220 L. Heydel et al. European Journal of Agronomy 11 1999 217–225
weed treatment. Weeds were recorded by species tive in limiting pesticide transfer from one plot to
and were further identified by location within the the others; 3 no other molecule interfered during
plot. Those that fell within a 20 cm band centered atrazine residue dosage.
on the corn-row were recorded as ‘in-row’ and all Atrazine residue concentrations measured in
others as ‘between-row’. Three measurements were broadcast and band treatments using a porous
taken per plot for each weed estimation. cup, throughout the 3 year study, are presented in
Fig. 2. For each treatment, the concentrations were extremely variable. Indeed, they ranged from 0.02
2.6. Weeding control cost detection limit to 18 mgl; the highest values being
observed 2–6 weeks after atrazine applications. Weeding
costs were
determined using
a machinery costs work sheet Table 2 provided by
These results are consistent with those of other the Bureau Commun du Machinisme Agricole
researchers Jayachandran et al., 1994, who Krebs, 1997. Weeding time requirements were
reported similar concentrations of atrazine residue evaluated by using the average speed observed on
found in shallow groundwater systems. large fields.
Despite the concentration variability, the gene- ral shapes of the two curves were similar: in June,
after atrazine application, the concentrations of 2.7. Statistical analysis
atrazine residue observed in the water samples Data were subjected to analysis of variance
reached a peak. Then, they decreased gradually using the SAS glm procedure, which tested treat-
until October or November. After that, they lev- ment effects and interaction of years. Means were
eled off until the next atrazine application. compared by Fisher’s protected LSD at the 0.05
Therefore, two levels of atrazine residue concen- probabilty level.
tration could be distinguished: 1 a higher level between June and October–November and 2 a
lower level from November to the next atrazine application. These results agree with those of Tasli
3. Results and discussion
et al. 1996, who reported the highest concen- trations in June after atrazine application and
3.1. Atrazine residue concentrations: general trend lowest concentrations after November.
The rapid increase in atrazine residue in June Atrazine residues were never detected in the
probably resulted from preferential flow through samples analysed for the mechanical weeding treat-
macropores. Once transported, atrazine residue ment. This result indicated that: 1 no atrazine
applied as a spray may be concentrated on or near residue remained in the soil solution before the
field investigations; 2 grass alley ways were effec- the surfaces of the large pores where they are again
Table 2 Machinery costs work sheet
Commercial value Use
Cost F Euros
F Euros Work short
60 9.1h Tractor 75 HP 2 wheel drive
170 000 25875 700 hyear
64 9.7h Six-row hoe with band sprayer 1.5 hah
65 000 9900 150 hayear
70 10.7ha 12 m sprayer 3 hah
70 000 10650 150 hayear
75 11.4ha Atraphyt 50
atrazine 20.9 3.2l
3 lha 63 9.6ha
Lentagran 45 pyridate
156 23.7l 2 lha
312 47.5ha
221 L. Heydel et al. European Journal of Agronomy 11 1999 217–225
Fig. 2. Dynamics of atrazine residue concentrations mgl in porous cups according to the method of atrazine application [average atrazine residue concentrations mgl : broadcast application: 1.95; band application+mechanical weeding: 0.52].
susceptible to transport by additional rainfall cup, was larger than the 20 cm band over the corn
row which received atrazine. Consequently, suction Isensee et al., 1990. This assumption seemed
relevant because we observed numerous macro- cup sampled water came from with in-row and
between-row which did not receive atrazine, 3 pores due to earthworms and clay desiccation.
Such rapid leaching through macropores has also the atrazine residue movement in the soil was not
vertical and only a part of the residues could be been observed by Baer et al. 1992 and Graham
et al. 1992. sampled by the suction cup. This hypothesis is
consistent with Sadeghi and Isensee 1992 who Atrazine residue identifications several months
after atrazine aplication may be explained by studied the spatial distribution of atrazine in soil
and found that the atrazine movement in soil is migration through the microporous structure and
by adsorptiondesorption on soil particles. Such not vertical. The spatial distribution of atrazine is
extremely variable and depends on tillage practice, slow leaching has also been observed by Buhler
et al. 1993. rainfall timing and rainfall distribution. This
hypothesis also agree with Heddadj 1996 who reported atrazine movement from with in-row to
3.2. Atrazine residue concentrations: comparison between broadcast and band treatment
between with row after a band treatment. Large differences appeared between the data for
the two weed treatments for concentration levels. 3.3. Corn yield
Average concentration of atrazine from band treat- ment was about 73
less than from broadcast There were no differences between treatments
at harvest in 1995, but differences were observed treatment Fig. 2. Factors that may have contrib-
uted to the lower concentration of atrazine residue in 1996 Table 3. Corn yields were lower in
mechanical weeding alone compared with the two in the band treatment are: 1 the lower amount
of applied atrazine due to the banded application other treatments. Differences between those treat-
ments were entirely attributable to the weed pop- only a 20 cm band over the corn row received
atrazine, 2 the recharge area of the suction cup, ulation for the mechanical weeding treatment.
Those results were similar to other studies Mulder i.e. the space in which the water flows towards the
222 L. Heydel et al. European Journal of Agronomy 11 1999 217–225
Table 3 Corn yield according to weeding method tha
a Year
Weeding method Broadcast application
Band application+mechanical weeding Mechanical weeding
Average yield and standard deviation 1995
13.16 0.99 a 13.68 1.02 a
13.19 0.37 a 1996
16.75 1.34 a 16.15 1.79 a
7.03 0.88 a 1997
14.41 1.22 a 13.60 1.26 a
– a Means followed by the same letter do not differ P=0.05, as deduced from the Newman–Keuls least difference test.
Yields were not measured in the mechanical weeding treatment in 1997.
and Doll, 1993; Pleasant et al., 1994; Seconda, combined herbicide plus mechanical weeding. The
weed cover ranged from 16 to 20 .
1994; Imgraben and Juncker-Schwing, 1995. 3.4. Weed control
3.4.3. Weed cover distribution In 1995 and 1996, the in-row weed cover was
higher, compared with the between-row cover, in 3.4.1. Composition of the weed population
Before the experiment, the weed population was the mechanical weeding alone Table 5. This
emphasized the difficulty of controlling weeds in essentially composed of Poa annua L., Poa trivialis
L., Alopecurus myosuroides Huds., Medicago sativa the corn row with conventional cultivation equip-
ment. Band application of herbicide over the row L., Taraxacum officinalis L., Capsella bursa pastoris
Moench., Veronica hederifolia L., Veronica persica eliminated this problem as there were no differ-
ences in the distribution of weed cover in any plots Poir., Lamium purpureum L. and Rumex crispus L.
There were no differences in composition of the of the band treatment. These results agree with
those of Pleasant et al. 1994, who reported the weed population among plots. Throughout the
3 years of the experiment, the weed population has efficiency of combining cultivation with banded
herbicides to control weeds in corn. changed Table 4, but there were no differences
in composition in the weed population between treatments.
3.5. Weeding control cost Armstrong et al. 1968 indicated that if only
3.4.2. Weed cover Weed cover in 1995 ranged from 14 to 58
yield and costs were considered and mechanical weeding was timely, mechanical weeding methods
with differences between weed control treatments. Weed cover was much higher in the plot with
were more profitable than chemical weeding. When the risk of untimely mechanical weeding was con-
mechanical weeding alone compared with the two other treatments. Among those two treaments,
sidered, banded atrazine with one cultivation gave the highest return Mulder and Doll, 1993. In
there were no differences in weed cover. The weed pressure in 1996 was higher than that
our research, corn yields were equivalent for the chemical weeding method and for the banded
of the previous year, ranging from 16 to 73 cover. Plots with cultivation alone averaged more
atrazine with one cultivation, and the weeding cost was lower for the combined method Table 6.
than 70 cover, compared with less than 21
in the treatment with herbicide or a combination of
This suggested that the combined weeding method gave higher economic returns than the broadcast
herbicides plus mechanical weeding. In 1997, there were no differences in weed cover
method. However, with the combined weeding method, the in-field time requirements increase.
between plots with herbicide alone or those that
223 L. Heydel et al. European Journal of Agronomy 11 1999 217–225
Table 4 Weed changes among years on mechanical weeding plots
a Weed
1995 1996
1997 Spring
Autumn Spring
Autumn Spring
Autumn Alopecurus myosuroides Huds.
++ +
++ +
++ +
Anagallis arvensis L ++
+ ++
+ ++
+ Capsella bursa pastoris Moench.
++ +
+ +
+ +
Chenopodium album L. +
+++ +++
+++ +++
+++ Fumaria officinalis L.
+ +++
++ +++
+++ +++
Lamium purpureum L. +
+ ++
+ ++
+ Matricaria recutita L.
+ ++
++ +++
++ +++
Medicago sativa L. +++
+ +
+ Poa annua L.
+++ +
+ +
+ +
Poa trivialis L. +
+ +
+ +
+ Rumex cripus L.
++ +
+ +
+ +
Stellaria media L. +
+ +++
+ ++
+ Taraxacum officinalis L.
+ +
+ Veronica hederifolia L.
++ ++
++ +
++ +
Veronica persica Poir. ++
++ ++
+ ++
+ a Relative abundance: 0, none; +, some; ++, presence; +++, coverage.
Table 5 Visual in-row, between-row and plot weed cover between weeding methods
a Localisation
Weeding method Broadcast application
Band application+mechanical weeding percentage weed cover Mechanical weeding
1995 1996
1997 1995
1996 1997
1995 1996
In-row 14 a
15 a 13 a
14 a 15 a
18 a 67 c
73 c Between row
14 a 16 a
16 a 24 a
24 a 22 a
43 b 70 c
Plot 14 a
16 a 16 a
20 a 21 a
20 a 58 bc
73 c a Means followed by the same letter do not differ P=0.05, as deduced by the Newman–Keuls least difference test.
Table 6 Operational costs estimated for the three weeding methods
Broadcast application Band application+mechanical weeding
Mechanical weeding Field time
20 minha 90 minha
60 minha Number of runs
Two broadcast applications One band application+one mechanical weeding
Two mechanical weeding Work force
40 F 6 Eurosha 150 F 23 Eurosha
120 F 18 Eurosha Draught
43 F 6.5 Eurosha 160 F 24 Eurosha
128 F 19 Eurosha Herbicide application
150 F 23 Eurosha 70 F 11 Eurosha
0 Fha Herbicides
372 F 57 Eurosha 99 F 15 Eurosha
0 Fha Mechanical weeding
0 Fha 70 F 11 Eurosha
140 F 21 Eurosha Total
605 F 92.5 Eurosha 549 F 84 Eurosha
388 F 58 Eurosha
224 L. Heydel et al. European Journal of Agronomy 11 1999 217–225
sons of mechanical and chemical weed control. Weed Sci.
4. Conclusions