Qualidade microbiológica da água da cultura do arroz irrigado, no sul do Brasil

Abstract

Total and fecal coliforms are bio-indicators of the environmental impact caused by anthropic action and are considered indicators of the microbiological quality of the water. In the cultivation of rice by irrigation much water is used and care in water management is required in order to increase the volume and quality of production while reducing the environmental impact. The objective of this research is to evaluate the quality of the irrigation water used in five rice-growing regions of the State of Rio Grande do Sul during the vegetative and reproductive phases. The results demonstrate that the indices of total and fecal coliforms in the rice field plots of the fields in all the rice producing regions of Rio Grande do Sul evaluated in this study were lower in the reproductive than in the vegetative phases. The irrigation channel presented low indices of fecal coliforms but a higher incidence of total coliforms. The data demonstrated that irrigated rice cultivation can alter the microbiological quality of the water in the plots by its potential capacity of circulating the nutrients with the result that the drainage water presents a smaller quantity of contaminating microbial agents.

Evaluation of the Microbiological Quality of Water in the Rice-Growing System of the Lis Valley, Portugal

“…This fact might be explained by the soil effect on the reduction in this group's values [23]. Our data agree with a study carried out in Brazil demonstrating that paddy agro-ecosystems have the potential ability to circulate the nutrients, thus leading to lower levels of those contaminating microbial agents in the drainage water than in the irrigation water [24]. These results may additionally be explained by the kind of crops grown at the outflow of the LVID (rice and pastures), where the soils TC values are very widespread, reaching averages above 700 MPN/100 mL in all sampled locations, aside from paddy drainage, with no significant differences between irrigation and drainage water counts.…”