Algunos aspectos de la biología y manejo de Digitaria sanguinalis (L). Scop. En asociación con el cultivo del arroz y otras especies adventicias

In the rice crop in Colombia there are 70 species of weed. The gramineae species are the plants in direct biological and economical competition with the crop. Echinochloa cotonum (L.) Link, Oryza sativa L. (red rice) Cyperus rotundus L. ,Rottboellia cochinchinensis U., Fimbristylis annua (Alt.) Riets , Murdania nudiflora (L.) Brenan and Digitaria sanguinalis (L.) Scop., are the most common weeds in the rice crop. This work was necessary tor two reasons: there is no work presenting the biological aspects of D. sanguinalis, and also there is an increasing population of weed in sorghum and rice crops in Lerida in the region Tolima. The objectives were: to know Phenology development, to evaluate the seed bank and to know the competitive ellects of three densities (one, live and twenty ptantslrn-) of Digitaria sanguinalis in the rice crop. Four stages were affected considerably in the rice plants by the presence of D. sanguinalis. Germination: D. sanguinalis needed three days of growth after the wetting of the land, however the rice seeds required two days more; Tillering: D. sanguinalis began this phase in 20 days as opposed to rice plants that began in 28 days. Booting: D. sanguinalis began this state in the 65 days compared with the rice plants, that took 70 days. Ripening: The seeds of D. sanguinalis needed 110 days to complete this phase with the seeds, needing 10 days more. D. sanguinalis began to free seeds at 100 days approximately. The method to evaluate the composition of the seed bank, was the emergence of seedlings obtaining the greater percentages M. nudiflora with 42,6 %, the second level the group frorn the broad leal with 39 %, D. sanguinalis with 12,5 % and Echinochloa sp., with 6 %. The results of the plant competition were: reduction in the tillering number by 25 %, to a density of a plant/m2 ; plant height, with reduction of the 8,7, 21 and 23,5 r to density of one, live and twenty plantslrn of D. sanguinalis respectively. The different yield components of the rice were affected by densities superior to a plant by m2. The results obtained upon studying the aspects of the biology of Digitaria sanguinalis, such as, the quantity of seeds in the soil bank, the similar development of their biological cycles of the competition weed and cultivated plants it is necessary to a plan a specilic treatments for implementation in the cycles of the rice crop.