Diversifying crop rotations with temporary grasslands - Université de ...
Diversifying crop rotations with temporary grasslands - Université de ...
Diversifying crop rotations with temporary grasslands - Université de ...
You also want an ePaper? Increase the reach of your titles
YUMPU automatically turns print PDFs into web optimized ePapers that Google loves.
C.II.3.1.4 Effect of weed seed addition<br />
During the first month of the experiment, field emergence rates were always much lower than<br />
the <strong>de</strong>nsities of viable seeds ad<strong>de</strong>d to the soil at the beginning of the experiment. However,<br />
this ratio showed consi<strong>de</strong>rable differences between the weed species, separating three groups<br />
of species (Fig. 15). Field emergence <strong>de</strong>nsities were about 2-5 times lower than sowing<br />
<strong>de</strong>nsities for a first group of species including G. aparine, V. persica, G. dissectum, S. media,<br />
A. myosuroi<strong>de</strong>s, and L. multiflorum. For a second group including C. bursa-pastoris, F.<br />
convolvulus, and B. sterilis, emergence rates were about 10 times lower (thus 10-15%<br />
emergence). For a third group containing the remaining 8 sown species, only 1-5% of the<br />
sown viable seeds emerged during the 8 first month of the experiment (Fig. 15).<br />
Emergence <strong>de</strong>nsity<br />
(seedlings m -2 )<br />
10<br />
8<br />
6<br />
4<br />
2<br />
0<br />
GALAP<br />
1:1 1:2<br />
PAPRH<br />
GERDI<br />
ALOMY<br />
0 10 20 30 40<br />
Sowing <strong>de</strong>nsity (viable seeds m -2 )<br />
Fig. 15: Relation between weed sowing <strong>de</strong>nsity and field emergence <strong>de</strong>nsities of 17 weed species.<br />
See Table 7 for species co<strong>de</strong>s. Field emergence are means (±SD) of maximum seedling <strong>de</strong>nsities on sown mi<strong>crop</strong>lots<br />
during the first 8 month of the field experiment. SD of sowing <strong>de</strong>nsity corresponds to the variability of seed<br />
viability tested in Petri dishes (cf. Table 7).<br />
Comparisons of weed emergence <strong>de</strong>nsities on sown and unsown micro-plots showed that<br />
weed seed addition increased the plant <strong>de</strong>nsities of all sown weed species (except C. bursapastoris)<br />
during the first month of the experiment ( Fig. 16).<br />
The initial positive effect of<br />
sowing increased <strong>with</strong> time for three species (group 1 in Fig. 16 including A. myosuroi<strong>de</strong>s, B.<br />
sterilis, and G. aparine, thus the species that showed strong population increases in the annual<br />
<strong>crop</strong>s). The positive effect of seed addition remained more or less stable for four species<br />
(group 2 in Fig. 16 including V. persica, S. arvensis, L. multiflorum and P. rhoeas) and<br />
89<br />
VERPE<br />
LOLMU<br />
POLCO<br />
BROST<br />
CAPBP<br />
VIOAR<br />
SINAR<br />
LAMPU CHEAL<br />
STEME<br />
POAAN<br />
ANGAR<br />
1 st group<br />
2 nd group<br />
3 rd group<br />
AMARE<br />
1:5<br />
1:10<br />
1:40