Corn yield and fertilizer N recovery in water-table-controlled corn–rye-grass systems
Introduction
There is growing concern that leaching of NO−3-N from soil used for monoculture corn production constitutes a major source of NO−3-N pollution of groundwater (Liang et al., 1991, Martel and MacKenzie, 1980). In Quebec, Madramootoo et al. (1992) found 40 mg of
NO−3-N l−1 in drainage water from a potato field. This exceeds the Canadian water quality guideline (10 mg NO−3-N l−1) for domestic water supplies. The adverse health and environmental impacts of NO−3-N contaminated groundwater make it imperative to determine NO−3-N leaching losses from cropland and to investigate crop production practices that could reduce leaching.
Grass species are very effective in reducing NO−3-N leaching (MacLean, 1977, Steenvoorden, 1989). Annual Italian rye-grass (Lolium multiflorum Lam), with its high dry-matter production and extensive root system, increases soil organic matter, improves soil structure, reduces soil erosion, and decreases the loss of NO−3-N through leaching, by uptake of soil NO−3-N (Bergstrom, 1986, Groffman et al., 1987, Kunelius et al., 1984, Musser and Pekins, 1969, Schery, 1961). The ability of rye-grass to absorb and recycle NO−3-N can be exploited in corn production systems to decrease soil NO−3-N and reduce leaching of soil NO−3-N (Claude, 1990). Intercropping systems can make more efficient use of light, water and nutrients than crops grown separately. Thus, it is possible to increase N uptake by corn intercropped with annual rye-grass during the growing season, thereby reducing potential NO−3-N leaching by winter rains. Corn yields were unaffected when corn was intercropped with legumes or grass species such as rye and rye-grass (Chang and Shibles, 1985, Scott et al., 1987). Intercropped sweet corn yields were comparable to monocrop yield when intercropped with white clover (Trifolium repens L.), ladino clover (T. repens L. forma lodigense Hort. ex Gams.) and alfalfa seeded at corn planting time or 4 weeks later (Vrabel, 1981). However, Nordquist and Wicks (1974) reported that corn dry matter was reduced by up to 47%, and grain yield was reduced up to 31% when alfalfa (Medicago sativa L.) was interseeded at the time of corn planting.
Water-table control is recommended as a management practice to reduce NO−3-N pollution from agricultural land and increase crop yield (Kalita and Kanwar, 1993, Madramootoo et al., 1993). Research by Evans et al. (1995) has shown that controlled drainage reduced N and P transport in drainage water by 30 and 50%, respectively, compared to conventional drainage. Meek et al. (1970) reported reductions of soil NO−3-N by up to 50% through water-table control, due to denitrification. Compared to conventional, free-outlet drainage, a water-table depth range from 0.6–0.9 m reduced the overall NO−3-N levels in the soil profile by up to 50% and increased soybean yield by 20% (Madramootoo et al., 1993). Kalita and Kanwar (1992) reported that water-table depths from 0.6 to 1 m increased corn yield, while water-table depths of 0.2–0.3 m reduced corn grain yields due to waterlogging. However, Chaudhary et al. (1975) concluded that corn response to water-table depths varied with rainfall during the growing season. They found that grain yield increased as the water-table depth increased under wet conditions but decreased as the water-table depth increased under dry conditions.
No previously reported work has evaluated the combination of both intercropping and water-table control as a method of increasing N uptake during the growing season without decreasing corn yield at harvest. Here, the term intercropping refers to the practice of seeding annual Italian rye-grass between corn rows 10 days after corn planting and plowing the corn stover and rye-grass residues into the soil after corn harvest. Our objective in this work was, under conditions of sufficient N supply, to compare corn yield, uptake of N and N use efficiency as affected by an annual Italian rye-grass intercrop component and controlled water-table depths (via subirrigation).
Section snippets
Field conditions
An experiment was conducted during the 1993 and 1994 growing seasons, in Soulanges County, Quebec, Canada. The field had been used for corn production during the 2 years prior to the experiment. Although the top soil was well drained Soulanges very fine sandy loam (fine, silty, mixed, non-acid, frigid Typic Humaquept), clay layers deeper in the soil profile impeded natural drainage. The characteristics of the soil layer (0–100 cm) are as follows: the top soil (0–20 cm) is a sandy loam with organic
Results and discussion
Precipitation levels varied between the two growing seasons (Fig. 1). The 1993 growing season was relatively wet, with accumulated rainfall from May to October, inclusive, being 30 mm above the 20 year average. By comparison, the 1994 growing season (May to October) was 98 mm below the 20 year average.
Conclusions
Intercropping corn with annual rye-grass is an effective method for increasing N uptake conditions of high fertilizer N application systems. Intercropping caused no reduction in corn grain yield if adequate nutrients and soil water were supplied. The intercrop system had a substantially greater N uptake than the monocrop system, even though N fertilizer recovery did not change between cropping systems. This indicated that the intercropping system used non-fertilizer N more effectively.
Acknowledgements
The authors thank Mr Stewart Leibovitch for his expert technical assistance and Mr Peter Kirby for his field assistance. The senior author also acknowledges the financial support of a Hydro-Quebec Major Fellowship through McGill University; the Frederick Dimmock Memorial Scholarship through the Macdonald Campus of McGill University; The Macdonald Class of '44 Graduate Student Bursary through the Macdonald Campus of McGill University; and Natural Sciences and Engineering Research Council of
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