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