84 X. Zhou et al. European Journal of Agronomy 12 2000 83–92
1. Introduction
up to 31 when alfalfa Medicago sativa L. was
interseeded at the time of corn planting. Water-table control is recommended as a man-
There is growing concern that leaching of agement practice to reduce NO−
3 -N pollution from
NO− 3
-N from soil used for monoculture corn pro- agricultural land and increase crop yield Kalita
duction constitutes a major source of NO− 3
-N and Kanwar, 1993; Madramootoo et al., 1993.
pollution of groundwater Martel and MacKenzie, Research by Evans et al. 1995 has shown that
1980; Liang
et al.,
1991. In
Quebec, controlled drainage reduced N and P transport in
Madramootoo et al. 1992 found 40 mg of NO− 3
- drainage water by 30 and 50
, respectively, com- N l−1 in drainage water from a potato field. This
pared to conventional drainage. Meek et al. 1970 exceeds the Canadian water quality guideline
reported reductions of soil NO− 3
-N by up to 50 10 mg NO−
3 -N l−1 for domestic water supplies.
through water-table control, due to denitrification. The adverse health and environmental impacts of
Compared to conventional, free-outlet drainage, a NO−
3 -N contaminated groundwater make it imper-
water-table depth range from 0.6–0.9 m reduced ative to determine NO−
3 -N leaching losses from
the overall NO− 3
-N levels in the soil profile by up cropland and to investigate crop production prac-
to 50 and increased soybean yield by 20
tices that could reduce leaching. Madramootoo et al., 1993. Kalita and Kanwar
Grass species are very effective in reducing 1992 reported that water-table depths from 0.6
NO− 3
-N leaching MacLean, 1977; Steenvoorden, to 1 m increased corn yield, while water-table
1989. Annual
Italian rye-grass
Lolium depths of 0.2–0.3 m reduced corn grain yields due
multiflorum Lam, with its high dry-matter pro- to waterlogging. However, Chaudhary et al. 1975
duction and extensive root system, increases soil concluded that corn response to water-table depths
organic matter, improves soil structure, reduces varied with rainfall during the growing season.
soil erosion, and decreases the loss of NO− 3
-N They found that grain yield increased as the water-
through leaching, by uptake of soil NO− 3
-N table depth increased under wet conditions but
Schery, 1961; Musser and Pekins, 1969; Kunelius decreased as the water-table depth increased under
et al., 1984; Bergstrom, 1986; Groffman et al., dry conditions.
1987. The ability of rye-grass to absorb and No previously reported work has evaluated the
recycle NO− 3
-N can be exploited in corn pro- combination of both intercropping and water-table
duction systems to decrease soil NO− 3
-N and control as a method of increasing N uptake during
reduce leaching of soil NO− 3
-N Claude, 1990. the growing season without decreasing corn yield
Intercropping systems can make more efficient use at harvest. Here, the term intercropping refers to
of light, water and nutrients than crops grown the practice of seeding annual Italian rye-grass
separately. Thus, it is possible to increase N uptake between corn rows 10 days after corn planting and
by corn intercropped with annual rye-grass during plowing the corn stover and rye-grass residues into
the soil after corn harvest. Our objective in this the growing season, thereby reducing potential
work was, under conditions of sufficient N supply, NO−
3 -N leaching by winter rains. Corn yields were
to compare corn yield, uptake of N and N use unaffected when corn was intercropped with
efficiency as affected by an annual Italian rye-grass legumes or grass species such as rye and rye-grass
intercrop component and controlled water-table Scott et al., 1987; Chang and Shibles, 1985.
depths via subirrigation. Intercropped sweet corn yields were comparable
to monocrop yield when intercropped with white clover Trifolium repens L., ladino clover T.
2. Materials and methods
repens L. forma lodigense Hort. ex Gams. and alfalfa seeded at corn planting time or 4 weeks
2.1. Field conditions later Vrabel, 1981. However, Nordquist and
Wicks 1974 reported that corn dry matter was An experiment was conducted during the 1993
and 1994 growing seasons, in Soulanges County, reduced by up to 47
, and grain yield was reduced
85 X. Zhou et al. European Journal of Agronomy 12 2000 83–92
Quebec, Canada. The field had been used for corn Brillion, USA on 6 June 1993 and 9 June 1994,
respectively. production during the 2 years prior to the experi-
Monocrop corn
plots were
treated with
ment. Although the top soil was well drained 4.0 l ha−1
atrazine 2-chloro-4-ethylamino-6-
Soulanges very fine sandy loam fine, silty, mixed, isopropylamino-1,3,5 triazine in both years.
non-acid, frigid Typic Humaquept, clay layers Herbicide was not applied to intercropped treat-
deeper in the soil profile impeded natural drainage. ments in 1993. In 1994, however, 2.25 l ha−1 basa-
The characteristics of the soil layer 0–100 cm gran
[bentazon; 3-1-methylethyl -1H -2,1,3-
are as follows: the top soil 0–20 cm is a sandy benzothiadiazin-43H -one
2,2-dioxide] were
loam with organic matter 50 g kg−1; total N applied to the intercrop treatment to control
4.5 Mg ha−1 and pH 5.5; the sub-soil layer 0.20– broad-leaf weeds. Ragweed Ambrosia artemisii-
0.50 cm is a sandy clay-loam, and the clay soil folia L. was the main weed in the intercropping
layer extends from 0.50 to 100 cm. The surface plots in 1993, while barnyard grass Echinochloa
topography is
generally flat
average slope
crusgalli L. was the main weed in 1994. 0.3
. The applied treatments included two cropping
2.2. Water-table control systems [monocrop corn cv. Pioneer 3921 and a
corn–annual Italian rye-grass cv. Barmultra Two buildings each 5 by 5 m were constructed
intercrop], and three levels of water-table control at the site for water-table control and to monitor
conventional free-outlet subsurface drainage, and drainage water flow. A subsurface drainage lateral
two subirrigation controlled water-table levels with 76 mm i.d. was centrally located in each plot
average water-table depths of 0.70 and 0.80 m, with 0.3
slope along the length of each plot in respectively, below the soil surface. The average
the same direction as the natural drainage. The water-table depth of the free drainage treatments
average depth of these laterals was 1 m. The down- over the two growing seasons of this study was
stream end of each drainage lateral was connected 1.0 m. The controlled water-table depths had origi-
to a 5 m length of a non-perforated PVC pipe with nally been set for 0.50 and 0.75 m, but due to
a 51 mm diameter. These non-perforated PVC seepage and evapotranspiration, the water-table
pipes entered the instrument buildings. The water- depths could only be maintained at 0.70 and
table depth was maintained by water tanks located 0.80 m, respectively. The resulting six treatment
in the instrument buildings Tait et al., 1995; combinations were fertilized with 270 kg N ha−1
Kaluli, 1996. Each plot was separated by a double each spring, the N rate resulting a maximum corn
thickness of 6 mil polyethylene plastic buried verti- production for this area Liang and MacKenzie,
cally below the soil surface to a depth of 1.5 m. 1994. The design of this experiment was a ran-
The purpose of this plastic sheet was to reduce domized complete block with three blocks.
intra-plot seepage. A complete description of the Each plot had a surface area of 1125 m
2 15 by entire water management research facility was
75 m and contained a total of 20 corn rows, with reported previously Tait et al., 1995.
0.75 m between adjacent rows. Corn was planted on 27 May 1993 and 31 May 1994, respectively.
2.3. Plant sampling and analyses The
population densities
were 6.3
and 7.1 plants m−2 in 1993 and 1994, respectively. The
2.3.1. Corn plants lower corn density in 1993 was caused by soil
Ten corn plants were randomly chosen at three compaction due to spring planting conditions,
subsampling sites within each plot and hand-har- which forced seeding into very wet soil. Before the
vested on 12 October 1993 and 13 October 1994. corn emerged, annual Italian rye-grass was sown
The remaining corn plants in each plot were com- between the corn rows of intercrop treatment plots
bine-harvested for grain. Corn stover leaves plus at a rate of 28 kg ha−1 using a forage seeder
stalks was plowed moldboard plow, incorpora- tion to 20 cm into the field shortly after harvest.
Brillion model SS60-01, Brillion Iron Works,
86 X. Zhou et al. European Journal of Agronomy 12 2000 83–92
Corn plant subsamples harvested from each plot randomly, starting at the fourth or fifth row from
the border of the larger plots. These unfertilized were used to determine grain yield and dry-matter
production. The harvested plants were separated areas were marked to prevent any unlabeled N
fertilizer application to the areas inside them, they into leaves, stalks and grain, then weighed,
chopped, subsampled, forced-air-dried 70°C , were later used for
15N microplots in each year. After the corn emerged, a 1.15 by 1 m area Zhou
and finally weighed again. Final grain yields in both years were expressed at 0
moisture. Dried et al., 1998 within the marked area 2.25 by 3 m
was selected as the 15N microplot. To delimit the
composite subsamples of grain, leaf and stalk samples were ground with a Wiley mill A.H.
microplot, a solid plastic barrier was hammered into the soil along both sides and both ends of
Thomas Co., Philadelphia, PA to pass through a 2 mm sieve for plant-tissue and grain total N
each microplot to a depth of 20 cm. A solution of 15NH
4 15NO
3 at 5
15N excess was sprayed evenly determinations.
in the microplot at the same rate of N fertilizera- tion 270 kg ha−1 as the rest of the large plot on
2.3.2. Rye-grass and weeds To allow estimation of the total above-ground
17 June 1993 and 16 June 1994, respectively. Immediately following the placement of the micro-
dry-matter production and N uptake, three areas 0.75 by 0.5 m of intercrop rye-grass and weeds
plot, the rest of the unferilizered area was hand- fertilized with 34–0–0 NH
4 NO
3 at the same rate
were harvested in the intercropped plots at the same time as the corn was harvested in both years.
as the rest of the large plot. Corn in the microplots was harvested at the same time as the larger plots
The rest of rye-grass and weeds were ploughed into soil after harvest in both years. The rye-grass
were harvested, as three separate sampling groups taken 50, 30 and 10 cm from both ends of the
and weeds were separated by hand and dried to a constant weight in a forced-air dryer 70°C for
microplots. All harvested plant samples were sepa- rated into leaves, stalks, and grain. Harvested
estimation of dry-matter production. Subsampled rye-grass and weeds were ground for estimation
samples were dried to a constant weight at 70°C. Total N was determined as described above. The
of total N content. Total plant N was determined by Kjeldahl
titration solutions from the Kjeldahl analysis were used for
15N analysis Martin et al., 1991. The analysis Tecator, Kjeltec 1030 auto analyzer,
Ho¨gana¨s, Sweden using the method of Bradstreet percentage
15N atom enrichment in the plant samples was determined by emission spectroscopy
1965. Nitrogen uptake by corn, rye-grass and weeds was determined from the total N concen-
using a JASCO –150 15N analyzer JASCO, LTD,
Tokyo, Japan. Fertilizer nitrogen recovery FNR tration of plant tissues and dry weights at the end
of each season. was calculated by the following equation:
2.3.3. 15N microplot establishment
Fertilizer N recovery =
pc−b×100 f a−b
, In both years, 141 kg K ha−1 were applied
before planting
in all
plots. At
planting, 52 kg P ha−1, as 18–46–0 N–P2O5–K2O, were
where p is the total N in corn grain, corn stover, rye-grass, or weeds, f is the amount of N fertilizer
applied into in each plot, respectively. Nitrogen fertilizer
was split
into two
applications: applied, and a, b, and c, are the atom
15N concentrations in the fertilizer, unlabeled control
47 kg N ha−1 as 18–46–0 N–P2O5–K2O at plant- ing and 223 kg N ha−1 as 34–0–0 NH4NO3
plants, and labeled plants, respectively. As
15N enrichment of plant tissue was 2 weeks after planting.
To determine the fertilizer N recovery, two unaffected by plant position within the microplot
Zhou et al., 1998, we used the percentage 15N
15N microplots on opposite sides of each of the larger plots were established in two blocks in this
enrichment from the plants at the central position to calculate the fertilizer nitrogen recovery FNR.
study. Before N fertilizer application in 1993 and 1994, a 2.25 by 3 m unfertilized area was chosen
In order to better relate the final plant growth
87 X. Zhou et al. European Journal of Agronomy 12 2000 83–92
values to the entire plot, the total N values of season May to October was 98 mm below the
20 year average. plant tissue from outside the microplots were used
to calculate FNR. Three sampling groups of rye-grass and weeds
3.1. Grain yield and total aboveground dry-matter production
were harvested in the same manner as the corn plants within the microplots. In order to obtain a
reliable 15N recovery Jokela and Randall, 1987,
Corn grain yields were unaffected by the pres- ence of rye-grass and weeds in either year
the rye-grass and weeds were sampled at least 0.38 m from the end of the microplots. The
Table 1. The average intercropped corn yield was
similar to
the 3 year
mean yield
of sampled rye-grass and weeds were separated by
hand, dried, weighed and ground. Total N and monocropped
corn in
Quebec Liang
and MacKenzie, 1994. Similar results have been noted
15N were determined as described above for corn plants.
previously with intercropped legumes Kurtz et al., 1952; Searle et al., 1981. Scott et al. 1987 found
that corn yield was unaffected by the presence of 2.4. Data analysis
underseeded intercrop components if the latter were seeded when the corn was 0.15–0.30 m high.
Data were analyzed using analysis of variance with the SAS PROC GLM General Linear
In our experiment, the rye-grass was planted about 9 days after the corn. The rye-grass started to
Models procedure SAS Institute, 1985 and single-degree-of-freedom contrasts. Because there
emerge when the corn plants were about 0.30 m tall in both years. Indigenous weeds had not fully
was no cropping system by water-table depth interaction for any of the measured variables, this
established by that time. Therefore, the lack of strong competition from the rye-grass or weeds
interaction has been omitted from the tables. during the early growth stages and sufficient N
270 kg N ha−1 applied to minimize any competi- tion between the corn, weeds or rye-grass for this
3. Results and discussion
