Agriculture Reference
In-Depth Information
80
BBCH 21
BBCH 25
BBCH 29
BBCH 30/31
BBCH 31/32
BBCH 32/33
BBCH 39
BBCH 49
BBCH 60
BBDH 69
60
40
growth stages in BBCH
are numerically identical
to those defined in EC
20
0
0
2
4
6
8
10
12
14
16
dry matter biomass in t per ha
Fig. 11.2
Sensing the aboveground biomass of winter wheat at various growth stages by ultrasonics
(From Reusch
2009
, altered)
Finally, sensing leaf-area-indices or biomasses via the bending resistance of
crops requires even a minimum growth stage of about EC or BBCH 35 (Ehlert et al.
2004
). This is when the fi rst fl ag leaf - still rolled - has appeared.
The
savings in fungicides
that can be realized with a site-specifi c control based on
biomass via a full-area preventive concept will vary with the heterogeneity of a crop.
When the sensing in ten fi elds with small cereals and growth stages between EC or
BBCH 39 and 71 was based on the bending resistance, savings in pesticides between a
minimum 7 % and a maximum of 48 % were realized (Ehlert and Dammer
2006
). The
average saving in fungicides was 23.1 %. The savings did not affect the grain yields.
11.3
The Discrete-Spot Sensing Concept Based
on Refl ectance
11.3.1
The Pinpointing Approach and the Field of View
Theoretically, the savings in fungicides could be much higher than indicated above
if only at the start of a fungal epidemic the infected loci were treated. This
pinpoint-
ing approach
still is in an experimental stage.
Site-specifi c spraying against fungi is much more diffi cult than site-specifi c
fertilizing of nitrogen, though the sensing might be based in both cases on the refl ec-
tance of the canopy. Because usually nitrogen defi ciencies occur in much larger
