Funcionalidade das micorrizas arbusculares em cafezais agroecológicos
Data
2011-09-29
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Universidade Federal de Viçosa
Resumo
A Zona da Mata de Minas Gerais é uma região que historicamente tem sofrido intensa degradação de solos e perda da floresta nativa. Nesse ambiente, os solos tendem a ser distróficos e álicos, ocorrendo solos eutróficos apenas nas partes mais baixas do relevo. O profundo manto de intemperismo que associado ao relevo acidentado, favorece a perda de nutrientes. Nessa região, a fragmentação das propriedades é acompanhada de uma distribuição bastante desigual de recursos, onde os pequenos agricultores não têm terra suficiente para a reprodução da unidade familiar. A cultura do café (Coffea arabica L.) é uma das principais atividades produtivas da região, praticada em solos de encosta, principalmente por pequenos agricultores. Nesse contexto, a implantação de sistemas baseados nos princípios agroecológicos é uma alternativa que permite a conservação do solo e a manutenção da biodiversidade local. Em 1994, os agricultores familiares do município de Araponga, Zona da Mata Mineira, optaram por conciliar a produção de café com a sustentabilidade ambiental, surgindo a idéia da produção de café agroecológico, agroflorestal ou a pleno sol. Os sistemas agroecológicos são manejados com o baixo uso de adubos químicos, a não utilização de agrotóxico e o não revolvimento dos solos, tendo como ênfase a ciclagem de nutrientes. Nos sistemas agroflorestais (SAF), ao contrário do sistema a Pleno Sol (PS) houve a incorporação do componente árboreo, priorizando a utilização de espécies nativas da Mata Atlântica e ou frutíferas. Após a consolidação desses agroecossistemas (18 anos) e diversos estudos (estoques de carbono orgânico e fósforo no solo; indicadores físicos, químicos e biológicos; fluxo hídrico; ciclagem de nutrientes e diversidade de espécies vegetais) surge a necessidade de avaliar a funcionalidade de organismos chave desses sistemas, como os fungos micorrízicos arbusculares (FMAs). Esses microssimbiontes desempenham diversas funções que são fundamentais para perpetuação desses agroecossistemas. A ação dos FMAs é atribuída, frequentemente, ao aumento no volume de solo explorado pela planta hospedeira, ocasionando uma maior absorção de água e nutrientes. Entretanto, outros benefícios são conferidos as plantas micorrizadas, como a proteção do sistema radicular contra patógenos; tolerância ao ataque de herbívoros; salinidade e elementos fitotóxicos, como o Alumínio (Al) ou metais pesados. Além disso, a rede micélial desses fungos é importante na estruturação e no aporte de Carbono (C) do solo (hifas e glomalina). A glomalina é uma glicoproteína hidrofóbica produzida pelos FMAs e que se acumula no solo em concentrações de mg por g-1. Essa glicoproteína permanece por anos ou décadas nos solos, com períodos de residência de 6 a 42 anos. A dinâmica da glomalina no solo ainda é pouco compreendida, entretanto, fatores como o manejo agrícola das áreas, a disponibilidade de espécies hospedeiras, balanço nutricional das plantas, disponibilidade de nutrientes, teores de CO2 na atmosfera do solo e os atributos físico-químicos do solo podem afetar os estoques dessa proteína, principalmente aqueles que alteram a abundância e a diversidade dos FMAs. O objetivo do presente estudo foi avaliar a dinâmica da glomalina em áreas da Zona da Mata de Minas Gerais. E, ainda, a transferência de sinais químicos entre plantas conectadas via hifa dos FMAs. Para avaliação da dinâmica da glomalina no solo, foram selecionadas três propriedades de agricultores familiares (An, Ro e Fe) que cultivam café (Coffea arabica L.), na região de Araponga-MG. Em cada propriedade, foi amostrado o solo de um sistema a PS e um SAF. Como referência, amostrou-se o solo de uma mata nativa secundária (MN) representativa da região e dentro dos domínios da Floresta Atlântica. Foram retiradas quatro amostras compostas de solo na entrelinha de plantio e próximo ao terço basal do dossel do cafeeiro, em diferentes profundidades. Analisou-se: os teores glomalina total (GT) e facilmente extraível (GFE); carbono orgânico total (COT); nitrogênio total; carbono da glomalina (CG); nitrogênio da glomalina (NG); teores de glomalina nas classes de agregados (4-2, 2-1 e 1-0,5 mm de diâmetro); diâmetro médio geométrico (DMG); diâmetro médio ponderado (DMP); índice de estabilidade de agregados (IEA); Carbono lábil (CL); Carbono não lábil (CNL); densidade do solo; teor de argila; argila dispersa em água (ADA); colonização micorrízica do cafeeiro; espécies espontâneas; espécies arbóreas dos agroecossistemas e raízes extraídas do solo; número de esporos dos FMAs; peso de raízes; pH; P disponível; soma de bases (SB); capacidade de troca catiônica total (CTCtotal) e efetiva (CTCefetiva); alumínio trocável (Al3+) e acidez potencial (H+Al). Por fim, para demonstrar a conexão entre plantas por hifas de MAs e a transferência de sinal entre plantas, foi construído um sistema de vasos duplos conectados. Os resultados indicaram que os agroecossistemas com cafezais da Zona de Mata de Minas Gerais apresentam elevados estoques de glomalina. Os FMAs aportam quantidades significativas de C e N orgânico no solo, na forma de glomalina. Os agregados de maior diâmetro apresentam maiores teores de glomalina. Alguns atributos físicos, químicos e biológicos do solo interferem nos teores de glomalina. Os sistemas agroflorestais podem contribuir para o aumento da restauração dos teores de glomalina, mas isso dependerá de características dos sistemas, como idade, espécie e quantidade de indivíduos arbóreos. Em um dos cafezais estudados, a introdução do componente arbóreo em área adjacente a um cafezal agroecológico a pleno sol, com o mesmo histórico de degradação, resultou em maiores estoques de glomalina no solo. Na transferência de sinais, verificou-se que a técnica do vaso duplo conectado é adequada para observar a indução de defesa indireta em plantas conectadas, via rede micelial, dos FMAs.
The Zona da Mata of Minas Gerais is a region that historically has suffered severe soil degradation and loss of native forest. In this environment, the soils tend to beundernourished and alic, eutrophic soils occurring only in the lower parts of the relief. The deep weathering mantle and associated to topography favors the loss of nutrients. In this region, the fragmentation of the properties is accompanied by a very unequal distribution of resources, where small farmers do not have enough land for reproduction of the family unit. The culture of coffee (Coffea arabica L.) is one of the main productive activities in the region, practiced on hillside soils, mainly by small farmers. In this context, the deployment of the systems based on agroecological principles in an alternative that allows for soil conservation and maintenance of local biodiversity. In 1994 farmers in the municipality of Araponga Forest zone mining chose to combine the production of the coffee with environmental sustainability, giving rise to the idea of coffee production in agroecological, agroforestry or the sun coffee. The agroecological systems are management with low use of chemical fertilizers, no use pesticides, the untilled soil and with an emphasis on nutrient cycling. In agroforestry systems (SAF), unlike the system to sun coffee (PS) the inclusion of the tree component, prioritizing the use of native Atlantic Forest and or fruit. After the consolidation of these agroecosystems (18 years) and several studies have as its theme: carbon stocks organic phosphorus in the soil, indicators of physical, chemical and biological water flow, nutrient cycling and plant species diversity, there is the need to assess the functionality of key organizations such systems, such as mycorrhizal fungi (AMF). These microsymbionts perform several functions that are critical to the perpetuation of these ecosystems. The action of AMF is attributed often to the increase in the volume of soil explored by the host plant, increases the absorption of water and nutrients. However, other benefits are conferred on the mycorrhizal plants, such as protection against root pathogens, tolerance to attack by herbivores, salinity, phytotoxic elements such as aluminium (Al) or heavy metals. Furthermore, the network mycelial fungi is important in the structure and carbon (C) input of the soil (hyphae and glomalin). Glomalin is a hydrophobic glycoprotein produced by the AMF and accumulates in the soil concentrations in mg per g-1. This glycoprotein remains for years or decades in the soil, with stays of 6-42 years. The dynamics of glomalin in the soil is still unclear, however, factors such as management of agricultural areas, the availability of host species, nutrient balance of plants, nutrient availability, levels of CO2 in the atmosphere and the soil physical and chemical attributes of the soil can affect the stocks of this protein, especially those that alter the abundance and diversity of AMF. The aim of this study was to evaluate the dynamics of glomalin in areas of Zona da Mata of Minas Gerais. And yet, the transfer of chemical signals between plants connected by hyphae of AMF. To assess the dynamics of glomalin in the soil were selected three family farms (An, Ro e Fe), which grow coffee (Coffea arabica L.) in the region of Araponga-MG. In each farm was sampled the soil from one an agroforestry system (SAF) and sun coffe system (PS). As a reference, sampled the soil is of a secondary native forest (MN) representative of the region and within the areas of Atlantic Forest. Were taken from four composite samples of soil between the rows of planting and near the basal third of the canopy of coffee at different depths. We analyzed the levels total glomalin (GT) and easily extractable glomalina (GFE), total organic carbon (COT), total nitrogen (NT), carbon glomalin (CG), the nitrogen of glomalin (NG), the levels of glomalin on aggregate classes (4- 2, 2-1 and 1 to 0.5 mm in diameter), geometric mean diameter (DMG), mean weight diameter (DMP) of aggregates stability index (ASI), labile carbon (CL) and carbon not labile (CNL), bulk density (Ds), clay content, water-dispersible clay (ADA), mycorrhizal colonization of coffee, pontaneous species, tree species of agroecosystems, and roots extracted from s the ground, number of spores of AMF, weight of roots, pH, available P, sum of bases (SB), total cation exchange capacity (CTCtotal) and effective (CTCefetiva), exchangeable aluminum (Al3+) and potential acidity (H + Al). Finally, to demonstrate the connection between plants of hyphae of an AM signal and the transfer plants built between a double system of vessels connected. The results indicated that agroecosystems with coffee Zone Mata de Minas Gerais have high stocks of glomalin. The AMF they contribute significant amounts of organic C and N in the soil as glomalin. Aggregates of larger diameter have higher levels of glomalin. Some physical, chemical and biological soil affect the levels of glomalin. The agroforestry systems can contribute to increase the restoration of the levels of glomalina, but this will depend on system characteristics, such as age, type and quality of individual trees. In a study of coffee, the introduction of tree component in an area adjacent to an agroecological sun coffee, with the same history of degradation, resulted in higher stocks of glomalin in the soil. In signal transduction, it was found that the technique of double pot proper is connected to note the induction of plant defense indirectly connected via the network mycelial AMF.
The Zona da Mata of Minas Gerais is a region that historically has suffered severe soil degradation and loss of native forest. In this environment, the soils tend to beundernourished and alic, eutrophic soils occurring only in the lower parts of the relief. The deep weathering mantle and associated to topography favors the loss of nutrients. In this region, the fragmentation of the properties is accompanied by a very unequal distribution of resources, where small farmers do not have enough land for reproduction of the family unit. The culture of coffee (Coffea arabica L.) is one of the main productive activities in the region, practiced on hillside soils, mainly by small farmers. In this context, the deployment of the systems based on agroecological principles in an alternative that allows for soil conservation and maintenance of local biodiversity. In 1994 farmers in the municipality of Araponga Forest zone mining chose to combine the production of the coffee with environmental sustainability, giving rise to the idea of coffee production in agroecological, agroforestry or the sun coffee. The agroecological systems are management with low use of chemical fertilizers, no use pesticides, the untilled soil and with an emphasis on nutrient cycling. In agroforestry systems (SAF), unlike the system to sun coffee (PS) the inclusion of the tree component, prioritizing the use of native Atlantic Forest and or fruit. After the consolidation of these agroecosystems (18 years) and several studies have as its theme: carbon stocks organic phosphorus in the soil, indicators of physical, chemical and biological water flow, nutrient cycling and plant species diversity, there is the need to assess the functionality of key organizations such systems, such as mycorrhizal fungi (AMF). These microsymbionts perform several functions that are critical to the perpetuation of these ecosystems. The action of AMF is attributed often to the increase in the volume of soil explored by the host plant, increases the absorption of water and nutrients. However, other benefits are conferred on the mycorrhizal plants, such as protection against root pathogens, tolerance to attack by herbivores, salinity, phytotoxic elements such as aluminium (Al) or heavy metals. Furthermore, the network mycelial fungi is important in the structure and carbon (C) input of the soil (hyphae and glomalin). Glomalin is a hydrophobic glycoprotein produced by the AMF and accumulates in the soil concentrations in mg per g-1. This glycoprotein remains for years or decades in the soil, with stays of 6-42 years. The dynamics of glomalin in the soil is still unclear, however, factors such as management of agricultural areas, the availability of host species, nutrient balance of plants, nutrient availability, levels of CO2 in the atmosphere and the soil physical and chemical attributes of the soil can affect the stocks of this protein, especially those that alter the abundance and diversity of AMF. The aim of this study was to evaluate the dynamics of glomalin in areas of Zona da Mata of Minas Gerais. And yet, the transfer of chemical signals between plants connected by hyphae of AMF. To assess the dynamics of glomalin in the soil were selected three family farms (An, Ro e Fe), which grow coffee (Coffea arabica L.) in the region of Araponga-MG. In each farm was sampled the soil from one an agroforestry system (SAF) and sun coffe system (PS). As a reference, sampled the soil is of a secondary native forest (MN) representative of the region and within the areas of Atlantic Forest. Were taken from four composite samples of soil between the rows of planting and near the basal third of the canopy of coffee at different depths. We analyzed the levels total glomalin (GT) and easily extractable glomalina (GFE), total organic carbon (COT), total nitrogen (NT), carbon glomalin (CG), the nitrogen of glomalin (NG), the levels of glomalin on aggregate classes (4- 2, 2-1 and 1 to 0.5 mm in diameter), geometric mean diameter (DMG), mean weight diameter (DMP) of aggregates stability index (ASI), labile carbon (CL) and carbon not labile (CNL), bulk density (Ds), clay content, water-dispersible clay (ADA), mycorrhizal colonization of coffee, pontaneous species, tree species of agroecosystems, and roots extracted from s the ground, number of spores of AMF, weight of roots, pH, available P, sum of bases (SB), total cation exchange capacity (CTCtotal) and effective (CTCefetiva), exchangeable aluminum (Al3+) and potential acidity (H + Al). Finally, to demonstrate the connection between plants of hyphae of an AM signal and the transfer plants built between a double system of vessels connected. The results indicated that agroecosystems with coffee Zone Mata de Minas Gerais have high stocks of glomalin. The AMF they contribute significant amounts of organic C and N in the soil as glomalin. Aggregates of larger diameter have higher levels of glomalin. Some physical, chemical and biological soil affect the levels of glomalin. The agroforestry systems can contribute to increase the restoration of the levels of glomalina, but this will depend on system characteristics, such as age, type and quality of individual trees. In a study of coffee, the introduction of tree component in an area adjacent to an agroecological sun coffee, with the same history of degradation, resulted in higher stocks of glomalin in the soil. In signal transduction, it was found that the technique of double pot proper is connected to note the induction of plant defense indirectly connected via the network mycelial AMF.
Descrição
Tese de Doutorado defendida na Universidade Federal de Viçosa.
Palavras-chave
Fungos micorrízicos, Micorriza, Sistemas agroflorestais, Fertilidade do solo, Estrutura do solo, Nutrição, Agricultura familiar, Controle biológico
Citação
TAVARES, R. C. Funcionalidade das micorrizas arbusculares em cafezais agroecológicos. 2011. 144 f. Tese (Doutorado em Solos e Nutrição de Plantas) - Universidade Federal de Viçosa, Viçosa-MG. 2011.