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
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