Impact of historical soil management on the interaction of plant-growth-promoting bacteria with maize (Zea mays L.).

Edaphic factors can modulate the effects of microbial inoculants on crop yield promotion. Given the potential complexity of microbial inoculant responses to diverse soil management practices, we hypothesize that sustainable management of soil and water irrigation may improve soil quality and enhance the effects of plant growth-promoting bacteria (PGPB). Consequently, the primary objective was to assess the effectiveness of microbial inoculants formulated with Herbaspirillum seropedicae (Hs) and Azospirillum brasilense (Ab) on maize growth in soils impacted by different historical conservation management systems. We evaluated two soil management systems, two irrigation conditions, and four treatments: T0 - without bioinoculant and 100% doses of NPK fertilization; T1 - Hs + humic substances and 40% of NPK fertilization; T2 - Ab and 40% of NPK fertilization; T3 - co-inoculation (Hs + Ab) and 40% of NPK fertilization. Using a reduced fertilization dose (40% NPK) associated with microbial inoculants proved efficient in increasing maize shoot dry mass : on average, there was a 16% reduction compared to the treatment with 100% fertilization. In co-inoculation (Hs + Ab), the microbial inoculants showed a mutualistic effect on plant response, higher than isolate ones, especially increasing the nitrogen content in no-tillage systems irrigated by swine wastewater. Under lower nutrient availability and higher biological soil quality, the microbial bioinputs positively influenced root development, instantaneous water use efficiency, stomatal conductance, and nitrogen contents.

Agroecological coffee management increases arbuscular mycorrhizal fungi diversity.

Agroecology aims to maintain ecosystem services by minimizing the impact of agriculture and promoting the use of biological potential. Arbuscular mycorrhizal fungi (AMF) are elements which are key to improving crop productivity and soil quality. It is pertinent to understand how agricultural management in the tropics affects the AMF spatio-temporal community composition, especially in crops of global importance, such as coffee (Coffea arabica L.). Soil and root samples were collected from three localities under three management systems (agroecological, conventional and forest fragment), during the phenological stages of coffee (flowering, grain filling, harvesting). Spores were extracted for morphological identification and molecular community analysis by PCR-DGGE. Dendrograms were prepared and the bands were sequenced and analyzed by bioinformatics. No differences were observed in the richness of morphospecies between management systems, localities and period, but little is known about tropical species. Molecular analysis showed that the agroecological management system was similar to natural forest and with a higher diversity indices than conventional management. Locality and period of sample affect AMF community composition. It is necessary to associate classical taxonomic evaluations with molecular biological techniques because different approaches can lead to different outcomes. This study contributes to the understanding of the impact of agriculture management systems on AMF and provides evidence that agroecology is a management system applicable to sustainable coffee production.

Soil, water, and nutrient losses from management alternatives for degraded pasture in Brazilian Atlantic Rainforest biome.

The objective of this study was to evaluate sediment, water and nutrient losses from different pasture managements in the Atlantic Rainforest biome. A field study was carried out in Alegre Espiríto Santo, Brazil, on a Xanthic Ferralsol cultivated with braquiaria (Brachiaria brizantha). The six pasture managements studied were: control (CON), chisel (CHI), fertilizer (FER), burned (BUR), plowing and harrowing (PH), and integrated crop-livestock (iCL). Runoff and sediment samples were collected and analyzed for calcium (Ca), magnesium (Mg), potassium (K), phosphorus (P) and organic carbon contents. Soil physical attributes and above and below biomass were also evaluated. The results indicated that higher water loss was observed for iCL (129.90mm) and CON (123.25mm) managements, and the sediment losses were higher for CON (10.24tha-1) and BUR (5.20tha-1) managements when compared to the other managements. Majority of the nutrients losses occurred in dissolved fraction (99% of Ca, 99% of Mg, 96% of K, and 65% of P), whereas a significant fraction of organic carbon (80%) loss occurred in a particulate form. Except for P, other nutrients (Ca, Mg and K) and organic carbon losses were higher in coarse sediment compared to fine sediment. The greater losses of sediment, organic carbon, and nutrients were observed for CON followed by BUR management (p<0.05). Our findings indicated that the traditional pasture management adopted in the Atlantic Rainforest needs to be rethought and burned management should be avoided. Based on the water, soil, and nutrient losses from various practices, to reduce pasture degradation, farmers should adopt edaphic practices by applying lime and fertilize to improve pasture growth and soil cover, and reducing soil erosion in the hilly Brazilian Atlantic Rainforest biome.

Simulation of use and management effects on the soil organic matter pools of the atlantic forest biome, Brazil / Simulação dos efeitos do uso e manejo sobre os compartimentos da matéria orgânica no solo no bioma da florestal atlântica, Brasil

Soil organic matter simulation in areas under long term use provides an important tool to test future scenarios, enabling the adoption of less impressive management to environment. The purposes of the present study were: a) to simulate, with the Century model, the impacts on soil organic matter, according to the adoption of different crop management, with forage purposes, in two different soils and; b) to validate the Century model for these managements and soils by comparing the simulated values with those measured in the field. The following treatments were evaluated: in the Oxisol area ­ brachiaria pasture with fertilizer (BPw) and without fertilizer (BPwo), the Incept area ­ corn for silage (CS), Coast Cross pasture (CC) and sugar cane field (SC). The microbial biomass represented the active compartment of carbon and nitrogen, the particle free light fraction represented the slow compartment of carbon and nitrogen and the passive pools were determined by the difference of the total minus the active and the slow pools (passive = total ­ (active + slow)). The Century model showed great potential to simulate the dynamics of the total C and N stocks for tropical soils, which was confirmed by similarity between the simulated values and those measured in the field.

Simulação da matéria orgânica no solo em longo prazo é uma ferramenta importante para testar cenários futuros, permitindo a adoção de uma gestão menos impactante ao meio ambiente. Os objetivos do presente estudo foram: (a) simular o modelo do CENTURY, com os impactos sobre a matéria orgânica do solo em função do manejo diferente em culturas com fins de forragem em dois solos diferentes e, (b) comparar o estoque simulado com os reais de matéria orgânica, medidos no campo. Foram avaliados os seguintes tratamentos: na área de Latossolo Vermelho em uso de pastagem com fertilizantes (BPW) e sem fertilizante (BPwo), no Cambissolo - testou os usos com milho para silagem (CS), e pastagem com coast cross (CC) e um plantio de cana-de-açúcar (SC). A biomassa microbiana ativa representa compartimento de carbono e do nitrogênio, a fração leve livre de partículas representada o compartimento lento do carbono e de nitrogênio e os compartimentos passivos foram determinadas pela diferença do total menos o ativo e os compartimentos lentos (Passivo Total = - Ativo + Lento). O modelo Century demonstrou grande potencial para simular a dinâmica do C total e estoques de N para solos tropicais, o que foi comprovado por semelhança entre os valores simulados e medidos no campo.

Indicadores participativos de qualidade do cafeeiro conilon e do solo em sistema agroflorestal e convencional / Participatory indicators of quality in conilon coffee and soil in agroforestry system and conventional

A avaliação participativa de agroecossistemas é uma técnica rápida e de fácil aplicação para avaliação da sustentabilidade de propriedades de agricultura familiar. Este trabalho teve por objetivo implementar e avaliar, em cinco propriedades rurais de Alegre (ES), uma metodologia prática e de fácil aplicação por agricultores na avaliação participativa de características indicadoras de qualidade do Coffea canephora e do solo. Foram avaliadas cinco áreas com sistemas de manejo convencional e conservacionista agroecológico de cultivo. A partir de observações feitas a campo notas foram atribuídas aos indicadores de qualidade do café e solo. As notas variam de 1 a 10 em 3 intervalos ( 0-5; 5-8 e 8-10). Gráficos em forma de radar foram elaborados, representando o estado de cada indicador, e comparados com as diferentes percepções dos produtores e técnicos da área agrícola. O diagrama da qualidade do café indicou no sistema convencional a alta dependência de insumos externos (nota 2) e grande efeito da radiação solar pela falta de cobertura vegetal na seca de ponteiros (nota 3). Já para a qualidade do solo no sistema conservacionista, notou-se controle da erosão (nota 9), maior profundidade da camada escura (nota 9) e maior diversidade de plantas (nota 9,5). Sistemas conservacionistas agroecológicos de cultivo promovem maior sustentabilidade da agricultura familiar e otimizam a produção agrícola.

Participatory evaluation of agroecosystems is a fast and easy application for assessing the sustainability of family farming properties. This study aimed to implement in five farms in Alegre (ES), a practical and easily applied by farmers in participatory evaluation of quality characteristics Coffea canephora and soil. Five sites were evaluated with conventional management system agroecological farming and conservation. From observations made in the field notes were assigned to the indicators of quality of coffee and soil. The scores range from 1 to 10 in 3 steps (0-5, 5-8 and 8-10). Graphics in the form of radar were plotted, representing the state of each indicator and being compared with the different perceptions of producers and technicians of the agricultural site. The diagram indicates the quality of coffee in the conventional high dependence on external inputs (note 2) and large effect of solar radiation by the lack of vegetation in dry hands (note 3). As for the soil quality in conservation system showed better erosion control (note 9), increased depth of the dark layer (note 9) and more diversity of plants (note 9.5). Agroecological farming systems conservationists promote greater sustainability of family farming and optimize agricultural production.

Impacto da conversão floresta - pastagem nos estoques e na dinâmica do carbono e substâncias húmicas do solo no bioma Amazônico / Impact of forest-pasture conversion on stocks and dynamics of soil carbon and humic substances in the Amazon

O presente estudo avaliou as consequências do desmatamento e a utilização do solo com Brachiaria brizantha em relação ao estoque e dinâmica de C e frações húmicas em duas floresta-pastagem no Acre. A primeira localizada sequências município de Rio Branco em área de Floresta Aberta com bambu e palmeira e duas pastagens de B. brizantha de 3 e 10 anos com predomínio de Argissolo Vermelho-Amarelo alítico plíntico. O segundo situado no município de Senador Guiomard em área de Floresta Densa e pastagem de B. brizantha de 20 anos em Latossolo Vermelho-Amarelo distrófico. Em cada local foram coletadas, em triplicata, amostras de solos nas profundidades de 0-5, 5-10, 10-20 e 20-40 cm. Nestas amostras foram avaliadas as características físico-químicas, o C das substâncias húmicas e da matéria orgânica leve, e a composição isotópica do solo e das respectivas frações orgânicas até 1 m de profundidade, determinando o percentual de C derivado da pastagem e da floresta. Houve incremento nos estoques de C do solo e nos valores de δ13C do solo com o tempo de utilização da pastagem, em ambas as sucessões. A porcentagem de C derivado de pastagem foi expressiva na camada superficial do sistema com 20 anos de uso, com proporções que chegaram a 70 por cento do C total. Os valores de δ13C para os ácidos húmicos variaram de -12,19 a -17,57 ‰, indicando maior proporção de C derivado da pastagem. A estabilidade estrutural da MOS, inferida pela relação humina com as frações ácido fúlvico e ácido húmico (HUM/FAF+FAH), tenderam a diminuir nos ecossistemas de pastagem quando comparada com as florestas naturais.

This study evaluates the impacts of converting natural Amazonian forests in Brazil to pasture dominated by Brachiaria brizantha concerning to C dynamics and humic fractions in two soil chronosequences in the Acre State, Brazil. The first site, dominated by Plinthic Red Yellow Argissols (Ultisols), is located in the municipality of Rio Branco and comprises an area of bamboo- and palm-dominated open forest with two B. brizantha pastures of 3 and 10 years old. The second site, dominated by a dystrophic Red Yellow Latosol (Oxisol), is located in the municipality of Senador Guiomard and comprises an area of dense forest and a 20-year old B. brizantha pasture. In each site soil samples were collected in triplicate at depths of 0-5, 5-10, 10-20 and 20-40 cm. Samples were evaluated for physical and chemical characteristics, C of humic substances and light organic matter, and the isotopic composition of soil and its organic fractions to 1 m depth, determining the percentage of C derived of both grassland and forest. There were increases in stocks of soil C and δ13C soil with the time of grazing in both sites. The percentage of C derived from pasture was much higher in the surface layer of the Senador Guiomard site following 20 years of grazing, with proportions that reached 70 percent of the total C. δ13C values for the humic acids ranged from -12.19 to -17.57 ‰, indicating a higher proportion of C derived from pasture. The MOS structural stability inferred by the relationship of the humin with both fulvic acid and humic acid fractions (HUM / FAF + FAH) tended to decrease in grassland ecosystems when compared with native forests.

Modelo Century de dinâmica da matéria orgânica do solo: equações e pressupostos / Century model of soil organic matter dynamics: equations and assumptions

A modelagem de processos biológicos tem por objetivos o planejamento do uso da terra, o estabelecimento de padröes ambientais e as estimativas dos riscos reais e potenciais das atividades agrícolas e ambientais. Diversos modelos têm sido criados nos últimos 25 anos. Century é um modelo mecanístico que analisa em longo prazo a dinâmica da matéria orgânica do solo e de nutrientes no sistema solo-planta em diversos agroecossistemas. O submodelo de matéria orgânica do solo possui os compartimentos ativo (biomassa microbiana e produtos), lento (produtos microbianos e vegetais, fisicamente protegidos ou biologicamente resistentes à decomposiçäo) e passivo (quimicamente recalcitrante ou também fisicamente protegido) com diferentes taxas de decomposiçäo. Equaçöes de primeira ordem säo usadas para modelar todos os compartimentos da matéria orgânica do solo e a temperatura e umidade do solo modificam as taxas de decomposiçäo. A reciclagem do compartimento ativo e a formaçäo do passivo säo controladas pelo teor de areia e de argila do solo, respectivamente. Os resíduos vegetais säo divididos em compartimentos dependentes dos teores de lignina e nitrogênio. Por meio do modelo, pode-se relacionar matéria orgânica aos níveis de fertilidade e ao manejo atual e futuro, otimizando o entendimento das transformaçöes dos nutrientes em solos de diversos agroecossistemas