High biomass yield achieved by Salix clones in SRIC following two 3-year coppice rotations on abandoned farmland in southern Quebec, Canada

Two species of willow, Salix discolor and S. viminalis, were planted in 1995 under short-rotation intensive culture on two abandoned farmland sites: sandy site (S1) and clay site (S2). After three seasons of growth the two species were coppiced. In the spring of the first season following coppicing, one dose of composted sludge equivalent to 100 kg of "available" N ha(-1) was applied to some plots (T1) while others were left unfertilized (T0). The aims of the experiment were to compare the growth performance and nutrients exported by willow species planted on marginal sites with different soil characteristics and to assess the impact of fertilization with wastewater sludge on yields during a second rotation cycle. Over three seasons, willow height, diameter and aboveground biomass were greater for S. viminalis than for S. discolor on all fertilized plots. The best growth performance of two willows were obtained on the clay site. S. viminalis, planted on the fertilized plots of the clay site, had the highest biomass yield (70.36 tDM ha(-1)). The application of a dose of wastewater sludge (100 kg of "available" N ha(-1)) was not enough to satisfy all nutritional requirements of willows for the period of growth. Over the second rotation the nutrients removed from the soil by willows (in kg per ton of dry mass harvested) were: from 5.3 to 7.5 for N; from 0.6 to 0.9 for P; from 1.8 to 3 for K; from 4.2 to 7.2 for Ca and from 0.4 to 0.7 for Mg. (C) 2003 Elsevier Science Ltd. All rights reserved.