Growth, Productivity and Biomass Quality of Kenaf Irrigated with Wastewaters - The Effect of Phosphate Ion
Fernando, A.L., Lopes, S.P., Mendes, B., Alexopoulou, E.
The aim of this work was to evaluate growth responses, as well as the quality and biomass productivity of the G4 variety of kenaf, irrigated with treated wastewaters (TWW) presenting different phosphate ion concentrations: 0, 0.6, 1.2 and 2.4 mg.L-1 (P). Wastewater was obtained at Campo de Tiro de Alcochete wastewater treatment plant, after secondary treatment. Essays were conducted in small pots, and for each treatment, in triplicate. A Control essay was also performed, with tap water. NPK fertilization effect was also studied. Throughout the experiment, in pots, percolated waters were analyzed in terms of phosphates. Results show that irrigation with wastewater enriched with phosphate ion does not affect the growth and productivity of kenaf, within the levels of phosphate studied (maximum concentration 2.4 mg.L-1 P). The use of wastewaters in the irrigation even contributed to a higher biomass production, ca 670-780 g/m2, by comparison with 270 and 550 g/m2 obtained, respectively, in the control and in the control+NPK pots. In terms of the biomass quality, the increment of phosphate ion in the irrigation did not affect the ash content of the several fractions of the aerial biomass and the phosphorus (P) content of core and leaves fractions. A trend on the increment of P content was observed on the bark fraction with the use of wastewaters in the irrigation. The evaluation of the phosphate content in the percolated waters showed a decrease along the growing cycle, thus indicating the increased absorption of phosphates by the growing biomass system. Nevertheless, the P content in the percolated waters was for most of the treatments, including control, higher than the P content of the tap water or the wastewaters, resulting from the leaching of P from soil. But, no significant differences on the phosphate content of the percolated waters were identified among treatments, including control, thus showing that the risk of contamination of groundwater due to irrigation with these wastewaters was controlled. However, it is important to balance the quantity of phosphorus added along the growing period with the plant needs, in order to prevent the degradation of the surface and groundwater quality due to excess P. Kenaf can assume a high importance on projects by merging the treatment of water bodies containing phosphate ion up to 2.4 mg.L-1 (P), with the production of highly valuable biomass, in a short time period and with low production costs.
biomass composition, kenaf, wastewater treatment, biomass yields
Energy crops and energy grasses
21st European Biomass Conference and Exhibition
381 - 384
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