Brachiaria Arrecta Research Articles

An investigation of the effect of drying methods on the nutritive value of forage grasses

Drying methods have been identified as a critical factor in forage evaluation because there are changes in their chemical components that are affected by different drying temperatures. The study evaluated the effect of three drying methods (sun-drying, shade-drying and oven-drying (60°C) on the chemical components of three local grass species (Pennisetum purpureum, Brachiaria ruziziensis and Brachiaria arrecta) grown under tropical conditions. The objective was to determine how drying methods influence the nutritive value of forage grasses to optimize feeding practices. The harvested grass samples were dried to a constant weight under the three drying methods before being milled and then subjected to chemical analysis. Dry matter (DM), organic matter (OM), ash, ether extract (EE), crude fibre (CF), and nitrogen free extracts (NFE) were determined. Across drying methods, the DM content was highest (p<0.05) in B. ruziziensis (908 g/kg DM). The OM of the oven dried species was significantly higher in B. ruziziensis (885 g/kg DM) when compared to the species of B. arrecta (867 g/kg DM) and P. purpureum (859 g/kg DM). The CP content was highest (p<0.05) in B. ruziziensis (123 g/kg DM) (shade dried) and lowest (p<0.05) in B. arrecta (87.6 g/kg DM) (sun-dried). Across drying methods, the CF content was highest (p<0.05) in B. arrecta (367 g/kg DM) (oven dried) and lowest (p<0.05) in P. purpureum (264 g/kg DM) (shade dried). Species demonstrated higher levels of OM, CP, and lowest CF levels under shade-drying when compared to other drying methods. It was concluded that drying methods do influence the chemical components of grass species with shade-drying, indicating a greater potential for laboratory analyses and field processing. Keywords: Chemical composition, drying temperatures, fibre, forages, sun-drying, shade-drying.

Grazing Management Targets for Tangolagrass Pastures

Tangolagrass (Brachiaria arrecta × Brachiaria mutica) is a stoloniferous warm-season grass considered as an alternative to forming permanent grasslands in waterlogged tropical regions. However, information about grazing management targets for such species is still scarce. This two-year study aimed to identify pre-grazing canopy heights that do not compromise both leaf lamina production and nutritive value of tangolagrass pastures, and to test whether lower canopy height could decrease stolon elongation process. To this end, three pre-grazing canopy heights (20, 30, or 40 cm, all lowered in 40% of their initial heights) were assigned to nine 390-m2 plots grazed by cattle. Herbage, leaf, and stem accumulation rates were not different among treatments (57, 23, and 27 kg DM ha−1 d−1, respectively; p > 0.05). Also, neutral detergent fiber (NDF) and acid detergent fiber (ADF) were similar among treatments (56 and 24% DM, respectively; p > 0.05), but crude protein (CP) was greater (p = 0.0180) in pastures managed with 30 cm (24.7% DM × 22.5% DM). Thus, pre-grazing canopy heights between 20–40 cm combined with low levels of defoliation (up to 40% of the initial height) provide the same primary productivity in tangolagrass pastures. However, stolon elongation could not be reduced within such canopy height targets.

Field-scale calibration of the PAR Ceptometer and FieldScout CM for real-time estimation of herbage mass and nutritive value of rotationally grazed tropical pasture

Destructive sampling method is regarded as the standard approach for evaluating pasture herbage. However, non-destructive methods for managing pastures are rapidly gaining acceptance because they provide faster results that can influence real-time decision-making. The objective of this study was to calibrate the PAR Ceptometer and FieldScout CM as non-destructive tools for real-time prediction of herbage mass and nutritive value, respectively of rotationally grazed pasture. Sixty (60) herbage samples were cut from three (3) rotationally grazed paddocks to determine herbage mass (HM) and nutritive value [crude protein (CP), apparent neutral detergent fiber (aNDF), apparent acid detergent fiber (aADF) and in vitro organic matter digestibility (IVOMD)] after leaf area index (LAI) and light interception (LI) [PAR Ceptometer], sward height (SH) and chlorophyll index (CI) [FieldScout CM] measurements were taken. There were strong positive correlations between sward physical characteristics and CI (r2 = 0.74 to 0.90) and between CI and CP (r2 = 0.81). The LAI (Y=4,287x−1762)and LI (Y=149.9x−5,925) accounted for 81 % and 75 % of variability in HM, respectively. The CI accounted for a maximum of 68 % variability of CP. However, concordance correlation coefficient (CCC) of these prediction models were poor. Models with highest prediction accuracy for HM were those with SH (cb= 0.89) and LAI (cb= 0.81). Regression bias was the main sources of error for HM prediction models, while the primary error for CI predicted aNDF (75.4 % MSPE) and IVOMD (95.5 % MSPE) occurred at random. It was concluded that the PAR Ceptometer produced unreliable estimates of HM while the FieldScout CM is capable of producing reliable predictions of aNDF and IVOMD of rotationally grazed mixed Brachiaria arrecta and Digitaria eriantha pastures.

Reuse of Treated Domestic Wastewater by Employing Artificial Wetlands in Panama

Reuse of treated wastewater in irrigation is an alternative to achieve greater water availability and benefits to the soil due to its nutrient content. It represents a solution to challenges in water management, climate change and water scarcity in dry seasons. In Panama’s Dry Arch, the lack of water is critical during dry season months, which makes it essential to look for sustainable alternatives as water source. This paper describes the use of artificial wetlands with horizontal subsurface flow, and we are going to use partially treated domestic wastewater. The aquatic plant types employed were Echinochloa polystachya (German grass) and Brachiaria arrecta (Tanner grass) with the objective of improve the quality of the effluent from the Wastewater Treatment Plant (WWTP) in Chitre for the irrigation of forages. This study was carried out from August to December 2019. Fine Gravel was used in this study as a substrate. The parameters analyzed were pH, Total dissolved solids, Electrical Conductivity, Chemical Oxygen Demand, Turbidity, Chlorides, Sulfates, Iron, Chromium+6, Copper; nutrients such as Total nitrogen and Total phosphorus. Fecal coliforms were also analyzed. Results showed that treated wastewater is a viable alternative for irrigation due to its high nutrient content, but it must be managed safely so as not to generate risks to public health.

Nitrogen balance of bullocks fed Cratylia argentea and Brachiaria arrecta Hay

Four experimental diets or treatments formed with incremental proportions of the foliage of tropical shrub legume Cratylia argentea and decremental proportions of Tanner grass (Brachiaria arrecta) hay: T1, 0:100; T2, 15:85; T3, 30:70; and T4, 45:55 were evaluated using four Holstein-Zebu bullocks (214.5 9.3 kg) conned in individual pens, under a balanced 4 x 4 latin square design. The crude protein (CP, %) content of C. argentea was 19.3 ± 6%, and in the grass was 6.2 ± 3%. The intake of DM increased as the C. argentea level in the diet increased. Blood urea-N (BUN) showed a linear increase from T1 to T4, observing its highest concentration at feeding time and six-hours after in T4: 12.00 and 14.75 mg dL-1, respectively. Purine derivatives (uric acid and allantoin) were not affected by treatments (p > 0.05). The increase of the legume in the diet improved the DM intake and digestibility, and led to N-balance from negative in T1 and T2, to positive in T3 and T4. The legume proportion in a basal diet of the grass B. arrecta must be 30% at least.

Selection of plants for phytoremediation of barium-polluted flooded soils

The use of barite (BaSO4) in drilling fluids for oil and gas activities makes barium a potential contaminant in case of spills onto flooded soils, where low redox conditions may increase barium sulfate solubility. In order to select plants able to remove barium in such scenarios, the following species were evaluated on barium phytoextraction capacity: Brachiaria arrecta, Cyperus papyrus, Eleocharis acutangula, E. interstincta, Nephrolepsis cf. rivularis, Oryza sativa IRGA 424, O. sativa BRS Tropical, Paspalum conspersum, and Typha domingensis. Plants were grown in pots and exposed to six barium concentrations: 0, 2.5, 5.0, 10.0, 30.0, and 65.0 mg kg−1. To simulate flooding conditions, each pot was kept with a thin water film over the soil surface (∼1.0 cm). Plants were evaluated for biomass yield and barium removal. The highest amount of barium was observed in T. domingensis biomass, followed by C. papyrus. However, the latter exported most of the barium to the aerial part of the plant, especially at higher BaCl2 doses, while the former accumulated barium preferentially in the roots. Thus, barium removal with C. papyrus could be achieved by simply harvesting aerial biomass. The high amounts of barium in T. domingensis and C. papyrus resulted from the combination of high barium concentration in plant tissues with high biomass production. These results make T. domingensis and C. papyrus potential candidates for phytoremediation schemes to remove barium from flooded soils.

Comparative effects of food processing liquid slurry and inorganic fertilizers on tanner grass (Brachiaria arrecta) pasture: grass yield, crude protein and P levels and residual soil N and P

AbstractThis small‐plot field study evaluated food processing liquid slurry (FPLS) as a potential fertilizer for tanner grass (Brachiaria arrecta) production on an acidic loam soil. The treatments, arranged in a randomized complete block design with three replicates, consisted of an unfertilized control, inorganic fertilizer applied at 50 and 200 kg nitrogen (N) ha−1 with and without phosphorus (P) at 50 kg P ha−1, and FPLS applied at 50 and 200 kg N ha−1. Compared to the unfertilized control, the FPLS applied at 200 kg N ha−1 significantly increased grass dry‐matter yield (DMY), herbage crude protein (CP) and P content, and N and P uptake in the second of two trials and P uptake in both trials. However, DMY and contents, of CP and P were generally lower for the FPLS treatments compared to the inorganic fertilizers. Apparent N recovery was higher for the inorganic fertilizer treatments than FPLS treatments in trial 1, while apparent P recovery was similar among all treatments in both trials. The FPLS treatments did not significantly increase soil NO3‐N and P concentrations, but increased NH4‐N in the 0–15 cm layer. The results suggest that application of FPLS to tanner grass pastures is an alternative to its disposal in landfill.

Brachiaria species identification using imaging techniques based on fractal descriptors

The use of a rapid and accurate method in diagnosis and classification of species and/or cultivars of forage has practical relevance, scientific and trade in various areas of study, since it has broad representation in grazing from tropical regions. Nowadays it occupies about 90% of the grazing area along Brazil and, besides the grazing areas to feed ruminants, Brachiaria also corresponds to about 80% of seeds being traded in all the world, bringing a large amount of money to Brazil. To identify species and/or cultivars of this genus is of fundamental importance in the fields that produce seeds, to ensure varietal purity and the effectiveness of improvement programs. Thus, leaf samples of fodder plant species Brachiaria were previously identified, collected and scanned to be treated by means of artificial vision to make the database and be used in subsequent classifications. Forage crops used were: Brachiaria decumbens cv. IPEAN; Brachiaria ruziziensis Germain & Evrard; Brachiaria brizantha (Hochst. ex. A. Rich.) Stapf; Brachiaria arrecta (Hack.) Stent. and Brachiaria spp. The images were analyzed by the fractal descriptors method, where a set of measures are obtained from the values of the fractal dimension at different scales. Therefore such values are used as inputs for a state-of-the-art classifier, the Support Vector Machine, which finally discriminates the images according to the respective species. The proposed method outperforms other state-of-the-art image analysis methods and makes possible the correct prediction of species in more than 93% of the samples. Such remarkable result is consequence of the better suitability of representing complex structures like those arising in the plant leaves by measures of complexity from fractal geometry. Finally, this high correctness rate suggests that the fractal method is an important tool to help the botanist.

Anatomical and physiological characteristics of tanner grass exposed to arsenic

Phytoremediation is a biological process that stands out as an effective and economic alternative for the removal of toxic elements; however, its success depends on previous studies of plant species and the species’ tolerance of certain pollutants. The aim was at evaluating the anatomy and physiology of Tanner grass (Brachiaria arrecta) to determine its anatomical and physiological plasticity characteristics that potentially enable arsenic tolerance. B. arrecta plants were cultivated in a greenhouse in a Hoagland-Arnon nutritive solution with the following As concentrations: 0.0, 0.25, 0.5, 1.0, 2.0 and 4.0 mg L–1. Gas exchange, anatomical characteristics, DNA quantification and arsenic absorption were evaluated at 18 and 21 days. An evaluation of plant growth was conducted to compare the selected plants at the beginning and after 21 days of the experiment. The plants absorbed the arsenic contained in the solution and showed an increase in the leaf stomatal density, mesophyll and leaf blade thickness and root endodermis and exodermis, and the anatomical modifications showed no evidence of stress in the plant structure. The gas exchange, growth and DNA content were not modified by arsenic in B. arrecta plants. The B. arrecta plants have anatomical and physiological characteristics that contribute to their survival in the presence of arsenic, possibly helped by the tolerance of this species of arsenic contamination from the nutrient solution and the lack of anatomical and physiological changes resulting in damage to this species.

Fractions of carbohydrates and of nitrogenous compounds of tropical grasses at different cutting ages

It was evaluated by the Cornell System carbohidrates fractions and nitrogenous compounds of the following grasses at the cutting ages of 14, 28, 42, and 56 days: nilo grass (Acroceras macrum), angola grass (Brachiaria purpurascens), aleman grass (Echinochloa polystachya), limpo grass (Hemarthria altíssima), setaria grass (Setaria anceps), tanner grass (Brachiaria arrecta), and tifton-85 grass (Cynodon spp). The experiment was carried out in a complete randomized block design, in a split plot arrangement in a way that the grasses were evaluated in the plots and the ages of cut in the split-plots. The age of cutting had an effect on the composition of the studied grasses. In most of the grasses, total carbohydrate levels, non-fibrous carbohydrates and A+B1 fraction carbohydrates increased linearly according to the age of cutting. The potentially degradable fraction of carbohydrates (fraction B2) showed a quadratic behavior according to the cutting ages for all grasses. The C fraction of the carbohydrates in tifton-85 grass linearly increased with the age but it did not increase significantly for the other grasses. In setaria grass, the intermediate levels of B2 and B3 nitrogenous fractions were high, which might represent a potential source of protein for ruminal degradation and for the small intestine. Except for setaria grass, all studied grasses show similar values of the A, B1, B2 and B3 nitrogenous fractions.

Determinación de la fijación biológica de N2 usando la técnica de abundancia natural del N15 en tres ecotipos de cacahuate forrajero

The percentage of nitrogen derived from N2 fixation was measured by the N natural abundance method, in three Arachis pintoi (Ap) ecotypes: CIAT 17434, 18744 and 18748, using an improved Bradyrhizobium strain CIAT 3101 (BS), and a mixing of native strains (NS). As reference plants, a non-nodulating Arachis hypogaea, Brachiaria arrecta, B. brizantha and Cynodon nlemfuensis were used.

Utilização de análise multivariada e redes neurais artificiais na determinação do comportamento de colonização de populações de macrófitas aquáticas no reservatório de Santana

As análises de agrupamento e de componentes principais e as redes neurais artificiais foram utilizadas na determinação de padrões de comportamento das populações de macrófitas aquáticas que colonizaram o reservatório de Santana, Piraí-RJ, durante o ano de 2004. As análises de agrupamento dividiram o comportamento das populações durante o ano em dois grupos distintos, apresentando um padrão no primeiro semestre que difere daquele observado no segundo semestre do ano. A análise de componentes principais demonstrou que esse comportamento da comunidade (grupo de populações) é influenciado principalmente pelas espécies S. montevidensis, Heteranthera reniformis, Ludwigia sp., Rhynchospora aurea, C. iria, C. ferax e Aeschynomene denticulata no primeiro grupo e por Echinochloa polystachya, Polygonum lapathifolium, Alternanthera phyloxeroides, Pistia stratiotes, Eichhornia azurea, Brachiaria arrecta e Oxyscarium cubense no segundo grupo. As redes neurais artificiais agruparam as populações de macrófitas aquáticas em nove grupos, conforme sua densidade nos diferentes meses do ano. A aplicação da análise de componentes principais (ACP) nos valores de frequência das populações presentes nos primeiros três grupos de Kohonen permitiu discriminar três grupos de meses, cujas populações apresentaram características diferentes de colonização. A aplicação das redes neurais artificiais permitiu melhor discriminação dos meses e das espécies que compõem as comunidades correspondentes, quando utilizada a análise de componentes principais.

Caracterização da comunidade de plantas aquáticas de dezoito reservatórios pertencentes a cinco bacias hidrográficas do Estado de São Paulo

O objetivo deste trabalho foi o de avaliar e comparar a composição florística de 18 reservatórios pertencentes a cinco bacias hidrográficas do Estado de São Paulo. Os levantamentos foram realizados no período de fevereiro a setembro de 2002, com o auxílio de um barco. Percorreu-se a margem dos reservatórios das bacias hidrográficas dos rios Paraíba, Paraná, Paranapanema, Grande e Tietê, à velocidade de 30 km h-1. A cada 20 minutos, estabeleceu-se um ponto de amostragem, determinando-se sua posição por meio de GPS. Em cada ponto, em área de 1.000 m², identificaram-se as espécies ocorrentes e respectivas densidades, em porcentagem da área amostrada. Foram identificadas 39 espécies, distribuídas em 21 famílias, destacando-se as flutuantes Salvinia auriculata, Eichhornia crassipes, Eichhornia azurea e Pistia stratiotes e as emersas Polygonum lapathifolium, Brachiaria arrecta,Brachiaria mutica, Cyperus sp. e Typha latifolia, considerando as quatro espécies com maior freqüência em cada bacia. O maior índice de similaridade (0,71) ocorreu entre as bacias dos rios Paranapanema e Grande, e o menor (0,49), entre as bacias dos rios Paraíba e Tietê.

Atividade enzimática em variedades de cana-de-açúcar cultivadas in vitro sob diferentes níveis de nitrogênio

O nitrogênio é considerado o elemento mineral mais abundante nas plantas, sendo componente essencial de biomoléculas e inúmeras enzimas. O objetivo deste trabalho foi avaliar a eficiência no processo de assimilação do nitrogênio e encontrar parâmetros indicativos do potencial de fixação biológica em variedades de cana-de-açúcar (Saccharum officinarum) cultivadas in vitro. Foram utilizadas as variedades de cana-de-açúcar RB 842021, RB 83102, RB 75126, RB 882980 e Co 997, além da Brachiaria arrecta (testemunha), cultivadas in vitro em diferentes níveis de nitrogênio [M1 (9,83 mM), M2 (2,46 mM), M3 (0,49 mM), M4 (0,0 mM)]. Todas as variedades e a cultura testemunha (Brachiaria arrecta) apresentaram atividade da nitrato redutase (NR) constitutiva e também da glutamina sintetase (GS), mesmo na ausência de amônio e nitrato no meio de cultura. A variedade RB 842021 apresentou a maior atividade da nitrato redutase e o maior conteúdo de clorofilas a e b, e a variedade RB 882980 a maior atividade da glutamina sintetase nas mesmas condições de cultivo, o que pode representar maior potencial de assimilação do nitrogênio.

Ocorrência de plantas aquáticas nos reservatórios da Light-RJ

O objetivo do presente trabalho foi caracterizar as comunidades infestantes de plantas aquáticas presentes nos reservatórios da Light-Sistema de Eletricidade S.A., localizada no município de Piraí-RJ. Os levantamentos foram realizados no período de julho a setembro de 1998. Os reservatórios analisados foram: Vigário, Pereira Passos e Lajes, sendo as quantidades de pontos amostrados de 19, 9 e 15, respectivamente. Em cada ponto amostrado fez-se a marcação das coordenadas geográficas e avaliou-se a porcentagem de ocupação do corpo d'água pelas espécies de plantas aquáticas presentes. Depois da identificação das plantas, pôde-se verificar quais eram as espécies mais freqüentes e a sua distribuição dentro do sistema de geração de energia. As espécies encontradas nos reservatórios foram: Brachiaria arrecta (Hack.) Stent.; Egeria densa Planch.; Eichhornia azurea (Sw.) Kunth.; Eichhornia crassipes (Mart.) Solms.; Hymenachne amplexicaulis (Rudge) Nees.; Panicum rivulare Trin.; Pistia stratiotis L.; Polygonum spp.; Sagitaria montevidensis Cham. & Schlecht; Salvinia auriculata (Micheli) Adans; e Thypha dominguensis L.

Natural enemies of the chinch bug, Blissus antillus Leonard (Hemiptera: Lygaeidae: Blissinae), pasture pest in Rio de Janeiro state, Brazil

This study aimed to identify natural enemies of the chinch bug, Blissus antillus Leonard, which attacks Tanner grass (Brachiaria arrecta) and Tangola (hybrid of B. arrecta and B. angola), in poorly drained pastureland in the northern region of Rio de Janeiro State. Immature stages of a parasitic mite, identified as Leptus sp. (Parasitengona: Erythraeidae), were commonly found attacking nymphs and adult chinch bugs in all sampled areas of Rio de Janeiro State. An egg parasitoid, Eumicrosoma sp. (Hymenoptera: Scelionidae), was observed on only two occasions attacking eggs which had been collected on plant stems in the field. These natural enemies are possible candidates for biological control programs. Despite extensive sampling, B. antillus was not observed to be infected by entomopathogenic fungi.

Effect of arbuscular mycorrhizas on uptake of nitrogen by Brachiaria arrecta and Sorghum vulgare from soils labelled for several years with 15N

summaryA pot experiment was conducted under glasshouse conditions to investigate the effect of the inoculation of arbuscular mycorrhizal (AM) fungi on the growth and N uptake of two graminaceous plants: Brachiaria arrecta (Hack. ex. Th. Dur & Schinz) Stent and Sorghum vulgare (Pers.) growing in four fumigated soils which had been labelled for several years with 15N. The four soils had different chemical characteristics, especially in their P availability. The levels of root colonization by AM fungi were inversely related to the P concentration in these soils. Positive responses to AM fungal inoculation were observed for all the yield parameters except in the soil with the highest P availability (40 μg P g−1 soil, extractant Mehlich‐1). In the other three soils, AM fungal inoculation of both crops increased N accumulation by between 17 and 46%, but the 15N enrichment of the N absorbed was significantly lower in the mycorrhizal plants than in those not colonized by mycorrhizal fungi. This suggests that some of the N absorbed from the soil by the mycorrhizal roots was derived from N sources other than the mineral N.

Contribution of Nitrogen Fixation to Sugar Cane: Nitrogen‐15 and Nitrogen‐Balance Estimates

AbstractContinuous sugarcane (Saccharum spp.) culture in Brazil, with low N inputs and almost total removal of plant biomass at each harvest, has not depleted soil N reserves. This, and high numbers of N2‐fixing bacteria associated with the plants, suggests that the crop may be obtaining considerable N from biological nitrogen fixation (BNF). This 3‐yr study assessed the importance of such contributions to three sugarcane species (S. officinarum L., S. barberi Jesw., and S. spontaneum L.), and seven commercial Brazilian hybrids. The plants were grown in a concrete tank containing 15N‐labeled soil in order to use 15N isotope dilution to estimate the BNF contributions. A grass, Brachiaria arrecta (cv. IRI 442), was included as a non‐N2‐fixing control. All aerial tissue was harvested annually, and the roots and stem bases were removed at the end of the experiment. For all 3 yr, the commercial hybrids and the S. spontaneum cultivar (Krakatau) accumulated more N at significantly lower 15N enrichments than the control. These data suggest that the plants obtained considerable BNF contributions, but interpretation of the 15N data was prejudiced by (i) the steadily declining 15N enrichment of the soil mineral N, (ii) carry‐over of N from one harvest to the next in the roots and stem bases, and (iii) shading of the control crop by the tall cane plants. Several of the sugarcane cultivars had significantly positive N balances, however, and there was good agreement between the estimates of BNF contributions derived from N balance and isotope dilution. Krakatau and the commercial hybrids CB 45‐3 and SP 70‐1143 obtained the largest contributions from BNF, but methodological problems did not allow exact determinations.

Selection of ecotypes of Panicum maximum for associated biological nitrogen fixation using the 15N isotope dilution technique

Ecotypcs of the tropical pasture grass, Panicum maximum, were screened by means of the 15N isotope dilution technique for their ability to support associated biological nitrogen fixation (BNF). The ecotypes were planted in pots containing 3kg of a purple latosol (allic rhodalf) mixed with 1.5g pot −1 of 15N-labelled organic matter (compost). The experiment consisted of 26 treatments (25 ecotypes and the non-N 2-fixing control plant, Brachiaria arrecta, IRI 442) with four replicates and was laid out in a randomized complete-block design. B. arrecta and P. maximum ecotype KK. 16 accumulated more N than most other ecotypes at the first two harvests (high soil N availability), but recovered the least N at the final two harvests (low soil N availability). At the last two harvests these two grasses had the highest 15N enrichment. The uptake pattern of labelled N of ecotype KK 16 was similar to that of the other P. maximum ecotypes, but distinctly different from that of B. arrecta, and for this reason KK16 was considered to be a better control plant and capable of obtaining little or no N from associated BNF. The other P. maximum ecotypes derived between 16 and 39% of their total N from BNF at the final two harvests.