Native Legume Species Research Articles

Management of the mycorrhizal soil infectivity with Crotalaria ochroleuca, an indigenous wild legume in the tropics: Impacts on microbial functional diversity involved in phosphorus mobilization processes in a sahelian soil

It is well known that the over exploitation of soil resources decreases the density and diversity of arbuscular mycorrhizal (AM) fungal propagules. It has been postulated that agricultural practices could promote the occurrence and functioning of remaining and resilient AM fungal ecotypes in order to benefit from AM associations. Using C. ochroleuca, a highly mycotrophic plant species, the aims of this study were to determine in controlled conditions, the impact of this legume species on: (i) the mycorrhizal soil infectivity (MSI), (ii) the Rock Phosphate (RP) solubilising activity and (iii) the soil microbial functions. The expected benefits of C. ochroleuca cultivation have been evaluated by comparing its biological influences with those recorded with a non-mycorrhizal plant species, Brassica oleracea in order to attest of the importance of the AM potential in RP weathering and soil functioning. The results show that: C. ochroleuca was effective in improving the mycorrhizal soil potential, (ii) functional abilities of soil microflora were influenced by the cultured plant species and the mycorrhizal soil potential and (iii) the efficiency of rock phosphate amendment on plant growth depended on the level of mycorrhizal soil potential and was linkedto the extent of the mycorrhizal network.The C. ochroleuca impact was significantly reinforced with KRP amendment (i.e. +29.3% for the Catabolic Eveness, +45.7% for the hyphal length). According to these results, it could be concluded that agricultural strategies based on the management of local biodiversity (i.e. the use of native legume species) could be considered as a sustainable practice to optimally manage AM fungi and to ensure their functionalities in order to maintain a sustainable production of food crops in the tropics.

Screening Allelochemical-Resistant Species of the Alien Invasive Mikania micrantha for Restoration in South China.

To screen allelochemical-resistant species of the alien invasive weed Mikania micrantha, we studied the allelopathic inhibition effects of the leaf aqueous extract (LAE) of Mikania on seed germination and seedling growth of the 26 species native or naturalized in the invaded region in South China. Seed germination was more strongly negatively affected by LAE than seedling growth. Responses of seed germination and seed growth to LAE differed differently among the target species. LAE more strongly negatively affected seed germination, but less strongly negatively affected seedling growth, in non-legume species than in legume species. LAE more strongly negatively affected seed germination and seedling growth in native species than naturalized exotic species. Therefore, naturalized exotic non-legume seedlings are more suitable than seeds of native legume species for restoration of Mikania-invaded habitats.

Native Australian shrub legume species may provide an alternative feed source for livestock

The feed quality of a variety of native shrub and herbaceous legume species from the Riverina area of southern New South Wales was determined to provide an indication of their potential use in livestock grazing systems. Fifteen species were sampled from each of two locations (chiefly low fertility roadsides or travelling stock reserves) at four times within a 12-month period viz. August, November, February and May according to the most likely plant parts to be consumed by grazing animals for each species. Digestibility was estimated using an in vitro rumen fluid digestion assay and crude protein was estimated from nitrogen analysed using the Dumas combustion method. Digestible organic matter in the dry matter (DOMD) was greater than 550 g/kg dry matter (DM) for seven of the native legume species and was highest for Daviesia spp. (D. latifolia 696.2 ± 15.0, D. leptophylla × latifolia 642.5 ± 15.1 and D. leptophylla 622.7 ± 15.4), Glycine spp. (G. clandestina 628.2 ± 18.1, G. tabacina 621.9 ± 28.0 and G. canescens 580.4 ± 25.4) and Indigofera australis (617.8 ± 15.3). Crude protein content was greater than 80 g/kg DM for all species analysed, suggesting that these plants are able to fix nitrogen under low phosphorus fertility conditions. Studies examining grazing management as well as nitrogen fixation and nitrogen transfer to companion grasses are required in order to optimise the management of these plants in grazing systems.

Facilitation among plants: A strategy for the ecological restoration of the high-andean forest (Bogotá, D.C.—Colombia)

Ecosystem invasion by the exotic legume Ulex europaeus (common gorse) impede the establishment of native vegetation by creating a closed canopy and its high resprouting capacity following a disturbance. Over a nine month period, plant–plant interactions between the native legumes, Lupinus bogotensis (shrub) and Vicia benghalensis (herb), and the native tree species Solanum oblongifolium and Viburnum tinoides, were evaluated in a zone close to the Chisacá reservoir in Bogotá, Colombia; that had previously been invaded by U. europaeus for at least 60 years. Experimental treatments corresponded to the identity of the native legume species and their sowing densities (high, medium and low), based on distance between individuals: 30, 60 and 90cm respectively. The native tree species were sown at the same density in all plots (25 individuals, 50cm between each other). Variables measured in all planted native tree species were: total height, basal diameter and number of leaves or branches. Both native tree species performed best with L. bogotensis at low and medium sowing densities, where the greater establishment of native species indicated a net positive interaction. Growth and survival were higher in all cases when compared with the control plots. There was evidence of facilitation by the native leguminous plants in all the treatments (index of interaction>0), with the exception of V. benghalensis at high sowing density with S. oblongifolium. We conclude that facilitation between plants can be employed as an effective strategy for the reestablishment of native vegetation and could thereby initiate recuperation of the high-andean forest by reactivating the process of dynamic succession.

Early productivity and crude protein content of establishing forage swards composed of combinations of native grass and legume species in mixed-grassland ecoregions

Mischkolz, J. M., Schellenberg, M. P. and Lamb, E. G. 2013. Early productivity and crude protein content of establishing forage swards composed of combinations of native grass and legume species in mixed-grassland ecoregions. Can. J. Plant Sci. 93: 445–454. We evaluated the early establishment productivity of forage swards of native, perennial, cool and warm season grasses, and legumes as they have the potential to provide non-invasive, productive, and drought resistant rangelands. Seven species with agronomic potential and a broad native geographic distribution were selected for testing including: nodding brome [Bromus anomalus (Coult.)], blue bunch wheatgrass [Pseudoregneria spicata (Pursh)], western wheatgrass [Pascopyrum smithii (Rydb.)], side oats grama [Bouteloua curtipendula (Michx.)], little blue stem [Schizachyrium scoparium (Michx.)], purple prairie clover [Dalea purpurea (Vent.)], and white prairie clover [Dalea candida (Willd.)]. Forage swards, including all seven monocultures, 21 two-species mixtures and a mixture with all species, were planted in two sites, Saskatoon and Swift Current, Saskatchewan. Western wheatgrass (WWG) had the highest overall plant density and the strongest effect on the forage yield of the forage swards; however, productivity and crude protein content were not reduced when other species were also included in the forage sward. Dalea spp. did not establish as well as the other species, but had the highest crude protein concentrations. This work provides insight into forage sward development at the establishment stage; additional work is required to determine long-term species impacts for well established forage swards.

Soil management of copper mine tailing soils — Sludge amendment and tree vegetation could improve biological soil quality

Mine soils at the depleted copper mine in Touro (Northwest Spain) are physico-chemically degraded and polluted by chromium and copper. To increase the quality of these soils, some areas at this mine have been vegetated with eucalyptus or pines, amended with sludges, or received both treatments. Four sites were selected at the Touro mine tailing in order to evaluate the effect of these different reclamation treatments on the biological soil quality: (1) Control (untreated), (2) Forest (vegetated), (3) Sludge (amended with sludges) and (4) Forest+Sludge (vegetated and amended). The new approach of the present work is that we evaluated the effect of planting trees or/and amending with sludges on the biological soil quality of mine sites polluted by metals under field conditions. The addition of sludges to mine sites recovered the biological quality of the soil, while vegetating with trees did not increase microbial biomass and function to the level of unpolluted sites. Moreover, amending with sludges increased the efficiency of the soil's microbial community to metabolize C and N, which was indicated by the decrease of the specific enzyme activities and the increase in the ratio Cmic:Nmic (shift towards predominance of fungi instead of bacteria). However, the high Cu and Cr concentrations still have negative influence on the microorganisms in all the treated soils. For the future remediation of mine soils, we recommend periodically adding sludge and planting native legume species.

Expression of a Medicago falcata small GTPase gene, MfARL1 enhanced tolerance to salt stress in Arabidopsis thaliana

To understand the role of small GTPases in response to abiotic stress, we isolated a gene encoding a small GTPase, designated MfARL1, from a subtracted cDNA library in Medicago falcata, a native legume species in semi-arid grassland in northern China. The function of MfARL1 in response to salt stress was studied by expressing MfARL1 in Arabidopsis. Wild-type (WT) and transgenic plants constitutively expressing MfARL1 showed comparable phenotype when grown under control conditions. Germination of seeds expressing MfARL1 was less suppressed by salt stress than that of WT seeds. Transgenic seedlings had higher survival rate than WT seedlings under salt stress, suggesting that expression of MfARL1 confers tolerance to salt stress. The physiological and molecular mechanisms underlying these phenomena were elucidated. Salt stress led to a significant decrease in chlorophyll contents in WT plants, but not in transgenic plants. Transgenic plants accumulated less amounts of H(2)O(2) and malondialdehyde than their WT counterparts under salt stress, which can be accounted for by the higher catalase activities, lower activities of superoxide dismutase, and peroxidase in transgenic plants than in WT plants. Transgenic plants displayed lower Na(+)/K(+) ratio due to less accumulation of Na(+) than wild-type under salt stress conditions. The lower Na(+)/K(+) ratio may result from less accumulation of Na(+) due to reduced expression of AtHKT1 that encodes Na(+) transporter in transgenic plants under salt stress. These findings demonstrate that MfARL1 encodes a novel stress-responsive small GTPase that is involved in tolerance to salt stress.

Microbial phylotype composition and diversity predicts plant productivity and plant–soil feedbacks

The relationship between ecological variation and microbial genetic composition is critical to understanding microbial influence on community and ecosystem function. In glasshouse trials using nine native legume species and 40 rhizobial strains, we find that bacterial rRNA phylotype accounts for 68% of amoung isolate variability in symbiotic effectiveness and 79% of host specificity in growth response. We also find that rhizobial phylotype diversity and composition of soils collected from a geographical breadth of sites explains the growth responses of two acacia species. Positive soil microbial feedback between the two acacia hosts was largely driven by changes in diversity of rhizobia. Greater rhizobial diversity accumulated in association with the less responsive host species, Acacia salicina, and negatively affected the growth of the more responsive Acacia stenophylla. Together, this work demonstrates correspondence of phylotype with microbial function, and demonstrates that the dynamics of rhizobia on host species can feed back on plant population performance.

Tolerance of Anadenanthera peregrina to Eucalyptus camaldulensis and Eucalyptus grandis essential oil as condition for mixed plantation

With the purpose of selecting the species of woody Caatinga for mixed plantations with Eucalyptus spp., the allelophatic effects of E. camaldulensis and E. grandis essential oil were studied on the growth activities of Anadenanthera peregrina. The plants were closed in glass chambers in the presence of volatile oil of E. camaldulensis or E. grandis at the concentration of 13 nl.cm-3. The number of leaves, height and diameter at soil lever were compared before, immediately after and after 30 days. Chlorophyll a and b, carotenoids and dry mass were evaluated after the treatment application. There was no inhibitory effect of E. camaldulensis and E. grandis oils on A. peregrina. E. camaldulensis, which was more adapted to semi-arid conditions, was planted in mixture stands with two native legume species, inoculated with Rhizobium and arbuscular mycorrhizal fungi. E. camaldulensis did not inhibit native species growth after two years of cultivation.

Sustainable, low‐input, warm‐season, grass–legume grassland mixtures: mission (nearly) impossible?

AbstractGrazing lands in warm‐temperate and subtropical North America have become less diverse. Pastures are typically grass monocultures, while rangelands are generally managed for the grass components. Overstocking, selective herbicides, fire exclusion and heavy rates of nitrogen fertilizer have contributed to near exclusion of native, warm‐season legumes. The simplicity of managing grass monocultures, pasture production responses to nitrogen fertilizer and profitability of grass‐only systems have limited interest in legume‐based approaches. Changing economics and ecological concerns with ecosystem accumulation of industrial inputs contribute to an increasing interest in legumes. Unlike the development of temperate pasture legumes and recent research in the tropics, legumes tolerant of both freezing temperatures and hot weather have received less attention. Poor establishment, limited persistence and potential invasiveness limit currently available introduced species. Native, herbaceous, warm‐season legume species occur throughout warm‐temperate North America, but little attention has been directed to these plants as potential forage species. Some success with a few native legume species, primarily in the genus Desmanthus, suggests potential for expanded assessment of forage value of the many species available. Current assessments of native legumes, primarily for conservation purposes, provide an opportunity to expand evaluations of these species for pasture and rangeland potential while economics of livestock production and public interest in ecosystem health are supportive. Experiences with legumes of warm‐temperate origin in North America, along with results with temperate and tropical pasture legumes globally, provide a starting point for future efforts at incorporating greater legume diversity in pastures and rangelands of subtropical and warm‐temperate regions around the world.

Breaking germination dormancy of Texas native perennial herbaceous legumes

Seed scarification requirements to improve initial germination in perennial herbaceous native legumes may vary among species. Mechanical abrasion (0, 5, 10, and 20 s) and hot water (0, 5, 10, and 15 min) treatments were tested as means for improving seed germination in the Fabaceae species prairie acacia ( Acacia angustissima (Mill.) Kuntze var. hirta (Nutt.) B.L. Rob.), panicled tick-clover ( Desmodium paniculatum (L.) DC.), and tall bush-clover ( Lespedeza stuevei Nutt.), which have potential for commercial native seed mixes in the southern Great Plains. All durations of abrasion and one minute in hot water increased germination rates of mechanically harvested prairie acacia. Hand-harvested tall bush-clover germination responded positively to one second of abrasion but was sensitive to seed damage at longer durations. Nonscarified (control) hand-harvested panicled tick-clover seed germination was 94% and did not respond positively to scarification. Results indicate that the need and best method for seed scarification vary among native perennial herbaceous legume species.

Assessment of N 2 fixation capability of native legumes from the longleaf pine–wiregrass ecosystem

Longleaf pine ( Pinus palustris) is a major ecosystem in the southeastern United States. Native legumes species are viewed as an important component of successful restoration of the longleaf pine–wiregrass ( Aristida stricta) ecosystem as a result of their ability to fix atmospheric nitrogen (N 2). However, virtually no measurements exist on the N 2 fixation potential of the various native legume species in this ecosystem. The objective of this study was to compare the N 2 fixation capability under ambient and half ambient light conditions of nine native legume species: Centrosema virginianum, Clitoria mariana, Crotalaria rotundifolia, Lespedeza hirta, Mimosa quadrivalvis, Orbexillum lupinellus, Rhyncosia reniformis, Tephrosia virginiana, and Chamaecrista nictitans. Their N 2 fixation activity was indexed using five approaches (nodule biomass, total plant N content, acetylene reduction assay, N transport and storage product analysis, δ 15N natural abundance) since no single measure by itself has proven to be a completely reliable result. Based on the results of these five approaches, a decrease in light levels by half had no impact on the N 2 fixation potential of any of the species. At least under a relatively open longleaf pine canopy, native legumes could be important contributors to the N balance. Considering all measures, two legumes proved consistently to be superior in N 2 fixation capability: Mimosa quadrivalvis and Centrosema virginianum.

Effects of shade on growth and nodulation on three native legumes with potential for use in agroforestry

In the Midwest US, native legume species adapted to savanna environments may grow well under varying shade conditions. These species may be ideal for use within tree rows in alley-cropping practices and on tree plantations by providing biologically fixed nitrogen, ground cover, and wildlife food and habitat. A greenhouse experiment was conducted to evaluate the effect of 3 different light levels (100%, 45%, 20%) on the growth and nodulation of 3 Desmodium (Fabaceae) species: Hoary ticktrefoil ( D. canescens (L.) DC.), Showy ticktrefoil ( D. canadense (L.) DC.), and Illinois ticktrefoil ( D. illinoense A. Gray). All species produced equal amounts of dry matter at 45% and 100% light, but significantly less dry matter at 20% light. All species had greater or equal concentrations of nitrogen (N) at 20% light compared with 45% or 100% light. The number of nodules per gram of plant dry weight and nodule dry weight was similar at all light levels within each species. A significant species x light interaction was found for the number of nodules per plant because nodule number decreased in both D. canescens and D. canadense but not in D. illinoense for plants grown at 20% in comparison with 45% light. The number of nodules per plant and the number of nodules per gram of plant dry weight were lower under all light conditions for D. illinoense compared with the other species. Results indicate that these native legumes grow as well at 45% light as they do at 100% light, and shade does not reduce N concentration. Houx JH III, McGraw RL, Fritschi FB, Navarrete-Tindall NE. 2009. Effects of shade on growth and nodulation of three native legumes with potential for use in agroforestry. Native Plants Journal 10(3): 232–238.

Population structure, races, and host range of Aphanomyces euteiches from alfalfa production fields in the central USA

Aphanomyces euteiches (races 1 and 2) causes root rot of alfalfa; however, its population biology and distribution are poorly understood where alfalfa is a major crop. The objectives of this study were to (1) characterise the distribution and frequency of races of A. euteiches in Illinois alfalfa fields, (2) determine host range of A. euteiches on cultivated and native legumes, and (iii) to describe genetic diversity and population genetic structure of A. euteiches in alfalfa fields. To accomplish this, soil samples (n = 103) were collected from 30 alfalfa fields in 18 Illinois counties. Using the susceptible cv. ‘Saranac’, 148 isolates of A. euteiches were baited from the soil. The virulence phenotype of isolates representing all 18 counties was tested, and 54% were R1 and 46% were R2. Both races were detected in 61% of the counties, whereas only R1 was detected in 22% and R2 in 17%. Thirteen legume hosts for isolates from alfalfa fields were identified based on symptoms and/or production of oospores in roots. In addition to six previously known hosts, seven species were susceptible to infection: kura clover, purple prairie clover, white prairie clover, ladino clover, hairy vetch, Canadian milk vetch, and Illinois tick trefoil. AFLP analysis revealed high levels of genetic diversity among the isolates from different fields and counties and a lack of genetic structuring of populations based on race or geographical origin. The results suggest that populations of A. euteiches in alfalfa fields are diverse, often composed of races 1 and 2, and create risk for alfalfa and to multiple cultivated and native legume species.

Potentialité des associations symbiotiques plantes–micro-organismes pour réhabiliter des sites fortement dégradés en milieu méd

Plant symbioses are fundamental for ecosystem stability and sustainability. Introduction of legumes associated with microorganisms efficient in nitrogen fixation and promoting nutrient biodisponibility in limited-nutrient degraded sites is a key step for a successful plant establishment in stress situations such as those encountered in Mediterranean soils. A vegetation strategy based on microbial engineering of locally-adapted plants was investigated and tested in field conditions within the framework of calcareous quarry rehabilitation. Choice of symbiotic plants requires, first, a prospection of native legume species growing in relatively degraded sites in Mediterranean areas and easy to multiply, and second, an identification and production of efficient rhizobial partners. Plants produced in nursery and then transplanted into the quarry showed a good capacity for establishment after three years. Shrub species performed best with spontaneous mycorrhizal association and ability to enrich topsoil with organic matter.

Evaluation of Native Legume Species for Forage Yield, Quality, and Seed Production

Illinois bundleflower (Desmanthus illinoensis (Michaux) MacMillan ex Robinson & Fern.) appears to have the greatest potential as a forage species among 15 species of native legumes (Fabaceae) evaluated for forage yield, quality, and seed production. It ranked among the top five for all agronomic characteristics measured. Hoary tick clover (Desmodium canescens [L.] DC.), panicled tick clover (Desmodium paniculatum [L.] DC.), and roundhead lespedeza (Lespedeza capitata Michaux), ranked among the top five for grams per plant of forage and seed. All of the native legumes contained greater concentrations of crude protein and lower concentrations of neutral detergent fiber than typically found in the native warm-season grasses commonly sown for pasture, suggesting that these native legumes should improve forage quality in mixed pastures. Only white prairie clover (Dalea candida Michaux ex Willd.), purple prairie clover (Dalea purpurea Vent.), and Illinois bundleflower had lower concentrations of acid detergent fiber than that typically found in native warm-season grasses.

Evaluation of Native Legume Species for Forage Yield, Quality, and Seed Production

Evaluation of Native Legume Species for Forage Yield, Quality, and Seed Production

Effects of Temperature on Germination of 10 Native Legume Species

Seeds of 10 species of legumes native to Missouri germinated poorly when the temperature was lower than 15 °C (59 °F). The fastest time to first germinated seed occurred at 20 °C (68 °F) for all species except purple and white prairie clover, which germinated first at 25 °C (77 °F). The fastest germination rate was first reached at 20 °C (68 °F) for hoary tick clover, sessile tick clover, and slender lespedeza, at 25 °C (77 °F) for white prairie clover, purple prairie clover, panicled tick clover, hairy lespedeza, and tall lespedeza, and at 30 °C (86 °F) for Illinois bundleflower and roundhead lespedeza. Maximum total germination percentage also varied among species. For both the prairie clovers and roundhead lespedeza, hairy lespedeza, and slender lespedeza, the lowest temperature at which maximum total germination percentage occurred was 15 °C (59 °F). For Illinois bundleflower and the 3 tick clovers, the lowest temperature at which maximum total germination percentage occurred was 20 °C (68 °F). For most species, the fastest germination rate occurred at a higher temperature than the maximum germination percentage. Many species attained maximum germination percentage and fastest germination rate across a range of temperatures rather than at a single optimal temperature. Species that rapidly and completely germinate across a wide range of temperatures should germinate more reliably under variable soil conditions than species that exhibit a narrow range.

Genetic and symbiotic characterization of rhizobia isolated from tree and herbaceous legumes grown in soils from ecologically diverse sites in Kenya

Natural genetic diversity and symbiotic status were studied among 41 root nodule bacteria from ecologically diverse sites in Kenya having no history of growing domesticated legumes, but where species of Acacia and Sesbania sesban grow naturally. Isolates originated either from nodules of field plants (trees and shrubs) or from trap host plants grown in field-collected soil. The host plants were Acacia mellifera, Acacia nilotica, Acacia nubica, Acacia polyacantha, Acacia seyal, Acacia tortilis, Acacia xanthophloea, and Faidherbia (Syn. Acacia) albida, Prosopis juliflora, S. sesban, Macroptilium atropurpureum, Phaseolus vulgaris and Vigna unguiculata. Two molecular methods were used to characterize these strains; PCR–RFLP of the 16S rRNA gene (12 distinct genotypes) and sequence analysis of a 230bp fragment of this gene (10 genotypes) with the former showing better discriminatory power. The two methods were in good agreement in delineating five bacterial genera: Agrobacterium, Bradyrhizobium, Mesorhizobium, Rhizobium and Sinorhizobium. Bradyrhizobium strains were all alkali-producing, exhibiting very slow to intermediate growth; Mesorhizobium strains were acid-producing with intermediate to fast growth; Rhizobium and Sinorhizobium were acid-producing with fast to very fast growth, and Agrobacterium strains were acid-producing and showed very fast growth. PCR–RFLP analysis further revealed strains corresponding to the species Bradyrhizobium elkanii, Bradyrhizobium japonicum, Rhizobium leguminosarum and Rhizobium tropici IIB, as well as others characterized to genus level only. Apparent diversity varied from site to site and was greatly influenced by host of isolation. For example, five rhizobial genotypes (four genera) were found using five different trap host species in a single Acacia tortilis woodland site, thus reaffirming occurrence of a heterogeneous population regardless of their nodulating ability with the native legume species. Bradyrhizobium spp. (F. albida), known for their preference of F. albida in tropical African soils, were abundant and widespread mainly because F. albida was the most frequently used trap host. Twenty Kenyan and eight reference strains were tested on tree species that are a priority for Kenyan use; these showed considerable diversity in symbiotic characters. Whereas Acacia species and F. albida showed variation in symbiotic effectiveness with test strains, S. sesban nodulated most effectively only with its homologous strains. Agrobacterium-allied strains failed to nodulate any of the host species tested. The high diversity (rhizobial genotypes, host affinities and their symbiotic effectiveness) found in the Kenyan sites will require rigorous selection for host×strain×site combinations in order to obtain effective and competitive inoculants for legume trees and crops in rehabilitation and agroforestry programmes.

EFFECT OF RHIZOBIUM INOCULATION AND PHOSPHORUS APPLICATION ON NATIVE TEXAS LEGUMES GROWN IN LOCAL SOIL

Greenhouse experiments were conducted to determine the effects of Rhizobium inoculation and addition of phosphorus to soil on the productivity and quality of the Texas range legumes Desmanthus illinoiensis (Michx.) MacMill. ex B.L. Rob. & Fernald, Desmanthus velutinus Scheele, Desmanthus virgatus (L.) Willd., and Neptunia lutea (Leavenw.) Benth. Phosphorus (P) fertilization was applied at 0, 40, 80, and 120 kg P ha−1 in Experiment 1 with half the pots also receiving D522-1/2 (a Desmanthus isolate). Experiment 2 consisted only the Desmanthus species and tested four different inoculant treatments (uninoculated control, inoculated with commercial cowpea Rhizobia, D522-1/2 from Desmanthus isolates, and L1145, a Leucaena isolate). Two soil treatments were used in Experiment 2, gamma radiation sterilized and unsterilized soil, to determine whether introduced Rhizobia were as effective as native populations. Shoot dry matter (DM) yield, root DM weight, and shoot nitrogen (N) and P concentration increased with increasing P application levels up to 80 kg P ha−1. Rhizobium strain D522-1/2 was an effective inoculant for all legumes when applied in combination with P fertilizer (Experiment 1). In sterilized P-deficient soil (Experiment 2), inoculation improved the parameters measured. In unsterilized soil, however, only D522-1/2 and L1145 improved shoot nitrogen concentration while the cowpea Rhizobium strain was detrimental in the case of D. velutinus. The low concentration of available soil P and the scarcity of active Rhizobium in the soil might be the cause of the slow establishment of native legume species in disturbed soils without native Rhizobia populations.