ABSTRACT High acidity and low soil P availability in the soils from the Pampa natural grasslands generally limit the forage growth and economic return. Thus, to increase the economic return and avoid environmental degradation and biodiversity loss due to replacement by intensive cropping systems, it is essential to improve the soil P availability. This study aimed to diagnose the nutritional status of the pluri-specific natural grasslands amended with different history of P sources. Additionally, we also try to indicate the most appropriate range of soil P availability for maximizing forage growth. The experiment started in 1997 in an area of Pampa natural grasslands in the state of Rio Grande do Sul, Brazil. The treatments evaluated the application of Gafsa hyperphosphate (HP) and triple superphosphate (SP) for four years (1997, 1998, 2002, and 2010). Soil and aboveground biomass sampling were performed five times from October 2010 to March 2011 to access aboveground biomass production, botanical composition, soil available P, and N and P nutrition index. Greater P availability in the soil amended with SP produced more forage and resulted in a higher P accumulation than in the soil amended with HP. The ideal range of soil P availability in the soils of natural grasslands ranged from 14 to 20 mg kg˗1, varying for different plant species. The species Paspalum plicatulum and Aristida laevis produce less aboveground biomass and accumulate less P in their tissue than Dichantelium sabulorum and Eustachys uliginosa, and P. notatum. Therefore, areas of natural grasslands dominated by D. sabulorum, E. uliginosa and P. notatum demand higher soil P availability to maintain high forage production. Soil P fertilization of pluri-specific natural grasslands in the Brazilian Pampa biome must consider the dominant forage species in the area and the soil P availability.

ABSTRACT Plants can stablish symbiosis with arburcular mycorrhiza fungi (AMF), in which the fungus uses carbohydrates synthesized by plant photosynthesis in exchange for soil nutrients. AMF symbiosis may benefit plants by increasing the rates of nutrient uptake, tolerance to abiotic stresses, protection against pathogens and, by promoting resilience of forest species to adverse conditions. Knowledge about the diversity of mycorrhizas may help stablish relationships of species selection, AMF production and inoculation. Therefore, the objective of this review is to compile information to identify existing patterns in AMF diversity in Brazilian forest ecosystems. Compilation was based in 74 articles (in English, Portuguese and Spanish languages) searched in the Web of Knowledge and selected for having the keywords “forest”, “diversity”, “mycorrhizal” and “Brazil”, and that identified AMF species by spore morphology. Compilation resulted in a list of 164 AMF species and indicated that AMF species are not plant host specific but they are selected by environmental conditions where the host grows. Some AMF species were ubiquitous and some were rare in forest ecosystems. Rare AMF species may be an artefact of AMF identification because, in comparison to molecular tools, spore morphology may underestimate AMF diversity. Four AMF species, Acaulospora scrobiculata, Acaulospora foveata, Clareoideglomus etunicatum and Glomus macrocarpum, were ubiquitous to several biomes, existed in different stage of forest succession and seemed to be adapted to different forest managements. Therefore, A. scrobiculata, A. foveata, A. mellea, C. etunicatum and G. macrocarpum could have potential to be used as AMF inoculant in forest species.

Agricultural sustainability depends on the soil functionality in mechanisms that support plant and animal productivity, water and nutrient cycling, and contamination buffering. Therefore, roots and soil samples from two typical agricultural systems in the Atlantic Forest biome were collected, to evaluate their sustainability through the relationship between roots and soil functionality. The agricultural systems were annual fields as, maize (Zea mays L.) and perennial, palm (Bactris gasipaes K.). The roots were collected from monoliths (48 x 30 x 5 cm) and after, they were gently washed. The root profiles with the IDRISI and SAFIRA softwares were scanned and then analyzed. Soil samples were submitted to evaluations of microbial-C biomass and physical and chemical attributes. The palm field produced more dry matter roots and had greater root area and volume than the maize field (cf. 1.37 versus 0.14 t ha-1). Considering the 0-5 cm layer, the palm field sustained larger mean weight diameter of soil aggregates (4.2 versus 3.4 mm) and held higher saturation of bases (65 versus 47 %) than the maize. Although the palm field did not have larger total organic C content (20 versus 24 g kg-1), it stimulated microbial biomass (MB-C; 942 versus 428 mg MB-C kg-1 soil) and decreased metabolic quotient (0.023 versus 0.034 mg C-CO2 g-1 MB-C h-1) in relation to maize field. This clear relationship between root and soil attributes indicates that better root development contributes to improve soil functionality and for consequence the sustainability of agricultural systems. Therefore, crop systems and soil managements that privilege root growth are better choice to reach the agricultural sustainability

La sustentabilidad agrícola depende de la funcionalidad del suelo en mecanismos que suporten la productividad vegetal y animal, el ciclo del agua y de los nutrientes y el tamponamiento de contaminación. Para tanto, las muestras de raíces del suelo de dos sistemas agrícolas típicos en el bioma de la Mata Atlántica fueron colectadas para evaluar su sustentabilidad a través de la relación entre raíces y funcionalidad del suelo. Los sistemas agrícolas eran cultivo anuales, maíz (Zea mays L.) y perennes palmeras, (Bactris gasipaes K.). Las raíces fueron colectadas de monolitos (48 x 30 x 5 cm) y lavadas suavemente. Los perfiles de raíz fueron digitalizados y después analizados con los softwares IDRISI y SAFIRA. Las muestras del suelo fueron sometidas a evaluaciones de biomasa microbiana-C y atributos físicos y químicos. El cultivo de palmeras produjo más materia seca de raíces y tuvo mayor área y volumen de raíz que el campo de maíz (cf. 1,37 contra 0,14 t ha-1). Considerando la camada de 0 a 5 cm, el campo de palmeras sostuvo mayor peso medio de diámetro de los agregados del suelo (4,2 contra 3,4 mm) y mantuvo mayor saturación de bases (65 contra 47 %) que el maíz. Aunque el cultivo de palmeras no tenga una cantidad total de C orgánico total (20 contra 24 g kg-1), estimuló la biomasa microbiana (MB-C; 942 versus 428 mg MB-C kg-1) y disminuyó el cociente metabólico (0,023 contra 0,034 mg C-CO2 g-1 MB-C h-1) en relación al cultivo de maíz. Esta relación clara entre los atributos de la raíz y del suelo indica que un mejor desarrollo de raíces contribuyó para mejorar la funcionalidad del suelo y, consecuentemente, la sustentabilidad de los sistemas agrícolas. Por tanto, los sistemas de culturas y manejo del suelo que privilegian el crecimiento de las raíces son mejores opciones para alcanzar la sustentabilidad agrícola

Eucalyptus benthamii is a tree species commonly planted in subtropical areas, including the Southern Brazil, due to its tolerance to low temperatures and frosts. The success of E. benthamii plantation depends on the seedlings vigor during transplantation. We hypothesized that improvement of chemical and biological properties of growth substrate would produce more vigorous E. benthamii seedlings. Thus, we applied increasing doses (0, 0.5, 1.0, 1.5 and 2.0 g per seedling) of the organic fertilizer Bacsol, which carries a consortium of potential plant growth promoting microorganisms, on the substrate, and measured the growth and development of E. benthamii seedlings. Two experiments were performed in 2011 and 2012. The first experiment included measurements in four growth stages to estimate the relative growth rates. The second one ended at the time that seedlings reached standard heights for transplantation (about ± 20 cm). Measurements on plant height, stem diameter, shoot dry weight and relative growth rates indicated that the application of Bacsol improved E. benthamii seedlings vigor and decreased the time needed in nursery, from 150 days to 90 days. The best responses occurred at doses from 1.3 g to 1.5 g per seedling. The data demonstrated that application of Bacsol in substrate is a promising technology to increase E. benthamii seedlings vigor.

Eucalyptus benthamii es una especie arbórea comúnmente plantada en áreas subtropicales, incluyendo el sur de Brasil, debido a su tolerancia a bajas temperaturas y heladas. El éxito de su plantación depende del vigor de las plántulas durante el trasplante. Se planteó la hipótesis que la mejora de las propiedades químicas y biológicas del sustrato de crecimiento produciría plantas más vigorosas de E. benthamii. Por ello, en el substrato se aplicaron dosis crecientes (0, 0,5, 1,0, 1,5 y 2,0 g por planta) del fertilizante orgánico Bacsol, que contiene un consorcio de potenciales microorganismos promotores del crecimiento vegetal y se midió el crecimiento de plantas de E. benthamii. Los experimentos fueron realizados en 2011 y 2012. El primero incluyó cuatro etapas de crecimiento para estimar tasas de crecimiento relativas. El segundo terminó cuando las plantas alcanzaron alturas estándar para trasplante (= 20 cm). La altura de la planta, el diámetro del tallo, el peso seco de los brotes y las tasas de crecimiento relativo indicaron que Bacsol mejoró el vigor de las plantas y disminuyó el tiempo necesario en vivero, de 150 a 90 días. Las mejores respuestas ocurrieron con 1,3 a 1,5 g por planta. Los datos demostraron que la aplicación de Bacsol al sustrato es una tecnología prometedora para aumentar el vigor de las plantas de E. benthamii.

A produtividade e sustentabilidade das culturas têm sido frequentemente relacionadas com a matéria orgânica e a biomassa microbiana do solo, especialmente devido ao seu papel na ciclagem de nutrientes do solo. Este trabalho teve como objetivo avaliar a biomassa de fungos e bactérias do solo por microscopia de epifluorescência e a densidade de esporos de fungos micorrízicos arbusculares (FMAs) em lavouras de cana de açúcar (Saccharum officinarum L.) sob diferentes manejos. Foram coletadas amostras de solo de lavouras manejadas com ou sem queima, com ou sem colheita mecanizada, com ou sem aplicação de vinhaça e de matas ciliares adjacentes. As amostras de solo foram coletadas a 10 cm de profundidade e mantidas a 4°C até o momento das análises. A biomassa fúngica variou de 25 a 37µg C g-1 de solo seco e a bacteriana, de 178 to 263µg C g-1 de solo seco. A razão média entre a biomassa fúngica e bacteriana do solo nos diferentes manejos de canaviais foi de 0,14. A densidade de esporos de FMAs variou de 9 a 13 esporos g-1 de solo seco. Os diferentes manejos da cana de açúcar não afetaram significativamente a densidade de esporos de FMAs. Em geral, não foram encontradas mudanças significativas na biomassa microbiana nos diferentes manejos de solo com cana de açúcar em comparação com a mata ciliar. Todavia, a soma das biomassas fúngicas e bacterianas (208 a 301µg C g-1 de solo seco) determinadas por microscopia de epifluorescência foram similares a resultados da biomassa total do solo encontrados em outros estudos com métodos tradicionais (e.g. fumigação-extração). Os resultados evidenciam que a determinação da razão fungo/bactéria por microscopia de epifluorescência, associada a outros parâmetros, é uma metodologia promissora para compreender a funcionalidade microbiana e ciclagem de nutrientes sob diferentes manejos do solo.

Crop productivity and sustainability have often been related to soil organic matter and soil microbial biomass, especially because of their role in soil nutrient cycling. This study aimed at measuring fungal and bacterial biomass by epifluorescence microscopy and arbuscular mycorrhizal fungal (AMF) spore density in sugarcane (Saccharum officinarum L.) fields under different managements. We collected soil samples of sugarcane fields managed with or without burning, with or without mechanized harvest, with or without application of vinasse and from nearby riparian native forest. The soil samples were collected at 10cm depth and storage at 4°C until analysis. Fungal biomass varied from 25 to 37µg C g-1 dry soil and bacterial from 178 to 263µg C g-1 dry soil. The average fungal/bacterial ratio of fields was 0.14. The AMF spore density varied from 9 to 13 spores g-1 dry soil. The different sugarcane managements did not affect AMF spore density. In general, there were no significant changes of microbial biomass with crop management and riparian forest. However, the sum of fungal and bacterial biomass measured by epifluorescence microscopy (i.e. 208-301µg C g-1 dry soil) was very close to values of total soil microbial biomass observed in other studies with traditional techniques (e.g. fumigation-extraction). Therefore, determination of fungal/bacterial ratios by epifluorescence microscopy, associated with other parameters, appears to be a promising methodology to understand microbial functionality and nutrient cycling under different soil and crop managements.

Neste estudo foram avaliados atributos qualitativos e quantitativos da microbiota do solo, visando monitorar alterações por diferentes manejos do solo e das culturas. As avaliações foram feitas em um ensaio a campo, conduzido há 14 anos em Londrina, PR, sob plantio convencional (PC) ou plantio direto (PD) e com sucessão (S) (soja/trigo) ou rotação (R) (tremoço/milho/aveia-preta/soja/trigo/soja/trigo/soja) de culturas, quando todos os sistemas estavam com soja no estádio de florescimento pleno. Os incrementos no C e N da biomassa microbiana (CBM e NBM) no PD foram de 114 e 157 %, respectivamente, em comparação ao PC; além disso, o quociente metabólico (qCO2) foi inferior em 37 % no PD, indicando maior eficiência metabólica da microbiota do solo. Não foram detectadas diferenças nesses atributos em função dos sistemas de rotação e sucessão de culturas. A diversidade genética da comunidade bacteriana total do solo foi superior no PD e inferior no PC com sucessão de culturas. Em relação à fixação biológica do N2, a massa, o N total e a fração de N-ureídos acumulados na parte aérea e a eficiência dos nódulos em fixar N2 foram superiores no PD. A diversidade genética dos rizóbios foi afetada, principalmente, pelo manejo das culturas, sendo superior com a rotação, provavelmente pelo maior número de espécies de plantas. Contudo, com a rotação ocorreu decréscimo na eficiência do processo de fixação biológica do N2, o que pode estar relacionado com os teores mais elevados de N no solo, ou com a menor pressão de seleção por bactérias eficientes. Desse modo, para microrganismos do solo com função específica, como os rizóbios, a diversidade genética pode ser distinta da funcionalidade.

In this study, quantitative and qualitative microbiological parameters were evaluated to detect differences related to soil and crop management. The study was carried out in a field experiment installed 14 years ago on a Rhodic Eutrudox, in Londrina, PR, Brazil. Treatments were a combination of a crop sequence (S) (soybean/wheat) and a crop rotation (R) (lupin/maize/black oat/soybean/wheat/soybean/wheat/soybean), either under conventional tillage (CT) or no-tillage (NT). Evaluations were performed when all systems were under the soybean cropping season, at full flowering. Amounts of microbial biomass carbon and nitrogen (MB-C and MB-N, respectively) were 114 and 157 % higher in NT than in CT. Furthermore, the metabolic quotient (qCO2) was lower under NT, indicating higher metabolic efficiency of the soil microbes. These parameters were not affected by the crop sequence/rotation. Genetic diversity of the total soil bacterial community was higher under NT and lower in the CT system with crop sequence. Regarding the biological N2 fixation, it was found that plant biomass, total N and fraction of N-ureides in shoots, as well as nodule efficiency, were higher under NT. Genetic diversity of rhizobia was affected mainly by crop management and was higher under crop rotation, probably due to the greater number of plant species. However, crop rotation decreased the efficiency of the biological N2 fixation process, which may be related to more abundant N in the soil or to a lower selection pressure for efficient rhizobia. For soil microbes with specific functions, e.g., rhizobia, genetic diversity may therefore differ from functionality.

Os térmitas (cupins) do solo carregam partículas de solo para construção de seus ninhos e desta forma, podem afetar algumas características pedológicas. Este estudo teve como objetivo verificar a influência da atividade de térmitas nas características do solo através de análises das propriedades químicas e físicas e da composição mineralógica de amostras coletadas na base, topo e centro dos ninhos e área de solo adjacente. Quatro cupinzeiros e suas respectivas áreas adjacentes foram aleatoriamente amostrados em Lages, Capão Alto, Painel, São José do Cerrito e Coxilha Rica (Santa Catarina). Os resutados das análises químicas mostraram que o conteúdo de K, P, Ca, Mg e C orgânico no centro dos ninhos foi maior e o pH menor em relação à área de solo adjacente. Não houve diferenças na composição dos argilominerais entre os ninhos e as áreas adjacentes, no entanto, a composição granulométrica dos solos diferiu entre os dois locais. Térmitas podem modificar outras características do solo, tais como as propriedades físicas e químicas, devido ao elevado volume de solo transportado per ascensum para construção dos cupinzeiros (entre 20,9 m³ ha-1 e 136,6 m³ ha-1 neste estudo) que promove a bioturbação e afeta a ciclagem de nutrientes.

Soil-feeding termites transport soil for mound building, and this process can affect soil characteristics. To verify the influence of soil termite activity on soil characteristics, samples were collected from top, bottom and center of termite mounds, and of the adjacent area, to assess chemical and physical properties and mineralogical composition. Four replicates of termite mounds and respective adjacent areas were randomly sampled in Lages, Capão Alto, Painel, São José do Cerrito and Coxilha Rica (State of Santa Catarina, southern Brazil). Results of chemical analyses showed a greater content of K, P, Ca, Mg and organic C in the inner part of termite mounds, accompanied by lower pH in relation to soil of the adjacent area. There were no differences regarding clay mineral composition between termite mounds and adjacent soil, however the proportion of sand and clay differed between them. It is concluded that termites modify soil characteristics due to great volume of soil transported per ascensum for mound construction (varying from 20.9 m³ ha-1 to 136.6 m³ ha-1, in this study) which promotes a strong pedo-bio-perturbation and affects nutrient cycling and soil physical properties.