Diversifying crop rotations with temporary grasslands - Université de ...

The viability and germination ability of the sown seeds was determined by germination and
dissection assays. 10 seeds of each species were kept in moist conditions in growth chambers,
three replicates at 30°C/20°C day/night and three replicates at 20°C/10°C day/night
temperature. Germinated seeds were counted and removed until germination ceased after
approximately one month. Further germinations were provoked by a) drying the seeds for one
week and re-humidifying them, b) stratifying the seeds for 3 weeks at 4°C and c) by twice
adding a solution of gibberellins. Seeds not germinated after all these treatments (about 4
month in total) were dissected to count the number of viable embryos and to calculate the rate
of viable seeds (Table 7).
C.II.2.2 Measurements
C.II.2.2.1
Plant densities
Weed plant densities were assessed approximately every month (except in winter) by
determining and counting the number of plants of all species on three permanently installed
metal frames of 0.36m² (0.6m*0.6m) per replicate plot (3*4 = 12 frames per treatment, * 9
treatments = 108 frames). As a control, additional frames were installed in the adjacent zone
of each plot not sown with weeds (‘unsown zone f’, Fig. 10).
C.II.2.2.2
Biomass
Crop and weed aboveground biomass was assessed 5-6 times per year in 2007 and 2008 by
manually cutting weed and crop shoots at 5cm from the soil surface on one non permanently
installed quadrat of 0.36 m² per replicate plot ( Fig. 10). Shoots were sorted to species, dried at
80°C for 48h, and weighted. These measurements were always done a few days prior to the
cutting dates of the perennial crops, when crops and weeds had maximum biomass and
impacts on the crop stand were minimal.
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