Water requirements of poplar and willow vegetation filters grown in lysimeter under Mediterranean conditions: Results of the second rotation

Poplar and willow short-rotation coppice have been shown to be suitable to improve wastewater quality in vegetation filters. Nevertheless, water requirements of these species are still uncertain. The aim of this work was to estimate crop evapotranspiration (ETc) and crop coefficient (k(c)) of these species grown under high fertilised (HF) and low fertilised (LF) conditions through the water balance of lysimeters. This paper deals with the results of the first growing season after coppicing of the second rotation (2006) in comparison with those of the first season of the first rotation (2004). During the 2006 growing season (around 132 days), ETc was 319 mm (LF) and 719 mm (HF) in poplar and 607 mm (LF) and 919 mm (HF) in willow, with maximum daily values of 11.55 mm in HF poplar and 15.09 mm in HF willow. Ten-day ETc rates were in general higher than those found in the 2004 growing season. Maximum k(c), reached in August and September, ranged between 1.2 and 2.9 in LF treatment and between 2,5 and 4.0 in HF ones, and were higher than maximum k(c) values reached during the 2004 growing season. In both growing seasons evapotranspiration and k(c) seemed to be related more to the availability of nutrients than to differences between the two species.