Soil arthropod community responses to restoration in areas impacted by iron mining tailings deposition after Fundão dam failure.

In 2015, the failure of the Fundão dam in Mariana, Brazil released ~43 million m3 of iron mining tailings into the environment. Despite restoration initiatives in the following years, few studies-and most focused on revegetation-have evaluated the effectiveness of the restoration process in areas impacted by the disaster. We aimed to evaluate the responses of the arthropod community in areas impacted by iron mining tailings deposition from the Fundão dam that is in the restoration process. We defined sampling units in the riparian zone of the Gualaxo do Norte River, which is under restoration, and in a native not impacted riparian zone. We collected soil arthropods using pitfall traps and sampled environmental variables in the same sites. We used generalize least squares models (GLS) to test if the restored areas already presented values of arthropod diversity and functional group abundance similar to the reference area and to test which environmental variables are influencing arthropod diversity. We also tested how large the differences of arthropod community composition between the study areas and used the index of indicator species (IndVal) to verify which species could be used as an indicator of reference or restoration areas. The diversity of arthropods and the functional groups of detritivores and omnivores were higher in the native riparian zone. Understory density, soil density, organic matter content, and microbial biomass carbon were the environmental variables that significantly explained the diversity and species composition of arthropods. We show that restoration areas still have different soil arthropod diversity values and community composition when compared to reference areas. Evaluating the response of the arthropod community to the restoration process and long-term monitoring are essential to achieve a satisfactory result in this process and achieve a self-sustaining ecosystem.

Towards direct and eco-friendly analysis of plants using portable X-ray fluorescence spectrometry: A methodological approach.

The assessment of the nutritional status of plants is traditionally performed by wet-digestion methods using oven-dried and ground samples. This process requires sampling, takes time, and it is non-environmentally friendly. Agricultural and environmental science have been greatly benefited by in-field, ecofriendly methods, and real-time element measurements. This work employed the portable X-ray fluorescence spectrometry (pXRF) to analyze intact and fresh leaves of crops aiming to assess the effect of water content and leaf surface (adaxial and abaxial) on pXRF results. Also, pXRF data were used to predict the real concentration of macro- and micronutrients. Eight crops (bean, castor plant, coffee, eucalyptus, guava tree, maize, mango, and soybean) with contrasting water contents were used. Intact leaf fragments (∼2 × 2 cm), fresh or oven-dried (60 °C) were obtained to be analyzed via pXRF on both adaxial and abaxial surface. Conventional wet-digestion method was also performed on powdered material to obtain the concentration of macro- and micronutrients via ICP-OES. The data were subjected to descriptive statistics, principal component analysis (PCA) and random forest (RF) algorithm regression. RF was used to predict the real concentration of macro- and micronutrients based on pXRF measurements obtained directly on intact leaves. Water content had a significant effect on pXRF results. However, a positive correlation between the concentration of macro- and micronutrients obtained via pXRF directly on intact leaves and conventional analysis performed on powdered samples was obtained. PCA analysis allowed a clear differentiation of crops based on elemental composition. The concentrations of macro- and micronutrients were very accurately predicted via RF. Even elements not detected by pXRF (N and B) were satisfactory predicted. From this pilot study, it is possible to concluded that pXRF is feasible for in-field assessment of nutritional status of plants. Further studies are needed to obtain specific and robust calibrations for each crop.

Proximal sensing provides clean, fast, and accurate quality control of organic and mineral fertilizers.

Farms use large quantities of fertilizers from many sources, making quality control a challenging task, as the traditional wet-chemistry analyses are expensive, time consuming and not environmentally-friendly. As an alternative, this work proposes the use of portable X-ray fluorescence (pXRF) spectrometry and machine learning algorithms for rapid and low-cost estimation of macro and micronutrient contents in mineral and organic fertilizers. Four machine learning algorithms were tested. Whole (i.e., as delivered by the manufacturer) (CP) and ground (AQ) samples (429 in total) were analyzed to test the effect of fertilizer granulometry in prediction performance. Model validation indicated highly accurate predictions of macro (N: R2 = 0.92; P: 0.97; K: 0.99; Ca: 0.94, Mg: 0.98; S: 0.96) and micronutrients (B: 0.99; Cu: 0.99; Fe: 0.98; Mn: 0.91; Zn: 0.94) for both organic and mineral fertilizers. RPD values ranged from 2.31 to 9.23 for AQ samples, and Random Forest and Cubist Regression were the algorithms with the best performances. Even samples analyzed as they were received from the manufacturer (i.e., no grinding) provided accurate predictions, which accelerate the confirmation of nutrient contents contained in fertilizers. Results demonstrated the potential of pXRF data coupled with machine learning algorithms to assess nutrient composition in both mineral and organic fertilizers with high accuracy, allowing for clean, fast and accurate quality control. Sensor-driven quality assessment of fertilizers improves soil and plant health, crop management efficiency and food security with a reduced environmental footprint.

A Proximal Sensor-Based Approach for Clean, Fast, and Accurate Assessment of the Eucalyptus spp. Nutritional Status and Differentiation of Clones.

Several materials have been characterized using proximal sensors, but still incipient efforts have been driven to plant tissues. Eucalyptus spp. cultivation in Brazil covers approximately 7.47 million hectares, requiring faster methods to assess plant nutritional status. This study applies portable X-ray fluorescence (pXRF) spectrometry to (i) distinguish Eucalyptus clones using pre-processed pXRF data; and (ii) predict the contents of eleven nutrients in the leaves of Eucalyptus (B, Ca, Cu, Fe, K, Mg, Mn, N, P, S, and Zn) aiming to accelerate the diagnosis of nutrient deficiency. Nine hundred and twenty samples of Eucalyptus leaves were collected, oven-dried, ground, and analyzed using acid-digestion (conventional method) and using pXRF. Six machine learning algorithms were trained with 70% of pXRF data to model conventional results and the remaining 30% were used to validate the models using root mean square error (RMSE) and coefficient of determination (R2). The principal component analysis clearly distinguished developmental stages based on pXRF data. Nine nutrients were accurately predicted, including N (not detected using pXRF spectrometry). Results for B and Mg were less satisfactory. This method can substantially accelerate decision-making and reduce costs for Eucalyptus foliar analysis, constituting an ecofriendly approach which should be tested for other crops.

Clean quality control of agricultural and non-agricultural lime by rapid and accurate assessment of calcium and magnesium contents via proximal sensors.

Ca and Mg are the most important chemical elements in lime. Properly measuring Ca and Mg contents is essential to assess the quality of lime products. Quality control guarantees the adequate use of lime in industrial processes, in soils, and helps avoiding adulteration. Proximal sensors can aid in this process by determining Ca and Mg contents easily, rapidly and without producing chemical waste. The objective of this study was to evaluate the use an environmentally-friendly method of analyzing the quality of lime. We studied 1) the use of portable X-ray fluorescence (pXRF) to predict concentrations of Ca and Mg in lime, 2) tested if NixPro™ sensor can improve prediction accuracy and 3) tested if sample preparation methods (grinding) affect analyses. 74 samples of lime were analyzed by two different laboratories (lab. 1 = 38, lab. 2 = 36). All samples submitted to pXRF and NixPro™ analyses. Sensor analyses were done in whole (CP) and ground (AQ) samples to test the effect of sample preparation in prediction performance. High correlation was found between Ca and Mg contents measured via pXRF and laboratory analyses. Mg-CP presented the highest correlation coefficient (r = 0.81); Mg-AQ, the lowest (0.57). Predictions presented good performance (R2 > 0.68); Mg had the best results (0.86). Separating models per laboratory showed that some datasets are harder to model, probably due to variability in the source material (limestone). The addition of NixPro™ data contributed to improve prediction accuracy, although slightly. Predictions using CP samples presented the best results, especially for Mg, indicating that grinding is not necessary. This pioneer study demonstrated that fused proximal sensors can be used to rapidly and easily determine contents of Ca and Mg in soil amendments without producing chemical waste.

Purple acid phosphatases in coffee-genome-wide identification and the transcriptional profile of selected members in roots upon Pi starvation.

Phosphorus (P) availability is determinant for crop productivity and, despite the sufficient amount of this nutrient in arable land, most of it remains insoluble, leading to the need of high fertilizer input. To cope with P scarcity forecasts and also for cropping costs alleviation, genotypes better adapted to promote P solubilization and absorption are required, especially for perennial crops. Coffee is one of these important perennial crops cultivated in soils with low P availability, and thus we aimed to study adaptive strategies to coffee genotypes in acquire phosphorus. In this study, we focused on rhizosphere phosphatase activity, a major characteristic related to P solubilization from organic pools. To explore the genetic basis of this characteristic, we firstly identified 29 Purple Acid Phosphatases (PAP) genes in C. canephora genome and selected five candidates with higher potential to encode secreted PAPs. We found that C. arabica genotypes have diverse profiles of rhizosphere phosphatase activity, as well as microbial biomass carbon, which we measured to explore the impact of the plant on microbiota and also to discriminate the phosphatase activity origin (plant or microorganism-derived). We selected two C. arabica cultivars with contrasting phosphatase activity and found that one PAP gene has a correlated gene expression profile with this characteristic. This work explores coffee adaptative responses to P starvation conditions, and the information provided can further contribute to breeding programs aiming better adapted genotypes for sustainable agriculture in face of current challenges. Supplementary Information: The online version contains supplementary material available at 10.1007/s13205-022-03399-6.

Potentially toxic elements in iron mine tailings: Effects of reducing soil pH on available concentrations of toxic elements.

Tailings from iron mining are characterized by high concentrations of iron and manganese oxides, as well as high pH values. With these characteristics, most of the potentially toxic elements (PTE) contained in the tailings are somewhat unavailable. The aim of the present study was to evaluate how a reduction in the pH of iron mine tailings may affect PTE availabilities. The tailings were collected on the banks of the Gualaxo do Norte River (Mariana, MG, Brazil), one of the main areas impacted by the rupture of the Fundão Dam (Barragem de Fundão). A completely randomized experimental design was used, including five pH values (6.4, 5.4, 4.3, 3.7, and 3.4) and five replications. The concentrations of the PTE (Ba, Cr, Cd, Co, Cu, Fe, Mn, Pb, Ni, and Zn) were determined after extraction following different methodologies: USEPA 3051A, DTPA, Mehlich-1, Mehlich-3, and distilled water. A comparison of the available concentrations of the elements in the tailings with those in a soil not impacted by tailings shows that Cr, Cd, Cu, Fe, Mn, Ni, Ba, and Co were higher in the soil impacted by the tailings. The different methods used for evaluating the availability of PTE in the tailings at various pH exhibited the following decreasing order in relation to the quantity extracted: Mehlich-3 > Mehlich-1 > DTPA > distilled water. However, regarding sensitivity to change in pH, the order was DTPA > water > Mehlich-1 > Mehlich-3. The increases in the concentrations of PTE due to the reduction in the pH of the tailings did not lead to concentrations that exceed the limits of Brazilian regulations. The DTPA extractant exhibited higher coefficients of correlation between the PTE concentrations and the pH of the tailings, proving to be suitable for use in areas affected by the deposition of iron mine tailings.

Chemical, physical, and biological attributes in soils affected by deposition of iron ore tailings from the Fundão Dam failure.

Monitoring degraded areas is essential for evaluation of the quality of the rehabilitation process. In this study, we evaluate how the physical and chemical characteristics of the mixture of iron ore tailings with the soil have affected the soil microbial biomass and activity in areas along the Gualaxo do Norte River after the Fundão Dam disaster. Composite soil samples were collected from areas that were impacted (I) and not impacted (NI) by the tailings. The following attributes were evaluated: chemical element content; soil density, porosity, and texture; microbial biomass carbon; basal respiration; and enzyme activity and density of microbial groups (bacteria, actinobacteria, fungi, arbuscular mycorrhizae, phosphate solubilizers, cellulolytic microorganisms, nitrifiers, ammonifiers, and diazotrophs). According to result, the deposition of tailings increased the pH and the soil available P, Cr, Fe, and Mn content and reduced organic matter. The physical and biological attributes were negatively affected, with increases in the silt content and density of the soil, and reduction in macroporosity and in the microbial biomass and activity of the soil (respiration and enzymes) in the impacted area. However, the impacted areas exhibited greater densities of some microbial groups (cellulolytic microorganisms, nitrifiers, and diazotrophic bacteria). Modifications in the organic matter and silt content are the main attributes associated with deposition of the tailings that affected soil microbial biomass and microbial activity. This may affect erosive conditions and the functionality of the ecosystem, indicating an imbalance in this environment. In contrast, the higher density of some microbial groups in the impacted areas show the high rehabilitation potential of these areas.

Rhizobia and endophytic bacteria isolated from rainforest fragments within an iron ore mining site of the Eastern Brazilian Amazon.

The aim of the present study was to isolate and evaluate the diversity of rhizobial and endophytic bacterial strains from undisturbed native rainforests within an iron ore mining site of the Serra Norte de Carajás in the Eastern Brazilian Amazon region to assess their biotechnological utility in reclamation of areas. Experiments were conducted to capture strains from samples of the soil of these forests at the sites Arenito II, Noroeste II, and Sul IV using Macroptilium atropurpureum and Mimosa acutistipula var. ferrea as trap host plants. Only M. atropurpureum nodulated, and the different bacterial strains were isolated from its nodules. There was no difference in the number of nodules among the areas, but the Arenito II bacterial community was the most efficient, indicated by the aboveground biomass production and suitable shoot mass/root mass ratio. Fifty-two (52) bacterial isolates were obtained, distributed in five groups, including nodulating and endophytic bacteria: 32 from Arenito II, 12 from Noroeste II, and 8 from Sul IV. The nodulating Bradyrhizobium genus was common to the three areas, whereas Paraburkholderia was found only in Arenito II. The nodD1 gene was amplified in all the strains of both nodulating genera. Strains of the nodulating genus Methylobacterium were also isolated from the three areas; however, they did not nodulate the host of origin, and their nodD1 gene was not amplified. Endophytic strains were also isolated from the genera Paenibacillus, Pantoea, and Leifsonia in Arenito II, Leifsonia in Noroeste I, and Paenibacillus in Sul IV. The greater nodulation and rhizobial and endophytic bacterial diversity observed in Arenito II were probably due to the more suitable edaphic properties of the area. The isolated strains were incorporated in the collection of the Department of Soil Science of UFLA and will be investigated in relation to their symbiotic characteristics with native host plants, as well as their ability to perform other biological processes.

Environmental drivers of shifts on microbial traits in sites disturbed by a large-scale tailing dam collapse.

This study aimed to assess the most affected traits related to microbial ecophysiology and activity and investigate its relationships with environmental drivers in mine tailings spilled from the Fundão dam at disturbed sites across Gualaxo do Norte river, Minas Gerais, Brazil. The mine tailings are characterized by increased pH value, silt percentage, and bulk density, while clay percentage, organic carbon (Corg), total nitrogen (Nt), and moisture contents are reduced. Microbial biomass, enzymatic activities (arylsulfatase, ß-1,4-glucosidase, acid and alkaline phosphatases), and the total microbial activity potential (FDA hydrolysis) were generally lower in tailings compared to undisturbed reference soil (Und). Enzyme-based indexes (GMea, WMean, and IBRv2) showed microbial communities with significantly lower degradative efficacy in the tailings than Und in all sites (R2 ≥ 0.94, p < 0.001). Non-metric multidimensional scaling and distance-based redundancy analysis revealed that microbial communities exhibited significant differentiation (R2 adjusted = 0.73, p = 0.0001) between mine tailings and Und over the different studied sites, which was strongly influenced by changes on physicochemical properties (pH, Corg and Nt contents, the predominance of small-sized particles of silt, and bulk density) and the presence of Se, Cr, Fe, and Ni, even at low concentrations. Our study suggests that the physicochemical properties and the presence of low bioavailable concentrations of heavy metals in dam tailings promote shifts on microbial communities through reductions in the C storage and biogeochemical cycling of nutrients by these communities compared to those in undisturbed reference soils surrounding and, therefore, has negative implications for the ecosystem functioning.

Integrating environmental variables by multivariate ordination enables the reliable estimation of mineland rehabilitation status.

Despite the wide variety of variables commonly employed to measure the success of rehabilitation, the assessment and subsequent definition of indicators of environmental rehabilitation status are not simple tasks. The main challenges are comparing rehabilitated sites with target ecosystems as well as integrating individual environmental and eventually collinear variables into a single tractable measure for the state of a system before effective indicators that track rehabilitation may be modeled. Furthermore, a consensus is lacking regarding which and how many variables need to be surveyed for a reliable estimation of rehabilitation status. Here, we propose a multivariate ordination to integrate variables related to ecological processes, vegetation structure, and community diversity into a single estimation of rehabilitation status. As a case, we employed a curated set of 32 environmental variables retrieved from nonrevegetated, rehabilitating and reference sites associated with iron ore mines from the Urucum Massif, Mato Grosso do Sul, Brazil. By integrating this set of environmental variables into a single estimation of rehabilitation status, the proposed multivariate approach is straightforward and able to adequately address collinearity among variables. The proposed methodology allows for the identification of biases towards single variables, surveys or analyses, which is necessary to rank environmental variables regarding their importance to the assessment. Furthermore, we show that bootstrapping permitted the detection of the minimum number of environmental variables necessary to achieve reliable estimations of the rehabilitation status. Finally, we show that the proposed variable integration enables the definition of case-specific environmental indicators for more rapid assessments of mineland rehabilitation. Thus, the proposed multivariate ordination represents a powerful tool to facilitate the diagnosis of rehabilitating sites worldwide provided that sufficient environmental variables related to ecological processes, diversity and vegetation structure are gathered from nonrehabilitated, rehabilitating and reference study sites. By identifying deviations from predicted rehabilitation trajectories and providing assessments for environmental agencies, this proposed multivariate ordination increases the effectiveness of (mineland) rehabilitation.

Arbuscular Mycorrhizal Fungi Favor the Initial Growth of Acacia mangium, Sorghum bicolor, and Urochloa brizantha in Soil Contaminated with Zn, Cu, Pb, and Cd.

This study evaluated the effect of inoculation with a mixture of spores of arbuscular mycorrhizal fungi (AMF) (Glomus macrocarpum, Paraglomus occultum, and Glomus sp.) on the initial establishment of Acacia mangium, Sorghum bicolor, and Urochloa brizantha in soil contaminated with heavy metals. The experiment was conducted in a greenhouse, in plastic pots containing 1.8 kg of soil, which presented 7200, 1140, 480, and 72 mg of Zn, Cu, Pb, and Cd, respectively. The chlorophyll content (SPAD index) of inoculated plants of A. mangium and U. brizantha was higher than those of non-inoculated plants (p < 0.05). No differences were detected for the concentration of heavy metals in plant shoots, whether the plant was inoculated or not. However, inoculated plants had greater root length (S. bicolor and U. brizantha) (p < 0.05) and greater plant height (A. mangium) (p < 0.05). The present results demonstrate that the beneficial effects of AMF on plant growth and the alleviation of contaminants are imperative factors for the rehabilitation of soils contaminated with heavy metals.

Arbuscular mycorrhizal fungal communities in an iron mining area and its surroundings: Inoculum potential, density, and diversity of spores related to soil properties / Comunidades de fungos micorrízicos arbusculares em área de mineração e seu entorno: Potencial de inóculo, densidade e diversidade de esporos relacionados a atributos do solo

ABSTRACT Arbuscular mycorrhizal fungi (AMF) interact symbiotically with most plant species, facilitating revegetation of areas under rehabilitation. The aim of this study was to evaluate the inoculum potential, density, and diversity of AMF spores in five environments, as well as the relation of species with soil properties. Soil samples were collected in five environments in a mining area and its surroundings in the Quadrilátero Ferrífero, Minas Gerais (Brazil): tailings piles in rehabilitation with grass, canga, Cerrado, native forest, and eucalyptus plantation; these samples were subjected to chemical and physical analyses. Spores were directly extracted from field samples and from trap cultures (TCs) established in two locations in the Southeast and South regions of Brazil for taxonomic identification of the species. Species richness, the Shannon diversity index (H'), and equitability were determined. Principal component analysis (PCA) was used to identify soil properties that most influenced AMF occurrence. Spore density showed no significant difference among the environments. A total of 59 AMF species were found. This is the first report of the occurrence of Acaulospora nivalis and Acaulospora alpina in Brazil. Higher H' and species richness in the field were found in tailings piles and lower in canga. Canga showed higher inoculum potential. The development of TCs in two locations allowed a wider diversity of AMF species to be captured. Environments of the Quadrilátero Ferrífero are hotspots of AMF diversity, and the soil pH and exchangeable S and P contents are the properties that best explain the distribution of AMF species.

RESUMO Fungos micorrízicos arbusculares (AMF) interagem simbioticamente com a maioria das espécies de plantas, facilitando a revegetação de áreas sob reabilitação. O objetivo deste trabalho foi de avaliar o potencial de inóculo, densidade e diversidade de esporos de AMF em cinco ambientes, e a relação das espécies com atributos do solo. Amostras de solo foram coletadas em cinco ambientes em área de mineração e seu entorno no Quadrilátero Ferrífero, Minas Gerais (Brasil): pilha de rejeitos em reabilitação com capim, canga, Cerrado, mata nativa e plantação de eucalipto, e submetidas a análises química e física. A extração de esporos direto de amostras de campo e de culturas armadilha (TCs), estabelecidas em dois locais nas regiões Sul e Sudeste do Brasil, foi feita para identificação taxonômica das espécies. Foram determinados riqueza de espécies, índice de diversidade de Shannon (H') e equitabilidade. Análise de componentes principais (PCA) foi utilizada para identificar atributos do solo que mais influenciaram a ocorrência de AMF. A densidade de esporos não diferiu significativamente entre os ambientes. Um total de 59 espécies de AMF foram encontradas, destacando-se o primeiro relato de ocorrência de Acaulospora nivalis e Acaulospora alpina no Brasil. Maiores H' e riqueza de espécies no campo foram encontradas em pilhas de rejeitos e menores em canga, embora canga tenha apresentado maior potencial de inóculo. A condução de TCs em dois locais proporcionou captura de maior diversidade de espécies de AMF. Ambientes do Quadrilátero Ferrífero são hotspots de diversidade de AMF e o pH do solo e teores trocáveis ​​de S e P são os atributos que melhor explicam a distribuição das espécies de AMF.

X-ray microanalytical studies of mineral elements in the tripartite symbiosis between lima bean, N2-fixing bacteria and mycorrhizal fungi.

The symbiosis between legumes, arbuscular mycorrhizal (AM) fungi, and N2-fixing bacteria (NFB) provides mutual nutritional gains. However, assessing the nutritional status of the microorganisms is a difficult task. A methodology that could assess this status, in situ, could assist managing these organisms in agriculture. This study used X-ray microanalyses to quantify and locate mineral elements in structures formed in a tripartite symbiosis. Lima bean (Phaseolus lunatus L. Walp) was cultivated in pots under greenhouse conditions, to which we have added AM fungal isolates (Glomus macrocarpum and Acaulospora colombiana) and NFB (Bradyrhizobium japonicum) inocula. Uninoculated control plants were also included. Symbionts were evaluated at the onset of flowering. Quantification of the mineral elements in the symbiotic components was performed using energy dispersive X-ray spectroscopy (EDX) and a scanning electron microscopy (SEM) was used to identify structures. EDX analysis detected 13 elements with the most abundant being N, Ca, and Se, occurring in all tissues, Fe in roots, Ni and Al in epidermis and P and Mo in nodules. Elemental quantification in fungal structures was not possible. The distribution of elements was related to their symbiotic function. X-ray microanalysis can be efficiently applied for nutritional diagnosis in tripartite symbiosis.

Arbuscular mycorrhizal fungi and colonization stimulant in cotton and maize / Fungos micorrízicos arbusculares e estimulante da colonização na cultura do algodoeiro e do milho

ABSTRACT: The objective of this study was to evaluate the effects of inoculation with different arbuscular mycorrhizal fungi native to Cerrado, associated with the application of colonization stimulant (7-hydroxy, 4’-methoxy-isoflavone) at the initial growth of cotton and maize plants in a greenhouse. The experiment was carried out in a completely randomized design and 7x2 factorial scheme, with five species of arbuscular mycorrhizal fungi and combined inoculation (uniting all species in equal proportion) and native fungi, in the presence and absence of colonization stimulant in maize and cotton crops. Shoots dry matter (SDM), roots dry matter (RDM), mycorrhizal colonization and accumulation of calcium, zinc and phosphorus in the SDM were evaluated at flowering. Inoculation of arbuscular mycorrhizal fungi and the use of colonization stimulant at low density of arbuscular mycorrhizal fungi propagules was beneficial to plant development. Inoculation with mycorrhizal fungi demonstrated different effects for the various parameters evaluated in cotton and maize, and the application of colonization stimulant promoted higher mycorrhizal colonization and initial growth in cotton, when associated with native AMF, and in corn, when associated with inoculation with Dentiscutata heterogama, Gigaspora margarita and Rhizophagus clarus.

RESUMO: O objetivo deste estudo foi avaliar os efeitos da inoculação com diferentes fungos micorrízicos arbusculares nativos do Cerrado, associados à aplicação de estimulante de colonização (7-hidroxi, 4’-metoxi-isoflavona) no crescimento inicial de plantas de algodão e milho em casa de vegetação. O experimento foi conduzido em delineamento inteiramente casualizado e esquema fatorial 7x2, com cinco espécies de fungos micorrízicos arbusculares e inoculação combinada (unindo todas as espécies em proporção igual) e fungos nativos, na presença e ausência de estimulante de colonização em culturas de milho e algodão. Avaliou-se a massa de matéria seca (SDM), matéria seca de raízes (RDM), colonização micorrízica e acúmulo de cálcio, zinco e fósforo na SDM. A inoculação com fungos micorrízicos arbusculares e o uso de estimulante de colonização em baixa densidade de propágulos de fungos micorrízicos arbusculares foi benéfico para o desenvolvimento da planta. A inoculação com fungos micorrízicos mostrou efeitos diferentes para os vários parâmetros avaliados no algodão e no milho, e a aplicação de estimulante de colonização promoveu maior colonização micorrízica e crescimento inicial no algodão quando associado à fungos micorrízicos arbusculares nativa e no milho quando associado à inoculação com Dentiscutata heterogama, Gigaspora margarita e Rhizophagus clarus.

Management systems and soil use on fractions and stocks of organic carbon and nitrogen total in cerrado latosol / Sistemas de manejo e uso do solo sobre as frações e estoque de carbono e nitrogênio em latossolo de cerrado

Cerrado areas are agricultural frontiers of Brazil, being important to know the dynamics of carbon and nitrogen in agricultural production systems. The objective of this study was to evaluate the effects of management and soil use in fractions and stocks organic carbon and nitrogen in the Cerrado soil. The experiment was conducted in Latosol with four treatments: native Cerrado (CE), no-tillage 18 years (NT), coffee 10 years (CF) and integrated system for agriculture (ISA) three years, evaluating the fractions and stocks of organic carbon and nitrogen in three depths. Soil management systems, at all depths, were not able to recover the organic carbon, nitrogen and their stocks in relation to the Cerrado. In the surface layer there was a decrease in the organic carbon content of 21, 33 and 46% for NT, CF and ISA respectively. Also there was a reduction in the nitrogen content in the surface layer of 33, 36 and 59% for the NT, CF and ISA respectively. Organic carbon varied from 74.3 Mg ha-1 in the CE, 58.8 Mg ha-1 in NT, 56.4 Mg ha-1 in CF and 50.8 Mg ha-1 in ISA. It was concluded that the total organic carbon, nitrogen and its fractions were effective in demonstrating the effects of managements and soil use; that of no-tillage and coffee were not efficient in the recovery of stocks of carbon and nitrogen requiring managements with more carbon input and the integrated production system is still in consolidation process.

Áreas de cerrado são fronteiras agrícolas do Brasil, sendo importante conhecer a dinâmica do carbono e nitrogênio em sistemas de produção agrícola. O objetivo deste estudo foi avaliar os efeitos do manejo e uso do solo em frações e estoques de carbono orgânico e nitrogênio em solo de Cerrado. O experimento foi realizado em Latossolo Vermelho com quatro tratamentos: Cerrado nativo (CE), plantio direto 18 anos (PD), área com café 10 anos (CF) e sistema integrado de produção agropecuária (SIPA) 3 anos avaliando as frações e estoques de carbono orgânico e nitrogênio em três profundidades. Os sistemas de manejo do solo, em todas as profundidades, não foram capazes de recuperar o teor carbono orgânico, nitrogênio e seus estoques em relação ao Cerrado. Na camada superficial houve diminuição no teor de carbono orgânico de 21, 33 e 46% para PD, CF e SIPA, respectivamente. Também verificou-se redução no teor de nitrogênio na camada superficial de 33, 36 e 59% para o PD, CF e SIPA, respectivamente. Os estoques de carbono orgânico variaram de 74,3 Mg ha-1 no CE, 58,8 Mg ha-1 no PD, 56,4 Mg ha-1 no CF e 50,8 Mg ha-1 no SIPA. Conclui-se que o carbono orgânico total, nitrogênio e suas frações foram eficientes para demonstrar os efeitos dos manejos e uso do solo; que os sistemas de PD e CF não foram eficientes na recuperação dos estoques de carbono e nitrogênio necessitando de manejos com maior entrada de carbono e que SIPA ainda esta em processo de consolidação.

Mycorrhization stimulant based in formononetin associated to fungicide and doses of phosphorus in soybean in the cerrado / Estimulante de micorrização a base de formononetina associado à fungicida e doses de fósforo em soja no cerrado

Arbuscular mycorrhizal fungi (AMF) are obligatory biotrophics, which complicates the feasibility of producing inoculants. Thus, the discovery of substances capable of stimulating mycorrhizal colonization, like the isoflavone formononetin emerges as a promising alternative to explore the benefits of AMF native soil in extensive crops system. The aim of this study was evaluate the application of the isoflavone formononetin (7-hydroxy-4'-methoxy isoflavone) andfungicide via seed in Cerrado soil in no-tillage system and fertilization with two doses of phosphorus in soybean under field and controlled conditions. In the field experiment the treatments were three levels of formononetin (0, 0.5 and 1.0 mg Formononetin seed-1) in the absence and presence of fungicide (Carbendazim + Thiram commercial mix) applied to seeds with two doses of phosphorus (100 % and 33% of the recommended fertilization). The study was conducted until the maturation of soybeans. The greenhouse conditions experiment was implemented with the same treatments used in the field research and the flowering stage of the soybean plant was simulated water stress during 10 days, returning to normal irrigation until to harvest the soybean grain. Applying of formononetin stimulated the increased of mycorrhizal colonization, number of nodules, vegetative growth and soybean production in the greenhouse. In the field research the treatments contributed to attenuate the negative effect of the fungicide Carbendazim + Thiram in soybean reflecting increased soybean production and adequate supply of soil phosphorus besides high density of propagules of natives AMF that contributed to reduce the benefits of stimulating mycorrhizal (formononetin) in this research.

Os fungos micorrízicos arbusculares (FMAs) são biotróficos obrigatórios, o que dificulta a viabilidade da produção de inoculantes. Com a descoberta de substâncias capazes de estimular a colonização micorrízica, o isoflavonóide formononetina surge como uma alternativa promissora para explorar os benefícios dos FMAs nativos do solo em cultivos extensivos. O objetivo do presente estudo foi de avaliar os efeitos das aplicações do isoflavonóide formononetina (7-hydroxy-4'-methoxy isoflavone) e de fungicida nas sementes em solo do Cerrado no sistema de plantio direto com duas doses de fósforo na cultura da soja em campo e em casa de vegetação. No experimento de campo os tratamentos foram três doses de formononetina (0, 0,5 e 1,0 mg de Formononetina semente-1); na ausência e presença de fungicida (Mistura comercial Carbendazim + Thiram) aplicado via semente e duas doses de fósforo (100 % e 33 % da adubação recomendada). O experimento de casa de vegetação foi implantado com os mesmos tratamentos utilizado no estudo em campo e na fase de florescimento das plantas de soja foi simulado um estresse hídrico, por 10 dias, retornando a irrigação normal até a colheita dos grãos. A aplicação de formononetina estimulou aumento da colonização micorrízica, número de nódulos, crescimento vegetativo e a produção de grãos soja em condições de déficit hídrico simulado em casa de vegetação e no no estudo de campo contribui para amenizar o efeito negativo dos fungicidas nas plantas de soja refletindo em aumento da produção da soja.

Atributos indicadores de qualidade em solos de cerrado no entorno do Parque Nacional das Emas, Goiás / Attributes quality indicators in cerrado soils surrounding the Parque Nacional das Emas, state of Goiás, Brazil

A incorporação de áreas nativas aos sistemas produtivos tem provocado alterações em ecossistemas, especialmente em regiões tropicais e, devido ao uso inadequado do solo, tem resultado na rápida perda do carbono orgânico. O objetivo deste estudo foi avaliar o impacto de sistemas de manejo e uso do solo sobre a biomassa e a atividade microbiana, assim como o estoque de carbono orgânico total e suas frações em um Latossolo Vermelho distrófico e um Neossolo Quartzarênico de Cerrado. Os sistemas de manejo e uso no Neossolo Quartzarênico foram: Cerrado nativo, integração lavoura-pecuária, pastagem, plantio direto 1 (soja/braquiária) e plantio direto 2 (milho/braquiária). No Latossolo Vermelho os sistemas foram: Cerrado nativo, integração lavoura-pecuária, plantio convencional, plantio direto 3 (soja/nabo/milho/nabo) e plantio direto 4 (soja/milho/sorgo/soja). Para ambos os solos avaliados, o sistema de integração lavoura-pecuária promoveu melhorias nos teores de carbono da biomassa microbiana e nos estoques de carbono do solo. No Neossolo Quartzarênico, os sistemas de plantio direto não foram capazes de promover incrementos no carbono da biomassa microbiana, na atividade da urease, na hidrólise do diacetato de fluoresceína e no estoque do carbono da fração leve. No Latossolo Vermelho, o sistema de plantio convencional promoveu redução no estoque de carbono orgânico total e no carbono da fração leve livre do solo. Além disso, os sistemas conservacionistas desse solo, apesar de incrementarem o estoque de carbono orgânico do solo, promoveram perdas de carbono da fração leve em relação ao Cerrado nativo.

Incorporation of native areas to production systems induced changes in ecosystems, especially in tropical regions, due to inappropriate land use, resulting in the rapid loss of organic carbon. This study aimed to evaluate impact of soil management and land use on biomass and microbial activity, as well as soil organic carbon and its fractions in an Oxisol and Quartzipsamment in Cerrado. Management and land use systems in Quartzipsamment were native vegetation, crop-livestock integration, pasture, no-till 1 (soybean/Brachiaria) and two no-till 2 (corn/Brachiaria). In Oxisol the systems were native vegetation, crop-livestock integration, conventional tillage, no-till 3 (soybean /radish/corn/radish) and no-till 4 (soybean/ corn/sorghum/soybean). Both soils evaluated, integrated crop-livestock improved the microbial biomass levels and soil carbon pools. In Quartzipsamment, management and land use systems not increased microbial biomass carbon, urease activity, hydrolysis of fluorescein diacetate and the carbon stock of the light fraction. In Oxisol, conventional tillage system decreased soil organic carbon and total carbon in the free light fraction soil. Furthermore, although it increased the organic carbon soil losses, the soil conservation systems enhanced the light fraction carbon in relation to native vegetation.

Atividade da enzima nitrato redutase em milho cultivado sob diferentes níveis de adubação nitrogenada e potássica / Activity of the enzyme reductase nitrate in corn cultivated under different levels of nitrogen and potassium fertilization

Em função de seu uso na alimentação humana e animal e de um elevado potencial produtivo, o milho constitui-se num dos mais importantes cereais cultivados e comercializados no mundo. O objetivo deste trabalho foi avaliar o efeito de diferentes doses de nitrogênio e potássio na atividade da enzima redutase do nitrato na cultura do milho em casa de vegetação. Foram utilizadas cinco doses de nitrogênio (0; 50; 100; 150 e 200kg ha-1) e cinco doses de potássio (0; 40; 80; 120 e 160kg ha-1). A atividade da enzima foi estimada in vivo após as plantas atingirem quatro folhas totalmente desdobradas. Utilizou-se o método baseado no princípio de que a quantidade de nitrito liberada por fragmentos de tecidos vivos num tampão, na presença de uma agente permanente e do substrato, reflete a atividade potencial da enzima. A atividade da enzima nitrato redutase sofreu influência significativa da interação das doses de nitrogênio e potássio, já que a interação N=100kg ha-1 e K=40kg ha-1 proporcionou as melhores médias do experimento. A partir dessa dose, o aumento no fornecimento tanto de nitrogênio quanto de potássio promoveu redução da atividade enzimática.

Because of the use in human feeding, animal, and high productive potential, corn is considered to be one of the most important cultivated and commercialized cereals in the world. The aim of this research was to evaluate the effect of different potassium doses and nitrogen in the activity of the enzyme nitrate reductase in the corn culture in a greenhouse environment. Five dosages of nitrogen (0; 50; 100; 150 and 200kg ha-1) and five potassium dosages (0; 40; 80; 120 and 160kg ha-1) were used. The activity of the nitrate reductase was esteemed, in vivo after the plants reached four leaves totally unfolded. The method that was used is based on the principle of the amount of nitrite liberated by fragments of alive tissue in a buffer in the presence of a permanent agent and substrate, reflects the potential in situ activity of the enzyme nitrate reductase. The activity of the enzyme nitrate reductase suffered significant influence of the f nitrogen and potassium dosage interaction, where the interaction N=100kg ha-1 and K=40kg ha-1 provided the best medium of the experiment. From this dosage on, the increase of nitrogen and potassium supplement caused a reduction of the enzymatic activity.

Qualidade física de neossolo quartzarênico submetido a diferentes sistemas de uso agrícola / Physical quality of quartzarenic neosol submitted to different systems of agricultural use

Apesar da existência de informações descritivas sobre solos arenosos das regiões tropicais, àquelas referentes ao manejo e conservação são escassas. No presente estudo, objetivou-se avaliar as alterações dos atributos físico-hídricos de um Neossolo Quartzarênico Órtico em função do uso e manejo com vistas à definição de sistemas de manejo sustentáveis. O estudo foi conduzido no município de Mineiros, GO, em áreas submetidas a cinco sistemas de uso e manejo do solo, sendo: Pastagem (PAS), Plantio direto de Soja (PDS) e de milho (PDM), Integração agricultura-pecuária (IAP) e cerrado nativo (CER). Coletaram-se cinco amostras por sistema nas camadas de 0 a 10 e 10 a 20 cm no inverno de 2005 e verão de 2006, para avaliação da densidade do solo, micro e macroporosidade e condutividade hidráulica do solo saturado. Os atributos físico-hídricos avaliados não variaram com a época de amostragem. Os valores de microporosidade indicam baixa retenção da água disponível às plantas. O uso agrícola do solo promoveu alterações em todos os atributos avaliados. A macroporosidade do solo foi o atributo mais sensível às alterações estruturais decorrentes do manejo, contudo, sem apresentar valores considerados limitantes ao crescimento das plantas. A redução da condutividade hidráulica do solo saturado em áreas de atividade antrópica comprometeu a qualidade do solo e pode afetar a recarga do lençol freático e aumentar o processo erosivo. A manutenção da cobertura vegetal do solo é considerada medida-chave para exploração agropecuária nessas áreas.

In spite of the existence of descriptive information on sandy soils in tropical areas, information regarding management and conservation is scarce. The present study aimed at evaluating changes in the physical-hydric attributes of Orthic Quartzarenic Neosol resulting from use and management having in view the definition of sustainable management systems. The study was carried out in the municipal district of Mineiros, GO, in areas submitted to five systems of use and management of the soil: pasture (PAS), soybeans under no-till (PDS), corn under no-till (PDM), agriculture-livestock integration (IAP), and native savannah (NSAV). Five samples were collected per area, at the depths of 0-10 and 10-20 cm, in the winter of 2005 and in the summer of 2006, for evaluation of bulk density, micro and macroporosity, and saturated soil hydraulic conductivity. The physical-hydric attributes evaluated did not vary within the sampling period. Microporosity values indicate low retention of the water available to the plants. Agricultural land use of the soil promoted alterations in all the appraised attributes. The macroporosity of the soil was the attribute most sensitive to structural changes resulting from management, but it did not, however, present values considered limiting to plant growth. The reduction of saturated soil hydraulic conductivity in human activity areas endangered the quality of the soil and it can affect the recharge of the water table and increase the erosive process. Maintenance of the soil covering is considered the key measure for agricultural exploration in these areas.