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Chapitre 3 Evaluation du modèle STICS version pesticide sur différents sites
expérimentaux
of anionic resin. Several micro-lysimeters were used and were randomly distributed
in the experimental field. At each sampling date two replicates were collected and
analyzed. Maize was seeded in spring, and the atrazine herbicide was sprayed
separately from bromide. The Bromide and Atrazine contents were analyzed on
5-cm-deep samples in each lysimeters collected. Pesticide on the activated carbon
could not be analyzed because of extraction problems.

3.2.4 Model set up
Three kinds of parameters have to be prescribed for the model : soil parame-
ters, crop parameters including cultural practices (sowing and harvest dates, crop
management), and pesticide parameters (Table 3.2).

Study site Soil Depth FC WP Bulk foc
3
-3
horizon (cm) (m .m ) (m .m ) density (%)
-3
3
kg m-3
Vredepeel 1 0.-30 0.21 0.12 1330 2.3
2 30-60 0.24 0.15 1550 1
3 60-100 0.22 0.04 1690 1
Kerlavic: soil of 1 0-20 0.309 0.123 1280 1.1
Lorraine 2 20-35 0.321 0.122 1370 0.9
3 35-60 0.350 0.145 1550 0.4
4 60-100 0.341 0.146 1530 0.3
Thiverval-Grignon 1 0.-30 0.271 0.128 1300 1.1
2 30-120 0.221 0.115 1300 1.1

Table 3.2 – Soil characteristics used in STICS : Fc : field capacity (m3/m3), wp :
wilting point (m3/m3), foc : fraction of organic carbon (%)

As the main objective of the study was to assess the STICS model in a confi-
guration that could be acquired in an experimental basin, the model was not
calibrated, and the parameters were set according to :measurements in situ, lite-
rature review, or default values. For the soil parameters, the field capacity, wilting
point and organic carbon profiles were derived from field data, except for the field
capacity and the wilting point at Vredepeel, for which we used the parameters
suggested by Nicholls et al., 28 . These authors made a study using PLM (Pesticide
Leaching Model) that used a similar approach for soil water transfer to that of
STICS, and had to modify the soil parameters in order to be able to capture the
observed variability of the soil moisture which was affected by the evolution of a
water table, processes that cannot be properly handled by a capacity model. The
plant parameters used for the simulations at the different study sites were specific

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