Physical and Cultural Weed Control Working Group of - European ...

9 th EWRS Workshop on Physical and Cultural Weed Control 85
Samsun, Turkey, 28 – 30 March 2011
Weed inhibitory effect of different paving constructions
B. De Cauwer 1 , M. Fagot 1 , D. Reheul 1 , R. Bulcke 1 , E. Boonen 2 and A. Beeldens 2
1 Ghent University, Faculty of Bioscience Engineering, Department of Plant Production, Coupure
Links 653, B-9000 Ghent, Belgium Email Benny.DeCauwer@UGent.be
2 Belgian Road Research Centre, Fokkersdreef 21, B-1933 Sterrebeek , Belgium
The recent phase out of herbicidal use on public pavements by the Flemish government triggers
the development of new alternative weed control strategies. Besides the search for effective nonchemical
curative methods, there is also a need for weed preventive strategies on pavements. In this
study, effects of type of joint filling material, joint width, pollution and type of street layer material
were assessed for their impact on weed germination and coverage.
In 2009, a paving experiment with 96 block paving plots was set up under a rain shelter. Block
paving plots were 60 cm x 24 cm and were arranged in a randomized complete block with 3
replications. Each block paving plot consisted of a conventional (non permeable) concrete block
paving (11cm x 11cm pavers + joint filling, thickness: 8 cm) on top of a street layer (thickness: 4
cm), supported by a base layer (thickness: 13 cm). Paving plots comprised factorial combinations of
five joint filling materials, two joint widths, two pollution levels and two street layer materials.
Tested joint filling materials were (in brackets grain size fraction): fine white sand (0-2 mm), sea
sand (0-2 mm), crushed porphyry (grain size fractions 2-6.3 mm), crushed limestone (0-6.3 mm)
and Dansand® (a sodium silicate enriched sand specifically designed for weed prevention). Joint
filling materials were evaluated in pure (0% fine compost by volume) and organically polluted state
(10% fine compost by volume). This pollution level was designed to mimic in situ organic pollution
of joints. Street layer materials tested comprised crushed porphyry (2-6.3 mm, a good water
permeable aggregate) and crushed limestone (0-6.3mm, a less water permeable aggregate). After
establishment of the block paving plots, each paving plot was oversown with a mixture (100
germinable seeds per species) comprising Taraxacum officinale, Poa annua, Plantago major and
Trifolium repens, all dominant, hard to control weed species on pavements. Weed inhibitory effect
of paving plots was determined by examining weed germination and weed coverage. Weed
germination was recorded weekly during the first five weeks after sowing. Weed coverage was
recorded monthly over a two-year period by using Image J Software. Pavings were watered three
times a day by automatic sprinkler irrigation (2.1 mm/day).
Weed germination and weed coverage was highest in pavings with wide joints and polluted
joint filling material. In pavings with polluted filling material, the type of street layer material
significantly influenced weed germination and weed coverage. Weed preventive ability of joint
fillers was highest for sodium silicate enriched sand (Dansand®) followed by crushed porphyry,
irrespective of pollution level, joint width or type of base layer. The weed inhibitory effect was
higher for the coarser filling materials porphyry and limestone than for the finer filling materials
white sand and sea sand, irrespective of pollution level or type of base layer. Within standard filling
materials, unpolluted sea sand and porphyry reduced seedling emergence of all species tested. Shifts
in weed composition occurred due to observed species-specific inhibitory effects of joint filling
materials. Overall, these results show an opportunity for weed prevention by using suitable paving
materials in the construction of pavements. Pavings showing long-lasting weed suppressive ability
might reduce total adverse environmental impact of curative weed control by reducing its frequency
required to keep weed density at an acceptable level.