Abstract

ORTIZ DOMINGUEZ, Aída; LOPEZ, Luís; CASARES, Marjorie  and  MORATINOS, Humberto. Evaluation of weedy rice and volunteer rice soil seed bank in one lot of la lucía farm. Agronomía Trop. [online]. 2009, vol.59, n.4, pp.423-432. ISSN 0002-192X.

Weedy rice (WR), Oryza sativa L., is one of the main weeds in Venezuela. The purpose of this study was to evaluate, the WR and volunteer rice (VR) soil seed banks at 8 seedbed that represent 24 ha of a rice farm of 500 ha, in Portuguesa, Venezuela. The sampling was realized in double diagonal. We excavated trench to extract soil samples to 0-10 and 10-20 cm deep, where was evaluated: (1) passive bank, counting seeds present in the soil sampling and (2) active bank, placing the soil in plates and counting the emerged seedlings. The results showed that in depth of 0-10 cm were found more seeds of WR than in 10-20 cm. Therefore, the density in the passive bank fluctuated between 230-2825-WR seeds m^-2, founded more WR seeds in the central seedbeds than in lateral seedbeds. In all the seedbeds, the seeds on the surface had higher seed viability than the seeds that were found deeper. In both depths, the viable seeds showed more of 90% of dormancy. This was corroborated with the technique of emergence in plate, which showed a lower density of WR seedlings compared with the amount of seeds found in the same points of the sampling and which represented the WR active seed bank, with the following distribution pattern: The first two seedbed did not show WR, the last three seedbeds showed low population (55, 25 and 55 seedlings m^-2, respectively) and the seedbeds on the middle had the highest density of WR (135, 391 and 65 seedlings m^-2). The VR showed medium density in soil seed bank (325 seeds m^-2), and its attributes of viability, mortality, dormancy y germination followed the same trend than WR. VR has more seeds density at 0-10 cm depth than 10-20 cm, similarly that WR

Keywords : Oryza sativa L; viability; dormancy; mortality; seedling emergence.