Diversifying crop rotations with temporary grasslands - Université de ...
Diversifying crop rotations with temporary grasslands - Université de ...
Diversifying crop rotations with temporary grasslands - Université de ...
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Weed biomass (g m -2 )<br />
500<br />
400<br />
300<br />
200<br />
100<br />
tillage after harvest (T9). The two other annual <strong>crop</strong> treatments (T10, T11) had similar <strong>crop</strong> and weed biomasses<br />
and are not shown. Dotted vertical lines indicate the 1 st<br />
January of each year (for orientation purposes).<br />
Comparisons of <strong>crop</strong> and weed biomasses for each replicate plot at each measurement date<br />
showed contrasting patterns. Negative relationships were observed for all five measurement<br />
dates in 2007, i.e. plots <strong>with</strong> high <strong>crop</strong> biomass had low weed biomass and vice versa ( Fig.<br />
19A).<br />
These relations followed negative exponential or power laws. For each successive<br />
measurement, regression lines moved closer to the axis, i.e. the weed biomasses strongly<br />
<strong>de</strong>creased <strong>with</strong> time during 2007. In contrast, <strong>crop</strong> and weed biomass did not show any<br />
negative relations in 2008 ( Fig. 19B).<br />
A majority of plots did not contain any weed biomass at<br />
all measurement dates in 2008 (as for the last measurement in 2007), some plots combined<br />
high <strong>crop</strong> and weed biomass at two dates in 2008 leading to slightly positive relations (Fig.<br />
19B). These cases correspon<strong>de</strong>d mainly to the annual <strong>crop</strong> treatments (spring barley) and to<br />
the autumn sown alfalfa <strong>crop</strong>s <strong>with</strong> a low cutting frequency (see T2 in Fig. 18). However, total<br />
weed biomass was mostly lower than <strong>crop</strong> biomass (Fig. 19B).<br />
A) 2007<br />
25.04.2007<br />
05.06.2007<br />
09.07.2007<br />
27.08.2007<br />
19.10.2007<br />
R 2 = 0.39 y = 9092x -0.94<br />
R 2 = 0.12 y = 1255x -0.58<br />
R 2 = 0.22 y = 559x -0.54<br />
R 2 = 0.42 y = 130094x -2.2<br />
R 2 = 0.11 y = 3.08x -0.37<br />
0<br />
0 100 200 300 400 500 600 700 800 900<br />
Crop biomass (g m-2 )<br />
Fig. 19: Relation between <strong>crop</strong> and weed biomass at five observation dates in 2007 (A) and 2008 (B).<br />
Each symbol corresponds to one replicate plot at one sampling date. The nine <strong>crop</strong> treatments are not<br />
distinguished. Continuous coloured lines show power regressions for each date in 2007. Broken grey lines show<br />
equal <strong>crop</strong> and weed biomasses.<br />
94<br />
500<br />
400<br />
300<br />
200<br />
100<br />
B) 2008<br />
24.04.2008<br />
26.05.2008<br />
09.07.2008<br />
26.08.2008<br />
04.11.2008<br />
0<br />
0 100 200 300 400 500 600 700 800 900 1000
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