Influence of physical attributes and pedotransfer function for predicting water retention in management systems/Atributos fisicos e funcoes de pedotransferencia para estimativa da retencao de agua em sistemas de manejo

The aims of this study were to evaluate the effects of the soil structural physical attributes on the water retention and to develop pedotransfer functions (PTFs) for the estimation of the soil water content ([theta]) at different matric potentials of a Dystrophic Red Latosol (Hapludox) under conventional tillage (CT) and no-tillage (NT) soil management systems. The effects of long-term CT and NT (over 25 years) management on the soil bulk density (BD), total porosity (TP), macroporosity (Ma), microporosity (Mi) and water retention were investigated. The PTFs were developed to predict [theta] and used to evaluate the soil water retention curve only for the NT system. The NT system was characterized by smaller values of the soil BD and higher values of the soil TP and Mi than the CT system. The NT system exhibited a higher [theta] retained than the CT system for the pore-size interval of 0.2-30 [micro]m. However, the CT system exhibited a large amount of water retention for pores smaller than 0.2 [micro]m. The PTFs were utilized to estimate [theta] at matric potentials of -1, -3, -6, -10, -33, -100, -400, -800, and -1,500 kPa with adequate accuracy. The soil BD, Ma, Mi and sand content were the main variables considered to estimate 0 for the different matric potentials evaluated. Key words: no-tillage conventional tillage soil porosity Os objetivos deste estudo foram avaliar os efeitos de atributos fisicos estruturais do solo sobre a retencao de agua e desenvolver funcoes de pedotransferencia (FPT) para a estimativa de conteudos de agua ([theta]) em diferentes potenciais matricos de um Latossolo Vermelho distrofico em sistema convencional (SC) e sistema plantio direto (SPD). Os efeitos de longo prazo dos manejos SC e SPD (mais de 25 anos) sobre a densidade do solo (DS), porosidade total (PT), macroporosidade (Ma), microporosidade (Mi) e retencao de agua foram investigados. As FPT foram desenvolvidas para predizer os [theta]s utilizados na determinacao da curva de retencao de agua apenas para o SPD. O SPD apresentou menor DS e maior PT e Mi que o SC. O SPD aumentou o conteudo de agua retido em poros de tamanho entre 0,2 e 30 [micro]m, em relacao ao SC. No entanto, o SC apresentou maior conteudo de agua retido em poros com raio menor que 0,2 [micro]m. As FPTs utilizadas para estimar [theta] para os potenciais matricos de -1, -3, -6, -10, -33, -100, -400, -800 e -1500 kPa tiveram acuracia adequada. A DS, Ma, Mi e teor de areia foram as principais variaveis con