Transferência de carbono de resíduos de leguminosas e não leguminosas para a matéria orgânica do solo e liberação de nutrientes
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Data
2019-02-21
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Universidade Federal de Viçosa
Resumo
A formação e estabilização da matéria orgânica do solo (MOS) consistem em importantes preocupações num contexto global, em razão das mudanças do padrão climático, e sustentabilidade dos sistemas agrícolas. Neste contexto, a composição bioquímica dos resíduos vegetais, entre outros fatores, desempenha importante papel nas transformações da MOS, regulando parte desses processos de transformação, transferindo além de C outros nutrientes via processo de mineralização. Assim, esse estudo teve como objetivo avaliar a influência da composição bioquímica de diferentes resíduos culturais nas transformações das frações da MOS – Matéria organica particulada (MOP) e associada aos minerais (MAM), e a liberação de nutrientes desses resíduos orgânicos no solo. Foi realizado um experimento por meio da incubação dos resíduos culturais no solo em condições controladas. Os tratamentos foram definidos por esquema fatorial 2x7x4, assim representados: i) com e sem a adição de resíduo C 4 – Milheto (Pennisetum americanum (L)); ii) seis resíduos culturais de espécies C 3 – Crotalária (Crotalaria juncea), Feijão de Porco (Canavalia ensiformes), Girassol (Helianthus annuus), Mucuna Preta (Mucuna pruriens), Eucalipto (Eucalyptus), um mix de resíduos de crotalária + eucalipto, e um controle sem resíduo; e iii) quatro tempos de avaliação (0, 0,08, 0,25 e 0,41 ano após o início da incubação). Os tratamentos foram distribuídos em um delineamento com blocos ao acaso, com quatro repetições. Para o referido estudo foram avaliados os fluxos de C-CO 2 em cada tratamento e o efeito priming resultante da adição desses resíduos; a massa de matéria seca remanescente (mSR) após 0,08, 0,25 e 0,41 ano, estimando a taxa de decomposição e os valores de tempo de meia-vida (t 0,5 ) dos resíduos. Os teores de macro e microntrientes presentes nos resíduos foram quantificados nos quatro tempos de avaliação para determinação da mineralização desses elementos. Foram determinado os incrementos de compostos orgânicos no solo por meio da análise de polissacarídeos (PST) e fenóis solúveis em água (FSA). A transferência de C desses resíduos para a MOS foi avaliada aos 0,41 ano após a incubação, por meio do fracionamento físico do solo para a separação da MOP e MAM. Os modelos descrevendo a cinética de mSR e conteúdo de nutrientes remanescentes (cNR), ao longo do tempo foram ajustados por meio de regressões. Além disso, os dados de PST e FSA foram submetidos à análise de variância fatorial (ANOVA) dentro de cada tempo. O C associado as frações MOP e MAM derivados dos resíduos e do solo também foi submetido à análise de variância fatorial (ANOVA) e as médias de PST e FSA e do C-MOP e C-MAM, quando analisadas em função dos resíduos, foram comparadas pelo teste de Scott-Knott (p = 0,05), quando comparadas em função do fator adição ou não de milheto utilizou-se o teste t de Student (LSD) (p = 0,05). De maneira geral, houve grande contribuição dos resíduos sem associação com o milheto para as emissões iniciais de C-CO 2 , e com o passar do tempo esses fluxos foram sendo estabilizadas. Porém, a adição do milheto em conjunto com os resíduos promoveu um efeito priming positivo nos períodos iniciais, favorecendo a degradação da MOS nativa. O tempo de incubação bem como a composição dos resíduos regulam os teores de compostos orgânicos e dos nutrientes disponíveis no solo provenientes de cada tipo de resíduo. Em manejos onde é realizado a cobertura vegetal do solo (ou adubação verde) com espécies leguminosas (Crotalária, Feijão de porco, Mucuna), não-leguminosas (Girassol e Eucalipto) e combinação de ambas (Mix) há contribuição de C dos diferentes resíduos para as frações da matéria orgânica do solo. Porém quando associados com resíduos de milheto as contribuições de C para as frações da MOS são significativamente maiores, principalmente na fração mais estável da MOS (MAM).
Soil organic matter formation and stabilization (SOM) are important concerns in a global context, due to changes in the climate pattern, and sustainability of agricultural systems. In this context, the biochemical composition of plant residues, among other factors, play an important role in the transformation of SOM, regulating part of these transformation processes, transferring C as well as other nutrients via the mineralization process. Thus, this study aimed to evaluate the influence of the biochemical composition of different cultural residues on the transformations of SOM fractions - Particulate organic matter (POM) and associated with minerals (MOAM), and the release of nutrients from these organic waste in the soil. An experiment was carried out by incubating the cultural residues in the soil under controlled conditions. The treatments were defined by 2x7x4 factorial scheme, as follows: i) with and without the addition of residue C4 - Millet (Pennisetum americanum (L)); ii) six cultural residues of C3 species - Crotalaria (Crotalaria juncea), Jack Bean (Canavalia ensiformes), Sunflower (Helianthus annuus), Mucuna preta (Mucuna pruriens), Eucalyptus (Eucalyptus), a residue mix of crotalaria + eucalyptus, and a control without residue; and (iii) four evaluation times (0, 0,08, 0,25 and 0,41 year after the start of incubation). The treatments were distributed in a randomized complete block design, with four replications. For this study, the fluxes of C-CO2 in each treatment and the priming effect resulting from the addition of these residues were evaluated; the remaining dry matter mass (mSR) after 0.08, 0.25 and 0.41 year, estimating the decomposition rate and the half-life values (t0.5) of the residues. The macro and micronrient contents present in the residues were quantified in the four evaluation times to determine the mineralization of these elements. Increases of organic compounds in the soil were determined by the analysis of total polysaccharides (TPS) and water soluble phenols (WSP). The transfer of C of these residues to the MOS was evaluated at 0.41 year after incubation, through the physical fractionation of the soil for the separation of POM and MOAM. The models describing the kinetics of rDM and the remaining nutrient content rNC over time were adjusted by means of regressions. In addition, the PST and FSA data were subjected to factorial variance analysis (ANOVA) within each time. The C associated with the MOP and MAM fractions derived from the residues and the soil was also submitted to analysis of factorial variance (ANOVA) and the mean values of PST and FSA and C-MOP and C-MAM were compared by the Scott-Knott test (p = 0.05), the Student's t test (LSD) (p = 0.05) was used when compared with the addition or not of millet factor. In general, there was a great contribution of the residues without association with the millet for the initial emissions of C-CO2, and with the passage of time these concentrations were stabilized. However, the addition of millet together with the residues promoted a positive priming effect in the initial periods, favoring the degradation of native SOM. The incubation time as well as the composition of the residues regulate the levels of organic compounds and nutrients available in the soil from each type of residue. Soil cover (or green manure) with leguminous species (Crotalaria, Jack Bean, Mucuna), non-leguminous (Sunflower and Eucalyptus) and combination of both (Mix), there is contribution of C of different residues for the fractions of the organic matter of the soil. However, when associated with millet residues the contributions of C are significantly higher, especially in the SOM stable fraction (MOAM).
Soil organic matter formation and stabilization (SOM) are important concerns in a global context, due to changes in the climate pattern, and sustainability of agricultural systems. In this context, the biochemical composition of plant residues, among other factors, play an important role in the transformation of SOM, regulating part of these transformation processes, transferring C as well as other nutrients via the mineralization process. Thus, this study aimed to evaluate the influence of the biochemical composition of different cultural residues on the transformations of SOM fractions - Particulate organic matter (POM) and associated with minerals (MOAM), and the release of nutrients from these organic waste in the soil. An experiment was carried out by incubating the cultural residues in the soil under controlled conditions. The treatments were defined by 2x7x4 factorial scheme, as follows: i) with and without the addition of residue C4 - Millet (Pennisetum americanum (L)); ii) six cultural residues of C3 species - Crotalaria (Crotalaria juncea), Jack Bean (Canavalia ensiformes), Sunflower (Helianthus annuus), Mucuna preta (Mucuna pruriens), Eucalyptus (Eucalyptus), a residue mix of crotalaria + eucalyptus, and a control without residue; and (iii) four evaluation times (0, 0,08, 0,25 and 0,41 year after the start of incubation). The treatments were distributed in a randomized complete block design, with four replications. For this study, the fluxes of C-CO2 in each treatment and the priming effect resulting from the addition of these residues were evaluated; the remaining dry matter mass (mSR) after 0.08, 0.25 and 0.41 year, estimating the decomposition rate and the half-life values (t0.5) of the residues. The macro and micronrient contents present in the residues were quantified in the four evaluation times to determine the mineralization of these elements. Increases of organic compounds in the soil were determined by the analysis of total polysaccharides (TPS) and water soluble phenols (WSP). The transfer of C of these residues to the MOS was evaluated at 0.41 year after incubation, through the physical fractionation of the soil for the separation of POM and MOAM. The models describing the kinetics of rDM and the remaining nutrient content rNC over time were adjusted by means of regressions. In addition, the PST and FSA data were subjected to factorial variance analysis (ANOVA) within each time. The C associated with the MOP and MAM fractions derived from the residues and the soil was also submitted to analysis of factorial variance (ANOVA) and the mean values of PST and FSA and C-MOP and C-MAM were compared by the Scott-Knott test (p = 0.05), the Student's t test (LSD) (p = 0.05) was used when compared with the addition or not of millet factor. In general, there was a great contribution of the residues without association with the millet for the initial emissions of C-CO2, and with the passage of time these concentrations were stabilized. However, the addition of millet together with the residues promoted a positive priming effect in the initial periods, favoring the degradation of native SOM. The incubation time as well as the composition of the residues regulate the levels of organic compounds and nutrients available in the soil from each type of residue. Soil cover (or green manure) with leguminous species (Crotalaria, Jack Bean, Mucuna), non-leguminous (Sunflower and Eucalyptus) and combination of both (Mix), there is contribution of C of different residues for the fractions of the organic matter of the soil. However, when associated with millet residues the contributions of C are significantly higher, especially in the SOM stable fraction (MOAM).
Descrição
Palavras-chave
Química do solo, Decomposição, Isótopos, Composição química
Citação
SILVA, Jônatas Pedro da. Transferência de carbono de resíduos de leguminosas e não leguminosas para a matéria orgânica do solo e liberação de nutrientes. 2019. 54 f. Dissertação (Mestrado em Solos e Nutrição de Plantas) - Universidade Federal de Viçosa, Viçosa. 2019.