Even though it is not officially recommended by the research institutes, water removal at tillering is a management practice frequently used by pre-germinated rice growers in the State of Santa Catarina, aiming to stimulate root growth and to reduce plant lodging. A green-house study was carried out with the objective of evaluate the changes in root and shoot morphological traits promoted by soil drainage at tillering. The experiment was performed in the city of Lages, SC, Brazil. Four water management systems were tested: continuous flooding, water removal at tillering and re-flooding at 7, 14 and 21 days after soil drainage. Two cultivars were evaluated for each irrigation system: 'Epagri 106' (short season) and 'Epagri 109' (long season). The experimental units were 7kg pots disposed in a completely randomized experimental design. The experiment was installed on 09/24/2004, using pre-germinated seeds. The shoot parameters were determined 22 days after soil drainage, when all experimental units were re-flooded. The root parameters were determined after shoot harvesting. The root length, area, volume and dry matter were reduced with the increase in soil drainage period for both cultivars. The water withdraw at tillering did not affect shoot dry matter but it decreased the root/shoot ratio. The number of senesced leaves was higher and plant height was lower in the treatments with the longer drainage period than when the irrigation was continuous. Soil drainage at tillering does not seem to be an effective management practice to enhance root development in the pre-germinated rice production system.
Oryza sativa; cultivars; irrigation; roots; tillering