Estimativa da capacidade extratora dos capins vetiver e tifton em sistemas alagados construídos

Abstract

The objective of this study was to obtain mathematical models to estimate the capacity of nitrogen (N), phosphorus (P) and potassium (K) extraction by the vetiver grass (Chrysopogon zizanioides) and tifton 85 grass (Cynodon spp.) when cultivated in horizontal subsurface flow constructed wetlands (HSSF-CWs) whose porous medium was saturated with solutions presenting different nutrient concentration. The grass shoots were cut every 30 days to determine the productivity and N, P and K contents in the plant tissue. Models of the extraction capacity of nutrient were obtained as a function of electrical conductivity (EC) in the nutrient solution. For validation of these models, the HSSF-CWs were also operated under full scale conditions (HSSF-CWsf) for the treatment of sanitary sewage. From the obtained results, it was verified that the extractions of N, P and K by the vetiver grass increased linearly with the increase in EC of the nutritive solution. In relation to tifton 85, quadratic models of N and K extraction were adjusted. Although the adjusted models were not able to accurately estimate the evaluated variable, the information obtained can be used to improve the HSSF-CWsf .