Behavior of water in soil cultivated with sunflower under water stress

Various soil attributes allow inferring about their behavior and function in the environment. With this work, the objective was to analyze the behavior of water retention in the soil after irrigation suppression for the BRS 323 hybrid sunflower cultivation in a sandy loam soil. The experiment was conducted at the Agrometeorological Station of the Federal University of Ceará, Brazil, from August to November, 2015. The behavior of soil water was evaluated by means of the retention curve, available water content, grain size, total porosity, and soil particle density in the 0.0 to 0.20 m soil layer. The water in the depth of 0.0 – 0.10 m drains rapidly in relation to the 0.10 – 0.20 m depth between potentials from -0.1 to -1.500 kPa after irrigation suppression, in this depth, at -4 kPa, there was greater water retention along the curve. The maximum water retained in the soil at field capacity in the layer depths of 0.0 – 0.10 m and 0.10 – 0.20 m is: 0.195 cm3 cm-3 and 0.221 cm3 cm-3, respectively. The 0.10 – 0.20 m depth presented a larger volume of available water influenced by density and porosity. It was concluded that the water in the soil cultivated with sunflower, 80 days after the irrigation ceases, gradually drains into larger pores, then retained in the smaller pores, being limited to the plants in the soil layer