RESUMO Objetivou-se com esta pesquisa estudar a influência de atributos físicos associados à estrutura do solo no índice Srelativo. Foram contempladas duas situações de solo (sob cultivo de Ficus carica L., sem aplicação e com aplicação de biofertilizante bovino líquido na lâmina de irrigação), nas camadas de 0-0,1 m e 0-0,3 m. Foram coletadas amostras de solo com estrutura preservada e não preservada nas camadas supracitadas e realizadas análises físicas pertinentes ao objetivo do estudo. Foi aplicado o modelo de função de resposta para verificar como as variáveis físicas do solo independentes influenciam no Srelativo, nas camadas de 0-0,1 m e 0-0,3 m tratadas com 0 e 60 % do biofertilizante combinadas duas a duas. Conhecidas as funções de resposta compararam-se as inclinações de ambas as funções, representadas pelos coeficientes β11-β12 e β21-β22, para verificar se houve efeito dos tratamentos na variável resposta. Além disso, calculou-se o erro padrão da diferença entre os coeficientes e aplicou-se o teste t de Student. Também foi aplicado o método de regressão múltipla para verificar o efeito das variáveis sobre o Srelativo para a camada de 0-0,3 m em ambos os tratamentos. Em seguida, por meio do método backward elimination foram selecionadas as variáveis com maior peso para a estimativa do Srelativo. Concluiu-se que o índice Srelativo é fortemente influenciado por atributos da fração porosa, sendo a porosidade total e a continuidade de poros os de influência significativa. O manejo com biofertilizante bovino líquido resulta em melhora na estrutura do solo, com efeitos mensuráveis pelo índice Srelativo.

ABSTRACT The present study aimed at assessing the influence of physical properties associated with soil structure on the Srelative index. Two soil conditions under Ficus carica L. cultivation were studied (with or without liquid bovine biofertilizer in the irrigation water), in the 0-0.1 m and 0-0.3 m layers. Disturbed and undisturbed soil samples were collected from the above-mentioned layers and physical analyzes, pertinent to the study objective, were performed. The response function model was applied to verify how the soil independent physical variables influence on the Srelative index in the 0-0.1 m and 0-0.3 m layers, with 0 and 60% biofertilizer, being combined two to two. Once the response functions were known, the slopes of both functions were compared, being represented by the coefficients β11-β12 and β21-β22. This comparison enabled verifying whether there was an effect of the treatments on the response variable. In addition, the standard error of the difference between coefficients was calculated, and the Student's t-test applied. The method of multiple regression was also used to confirm the effect of the variables on the Srelative index for the 0-0.3 m layer in both treatments. Then, the variables with greater weight were selected by a backward elimination method to estimate the Srelative. The results showed that the Srelative index is strongly influenced by properties of the porous fraction, with total porosity and continuity of pores being of significant influence. Management with liquid bovine biofertilizer results in improvement in the soil structure, with effects measured by the Srelative index.

ABSTRACT The soil porous space is where processes related to gases and soil solution occur, and provides an adequate guide for agricultural practices. This study aimed to evaluate the integrated effects of cultivation and the application of liquid bovine biofertilizer on the porous network of a Typic Haplocambids (Cambissolo Háplico Ta Eutrófico) cultivated with figs (Ficus carica L.). Four treatments were evaluated (under fig cultivation with the application of 20, 40 and 60 % of biofertilizer through irrigation, a control treatment without biofertilizer and an additional treatment – soil under natural vegetation). Disturbed and undisturbed soil samples were collected in three soil layers (0.0-0.1, 0.1-0.2 and 0.2-0.3 m) with four replicates. The following physical properties were analyzed: particle-size distribution, soil bulk and particle densities, and soil water retention curve. The coefficient of intrinsic soil air permeability was calculated based on the equation that considers the decreasing pressure method. Soil porosity, pore continuity index and blocked porosity were calculated and pore length was estimated. Compared with the native forest, pore network quality is improved, if not maintained, when the soil is cultivated under the conditions described in this experiment. In the conditions of cultivation, the application of bovine biofertilizer, for supplying sediments that block or reduce the size of the pores, did not improve soil air permeability. The cases where pore network quality was worsened in soil porosity as a result of the applied treatments (Biofertilizer 20 %, Biofertilizer 40 % and Biofertilizer 60 % for the layer of 0.0-0.1 m and Biofertilizer 60 % for 0.1-0.2 m), although not considered critical to plant development, point to the need for specific management practices (for instance, avoid coarse residues in the biofertilizer before its application) to avoid soil degradation.

O conhecimento sobre as alterações físicas e qualidade do solo é importante para o direcionamento adequado das estratégias de manejo a serem utilizadas quando da exploração do solo por cultivos agrícolas. Este trabalho teve como objetivo avaliar os efeitos do cultivo e da aplicação de um biofertilizante, obtido a partir de esterco bovino, sobre a qualidade física de um Cambissolo cultivado com Ficus carica L., irrigado por sistema de gotejamento. Para fins de avaliação da qualidade física, foram contempladas cinco situações de solo: sob cultivo de figo sem aplicação do biofertilizante (testemunha); com aplicação de 20, 40 e 60 % do biofertilizante na lâmina de irrigação; e mata nativa secundária (testemunha adicional), até a profundidade de 0,3 m, nas camadas de 0,0-0,1, 0,1-0,2; e 0,2-0,3 m, com quatro repetições. Nessas camadas, foram coletadas amostras de solo com estrutura deformada e indeformada para realizar análises físicas, como granulometria, argila dispersa em água, carbono orgânico, densidade das partículas e do solo, resistência do solo à penetração e curva característica de água no solo. O cultivo do solo nas condições descritas nesta pesquisa, como preparo do solo por aração e gradagem, uso de irrigação e todos os tratos culturais necessários à condução da cultura de figo, não piora a qualidade física do solo em nenhuma das camadas avaliadas. A aplicação de biofertilizante melhora a qualidade física do solo, particularmente no tocante à retenção de água em decorrência do aumento da microporosidade.

Knowledge of soil physical changes and soil quality is important for creating adequate management strategies to be adopted for soil under crop production. The aim of this study was to evaluate the effects of cultivation and application of biofertilizer (obtained from cattle manure) on the physical quality of a Cambisol planted to Ficus carica L. with a drip irrigation system and to verify the efficiency of indicators in assessing changes in its physical properties. In order to evaluate physical quality, five soil scenarios were analyzed: soil under fig cultivation without application of biofertilizer (control), soil with application of 20, 40, and 60 % of the biofertilizer through irrigation, and soil from secondary native forest (additional control). Analyses were made in the 0.0-0.1, 0.1-0.2, and 0.2-0.3 m layers, with four replicates. In these layers, disturbed and undisturbed soil samples were taken for physical analyses (particle size distribution, dispersed clay, organic carbon, particle density, soil bulk density, resistance to penetration, and soil water retention curve). Soil cultivation under the conditions described in this study (soil tillage with moldboard plow and disking, use of irrigation, and all crop practices needed to grow the fig crop) did not worsen soil physical quality in any of the layers evaluated. The application of biofertilizer improves the quality of soil physical properties, especially water retention, due to the increase in microporosity.