Site‐related set‐back by weeds on the establishment of 12 biomass willow clones

Abstract

Ten commercial clones of willow and two breeding clones were studied for their ability to compete with weeds during the establishment year at three different sites in southern Sweden. Cuttings were planted according to commercial practice in April, and the two treatments, 'Weeded' and 'Unweeded', were laid out in a strip-plot design. Weeds in the 'Weeded' treatment were removed mechanically and by hand hoeing. Willow plant shoot weight and plant mortality were measured after the first growing season to evaluate the initial effect of weeds. In addition, weed flora, weed aboveground biomass, soil properties, shoot damage and soil moisture were assessed during the growing season. Plant mortality was <1% in the 'Weeded' treatment at the three study sites, while in 'Unweeded' it was significantly higher, 2.7%, 24.6% and 37.4%. Weeds reduced willow plant shoot weight by 93.4%, 94.0% and 96.1% at the three sites. Only one site showed clonal differences in shoot growth reduction, as well as in plant mortality. These results show the importance of weed control in willow plantations, as growth of all clones tested were dramatically hampered by weeds during the first growing season, regardless of trial site conditions. Moreover, conditions at certain sites, such as soil properties in combination with weed cover, may cause high plant mortality during the establishment year in this perennial biomass crop.

Effects of competition between short-rotation willow and weeds on performance of different clones and associated weed flora during the first harvest cycle

“…The preparation, planting, management and local conditions of the three trial sites (J, P and S) and the pedigree of the clones are described in detail in a previous paper [8]. That paper focuses on the establishment year whereas this paper mainly focuses on the two subsequent growing seasons.…”

“…If differences exist between willow clones in weed competitive ability it would be possible to select for this trait during breeding. Albertsson et al [8] found only small differences in weed tolerance between 12 willow biomass clones during the establishment year. In other crops such as wheat [12], soybean [14] and maize [15], there are differences between cultivars in their ability to compete with weeds.…”

“…Several reasons for this have been suggested with reduced growth due to weed problems being one important agronomic factor [4]. Willow SRC is severely hampered by weeds during the establishment year both in terms of growth [6e8] and plant survival [8]. If weeds are not controlled during the establishment year, this has a negative effect on yields in subsequent seasons [9].…”

Quality Testing of Short Rotation Coppice Willow Cuttings

“…At the start of the experiment the rods were divided into cuttings of 20 ± 0.1 cm in length as long as their diameter was more than 7 mm and their location along the rod in terms of position from the ground (1)(2)(3)(4)(5)(6)(7)(8), number of visible buds on the bark and diameters of the apical cutting part were recorded and the cutting was marked using a waterproof pencil. In total, 120 cuttings per clone in 2009 and 60 cuttings in 2010 were made.…”

“…It is especially important to ensure fast, equal sprouting of cuttings with consecutive rapid shoot growth occur during the first growing season of SRC, since this is the period where the largest seed bank of weed species in the plantation soil exists and competition between sprouting cuttings and weeds can be expected [5][6][7]. Therefore, a lot of attention has been paid to the study of critical factors that may impact the growth potential of cuttings [8].…”