ABSTRACT: Soil enzymes play a fundamental role in nutrient cycling in forest systems. The stoichiometry of C, N, and P–acquiring enzymes has been used to indicate nutrient limitation in the soil. However, the enzymatic stoichiometry remains poorly understood in pure and mixed eucalypt plantations. Thus, this study aims to assess the activity of enzymes in the soil to address the hypothesis that the introduction of N2-fixing trees could influence the enzymatic stoichiometry on C, N, and P cycling. The activity of β-glucosidase (BG), urease (U), and acid phosphatase (AP) was assessed in soil (0-20 cm depth) of pure Eucalyptus grandis without (E) and with N fertilization (E+N), and a mixed system with E. grandis and Acacia mangium (E+A), and a pure A. mangium (A) plantation at 27 and 39 months after planting. The activities of BG/U, BG/AP, and U/AP were used to calculate the enzyme C/N, C/P, and N/P ratios, respectively. Rates of N–acquiring enzymes were higher in E and E+N, while soil microorganisms invested in P–acquiring enzymes in A and E+A. The vector length and angle demonstrated that C demand by microorganisms does not change in relation to N and P, regardless of the treatment. However, N demand decreased in relation to P in A and E+A (mainly at 27 months). Our results suggest that enzymes activity in pure eucalypt systems is limited for their soil-litter nutrient contents. At the same time while acacia and mixed plantation seem to invest in P–acquiring enzymes to improve biological N2 fixation promoted by diazotrophic bacteria associated to acacia.

ABSTRACT. This study was performed to investigate the effects of composted tannery sludge (CTS) on the physical properties of tropical sandy soil after seven years of CTS application. CTS was applied to a Fluvisol at five rates (0.0, 2.5, 5.0, 10.0, and 20.0 Mg ha-1) in experimental plots (sized 20 m2) with four replications. Water infiltration into the soil was determined in the field with the concentric-ring infiltrometer method. Bulk density, total porosity, macroporosity, and microporosity were determined in the soil samples. The permanent CTS application altered the physical properties of the soil and led to a decrease in bulk density. The total porosity, microporosity and macroporosity values in the CTS-applied soil ranged from 44.1-51.7, 34.6-39.4, and 9.1-12.8%, respectively. Water-infiltration rates were significantly influenced by CTS. The cumulative infiltrated water in the soil varied from 21.3-34.7 cm. The basic infiltration rate was lower in the unamended soil and increased with an increase in the rate of CTS application. This study confirmed that the physical soil parameters improved after the permanent CTS application. Therefore, this application may be a suitable strategy for improving physical soil properties over time.

ABSTRACT Chromium contamination in soils affects plant growth and this metal can accumulate in plants tissues. In addition, Cr can affect soil microbial biomass and activity. On the other hand, plant growth-promoting rhizobacteria (PGPR) can protect plants against metals and, at the same time, promote plant growth and could alleviate adverse effects on microbial biomass. This study evaluated five PGPR on maize growth, Cr accumulation and soil microbial biomass in a Cr-contaminated soil. Five PGPR (LCC04, LCC41, LCC69, LCC81 and IPA403), isolated from soil under permanent application of composted tannery sludge and contaminated with Cr, were inoculated in maize plants grown in soils with (+Cr) and without (–Cr) Cr. In Cr-contaminated soil, LCC41 promoted the highest growth of maize, while LCC04 contributed with the highest N accumulation. The shoots of maize accumulated less Cr with LCC81, while LCC41 contributed to the highest Cr accumulation in roots. The translocation of Cr was highest with IPA403, while LCC81 contributed to reduce Cr translocation. In conclusion, LCC41 and LCC81 could be effective as PGPR inoculants to promote plant growth and reduce Cr accumulation in maize, respectively, in Cr contaminated soil.

ABSTRACT Oxisols are important soils that have been converted from native vegetation to croplands, and can affect soil biological properties such as microbial biomass and enzyme activity. Thus, the aim of this study was to evaluate the changes on soil microbial biomass and enzyme activity when native vegetation (NV) was converted to cropland (CL), such as maize or sugarcane in six oxisols from São Paulo state, Brazil. Soil microbial biomass C (MBC) and N (MBN), and the activity of arylsulphatase, dehydrogenase and fluorescein diacetate hydrolysis (FDA) were assessed in samples collected at 0-0.20 m. In general, MBC was higher under NV than CL (about + 40%), while MBN and FDA did not show a consistent pattern between NV and CL. All soils showed higher values of arylsulfatase (increased from 101 to 717%) and dehydrogenase (increased 15 to 220%) under NV than CL. In conclusion, soil microbial biomass C is usually higher under native vegetation than cropland. Arylsulphatase and dehydrogenase were the attributes that presented better differentiation between native and cropped soils.

ABSTRACT The inoculation of rhizobia in lima bean can increase its yield and contribute to smallholder farms. In this study, the potential of rhizobia in increasing the lima bean yield was evaluated in two regions from Piaui and Ceará states. The experiments were conducted in field comparing three rhizobia strains (UFPI32, UFPI38, UFPI59), one strain of reference to Phaseolus vulgaris (CIAT899) and two controls (with and without nitrogen). The parameters of nodulation, N accumulation and yield varied between treatments and locations. The nodule biomasses were higher in UFPI59 and UFPI32 (Piauí), and CIAT899 and UFPI32 (Ceará). The highest values of nodule size were found in treatments UFPI59 in both locations. Lima bean presented highest values of leaf N in UFPI59 and CIAT899. The highest values of grain yield were found in the treatment UFPI59 as compared to CIAT899 and the controls. The results confirmed the potential of UFPI59 in promoting nodulation, N accumulation, plant growth and yield of lima bean in both locations.

RESUMO: Este estudo avaliou a resposta do feijão-fava (Phaseolus lunatus L.) a aplicação de lodo de curtume compostado na nodulação, absorção de N e crescimento. Durante oito anos, o composto foi aplicado em doses de: 0, 2.5, 5, 10, e 20 Mg ha-1 (base seca). As plantas de feijão-fava mostraram maior nodulação nos tratamentos com o composto. Entretanto, os nódulos encontrados nestes tratamentos apresentaram menor biomassa, tamanho e diversidade do que os observados no tratamento sem composto. A acumulação de N aumentou com a aplicação da maior dose do composto (20 Mg ha-1), enquanto que houve um aumento nos teores de crômio na parte aérea com o aumento das doses do composto. Desta forma, o uso do lodo de curtume compostado, em longo prazo, aumenta a acumulação de crômio, aumentando a nodulação, enquanto diminui a diversidade de rizóbios nos nódulos.

ABSTRACT: This study evaluated the responses of lima bean (Phaseolus lunatus L.) to application of composted tannery sludge on nodulation, N uptake and plant growth. For eight years, the compost was applied at rates of: 0, 2.5, 5, 10, and 20 Mg ha-1 (dry basis). Plants of lima bean showed higher nodulation in treatments with compost; however, nodules reported in these treatments presented lower biomass, size and diversity than those reported in treatment without compost. Accumulation of N increased with the application of the highest rate (20 Mg ha-1), while there was an increase in chromium content in shoot with the increase in compost rates. Thus, the use of composted tannery sludge, in long-term, increases the accumulation of chromium in plants, increasing nodulation, while decrease rhizobia diversity in nodules.

RESUMO Bactérias promotoras de crescimento em plantas (BPCP) são encontradas em tecidos vegetais e promovem o crescimento vegetal por meio da secreção de hormônios e enzimas, ou auxiliando a absorção de nutrientes. Avaliaram-se quarenta isolados de BPCP para determinar seus efeitos sobre o crescimento de milho e sorgo. Estes isolados foram também comparados com plantas não inoculadas, como controles negativos (-N; sem fertilização nitrogenada) e positivos (+N; com fertilização nitrogenada). A altura, diâmetro de caule, massas secas da parte aérea e raízes, acúmulo de N e conteúdo de clorofila foram avaliados. Em ambos o milho e o sorgo, a altura, diâmetro do caule e a massa seca da parte aérea em plantas inoculadas com BPCP foram similares aos das plantas não inoculadas e fertilizadas com N, e as respostas da massa das raízes foram maiores que das plantas fertilizadas com N. Entretanto, os isolados de BPCP não promoveram acúmulo de N e conteúdo de clorofila semelhantes aos das plantas não inoculadas e fertilizadas com N. IPACC26 e IPACC30, ambos identificados como Bacillus subtilis, apresentaram melhores respostas para o crescimento das plantas e acúmulo de N do que os outros isolados.

ABSTRACT Plant growth-promoting bacteria (PGPB) are found in plant tissues and promote plant growth by secretion of hormones and enzymes, or by facilitating the nutrient uptake. This study assessed forty PGPB isolates to determine their effects on maize and sorghum growth. These isolates were also compared with uninoculated plants, as negative (-N; without N fertilization) and positive (+N; with N fertilization) controls. Plant height, stem diameter, shoot and root dry mass, leaf N accumulation and chlorophyll content were evaluated. For both the maize and sorghum, the height, stem diameter and shoot dry mass in plants inoculated with PGPB were similar to those of uninoculated plants supplied with N, and the responses for root mass were higher than in plants supplied with N. However, the PGPB isolates did not promote N accumulation and chlorophyll content similar to those of uninoculated plants supplied with N. The IPACC26 and IPACC30 isolates, both identified as Bacillus subtilis, resulted in better responses for plant growth and N accumulation than the other isolates.

RESUMO Avanços tecnológicos para melhorar a etapa de semeadura de forrageiras são importantes, pois, além de aumentarem a eficiência na operação, podem proporcionar ganhos no crescimento da planta. Objetivou-se avaliar a inoculação de Bacillus subtilis em sementes de Urochloa brizantha, utilizando-se procedimentos de revestimento, condicionamento fisiológico e armazenamento, bem como seus efeitos na germinação e no crescimento das plantas. Utilizou-se delineamento inteiramente casualizado, em esquema fatorial 2 × 3 × 5 + 1 [dois procedimentos de inoculação (revestimento e condicionamento), três inoculantes (B. subtilis AP-3, B. subtilis PRBS-1 e sem bactérias), cinco períodos de armazenamento (0, 30, 60, 90 e 120 dias) e controle (sementes nuas)], com cinco repetições. Foram utilizados dois lotes de sementes de U. brizantha, caracterizados como de maior e menor viabilidade. Após os tratamentos, parte das sementes foi utilizada para avaliar a promoção de crescimento de plantas em casa-de-vegetação, durante 180 dias, e o restante foi armazenado sob temperatura de 15 ºC, com avaliação da germinação a cada 30 dias, durante 120 dias. O condicionamento fisiológico apresentou melhor desempenho nas avaliações efetuadas para sementes de U. brizantha com B. subtilis. O revestimento e o condicionamento nas sementes de U. brizantha com menor viabilidade, com e sem inoculação de bactérias, aumenta a massa da parte aérea nas plantas após 180 dias de crescimento.

ABSTRACT Technological advances for improving the sowing stage of forage plants are important because, besides increasing the operation efficiency, they may also positively affect the plant growth. This study aimed to evaluate the inoculation of Bacillus subtilis in Urochloa brizantha seeds, using coating, physiological conditioning and storage procedures, as well as to observe its effects on seed storage and plant growth. A completely randomized design, in a 2 × 3 × 5 + 1 factorial scheme [two inoculation procedures (coating and conditioning), three inoculants (B. subtilis AP-3, B. subtilis PRBS-1 and without bacteria), five storage periods (0, 30, 60, 90 and 120 days) and control (bare seeds)], with five replicates, was used. Two lots of U. brizantha seeds were used, characterized as being of higher and lower viability. After the treatments, part of the seeds was employed to evaluate the plant growth promotion in a greenhouse, during 180 days, while the remaining portion was stored at a temperature of 25 ºC, with the seed germination being evaluated every 30 days, for 120 days. The physiological conditioning showed the best performance in the evaluations carried out for U. brizantha seeds with B. subtilis. The coating and conditioning of the U. brizantha seeds with lower viability, both with and without the inoculation of bacteria, increases the shoot mass of plants after 180 days of growth.

Abstract We used 16S rRNA sequencing to assess the archaeal communities across a gradient of Cerrado. The archaeal communities differed across the gradient. Crenarcheota was the most abundant phyla, with Nitrosphaerales and NRPJ as the predominant classes. Euryachaeota was also found across the Cerrado gradient, including the classes Metanocellales and Methanomassiliicoccaceae.

O objetivo do trabalho foi avaliar o efeito de biochar sobre a atividade das enzimas em um Latossolo sob Cerradono Brasil. O experimento foi conduzido em blocos casualizados consistindo de dois níveis de fertilização (0 e200 kg ha-1 NPK 00-20-20) e cinco níveis de biochar (0, 2, 4, 8 e 16 Mg ha-1). A atividade das enzimas urease,β-glucosidase, fosfatase acida e hidrolise de diacetato de fluoresceína - FDA, foi avaliada. As atividades daurease e β-glucosidase foram aumentadas pela aplicação do biochar com e sem fertilização química. As dosesintermediarias do biochar aumentaram a atividade do FDA no solo. Não houve efeito do biochar sobre a fosfataseacida. A aplicação do biochar promove aumentada atividade das enzimas urease, β-glucosidase e a atividadeenzimática total.

The objective of this work was to assess the long-term effect of biochar application on enzyme activity in anOxisol of Brazilian Cerrado. The experiment was conducted with a randomized block design consisting of thecombination of two levels of fertilization (0 and 200 kg ha-1, NPK 00-20-20 formulation) and five levels ofbiochar (0, 2, 4, 8 and 16 Mg ha-1). The activity of urease, β-glucosidase, acid phosphatase, and total soilenzyme (hydrolysis of fluorescein diacetate - FDA) were evaluated in soil samples. The activity of urease andβ-glucosidase were significantly increased by the application of biochar with and without chemical fertilization,respectively. Intermediate doses of biochar increased total soil enzyme activity. There was no effect of biocharon acid phosphatase activity. The application of biochar associated with chemical fertilization promotes urease,β-glucosidase and total soil enzyme activity.

RESUMO: O objetivo do estudo foi avaliar a resposta bioquímica do milho, sob stresse salino, inoculado com Bacillus subtilis. Quatro níveis de salinidade foram avaliados: 0mM, 50mM, 100mM e 200mM de cloreto de sódio (NaCl). Condições salinas influenciaram negativamente o crescimento do milho. Entretanto, a inoculação com B. subtilis melhorou o crescimento das plantas no maior nível de NaCl. O teor de clorofila decresceu enquanto que a prolina aumentou em plantas submetidas aos níveis salinos e inoculadas com B. subtilis. B. subtilis também aumentou o conteúdo de agua foliar. A inoculação com B. subtilis promove melhor crescimento das plantas sob salinidade e atenua os danos bioquímicos no milho.

ABSTRACT: The aim of this study was to evaluate the biochemical responses of maize, under saline stress, inoculated with Bacillus subtilis. Four levels of salinity were assessed: 0mM, 50mM, 100mM, and 200mM of sodium chloride (NaCl). Saline conditions influenced negatively maize growth. However, the inoculation of B. subtilis improved the plant growth at highest level of NaCl. Chlorophyll content decreased while proline increased in inoculated plants submitted to highest salt levels. Also, B. subtilis increased the relative water content in leaves. B. subtilis improves the plant growth under salinity and ameliorates the biochemical damages in maize.

RESUMO. A acumulação de cromo (Cr) no solo e nas plantas tem sido relatada após sucessivas aplicações de lodo de curtume, o que é motivo de preocupação tendo em vista que este elemento pode promover a contaminação ambiental e afetar a cadeia alimentar. Neste estudo, avaliou-se o crescimento e a acumulação de Cr no milho e caupi após sete anos de aplicações consecutivas de lodo de curtume compostado (LCC) em condições de campo. O experimento consistiu na aplicação de LCC em cinco doses: 0 (controle); 2,5; 5; 10 e 20 Mg ha-1 (base seca). O crescimento e o acúmulo de Cr no milho e no caupi foram avaliados aos 75 e 65 dias após a emergência das plantas, respectivamente. A aplicação de LCC aumentou a biomassa do milho e caupi. A acumulação de Cr foi semelhante para ambas as espécies, com maior acumulação relatada nas raízes. No entanto, a acumulação de Cr nos grãos diferiu entre as espécies: o caupi acumulou Cr, enquanto o milho não acumulou esse elemento nos grãos. Em conclusão, a aplicação de LCC proporcionou maior crescimento de plantas de milho e feijão-caupi, e ambas as espécies apresentaram respostas semelhantes à acumulação de Cr nas raízes e parte aérea.

ABSTRACT. Chromium (Cr) accumulation in soil and plants has been reported after successive applications of tannery sludge, which is a matter of concern because Cr can promote environmental contamination and affect the food chain. In this study, we evaluated the growth of and Cr accumulation in maize and cowpea after seven years of consecutive applications of composted tannery sludge (CTS) under field conditions. The experiment consisted of application of CTS at five levels: 0 (control), 2.5, 5, 10, and 20 Mg ha-1 (dry basis). The growth of and Cr accumulation in maize and cowpea were evaluated at 75 and 65 days after plant emergence, respectively. CTS application increased the shoot biomass of maize and cowpea. Accumulation of Cr was similar for both plant species, with higher accumulation in roots. However, Cr accumulation in grains differed as the CTS doses increased; cowpea accumulated more Cr while maize did not accumulate more Cr in grains with higher CTS doses. In conclusion, application of CTS led to higher growth of maize and cowpea plants, and both species exhibited similar Cr accumulation in roots and shoots.

RESUMO. Este estudo avaliou as propriedades do solo e a produtividade do feijão-caupi após seis anos de aplicações consecutivas de lodo de curtume compostado. Anualmente, o composto foi aplicado a 0, 2,5, 5, 10 e 20 Mg ha-1 e no sexto ano as propriedades químicas e físicas do solo e a produtividade do feijão-caupi foram avaliadas em experimento de blocos casualizados. Cr, P, K, C orgânico, pH, Ca, Na, e a capacidade de troca de cátions aumentaram linearmente após seis anos de aplicação do composto. A densidade do solo diminuiu linearmente enquanto a estabilidade de agregados aumentou após a aplicação do composto. Em consequência das mudanças nas propriedades químicas e físicas do solo, a produtividade do feijão-caupi apresentou resposta quadrática às doses de lodo de curtume compostado com máxima produtividade estimada encontrada na dose de 8,3 Mg ha-1. Em conclusão, as propriedades químicas e físicas do solo melhoraram após seis anos de aplicação do lodo de curtume compostado. Entretanto, o pH do solo, bem como os teores de Cr e Na aumentaram com aplicação do lodo de curtume compostado e estes parâmetros influenciaram a produtividade do feijão-caupi que apresentou resposta quadrática.

ABSTRACT. This study evaluated soil properties and cowpea yield after six years of consecutive amendment of composted tannery sludge. The compost was applied annually at 0, 2.5, 5, 10, and 20 Mg ha-1 and at the end of the sixth year, the chemical and physical properties of the soil were evaluated using a randomized block design. The Cr, P, K, Ca, Na and organic C contents and the pH and cation exchange capacity increased linearly after six years of compost amendment. The soil bulk density decreased linearly while the aggregate stability index increased after compost amendment. As a consequence of the changes in the chemical and physical properties of the soil, cowpea yield showed a quadratic response to the tannery rates, with an estimated maximum cowpea yield at 8.3 Mg ha-1. In conclusion, the soil chemical and physical properties improved after six years of composted tannery sludge amendment. However, the soil pH and the Cr and Na contents increased with composted tannery sludge amendment, which influenced the cowpea yield and resulted in a quadratic response to the compost.

O lodo de curtume compostado contém elevadas concentrações de elementos inorgânicos, como o crômio (Cr), que podem levar à poluição ambiental e influenciar na saúde humana. O comportamento envolvendo o Cr nas frações da matéria orgânica e no crescimento do feijão-caupi (Vigna unguiculata L.) foi estudado em solo arenoso, após quatro anos de aplicações anuais consecutivas de lodo de curtume compostado (LCC). Durante quatro anos, o LCC foi aplicado em parcelas permanentes (2 × 5 m) e incorporado no solo (0-20 cm), nas doses de 0; 2,5; 5,0; 10,0 e 20,0 Mg ha-1 (base seca). Esses tratamentos foram repetidos quatro vezes em blocos ao acaso. No quarto ano, o feijão-caupi foi semeado e cresceu por 50 dias, quando se analisaram as concentrações de Cr no solo, nas frações ácidos fúlvicos, ácidos húmicos e humina, nas folhas, nas vagens e nos grãos do feijão-caupi. O LCC promoveu aumento na concentração de Cr no solo. Entre as substâncias húmicas, a maior concentração de Cr foi encontrada na humina. As doses de LCC elevaram o teor de Cr nas folhas e grãos.

Tannery sludge contains high concentrations of inorganic elements, such as chromium (Cr), which may lead to environmental pollution and affect human health The behavior of Cr in organic matter fractions and in the growth of cowpea (Vigna unguiculata L.) was studied in a sandy soil after four consecutive annual applications of composted tannery sludge (CTS). Over a four-year period, CTS was applied on permanent plots (2 × 5 m) and incorporated in the soil (0-20 cm) at the rates of 0, 2.5, 5.0, 10.0, and 20.0 Mg ha-1 (dry weight basis). These treatments were replicated four times in a randomized block design. In the fourth year, cowpea was planted and grown for 50 days, at which time we analyzed the Cr concentrations in the soil, in the fulvic acid, humic acid, and humin fractions, and in the leaves, pods, and grains of cowpea. Composted tannery sludge led to an increase in Cr concentration in the soil. Among the humic substances, the highest Cr concentration was found in humin. The application rates of CTS significantly increased Cr concentration in leaves and grains.