. The nursery was established in 1995.

Papachristou, T.G., and V.P. Papanastasis. 1994. Forage value of Mediterranean deciduous woody fodder species and its implication to management of silvo-pastoral systems for goats. Agroforestry Systems 27:269-282.

Posler, G.L., A.W. Lessen, and G.L. Fine. 1993. Forage yield, quality, compatibility, and persistence of warm-season grass-legume mixtures. Agronomy Journal 85:554-560.

Roth, et al. 1984. Evaluation of 107 Legumes for Renewable Sources of Energy. Economic Botany 38:358-364.

Towne, E.G., and A.K. Knapp. 1996. Biomass and density responses in tallgrass prairie legumes
to annual fire and topographic position. American Journal of Botany 83:175-179.