Atributos do solo e desenvolvimento radicular em plantações de eucalipto no Brasil
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2019-02-15
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Universidade Estadual Paulista (Unesp)
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O desenvolvimento radicular em plantações de eucalipto tem sido apontado como uma das estratégias cruciais para sua adaptação e crescimento, em especial, em condições tropicais, que possuem solos pobres em nutrientes. Neste contexto, torna-se extremamente importante avaliar o perfil do solo nestas plantações, a luz de uma perspectiva de fornecimento de nutrientes e água para as plantações de eucalipto. Tendo isto em vista, especificamente nesta tese, dois trabalhos foram conduzidos para avaliar os atributos do solo e o desenvolvimento radicular em plantações de eucalipto no brasil, a saber: 1) Disponibilidade de Água no Solo em Plantios de Eucalipto em uma Cronossequência, e suas Relações com a Produtividade e Densidade Básica da Madeira e suas Estimativas Através de Redes Neurais Artificiais no Brasil; 2) Padrões e Distribuição Vertical dos Atributos do Solo na Plantação de Eucalipto no Brasil. A rede experimental completa possui 34 experimentos plantados em um gradiente climático no Brasil e 2 locais no Uruguai, com 36 locais experimentais no total. Avaliaram-se sítios desde baixo incremento médio anual (13,7 m³ ha-1 ano-1, 61% abaixo da média nacional de produtividade), até sítios com elevada produtividade com IMA de 67,2 m³ há-1 ano-1 (92% acima da média nacional de produção de madeira). No trabalho 1, avaliaram-se14 experimentos, e no trabalho 2, 4 experimentos, todos eles ao longo de um forte gradiente climático no Brasil. No caso do trabalho 1 foram avaliados atributos físico dos solos (teores de argila, silte, areia total, capacidade de campo, ponto de murcha permanente, etc.) amostrando-se os horizontes A e B do solo; e já no trabalho 2 os teores de P, K, Ca, Mg, S, e a granulometria do solo até onde houvesse ocorrência de raízes do eucalipto. Os valores potenciais de absorção de água (AD) aos 24 e 65 meses observados neste estudo foram superiores aos observados na literatura, indicando maior importância ou contribuição das raízes profundas na absorção de água do eucalipto na vida adulta. Por outro lado, os valores de AD aos 3 e 9 meses observados neste estudo foram inferiores aos observados na literatura, indicando que as raízes e a profundidade do solo são provavelmente subestimadas para os cálculos de AD nas idades mais jovens de eucalipto. Percebe-se que são necessários mais modelos sistêmicos que considerem e padronizem o AD de acordo com a idade e profundidade da raiz. Para concluir o estudo sobre distribuição vertical de raízes, este trabalho mostra uma exploração do solo muito profunda por raízes finas até uma profundidade de 20 m em plantações de eucalipto no Brasil. A distribuição vertical mostra claramente que os nutrientes estão concentrados na superfície do solo, mas há uma “fertilidade profunda do solo” que muitas vezes não é considerada na amostragem operacional nos sistemas de recomendação de fertilização das empresas florestais brasileiras, nem estão descritos nos principais manuais de agricultura e recomendação de fertilização no Brasil. Também na distribuição vertical, pode-se verificar que com o aumento do número de rotações e anos de ocupação dos solos com os plantios florestais, ocorre a hipótese do “aumento de nutrientes (P, K, B)”. Por outro lado, com o aumento da profundidade do sistema radicular constatou uma redução do estoque de nutrientes na superfície dos solos.
The root development in eucalyptus plantations has been pointed out as one of the crucial strategies for their adaptation and growth, especially in tropical conditions, which have nutrient poor soils. In this context, it is extremely important to evaluate the soil profile in these plantations, considering a nutrient and water supply perspective for eucalyptus plantations. With this in mind, specifically in this thesis, two studies were conducted to evaluate soil attributes and root development in eucalyptus plantations in Brazil, namely: 1) Availability of Soil Water in Eucalyptus Plantations in a Chronosequence, and their Relationships with the Productivity and Basic Density of Madeira and its Estimates through Artificial Neural Networks in Brazil; 2) Patterns and Vertical Distribution of Soil Attributes in Eucalyptus Plantation in Brazil. The complete experimental network has 34 experiments planted in a climatic gradient in Brazil and 2 sites in Uruguay, with 36 experimental sites in total. Sites were evaluated from low average annual increment (13.7 m³ ha-1 year-1, 61% below the national average of productivity), to sites with high productivity with an IMA of 67.2 m³ ha-1 year -1 (92% above the national average of wood production). In work 1, 14 experiments were evaluated, and in the work 2, 4 experiments, all of them along a strong climatic gradient in Brazil. In the case of work 1, physical attributes of the soils (clay, silt, total sand, field capacity, permanent wilting point, etc.) were evaluated; soil A and B horizons were sampled; and already at work 2 the contents of P, K, Ca, Mg, S, and the grain size of the soil up to where there was occurrence of eucalyptus roots. Potential water absorption (AD) values at 24 and 65 months observed in this study were higher than those observed in the literature, indicating greater importance or contribution of deep roots in the eucalyptus water absorption in adult life. On the other hand, the AD values at 3 and 9 months observed in this study were lower than those observed in the literature, indicating that roots and soil depth are probably underestimated for AD calculations at younger eucalyptus ages. It is noticed that more systemic models are needed that consider and standardize AD according to root age and depth. To conclude the study on vertical root distribution, this work shows very deep soil exploration by fine roots to a depth of 20 m in eucalyptus plantations in Brazil. The vertical distribution clearly shows that nutrients are concentrated on the soil surface, but there is "deep soil fertility" that is often not considered in the operational sampling in the fertilization recommendation systems of Brazilian forest companies nor are they described in the main manuals and fertilization recommendation in Brazil. Also in the vertical distribution, it can be verified that with the increase of the number of rotations and years of occupation of the soils with the forest plantations, the hypothesis of the "increase of nutrients (P, K, B)" occurs. On the other hand, at deeper of the root system verified a reduction of the nutrient stock in the surface of the soils.
The root development in eucalyptus plantations has been pointed out as one of the crucial strategies for their adaptation and growth, especially in tropical conditions, which have nutrient poor soils. In this context, it is extremely important to evaluate the soil profile in these plantations, considering a nutrient and water supply perspective for eucalyptus plantations. With this in mind, specifically in this thesis, two studies were conducted to evaluate soil attributes and root development in eucalyptus plantations in Brazil, namely: 1) Availability of Soil Water in Eucalyptus Plantations in a Chronosequence, and their Relationships with the Productivity and Basic Density of Madeira and its Estimates through Artificial Neural Networks in Brazil; 2) Patterns and Vertical Distribution of Soil Attributes in Eucalyptus Plantation in Brazil. The complete experimental network has 34 experiments planted in a climatic gradient in Brazil and 2 sites in Uruguay, with 36 experimental sites in total. Sites were evaluated from low average annual increment (13.7 m³ ha-1 year-1, 61% below the national average of productivity), to sites with high productivity with an IMA of 67.2 m³ ha-1 year -1 (92% above the national average of wood production). In work 1, 14 experiments were evaluated, and in the work 2, 4 experiments, all of them along a strong climatic gradient in Brazil. In the case of work 1, physical attributes of the soils (clay, silt, total sand, field capacity, permanent wilting point, etc.) were evaluated; soil A and B horizons were sampled; and already at work 2 the contents of P, K, Ca, Mg, S, and the grain size of the soil up to where there was occurrence of eucalyptus roots. Potential water absorption (AD) values at 24 and 65 months observed in this study were higher than those observed in the literature, indicating greater importance or contribution of deep roots in the eucalyptus water absorption in adult life. On the other hand, the AD values at 3 and 9 months observed in this study were lower than those observed in the literature, indicating that roots and soil depth are probably underestimated for AD calculations at younger eucalyptus ages. It is noticed that more systemic models are needed that consider and standardize AD according to root age and depth. To conclude the study on vertical root distribution, this work shows very deep soil exploration by fine roots to a depth of 20 m in eucalyptus plantations in Brazil. The vertical distribution clearly shows that nutrients are concentrated on the soil surface, but there is "deep soil fertility" that is often not considered in the operational sampling in the fertilization recommendation systems of Brazilian forest companies nor are they described in the main manuals and fertilization recommendation in Brazil. Also in the vertical distribution, it can be verified that with the increase of the number of rotations and years of occupation of the soils with the forest plantations, the hypothesis of the "increase of nutrients (P, K, B)" occurs. On the other hand, at deeper of the root system verified a reduction of the nutrient stock in the surface of the soils.
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Atributos químicos e físicos do solo, Raízes das camadas profundas do solo, Eucalyptus sp., Plantações florestais, Chemical and physical soil attributes, Roots of deep soil layers, Forest plantations