95 O.A. Abdin et al. European Journal of Agronomy 12 2000 93–102
Table 1 Seeding rates of the interseeded cover crops in 1993 and 1994 at Macdonald and l’Assomption, Que´bec
Common name Cultivar
Seeding rate kg ha−1 Fall rye
Prima 110
Hairy vetch Canada no. 1
a 30
Red clover+ryegrass Khun+Marshall
10+8 White clover+ryegrass
Ladino+Marshall 7+8
Subterranean clover Northam
12 Yellow sweet clover
Canada no. 1 7
Black medic Canada no. 1
15 Persian clover
Canada no. 1 10
Strawberry clover Salina
7 Crimson clover
Canada no. 1 22
Alfalfa Nitro
12 Berseem clover
Canada no. 1 20
a Canada no. 1 is a category used to designate an unregistered variety.
the suppression of cover crops, but this does not in 1994, corn yield data were not available for this
site year. contribute to decreasing herbicide use.
Interrow cultivation can provide adequate weed The Macdonald site was fallowed the year
before starting
the experiment,
and the
control in maize. It was reported that interrow cultivation controlled up to 82
of the weeds in l’Assomption site was in pasture the previous year.
The soil type at the Macdonald site was a mixture wide row crops such as maize Forcella et al.,
1992. Greater than 85 weed control was
of Chateauguay clay fine loamy, mixed, non-acid, Frigid Gapludalf in 1993 and St. Bernard clay
reported Parks et al., 1995 when cultivation was combined with lower rate application of herbicides.
fine loamy, mixed, non-acid, Frigid Eutrochrept in 1994. Soil tests prior to planting showed that
In an effort to reduce herbicide use, our study focuses on eliminating the use of herbicides and
the soil at the Macdonald campus site had a pH of 5.5 0.01 M CaCl
2 as a extractant. 5 ton ha−1
utilizing cover crops in combination with interrow tillage as an effective alternative means of weed
of agricultural limestone was applied to raise the pH at this site. At l’Assomption the soil type was
control. The objective of this experiment was to evaluate
a Soulange silt loam fine silty, mixed, non-acid, Frigid Humaquept. 210 and 95 kg ha−1 of 39–
the effects of interseeded cover crops, in conjunc- tion with interrow tillage, for weed control in
18–33 and 18–8–15 N–P–K were added to the soil through the maize seeder at the Macdonald
maize. and l’Assomption sites, respectively. Additional
fertilizer was broadcast immediately prior to plant- ing to achieve the recommended rates of 180, 37
2. Materials and methods
and 100 kg ha−1 of N, P, and K, respectively. The soil was moldboard plowed in the fall of 1993 and
An experiment was conducted in 1993 and 1994 at two Que´bec Canada sites, the E.A. Lodds
harrowed 7 days before planting in the spring of 1994 after which the lime and fertilizer were broad-
Agronomy Research Center, Macdonald Campus of McGill University, Ste Anne de Bellevue, and
cast and disked in, to produce a smooth seed bed. The experiment was arranged in a split-plot
the Agriculture and Agri-Foods Canada Research Station at l’Assomption. The two sites are approxi-
randomized complete block design with four repli- cations at each site. The main plots were cover
mately 80 km apart. However, due to premature mechanical harvest of the entire l’Assomption site
crop planting dates 10 and 20 days after maize
96 O.A. Abdin et al. European Journal of Agronomy 12 2000 93–102
emergence. Scott et al. 1987 suggested that planter model SP510, Pordenone, Italy at the
Macdonald site, and with a John Deere planter interseeded cover crops be seeded when maize is
15 to 43 cm high, corresponding approximately to model Max Emerge2 7200 at the l’Assomption
site in both years. The 1994 experiments were 20 days after maize emergence. However, at north-
ern locations this leaves a shorter period for cover planted on the same sites as the 1993 ones and the
plots of each treatment were planted in the same crop development and earlier seeding could be
desirable. Thus we also included a cover crop location each year. Cultivation was conducted
weekly until forage seeding, with a Rabe Werk seeding treatment 10 days after maize emergence.
At this stage the maize was approximately 11 cm tine cultivator Rabe Werk Machinerie Agricole,
St. Cesaire, Que´bec, Canada. In 1994 an extra tall. The subplots were the type of cover crops [the
12 cover crops and three control treatments includ- cultivation, immediately prior to cover crop seed-
ing, was added. The tines were raised above the ing hand weeded, chemically weeded atrazine plus
dual , and unweeded ] Table 1. The interseeded crop rows so that only the interrows were culti-
vated in 1993, but this was not done in 1994. cover crop cultivars and seeding rates used at all
four site years are given in Table 1. Legumes were A mixture of atrazine 1.0 kg a.i. ha−1 and
metolachlor 1.9 kg a.i. ha−1 was applied pre- inoculated prior to planting with the appropriate
commercial inoculant. In 1993 the three controls emergence to the chemically treated control plot
using a bicycle-wheel plot sprayer. The cover crops were
hand weeded,
chemically weeded
and unweeded treatments. In 1994 a control consisting
were hand broadcast over the plots at their respec- tive densities Table 1. Crop growth was depen-
of mechanical weeding only was added for each planting date. This control was carried out on
dent on precipitation; no irrigation was applied. Total monthly rainfalls and average temperatures
plots in which black medic had been seeded in 1993.
for each site year along with 30 year averages are given in Table 2.
The main plot size was 15 by 21 m and the subplot size was 3 by 7 m. Each subplot consisted
Maize was harvested at maturity during the second week of October in both years. Ears were
of four maize rows planted 76 cm apart with 16.4 cm between plants. The maize hybrid Pioneer
harvested by hand from the two center rows of each plot leaving 1 m unsampled at each end. Corn
3927 was planted on 11 and 13 May 1993, 11 and 14 May 1994 at the l’Assomption and Macdonald
ears were shelled on site with a small plot combine Wintersteiger America Inc., Lincoln, NE . Corn
sites, respectively. Maize was seeded at a planting density of 80 000 seed ha−1 with a Gaspardo
grain was then weighed to determine wet grain
Table 2 Total monthly precipitation and average temperature recorded at Macdonald and l’Assomption during 1993 and 1994 and 30
year averages Year
Precipitation mm Temperature °C
May June
July August
September Total
May June
July August
September Macdonald
1993 79.1
74.8 94.6
57.2 119.2
424.9 13.3
17.6 21.4
20.5 13.9
1994 148
194 61.3
99.9 105.5
607.8 12.1
18.9 21.3
18.0 14.3
Average a
70.6 88.3
89.7 92.6
97.9 439.1
13.1 18.1
21.1 19.8
14.7 l’Assomption
1993 95.6
74.2 75.4
95.6 89.1
429.9 12.7
17.4 20.7
20.3 13.6
1994 93.8
285.9 122.8
67.8 121.6
691.9 11.8
19.3 21.0
19.2 14.7
Average a
72.5 87.0
84.5 94.4
84.6 423.0
12.3 17.5
20.2 18.8
13.8 a 30 year averages.
97 O.A. Abdin et al. European Journal of Agronomy 12 2000 93–102
yield after which it was dried at 70°C to constant album L. and foxtails Setaria spp. were the
predominant weeds there. These were not success- weight to determine the moisture content. Grain
yield is reported on a 0 moisture basis.
fully controlled by initial cultivation and had a significant effect on the efficacy of the tillage cover
Two quadrats 0.5 m by 0.2 m were established parallel to maize rows in each subplot. One quad-
crop system. rat was placed between the maize rows, and the
other on one of the two middle maize rows. During 3.3. Weed density and biomass
the second week of August, a destructive sample was taken in the quadrats and the weeds and cover
Weed density and biomass were lower in 1994 than 1993. This was probably due to the extra
crops were identified, grouped into broadleaves and grasses, and counted. These groups were
cultivation the plots received immediately prior to the seeding of cover crops in 1994, which is in
counted separately and placed in paper bags for drying. The harvested samples were dried to a
agreement with results from previous research Pava and Ulanday, 1993. Weed biomass and
constant weight at 70°C in a forced air dryer, after which they were weighed and their biomass
density were higher on the maize rows than between the rows Tables 3 and 4 at the
recorded. The GLM procedure of the Statistical Analysis
Macdonald site in both years. The same trend was observed at l’Assomption only in 1993. This may
System SAS Institute, 1985 was used to conduct the analysis of variance for all data reported.
have been due to the better growing conditions in 1993 than 1994 Table 2. The generally higher
Probabilities equal to or less than 0.05 were consid- ered significant for main effects and interactions.
weed biomass on the rows than between the rows was probably due to interrow cultivation. A similar
The Waller–Duncan test of significance was used to separate differences between treatment means if
study, investigating the use of intercropped large seeded legumes for weed control, also found that
analysis of variance indicated the presence of such differences Steel and Torrie, 1980. Since no
interrow tillage of the intercrop, prior to seeding, provided the bulk of the weed control Carruthers
difference was found between seeding dates for any of the measured variables, the data were
et al., 1997. In 1993 the cultivator tines were raised over the maize rows so as to minimize the
pooled over cover crop planting dates for each site year.
maize damage. As a result, the rows themselves and the space near the rows were not cultivated,
allowing weeds to establish and grow more readily there. In 1994 the tines were lowered in order to
3. Results and discussion
