ABSTRACT. The BRSMG Uai common bean cultivar (Phaseolus vulgaris L.) unites traits required by producers, such as high yield and upright stands, the latter of which is considerably improved in relation to previously released cultivars such as BRSMG Madrepérola and Pérola. However, the potential of the cultivar to form symbiotic relationships with rhizobia to fix N2 has not yet been assessed. Here, field experiments were conducted to assess the efficiency of biological nitrogen fixation (BNF) in the cultivar, and to compare this to the efficiencies of other genetic materials widely grown throughout Brazil (BRSMG Madrepérola and Pérola). Experiments were conducted on two Oxisols in Minas Gerais State, Brazil (one during the dry season in the south, and the other during the winter season in the Alto-Paranaíba region), under a no-tillage system over maize stover. A randomized block experimental design was implemented in a 3 × 3 factorial arrangement with four replicates. Individual and combined Analysis of Variance were performed and the data were normalized. Homogeneity of the residual mean squares was observed. Significant effects of factors were identified by Scott-Knott tests and F tests. The BRSMG Uai cultivar responded to inoculation with the rhizobial strain CIAT 899, with yields similar to those achieved upon fertilization with 80 kg ha-1 of N-urea and to the yields of the BRSMG Madrepérola and Pérola cultivars inoculated with the same rhizobial strain. In terms of commercial use, this cultivar may be successful under either of the management practices adopted for N supply, and from the perspective of plant breeding, it has potential for inclusion in breeding programs directed toward improving BNF.

ABSTRACT In spite of the chemical, physical, and biological benefits that Crotalaria spectabilis can provide to the soil, it is little used as a green manure crop by farmers. Inoculation with strains of legume-nodulating nitrogen-fixing bacteria that are efficient and competitive may be a strategy to enhance accumulation of N in C. spectabilis and stimulate adoption of this green manure crop. The aims of this study were i) to evaluate the symbiotic and agronomic efficiency of new strains of Bradyrhizobium on C. spectabilis in an oxisol (red latosol) compared to that of noninoculated controls (without and with mineral N) and with the approved strain BR2811, seeking to corroborate possible recommendation as inoculants for this species; and ii) to determine, the contribution of these treatments to N accumulation in the plant of C. spectabilis in four periods of cutting for determining possible and ideal periods for its incorporation in the soil. Experiments were carried out in pots and field. Inoculation with the new strains UFLA05-03, UFLA05-09, and UFLA05-14 and with BR2811 on C. spectabilis is effective since it increases the production of N-enriched plant biomass when compared to the control without N mineral. However, UFLA05-03 stands out among these strains because it behaves similarly to the control with mineral N both in relation to shoot N accumulation and dry matter just after 150 days in the field.

ABSTRACT Studies in the Amazon indicate a wide diversity of rhizobia with the ability for biological nitrogen fixation (BNF), which could expand the number of strains approved for cowpea. Thus, the aim of this field study was to evaluate the agronomic performance in cowpea of the several strains isolated from the soils of the Brazilian states Acre and Rondônia, and to compare them withstrains approved by the Ministry of Agriculture (MAPA) and withnon-inoculated controls (without and with mineral nitrogen fertilizer). The inoculants performed well. Though less effective than the other strains, the UFLA 03-36 strain also was prominent with respect to grain yield. Because of the positive response of the UFLA 03-129 strain, which led to yield increases greater than the obtained from the control without inoculation plus mineral-N, it can be recommended as an inoculum for cowpea. Further investigations should be carried out to obtain MAPA’s approval for their use. Other experiments involving this strain and several cultivars are being carried out on other types of soil and environmental conditions of the state of Minas Gerais.

ABSTRACT Although the use of inoculants containing rhizobia is encouraged, there are no official recommendations for inoculation of snap bean. In this respect, the aim of this study was to evaluate the agronomic performance of Rhizobium strains in symbiosis with snap bean cultivars with different growth habits and crop cycles. The experiment was carried out in pots with soil in a greenhouse in the spring-summer season in Lavras, state of Minas Gerais, Brazil. A completely randomized experimental design was used, with 4 replications, in a 4 × 7 factorial arrangement involving four snap bean cultivars and seven treatments – five strains of Rhizobium (UFLA 02-100, UFLA 02-127, UFLA 04-173, CIAT 899, and PRF 81), plus two controls without inoculation (with and without 500 mg N-NH4NO3∙dm–3). We conclude that: i) while genetic differences were observed among cultivars with respect to nodulating capacity, in all cases significant benefits were observed from BNF inoculation and ii) inoculation with selected strains of Rhizobium, as well as fertilization with mineral N, favors plant growtht, snap bean yields, and accumulation of N in the pods and, therefore, can fully substitute nitrogen fertilization in snap bean grown under protected cultivation.

Resumo: O objetivo deste trabalho foi avaliar a viabilidade da inoculação líquida de Rhizobium etli no sulco de semeadura e certificar a eficiência da estirpe UFLA 02-100 como inoculante potencial para o feijoeiro-comum (Phaseolus vulgaris). Os tratamentos consistiram de três doses do inoculante líquido aplicadas aos sulcos e uma dose aplicada às sementes de feijão-comum, além de dois controles sem inoculação. O inoculante continha 109células de Rhizobium etli mL-1. Independentemente do método de aplicação, a produtividade obtida com a inoculação foi equivalente à da aplicação de N da ureia, mas a aplicação ao sulco, com 0,6 L ha-1, é mais vantajosa pela praticidade operacional e redução de custos.

Abstract: The objective of this work was to evaluate the viability of liquid medium inoculation of Rhizobium etli in the planting furrow and to certify the efficiency of its strain UFLA 02-100 as a potential inoculant for common bean (Phaseolus vulgaris). The treatments consisted of three application rates of liquid inoculant applied in the planting furrows or in common bean seed, besides two controls without inoculation. The inoculant contained 109 cells of Rhizobium etli mL-1. Regardless of the application method, the yield obtained with the inoculation was equivalent to that of N from urea; however, the application in the furrows, at 0.6 L ha-1, is more advantageous due to the operational practicality and reduced costs.

RESUMO Para maximizar a contribuição da fixação biológica de nitrogênio no feijoeiro-comum é necessária a utilização de estirpes de bactérias mais adaptadas, competitivas e eficientes no processo simbiótico. Nesse sentido, objetivou-se avaliar, em um Argissolo Vermelho Distrófico típico do município de Formiga-MG, a eficiência agronômica (EA) de três estirpes isoladas de solos ácidos e com alto teor de Al da Amazônia e comparar suas EA à da estirpe referência CIAT 899T e à de dois controles sem inoculação (um sem e outro com 80 kg ha-1 of N-ureia). Os resultados indicaram que a inoculação com as estirpes UFLA 02-100 e UFLA 02-127 propicia rendimento de grãos equivalente ao da estirpe referência e ao do controle com N mineral e que por isso, ambas têm potencial para ser recomendadas como inoculantes para o feijoeiro-comum.

ABSTRACT To maximize the contribution of biological nitrogen fixation in common bean, it is necessary to use bacterial strains that are more adapted, competitive, and efficient in the symbiotic process. In this regard, the aim of this study was to evaluate the agronomic efficiency (AE) of three bacterial strains isolated from acid soils with high Al content from the Amazon region in an Argissolo Vermelho Distrófico típico soil (Typic Rhodustults - USDA Classification) from the municipality of Formiga, MG, Brazil. We compared their AE to that of the reference strain CIAT 899T and of two controls without inoculation (one without and another with 80 kg ha-1 of N-urea). The results indicated that inoculation with the strains UFLA 02-100 and UFLA 02-127 provides grain yield equivalent to inoculation with the reference strain and to the control with mineral N. Thus, both have potential for recommendation as inoculants for common bean.

RESUMO. Objetivou-se avaliar os efeitos da aplicação foliar de molibdênio e do emprego de pequena dose de nitrogênio no plantio sobre a produção do feijoeiro quando se utiliza a inoculação das sementes com rizóbio. Foram conduzidos dois experimentos em campo, em delineamento de blocos ao acaso, esquema fatorial (3x2x2) + 1, com três repetições. Os tratamentos foram inoculação (estirpe CIAT 899T, estirpe UFLA 02-100 e ausência de inoculação), aplicação foliar de molibdênio (0 e 80 g ha-1) e de nitrogênio na semeadura (0 e 20 kg ha-1), mais tratamento adicional com N (40 na semeadura e 40 kg ha-1 na cobertura). A aplicação foliar de molibdênio não favoreceu a nodulação, mas seu efeito sobre o rendimento de grãos foi dependente das características químicas do solo, fornecendo maior produtividade em solo de Patos de Minas, com pH mais ácido e maiores teores de fósforo e matéria orgânica. Pequena dose de nitrogênio no plantio não reduziu a nodulação do feijoeiro inoculado com rizóbio, mas pode reduzir a emergência das sementes, com reflexo negativo na produtividade. Os rizóbios nativos proporcionaram nodulação, crescimento vegetal, acúmulo de nitrogênio na parte aérea e rendimento equivalentes aos tratamentos inoculados com as estirpes de rizóbio.

ABSTRACT. The aim of this study was to evaluate the effects of foliar application of molybdenum and small dose of nitrogen at planting on common bean production when using seed inoculation with rhizobia. Two field experiments were conducted, applying a randomized block design and a factorial arrangement (3x2x2) + 1, with three replicates. Treatments consisted of inoculation with Rhizobium spp. (strain CIAT 899T, strain UFLA 02-100, and uninoculated), foliar application of molybdenum (0 and 80 g ha-1), and fertilization with N-urea at planting (0 and 20 kg ha-1), with an additional N treatment of 40 applied at planting and 40 kg ha-1 applied as topdressing. The foliar application of molybdenum did not favor the nodulation, but its effect on yield was dependent on the chemical soil characteristics, providing highest yield in soil at Patos de Minas with pH more acid and with higher phosphorus and organic matter concentrations. Small dose of nitrogen applied at planting did not reduce nodulation of bean inoculated with rhizobia, but it can reduce the seeds emergence, thus negatively affecting yield. The native rhizobia promoted nodulation, the plant growth, shoot N accumulation and yield similar to the treatments that received inoculations of rhizobia strains.

ABSTRACT: Optimization of symbiosis between nitrogen-fixing bacteria and legumes has been extensively studied, seeking agricultural sustainability. To evaluate the symbiotic efficiency of nitrogen-fixing bacterial strains belonging to the Bradyrhizobium genus with pigeon pea (Cajanus cajan (L.) Millsp.) cv. Fava-Larga, experiments were conducted in Leonard jars (axenic conditions), pots with soil, and in the field. Ten strains were tested in Leonard jars, and three strains, in addition to BR 29, were selected according to their ability to promote the growth of pigeon pea, for further tests in pots with different soil types (Inceptsol and Oxisol) and in the field (Oxisol). Treatments were compared with strains BR 2003 and BR 2801 (approved as inoculants for pigeon pea), with a non-inoculated control with mineral N fertilization, and with another non-inoculated control (absolute control) with low mineral N concentration (Leonard jars) or without mineral N fertilization (soil). The efficiency of Bradyrhizobium strains in axenic conditions varies among strains, being higher when pigeon pea cv. Fava-Larga establishes symbiosis with the strains UFLA 03-320, UFLA 03-321, UFLA 04-212, BR 2801, and BR 2003. The soil type influences the symbiotic efficiency of Bradyrhizobium-pigeon pea in soil in the greenhouse, mainly in Inceptsol, in which strains UFLA 04-212, BR 2801, and BR 2003 increased N accumulation in the plant. The strain UFLA 03-320 increased shoot dry matter and N accumulation in the shoot equivalent to the mineral N treatment under field conditions. UFLA 03-320, BR 29, UFLA 03-321, and UFLA 04-212 promoted yields similar to those of the reference strain (BR 2801), and of the mineral N treatment with 70 kg ha-1 urea-N. These results confirm that pigeon pea establishes efficient symbiosis, which provides the N required for its growth. All strains, except for BR 2003, show potential for recommendation as inoculants for grain production. The strain UFLA 03-320 also shows potential for use in green manure crops.

ABSTRACT Management of biological nitrogen fixation in common bean still requires improvement. The objective of this study was to verify the compatibility of nitrogen fertilization with biological N2 fixation to increase common bean yield and profitability. Four field experiments were performed in four municipalities of Minas Gerais, Brazil, during the 2009 and 2010 winter crop season. The 2009 crop experiments were set up under a no-till system and the 2010 crop was conducted using conventional tillage. A randomized block experimental design was used with four replications and seven treatments combining application rates of mineral N (at sowing and/or topdressing) and seed inoculation with Rhizobium tropici strain CIAT899. Inoculation with 20 kg ha-1 N-urea at sowing and seed inoculation does not interfere with nodule dry matter and promotes yield comparable to that observed with 80 kg ha-1 N-urea with economic profitability in both no-till and conventional tillage systems. These results show the possibility of economic savings with respect to N fertilizers, but also a significant ecological contribution by avoiding problems associated with misuse of these fertilizers, such as eutrophication of waterways and denitrification.

The objective of this research was to evaluate the effect of the addition of two Lactobacillus strains on the aerobic stability of the sugar cane (Saccharum spp.) silages. The experiment was carried out in a completely randomized design with three replicates in split-plot in time scheme, so that the treatments (silages without inoculant and with novel strain or commercial inoculants) were randomized on plot and in times of aerobic evaluation of the silages (zero, two, four, and six days after the opening of the silos) as subplots. The loss of stability of silages was continuous during the time of aerobic exposure. Inoculants influenced the changes in populations of lactic acid bacteria and yeasts and in the ammoniacal nitrogen, acetic acid and ethanol concentrations. The dry matter, crude protein, soluble carbohydrates contents and pH values showed similar changes in all three silages studied. A linear increase in crude protein content and pH values and decrease in the soluble carbohydrates content were observed. The dry matter contents increased to a maximum of 335 g/kg on fresh matter at four days, followed by reduction after six days. The results showed that the use of inoculants is recommended because it promoted higher production of acetic and propionic acids, reducing the population of yeast and, therefore, improving the aerobic stability of silages.

O objetivo deste trabalho foi avaliar o efeito do pH do meio de cultivo na eficiência simbiótica de estirpes de Rhizobium, em solo com e sem calagem. Foram realizados experimentos em casa de vegetação, com e sem calagem, e no campo, apenas com calagem. O delineamento experimental utilizado foi de blocos ao acaso com quatro repetições, e os tratamentos foram cinco estirpes de Rhizobium (UFLA 02-100, UFLA 02-68, UFLA 04-195, UFLA 04-202 e CIAT 899), cultivadas em meio de cultura 79 com diferentes valores de pH (5,0, 6,0 e 6,9), e testemunhas sem inoculação, com ou sem nitrogênio mineral. Foram avaliados número e massa de matéria seca de nódulos, massa de matéria seca da parte aérea, eficiência relativa, teor e acúmulo de nitrogênio na parte aérea e nos grãos, número de vagens por planta, número de grãos por vagem e rendimento e massa de 100 grãos. O valor de pH ideal para o meio de cultivo variou com as estirpes e com a variável analisada. Os tratamentos que receberam calagem foram superiores aos demais. No campo, independentemente do pH do inoculante, as populações nativas do solo e as estirpes introduzidas promoveram rendimento de grãos semelhante ao da testemunha com 70 kg ha-1 de N e ao da estirpe referência CIAT 899.

The objective of this study was to evaluate the effect of the culture medium pH in the symbiotic effectiveness of Rhizobium strains in soil, with and without liming. Assays were performed in greenhouse, with and without liming, and in the field, with liming. The experimental design was randomized blocks with four replicates, and treatments were five strains (UFLA 02-100, UFLA 02-68, UFLA 04-195, UFLA 04-202 and CIAT 899), grown in a 79 culture medium with different pH values (5.0, 6.0 and 6.9), and two controls without inoculation: with or without mineral nitrogen. Variables analyzed were number and weight of dry nodules, shoot dry matter, relative efficiency, nitrogen content and accumulation in shoots and grains, number of pods per plant, number of grains per pod, and yield and weight of 100 grains. The optimum pH value for the culture medium varied with the strains and the variable analyzed. Treatments with liming were superior to the others. In the field, regardless of the inoculant pH, the native soil populations and the introduced strains promoted grain yields similar to those of the control with 70 kg ha-1 of N and to those of the reference strain CIAT 899.