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SWEEP Report #12

Choice and Management of Cover Crop Species and Varieties
for Use in Row Crop Dominant Rotations

R. Samson, C. Foulds, D. Patriquin, Resource Efficient Agricultural Production (REAP) - Canada, Ste. Anne-de-Bellevue, Quebec

Executive Summary

Evaluation Summary (Tech. Transfer Report Summaries)

View / Download Final Report  [584 KB pdf]

Associated SWEEP/LSP Research



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Completed: May, 1990

Key Words:

cover crops, corn, interseeding, ryegrass, weed suppression, soybeans, winter barley, rye, relay cropping, ground cover, winter wheat, catch crop, red clover, hairy vetch, oilseed radish

Executive Summary

The management of cover crops in four major field crops (corn, soybeans, winter wheat and spring cereals) was evaluated over a two year period on farms in southwestern Ontario. The research was established within the framework of a corn-soybean-cereal rotation sequence. The presumption is that from an economic and environmental standpoint this sequence will develop in the 1990's to become the dominant farming sequence used in southwestern Ontario on farms that do not grow forages. The experiments are classified in three stages around this rotation with overlap between years.  

Stage 1

Stage 2

Stage 3




Individual findings are summarized below.


1. Comparison of Ryegrass Cultivars for Interseeding in Corn

There was no suppression of corn yield when ryegrass interseedings were performed on the final cultivation approximately 35 days after corn planting. Ryegrass cultivars demonstrated considerable differences in biomass production. Only one perennial ryegrass cultivar (Ellett) produced as much fall biomass as the four annual cultivars. In general, biomass production was low. To increase biomass production, the interseedings should likely be overwintered and restricted to sites with corn yields below 10 t/ha. Aside from the soil conservation value of the interseedings, a major benefit was weed suppression. Biomass of the weeds present on the sites (quack grass and a variety of annual grass and broadleaf weeds) was on average reduced by 50% by the productive ryegrass interseedings.

2. (a) Rye Tillage Management Systems for Soybeans

Very high ground cover was obtained when winter rye was managed as a no-till mulch versus systems where the rye was disced or plowed. Achieving adequate soybean stands proved difficult in the treatments where tillage occurred and soybean yields were low. In tilled plots, the most promising treatment appeared to be that in which rye was harvested as a forage and the stubble subsequently plowed before soybean planting.

2. (b) Soybean No-Till Systems with Rye

In the drought year of 1988, better soybean stands and yields were obtained where soybeans were no-tilled into standing rye, than where rye was first mulched and soybeans subsequently no-tilled. A high soybean yield (3.0 t/ha dry matter) was obtained when planting before mowing was performed at rye heading. Delaying no-till seeding until rye anthesis (1 week later) reduced soybean yields to 1.7 t/ha as germination was delayed until the drought ended. Rye harvested as a silage at heading yielded 3.45 t/ha dry matter and enabled timely no-till soybean planting. When the rye was left on the surface as a mulch, no annual weeds were observed in any of the treatments, and 100% ground cover was obtained.

2. (c) Evaluation of Rye Varieties for No-Till/Mow-Kill Soybean Production

Rye varieties demonstrated considerable differences in early spring ground cover, biomass production at heading, and heading date. After no-till planting and mowing, Kustro grain rye had 50% less regrowth than the forage rye Wheeler. Soybean yields were 40% lower on average on the rye cover cropped plots than the no-tilled soybeans without a rye cover crop. Soybeans on the rye mow-kill plots were shorter and chlorotic. The mow-kill system provided good weed control without herbicides and eliminated the need for a contact and broadleaf herbicide which was required in the no-till treatment without a cover crop.

2. (d) High Moisture Winter Barley Soybean Relay Cropping

Dry weather, poor winter barley survival, and poor penetration by the no-till drill combined to cause poor success with this system. No soybeans suitable for combining were obtained from any of the relay cropped soybeans. The high moisture relay cropped winter barley (on average harvested at 43% moisture) provided for a winter barley harvest two weeks earlier than when left for grain. However, high moisture relay cropped winter barley, on average resulted in 35% lower winter barley yields than monoculture winter barley. The barley was likely harvested earlier than physiological maturity. When the relay cropped barley was combined as dry grain in 1989, a 50% reduction in barley yield resulted from barley lodging, and soybeans growing into the barley canopy.

3 (a) No-Till Winter Wheat and Red Clover Plowdown Following Soybeans

No-till wheat systems of aerial seeding at leaf yellowing in soybeans and zero-till drilling after soybean harvest provided good establishment and wheat yields equivalent to conventionally tilled and planted winter wheat. Ground cover was substantially increased by both no-till planting methods. Aerial seeding provided slightly higher ground cover than no-till drilling at both sites. On average, aerial seeding provided 90% ground cover when measured in late October and late April. Following winter wheat harvest, neither weed growth or fall biomass production of red clover plowdown was affected by the method of establishment of the winter wheat.

3 (b) Interseeding and Catch Crop Systems for Winter Wheat

In 1988, hairy vetch drill seeded in winter wheat in mid May produced significantly higher quantities of above ground biomass (3367 and 2554 kg/ha on the silt loam and sandy loam sites respectively in 1988) than other interseeded species (red clover, crimson clover, and nitro alfalfa). Clover established poorly on the sandy loam site in the drought year. On the silt loam site in 1988, establishment and biomass production were highest the earlier the red clover was seeded (March 15) while in 1989 the best establishment and biomass production was achieved at the latest seeding date (May 15). A fall catch crop of oilseed radish produced very high fall biomass in 1988 on the sandy loam site (3654 kg/ha) while the growth on the silt loam site (950 kg/ha averaged over two years) was poorer. The difference was likely related to low residual soil N on the silt loam site. Interseeded hairy vetch and oilseed radish seeded after wheat harvest were competitive with fall weed growth when a diverse weed flora was present. However, at the sandy loam site in 1989, all the cover crops were outcompeted by a heavy quack grass infestation.

3 (c) Interseeding and Catch Crop Systems for Spring Cereals

Red clover, hairy vetch and crimson clover interseedings were extensively killed in the drought on the sandy loam. Alfalfa was the interseeded cover crop producing the highest biomass. The few crimson clover plants that did survive the drought grew very well on the sandy loam soil. Blind harrowing, just prior to grain emergence, increased the weed infestation. On the clay loam site, hairy vetch seeded at blind harrowing produced very high fall biomass (3446 kg/ha) but climbed extensively in the grain at harvest. The highest biomass-producing system at both sites was the treatment in which liquid manure was applied; it stimulated growth of both oilseed radish and regrowth of the cereal. However, the oilseed radish seems to be more suited for use after winter cereals because the spring cereals regrew aggressively and provided approximately 50% of the fall biomass.

3 (d) Interseeded Cover Crops and Mechanical Weeding Systems in Spring Cereals in 1989

A more extensive study was performed to further evaluate mechanical weeding systems and their compatibility with establishment of red clover and the annual cover crops (crimson clover and hairy vetch). Hairy vetch introduced at finger weeding (approximately 30 days after main crop seeding) and drill seeding (approximately 45 days after main crop seeding) produced the highest fall biomass amongst cover crop treatments. Climbing of the hairy vetch in the grain at harvest was greatly reduced compared to 1988, with no appreciable climbing occurring in the drilled treatment. On the clay loam site, the mechanical weeding devices (finger weeding, harrowing, and rotary hoeing) doubled fall biomass production from the clover cover crops compared to surface broadcasting without shallow incorporation. Post emergent harrowing appeared to be too aggressive on the grain crop and caused significant plant loss, particularly in the wheel traffic areas. Both finger weeding and rotary hoeing significantly reduced weed biomass at grain harvest at the silt loam site. Overall, the rotary hoe appears to hold the most promise of the two devices as the finger weeder plugs where corn stalks are present.

4 (a) Effect of 1988 Interseeded Cover Crop and Catch Crop Systems In Winter Wheat on Nutrient Cycling and Corn Yield in 1989

The most promising cover crop treatments at the silt loam site and sandy loam site were evaluated for their effect on nutrient cycling and corn yield. Whether measured by differences in corn grain yield or leaf ear N content at silking, estimates of nitrogen release from cover crops were very similar. Unfertilized hairy vetch provided corn yields equivalent to corn fertilized with approximately 100 kg/ha fertilizer N at both sites. The other cover crop species tested: red clover (on the silt loam site), and crimson clover and oilseed radish (on the sandy loam site), provided unfertilized corn yields equivalent to corn fertilized with approximately 75 kg N/ha. Sampling to determine differences in phosphorus nutrition among treatments taken at the five leaf stage indicated a high correlation between N and P content. Legumes cover crops showed positive effects on N and P content. Oilseed radish significantly reduced uptake of phosphorus and nitrogen at the five leaf stage.

4 (b) Effect of 1988 Interseeded Cover Crop and Catch Crop Systems in Winter Wheat and August Manure Applications on Nutrient Cycling and Corn Yield in 1989

Red clover generally provided higher leaf ear N contents and corn yields than other cover crop species tested (crimson clover, hairy vetch, nitro alfalfa). Unfertilized red clover provided corn yields equivalent to corn fertilized with approximately 50 kg N/ha. Cultivation after the cereal grain harvest in 1988 reduced 1989 corn leaf ear N and corn yields by approximately 20% compared to the uncultivated control plot. Application of manure in August 1988 had little impact on leaf ear N or corn grain yield in 1989. Significant loss of nitrogen may have been experienced at this site as a result of wet field conditions and early release of nitrate from the annual cover crops. Comparisons indicated that although the five legume cover crop treatments had lower soil P than manure treatments, P content of the corn at the five leaf stage was increased significantly. Nitrogen levels in the corn at the five leaf stage were also increased significantly by the legume cover crops.

Evaluation Summary

(From Technology Transfer Report Summaries - A. Hayes, L. Cruickshank, Co-Chairs)

The study was conducted in three separate parts.

  1. The two year study evaluated different ryegrass cultivars as interseeded crops into standing corn. The ryegrass was broadcast into standing corn at the five leaf stage of the corn (after the critical period for weed control). Weed control prior to ryegrass planting was accomplished by banded herbicide plus cultivation.

    Ryegrass establishment was variable, and was negligible in corn yielding over 10 tonnes per hectare. In lower yielding fields, the interseed reduced weed biomass by up to 50%, proportional to ryegrass growth. There were no significant corn yield differences with any of the treatments.


  2. This study looked at different methods of managing rye mulched or winter barley grain crops in a soybean production system. Treatments for rye included mowing at heading, plowing or disking and then planting soybeans into the resulting residue. Regrowth of the rye, planter operation and final soybean yields were monitored.

    Relay cropping soybeans into winter barley harvested as high moisture grain was not successful. Barley yields were low and inconsistent, and soybeans did not provide any grain yield.


  3. For this study different methods of winter wheat establishment were compared following soybeans. Also different types of interseedings and catch crops in cereals were compared. There was no difference in wheat establishment or yield with the methods used (aerial seeding, no-till, conventional tillage). Post harvest weed growth or red clover interseeding were not affected by the establishment method.

    Hairy vetch as an interseeded crop, or oilseed radish planted after cereal harvest were shown to have some potential for nutrient cycling to the next crop. Hairy vetch appeared to release larger amounts of nitrogen to the following corn crop, more than other legume crops. Oilseed radish was able to absorb large quantities of nitrogen from manure in late summer and release it the following spring.


There appears to be a number of concerns with the various parts of this study.

  1. Weed seed production was not measured and weed growth was not monitored in subsequent crops to determine if there were any long-term weed control benefit. The issue of nitrates was not addressed. However, the total biomass (weeds plus ryegrass) was not significantly affected, and therefore would not expect nitrate uptake to be increased by adding the ryegrass crop.


  2. Killing rye by mowing was not compared to the usual practice of herbicide burn down, which would provide weed suppression without rye regrowth. Failure to obtain good stands because of poor drill operation made interpretation of the results difficult.


  3. Spring cereals as potential crops for nutrient cycling were not studied. These crops may be just as effective at a lower cost to the producer. The fertilizer response curves shown in the report indicate that the maximum yield had not been reached at the nitrogen levels used, therefore it is difficult to determine if the nitrogen release came from the catch crops.

Associated SWEEP/LSP Research:

  • SWEEP Report #27 - Cereal Cover Crop Study

  • SWEEP Report #29 - The Effect of Organic Mulches on Soil Moisture and Crop Growth

  • SWEEP Report #32 - Optimal Herbicide Use in Conservation Tillage Systems

  • SWEEP Report #36 - Red Clover Cover Crop Studies 1987-1990

  • SWEEP Report #43 - The Use of Cover Crops for Nutrient Conservation

  • SWEEP Report #52 - Field Scale Tests of Cover Crops I and II

  • SWEEP Report #57A - Field Testing of Cover Crop Systems for Corn and Soybean Production

  • LSP 7005 - Crop Rotations and Cover Crop Effects on Erosion Control, Tomato Yields and Soil Properties in Southwestern Ontario

  • LSP 7009 - A Cover Cropping Strategy for First Early Potato Production

Future Research: ( ) indicates reviewers suggestion for priority, A - high, C - low.

None required.




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Created: 05-28-1996
Last Revised: Thursday, May 19, 2011 01:44:14 PM