soil bulk density and crop yield under eleven consecutive years of corn with different tillage and...
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Soil & Tillage Research 84 (2005) 41–53
Soil bulk density and crop yield under eleven consecutive
years of corn with different tillage and residue practices
in a sandy loam soil in central Canada
R.F. Dama, B.B. Mehdia, M.S.E. Burgessb, C.A. Madramootooa,*,G.R. Mehuysa,b, I.R. Calluma
aBrace Centre for Water Resources Management, 21,111 Lakeshore Road,
3 Stewart Park, Ste-Anne-de-Bellevue, Que., Canada H9X 3V9bDepartment of Natural Resources, McGill University, 21,111 Lakeshore Road,
3 Stewart Park, Ste-Anne-de-Bellevue, Que., Canada H9X 3V9
Received 4 July 2003; received in revised form 23 August 2004; accepted 26 August 2004
Abstract
Different tillage and residue practices could potentially lead to significant differences in both crop production and soil
properties, especially if both practices are implemented over a long time period and on continuous monoculture corn (Zea mays
L.). The objective of this research was to determine how differing tillage practices and corn residues affected soil bulk density,
corn emergence rates and crop yields over an 11-year period. The experimental site consisted of three tillage practices (no-till,
NT; reduced tillage, RT; and conventional tillage, CT) and two residue practices (with grain corn residue, R; without residue
(corn crop harvested for silage), NR). Bulk density was 10% higher in NT (1.37 Mg m�3) than in CT (1.23 Mg m�3),
particularly at the 0–0.10 m depth. Spring corn emergence in NTR was slower by 14–63% than all other treatments in 1992–
1994. In 1996, corn emergence in the NTR treatment was 18–30% slower, and NTNR was 5–30% faster than all other
treatments. No-till with residue (NTR) possibly had the slowest overall emergence due to the higher surface residue cover
(8.5 Mg ha�1 in 1996) and higher bulk density (1.37 Mg m�3 over the 11 years). Long-term mean dry matter corn yields were
not affected by tillage and residue practices during the course of this study; rather climatic-related differences seemed to have a
greater influence on the variation in dry matter yields. The long-term cropping of corn under different tillage and residue
practices can change bulk density in the surface soil layer, vary the corn emergence without affecting yields, and produce
comparable yields between all the tillage and residue practices.
# 2004 Elsevier B.V. All rights reserved.
Keywords: Bulk density; Grain yield; Tillage; Residue; Maize; No-till; Corn; Conservation tillage
* Corresponding author. Tel.: +1 514 398 7833; fax: +1 514 398 7767.
E-mail address: [email protected] (C.A. Madramootoo).
0167-1987/$ – see front matter # 2004 Elsevier B.V. All rights reserved.
doi:10.1016/j.still.2004.08.006
R.F. Dam et al. / Soil & Tillage Research 84 (2005) 41–5342
1. Introduction
Agricultural tillage practices have changed in
Canada over the decades. The 2001 Canadian
Agricultural Census showed an increasing trend in
farms using conservation tillage practices (Statistics
Canada, 2002). In 1991, for example, 31% of
Canadian farms used conservation tillage practices.
This rose to 60% in 2001. Conservation tillage is
intended to leave residue on the soil surface, and may
include reduced till (using disks or chisel plough, for
example) or no-till. Meanwhile, conventional tillage
typically involves moldboard plowing after harvest
and disking in the spring before seeding.
Conventional tillage helps to control weeds,
enhance porosity, and incorporate organic matter into
the soil. However, conventional tillage also tends to
increase soil erosion and degrade natural soil structure
(Hillel, 1982). In contrast, conservation tillage
minimizes erosion, conserves water within the root
zone, and improves soil productivity (Durr et al.,
2001).
Conservation tillage practices can also impact soil
physical properties, such as bulk density, total
porosity, hydraulic conductivity and aggregate stabi-
lity, both positively and negatively. For example,
Ausilio et al. (2001) found that after 5 years of
conventional tillage corn (Zea mays L.), the clay loam
soil had a higher aggregate instability than no-till.
Also, Kushwaha et al. (2001) found that no-till had a
10% higher bulk density than conventional tillage in a
sandy loam soil study cropped to corn over 2 years.
Bulk density is considered to be a measure of soil
quality due to its relationships with other properties
(eg., porosity, soil moisture, hydraulic conductivity,
etc.). Blevins et al. (1994) found that no-till and
conventional tillage had no significant bulk density
differences. Fausey et al. (1994) found that on
continuous corn, corn-soybean (Glycine max. L.
Merrill) and corn-oat (Avena sativa L.)-meadow
rotations that no-till had a 7% lower bulk density in
all rotations compared to conventional tillage. Fausey
et al. (1994) concluded that, after 28 years, bulk
density was lowest in no-till likely due to crop residues
maintained on the soil surface.
Corn yields are undoubtably affected by such field
characteristics and operations as soil strength,
compaction, soil water, tillage and residue practices,
time of field operations and soil fertility, which
together influence emergence, root development and
nutrient availability (Curnoe et al., 2001). Residues
from the previous year left on the soil surface can
influence subsequent yields, which Denton and
Wagger (1992) attributed to the presence of residue
cover, which increased soil water availability and
grain yield in their no-till plots. Kapusta et al. (1996)
found that no-till had a lower corn population and
greater barrenness (where no corn grew) compared to
conventional, reduced and alternating tillage practices
over 20 years on a silt loam. They concluded that no-
till was not beneficial on imperfectly drained soils
(Kapusta et al., 1996). Poorly drained soils are of
concern in parts of Quebec where corn production on
heavy clay soils is common.
Considering that to obtain good yields, the early
stages of growth are critical, especially optimal soil
and air temperatures and soil moisture conditions for
healthy emergence, no-till is generally perceived to
produce lower yields than conventional tillage. Drury
et al. (1999) found that no-till plots had delayed corn
emergence on a clay loam site in Ontario, Canada
due to cooler soil temperatures and wetter seed beds.
Some of these poor seed bed conditions in no-till
systems could be attributed to residue cover
remaining on the soil surface. Residue cover in the
spring can trap melting snow and also reduce
evaporation from the soil surface in the spring, thus
keeping the soil cooler which can be detrimental to
early crop growth (Drury et al., 1999; Jamieson et al.,
1999). Delayed corn emergence rates are a concern
within minimally tilled sites. Early season growth
might be delayed in conservation tillage systems
due to higher water contents and lower soil
temperatures. However, no-till systems could be
beneficial to crop growth in seasons that are drier
than normal, as Kapusta et al. (1996) found on a silt
loam in Illinois.
Crop yield studies are difficult to compare due to
variations in length of the study, soil type and climatic
region between studies. Kapusta et al. (1996) found
after 20 years of corn on no-till, reduced tillage and
conventional tillage on a silt loam in southern Illinois,
there were no significant differences in pooled corn
yields between treatments. Clapp et al. (2000)
working on a silt loam soil in east central Minnesota,
found that in 9 out of 13 years of corn under no-till,
R.F. Dam et al. / Soil & Tillage Research 84 (2005) 41–53 43
chisel plow and moldboard plow, there were no tillage
effects on grain yield, but there were differences due to
residue management in 8 of the 13 years. In Atlantic
Canada, Carter et al. (2002) found that after 6 years of
corn on no-till, conventional and rotational tillage, the
mean yield was 7.2–7.7 Mg ha�1 and it was not
consistently influenced by tillage. Also, dry matter
yield had a yearly variation of 5.1–10.6 Mg ha�1,
which Carter et al. (2002) attributed to plant
population and corn heat units rather than tillage or
rotation.
Since the establishment in1991of the research site
described in this paper, Burgess et al. (1996), Mehdi
(1998), Mehdi et al. (1999), Callum (2001) and Dam
(2003) have conducted research in different years each
with different objectives related to tillage and residue
differences. The common parameters taken during
each study was bulk density, corn emergence rates (in
some years) and crop yield. In order to investigate the
trends or differences due to tillage practices or residue
treatment, data was complied from those studies.
Therefore, the objective of this study was to determine
how 11 years of continuous and differing tillage and
residue treatments affected soil bulk density, corn
emergence rates, and yields on loamy sand–sandy
loam soil cropped to corn in southwestern Quebec,
Canada.
2. Materials and methods
2.1. Site description
The site was located on a 2.4-ha area on the
Macdonald Campus Research Farm of McGill
University in Ste-Anne-de-Bellevue, Quebec, Canada
(latitude 458300N, longitude 738350W). The soil is St.
Amable loamy sand and shallow loamy sand with
pockets of Courval sandy loam, overlying clay at a
mean depth of 0.46 m. It is classified as a Dystric
Gleysol in the FAO soil classification system. The
mean sand, silt and clay contents over the 0–0.20 m
depth were 815, 89, 96 g kg�1, respectively. The
average slope at the site is less than 1%. In 1990, the
year prior to establishment of the experiment, the site
was planted to an alfalfa (Medicago sativa L.)–grass
mix (Burgess et al., 1996). Regrowth was plowed
under in May 1991 and the site was amended with 6–8
Mg lime ha�1. Subsurface drains were installed within
the centre of each plot in the 1970s, to a mean depth of
1.2 m. Since 1991, the site has been under continuous
corn (Zea mays L.).
2.2. Experimental design and treatment
applications
The experiment was laid out as a randomized
complete block design with a factorial arrangement
of treatments consisting of two levels of crop residue
(without residue and with residue) and three levels of
tillage (no-till, reduced tillage and conservation
tillage), replicated in three blocks, resulting in a
total of 18 plots. Each plot measured 18.5 m � 80 m.
The plots were separated by 2 m wide buffer strips
and the blocks were separated by 3–4 m wide buffer
strips. Conventional tillage (CT) consisted of mold-
board plowing after harvest to a depth of about
0.20 m and tandem disking in the spring before
planting to a depth of 0.10 m. Reduced tillage (RT)
consisted of offset disking to 0.15 m after harvest and
tandem disking to a depth of 0.10 m in spring, before
planting. Tandem disks were used for fall tillage in
RT plots in 1991 and 1992. No-till (NT) was not
tilled at any time. Without residue (NR) treatment
consisted of corn harvested as silage corn, where
only stubble (0.15 m of stalk) remained, resulting in a
smaller amount of residue coverage (Burgess et al.,
1996). The with residue (R) treatment consisted of
harvesting only the kernels as grain corn. The cobs,
leaves and stalks were chopped by the combine and
returned to the field. The residues remaining on the
soil surface in no-till were partially incorporated in
reduced till and were completely incorporated in
conventional tillage.
Corn was planted with a modified John Deere
planter (7100 MaxEmerge integral, double-disk seed
opener) with the corn at 0.76 m row spacing and at a
density of 76,000 plants ha�1. Phosphate was applied
with the seed at planting, and ammonium nitrate (or
urea, 1996 only) and potassium were top-dressed 2–6
weeks later. Applied nitrogen totalled 180 kg N ha�1
year�1, phosphorus 70–100 kg P ha�1 year�1, and
potassium 69–150 kg P ha�1 year�1. Both P and K
application rates were selected on the basis of soil tests
(for plant extractable K and P) using the Melich III
test, which is the standard fertilizer test in Quebec. For
R.F. Dam et al. / Soil & Tillage Research 84 (2005) 41–5344
a detailed summary of field operations for the duration
of this study (see Table 1).
Field measurements were conducted from 1991 to
2002 under several different projects each with a
different objective. Due to the difference in objectives,
some measurements were not taken in all years, or at
the same frequency.
2.3. Soil data collection
Bulk density was determined from 1991 to 2002,
except in 1994 and 1998 when no samples were
taken. For each sampling period, soil cores (0.10
diameter by 0.10 m height) were taken at 0–0.10 m
and 0.10–0.20 m depths in all years, except in 1991
(0–0.10 m and 0.15–0.25 m), 1999 and 2000 (0–
0.077 m and 0.10–0.177 m). Bulk density core
samples were taken from random locations in all
years, except in 1995–1997. In each of these years at
each sample location, two bulk density sub-samples
were taken, one from a wheel tracked inter-row and
one from an untracked inter-row. Sampling for bulk
density also occurred at different times during the
growing season depending on the objectives, con-
venience and climatic conditions for the particular
period of study, depending on the researcher’s
objectives.
2.4. Crop data collection
Emerging seedlings were counted in 10 randomly
selected rows from each plot in 1-m long sections.
The seedlings were counted in 1992–1994, 1996 and
1997 at 2–4 weeks following planting. There were
two emergence counts conducted in 1996 and 1997,
while there was only one emergence count in 1992–
1994.
Dry matter yield was determined by hand harvest-
ing a 2.5-m length of corn row at six random locations
per plot at the end of the growing season (between
October 3 and November 7). There was no differ-
entiation of harvesting time between tillage or residue
practices in any year; therefore, the maturity
differences of corn between the treatments was not
part of the scope of this study. Harvesting took place in
each year when the corn dried sufficiently in all
treatments, thus harvesting occurred on different dates
year to year. During harvest, the stalks and cobs were
collected and counted. The cobs were removed from
their husk and stored in brown paper bags to be dried.
Once dried (over 2–3 days at 70 8C), the cobs were
shelled, the kernels were weighed and grain yield was
determined. The stover (stalks, leaves and husks) from
each sample location was weighed and chopped by a
single row harvester (1 row New Holland 890
Harvester) and a subsample was collected and
weighed for drying at 70 8C for at least 48 h. Once
the stover subsample was dried and reweighed, the
stover yield was determined. Dry matter yield was
determined by adding both stover yield and grain yield
together.
2.5. Climatic conditions
Ambient temperature and precipitation were
obtained from the Environment Canada Atmospheric
Station at the Montreal International Airport approxi-
mately 15 km east of the study site (Fig. 1;
Environment Canada, 1991–2002). During the study
period, the St. Lawrence–Great Lakes region experi-
enced some of the more extreme weather events
recorded in 54 years of recorded data. The second,
third and eighth wettest summers on record were
experienced in 1992, 1994 and 2000, respectively. The
first, third and eighth driest summers were experi-
enced in 2001, 1991 and 2002, respectively. The fifth,
sixth and seventh warmest summers were experienced
in 1995, 1999 and 1991, respectively and finally, the
coolest summer on record was in 1991 (Meteorolo-
gical Service of Canada, 2002).
2.6. Statistical analyses
Repeated-measures analysis of variance (ANOVA)
with depth as a repetition factor was used to evaluate
depth effect on bulk density in each year. For each
depth, treatment differences from each year were
evaluated using the Student–Newman–Kuels (SNK)
test at 0.05 level of probability.
Corn emergence data, grain and dry matter yields
were analysed for each sampling period using the
general linear model ANOVA. The SNK test at 0.05
level of probability was used to determine treatment
differences. All of the above procedures were
conducted using SAS Statistical Software (Statistical
Analysis Systems Institute Inc., California, 1990).
R.F.Dam
etal./S
oil&
Tilla
geResea
rch84(2005)41–53
45
Table 1
Field operations at study site since initiation of experiment in 1991a
Operation 1992 1993 1994 1995 1996 1997 1998 1999 2000 2001 2002
Secondary tillage May 15 May 11 May 11 nd May 15 May 22 Apr 28 May 5 May 2,
May 3
May 1 May 6
Spring soil sampling May 14,
May 15
May 10 None None May 14 May 22 Apr 24 May 30 May 30 May 2–7 May 6–8
Seeding; subsurface
fertilizer
May 19 May 11 May 18 May 8 May 16 May 26 May 11 May 6 May 8 May 8–9 May 21
Seed hybrid Funk 4120 Funk 4120 nd nd Cargill
2827
Cargill
2827
Cargill
2827
Cargill
2277
Cargill
2610
Cargill
2610
Mycogen
2610
Top-dressed fertilizer
(Wheel-tracked
interows)
June 2 June 8 June 20 June 15 June 3:Urea,
K June 18:K
June 9:K
June 12:N + K
June 5 June 4 June 19 June 15 July 3
Total K (kg ha�1 year�1)
(N 180, P 70–100)
70 70 70 150 150 150 150 70 70 69 69
Herbicides June 2 May 12,
June 17
May 11,
May 20,
June 8
May 10,
June 8,
June 14
May 21,
May 29,
June25
May 27,
June 17
May
13–14,
June 22
May 11,
June 8,
June 17
June 7 June 1,
June 28
(selected
plots)
May 8 (NT),
June 20, July
11(B1),
July 25
Yield subsamples October
19–20
October
13–14
October
13–14
October 10 October 7 October 16 October
4–5
September
28–29
October 5 October
1–2
October 4,
October 21
Harvestb October
29–November 2
November 9 October 31,
November 7
November 6,
November 7
October 25 October 20,
November 5
October 9,
October 16
October 7,
October 1
October 12,
October 16
October 3,
October 18
November 2,
November 4
Fall soil
sampling
November 5, 6 November 12 November 15 November 14 October 29 November 6 October 23 None None October 22 None
Primary tillage (CT) November 6 November 12 November 16 nd November
1–4
April 22,
1998
October 26 October 20 October 24 October 19 November 5
Primary tillage (RT) November 18 November 17 November 17 November 24 October 31 April 23 1998 October 25 November 1 October 25 October 22 November 7
a 1991: Harvest: October 28–31; fall soil sampling November 13 and 18.b Where two dates are shown, grain-corn plots were harvested on first date; second date is for no-residue (NR, ‘silage’) plots. nd, No data.
R.F. Dam et al. / Soil & Tillage Research 84 (2005) 41–5346
Fig. 1. Temperature and precipitation from 1991 to 2002 with 30-year average (1961–1990) temperature and precipitation including the months
of May to September.
3. Results and discussion
3.1. Bulk density
Average bulk density was generally significantly
lower at 0–0.10 m than in the underlying layer (1.29
and 1.35 Mg m�3, respectively). There was no
depth � residue interaction in any of the 11 years
and only one instance of depth � tillage � residue
interaction was confined to 1996 (Table 2). The
depth � tillage � residue interaction in 1996 could be
attributed to significantly greater soil strength mea-
sured in the NTR and NTNR compared to the other
treatments in early spring 1996 (Mehdi et al., 1999).
Differences in bulk density between the shallow and
deeper depths were seen every year, with higher bulk
density values in the deeper layer. A significant depth–
tillage interaction was found in 1996, 1999, 2001 and
2002, which was attributed to the primary fall/spring
tillage operations taking place predominately in the
top soil layers (tandem disk to 0.10 m, offset disking to
0.15 m and moldboard plowing to 0.20 m).
At the 0–0.10 m depth, NT was found to have a
greater bulk density than RT or CT in all years except
R.F. Dam et al. / Soil & Tillage Research 84 (2005) 41–53 47
Table 2
Bulk density by tillage and repeated measures analysis with depth as a repetition factor for 1991 to 2002 excluding 1994 and 1998
Year Depth (m) Tillage Repeated-measures analysis with depth as repetition
NT RT (Mg m�3) CT Depth Depth � tillage Depth � residue (Pr < F) Depth � tillage � residue
1991 0–0.10 1.41 1.38 1.36 0.0739 0.9502 0.1552 0.3850
0.15–0.25 1.44 1.41 1.40
1992 0–0.10 1.30 a 1.30 a 1.17 b 0.0140 0.2935 0.1397 0.8307
0.10–0.20 1.35 1.36 1.29
1993 0–0.10 1.25 a 1.19 ab 1.12 b 0.0685 0.1593 0.1904 0.7040
0.10–0.20 1.24 1.22 1.14
1995 0–0.10 1.39 1.33 1.29 0.0130 0.2290 0.4220 0.2711
0.10–0.20 1.43 1.42 1.32
1996 0–0.10 1.34 a 1.26 b 1.24 b <0.0001 0.0012 0.1958 0.0420
0.10–0.20 1.36 1.38 1.34
1997 0–0.10 1.36 a 1.24 b 1.25 b 0.0239 0.1018 0.2870 0.8342
0.10–0.20 1.40 1.37 1.26
1999 0–0.10 1.43 a 1.32 b 1.32 b <0.0001 0.0006 0.0528 0.8080
0.10–0.20 1.44 1.43 1.39
2000 0–0.10 1.46 a 1.35 b 1.34 b 0.0840 0.1059 0.2366 0.4344
0.10–0.20 1.45 a 1.39 ab 1.36 b
2001 0–0.10 1.44 a 1.26 b 1.19 b 0.1423 0.0212 0.1658 0.5193
0.10–0.20 1.38 a 1.32 ab 1.26 b
2002 0–0.10 1.34 a 1.06 b 0.96 c 0.0026 0.0336 0.6042 0.6830
0.10–0.20 1.36 1.24 1.24
Within a given year, treatments with the same letter or no letter did not differ significantly at p � 0.05. NT: no-till; RT: reduced tillage; CT:
conventional tillage; NTNR: no-till without residue; RTNR: reduced tillage without residue; CTNR: conventional tillage without residue; NTR:
no-till with residue; RTR: reduced tillage with residue; CTR: conventional tillage with residue.
1995 (Table 2). Tillage influenced bulk density in the
deeper depth in 2000 and 2001 only. In those years,
bulk density in NT treatments (1.45 Mg m�3 in 2000
and 1.38 Mg m�3 in 2001) was significantly greater
than that of the CT treatment (1.36 Mg m�3 in 2000
and 1.26 Mg m�3 in 2001). The presence of residue
did not affect bulk density in any year at any depth.
There was one instance of a significant tilla-
ge � residue effect in 1993 within the 0–0.10 m
depth, where NTNR (1.28 Mg m�3) had a signifi-
cantly higher bulk density than CTR (1.09 Mg m�3),
but none of the other practices was significantly
different from NTNR or CTR.
From 1991 to 2002, bulk density values varied
mostly at the 0–0.10 m depth, fluctuating between 0.9
and 1.46 Mg m�3. Bulk density was measured at the
site to determine if any differences existed before the
tillage practices were implemented in 1991. The
results are presented in Table 2. Although there were
no significant differences in 1991, the bulk density was
higher in those plots implemented as NT and lower in
CT. Bulk densities varied from year to year, but there
appeared to be no consistent increase or decrease in
bulk density at the 0–0.10 m depth over the 11-year
study period. At the deeper depth, bulk density values
ranged between 1.25 and 1.45 Mg m�3 (Table 2).
Some variations in bulk density throughout the study
were likely related to the different times in the year
that the soil samples were collected.
Averaged over 11 years, NTNR had the highest bulk
density at both the 0–0.10 m depth (1.36 Mg m�3) and
at the deeper depth (1.40 Mg m�3), while CTR had the
lowest (1.21 Mg m�3 at the 0–0.10 m depth and
1.28 Mg m�3 at the deeper depth). The higher bulk
density found in NTNR was attributed primarily to the
lackof annual loosening from tillagemachinery coupled
with no residues on the soil surface. Field machinery
therefore had direct contact with the soil surface, thus
R.F. Dam et al. / Soil & Tillage Research 84 (2005) 41–5348
Table 3
Corn emergence by tillage � residue combination for 1992–1996
and 1997, measured 2–4 weeks after planting
Year Date Tillage � residue treatment
NTNR RTNR CTNR NTR RTR CTR
Number of plants emerged per m of row
1992 June 2 6.0 a 5.7 a 5.9 a 4.5 c 5.6 a 5.2 b
1993 June 1 5.2 a 5.6 a 4.8 a 2.1 c 3.4 b 4.8 a
1994 June 8 5.7 a 5.8 a 5.9 a 4.2 b 5.7 a 5.6 a
1996 May 31 6.6 a 6.3 ab 5.8 b 4.6 c 5.8 b 5.6 b
June 5 6.1 6.1 6.0 5.5 5.7 6.1
1997 June 9 6.3 6.4 6.1 5.5 6.0 6.0
June 30 6.1 6.0 5.7 6.2 5.9 5.8
Within a given year, treatments with the same letter or no letter did
not differ significantly at p � 0.05. NTNR: no-till without residue;
RTNR: reduced tillage without residue; CTNR: conventional tillage
without residue; NTR: no-till with residue; RTR: reduced tillage
with residue; CTR: conventional tillage with residue.
leading to compaction. The lower bulk densities found
in CTR were likely caused by annual moldboard
plowing which help maintain a fairly loose structure,
increasing porosity and encouraging microbial activity.
In studies conducted byCallum (2001) andDam (2003),
R plots at 0–0.10 m depth were found to have
significantly greater soil microbial biomass-carbon than
NR (average values for 1999–2002, 1.94 mg C g�1 soil
in R treatment and 1.46 mg C g�1 soil in the NR
treatment). High bulk density values for RTR in the first
few years (average of both depths for 1991–1993 was
1.35 Mg m�3) indicated insufficient loosening in the
fall of 1991 and 1992, due to the use of lighter tandem
disks for fall primary tillage in those years. Heavier
offset disks were used from 1993 onwards in the fall
after harvest.
Our results were consistent with those of other
studies that show differences in bulk density due to
tillage practices. For example, Kushwaha et al. (2001),
when comparing no-till and conventional tillage and
residue practices, found over two seasons that CTNR
had a significantly lower bulk density (1.27 g cm�3)
than NTR (1.40 g cm�3) on a sandy loam site. Da Silva
et al. (2001) found NT had a significantly higher bulk
density than CT; the bulk density varied from 0.96 to
1.71 Mg m�3 on a loam site over 3 years. The
conclusion made by Kushwaha et al. (2001) and Da
Silva et al. (2001) was that tillage practices had the
largest impact on bulk density. From this study, it
appeared that on a sandy loam soil, tillage had a
greater influence on bulk density than residues.
3.2. Corn emergence rates
Emergence showed significant tillage � residue
interaction in most years. Generally, NTR was found
to have significantly slower emergence than the other
treatments (Table 3). In 1992, 1993 and 1994, NTNR,
RTNR and CTNR had emergence rates significantly
higher than NTR, and in some cases also higher than
RTR and CTR (Table 3).
A significant tillage � residue interaction was
found during the first emergence sampling in 1996:
NTNR had a significantly faster spring emergence
than all treatments, except for RTNR, while NTR had
a significantly slower spring emergence compared to
all other treatments (Table 3). With residue (R) had
significantly slower emergence (5.8 plants emerged
per m of row) than NR (6.1 plants emerged per metre
of row) during the second sampling period in 1996
(June 5). These emergence delays in early 1996 were
attributed to higher amounts of residue cover in R sites
in conjunction with greater soil compaction in the
NTR plots (Mehdi et al., 1999). During the first
sampling period in 1997 (June 9), the R treatment (5.8
plants emerged per m of row) had a significantly
slower emergence than the NR treatment (6.3 plants
emerged per m of row), which was again attributed to
greater residue cover (Mehdi et al., 1999). No-till (NT)
(6.2 plants emerged per m of row) had a significantly
faster emergence than CT (5.7 plants emerged per m of
row), but not RT (5.9 plants emerged per m of row)
during the second emergence sampling in 1997 (June
30). Mehdi et al. (1999) attributed the faster
emergence in NT in spring 1997 to factors such as
less rainfall in spring 1997, compared to the same
period in 1996.
No-till with residue (NTR) treatments had the
slowest emergence rates within the 2–3 weeks after
planting during most sampling periods (Table 3). This
could be attributed to the large amount of residues
remaining on NTR plots (8.53 Mg ha�1) compared to
the amount remaining on the surface after cultivation
on CTR (0.45 Mg ha�1) (Mehdi, 1998). All tillage
practices without residue cover showed earlier
emergence. Corn emergence in 1993 and 1994 was
slower than in all other years (Table 3), which was
attributed to cool, wet conditions at seeding and/or
R.F. Dam et al. / Soil & Tillage Research 84 (2005) 41–53 49
post-seeding soil conditions affecting the yields in
1994. However, Burgess et al. (1996) noted that late
spring emergence did not necessarily result in a
reduced plant count. After 1994, a more suitable NT
seeder was used which enabled a better cut through the
surface residue.
No-till is known for poor seed germination. Drury
et al. (1999) found NT had a 23.8% lower corn
emergence than CT plots in a 3-year study. Cooler soil
temperatures and higher soil moisture in NT plots can
lead to poor seedbed conditions, which may cause
poor germination. Seedbed conditions are heavily
influenced by climatic conditions. On no-till plots with
residue, poor seedbed conditions could result from
cooler soil temperatures and higher soil moisture. In
May and June 2002, NTwas found to have a lower soil
temperature (15.6 8C) than RT and CT (16.8 and
16.9 8C, respectively) (Dam, 2003). Also, during May
and June 2002, NTwas found to have higher soil water
content compared to CTand RT in the 0–0.10 m depth
(31.9, 22.3 and 18.7% volumetric, respectively) (Dam,
2003), which confirms the findings of Drury et al.
(1999). Drury et al. (1999) studied soil temperature
and soil water content in no-till and conventional
tillage on a corn site in Ontario with and without an
under seeded cover crop. They found that NTwith and
without cover crop had 2–5% higher soil water content
and 1–2 8C lower soil temperature compared to CT.
Table 4
Grain yield by tillage � residue combination from 1991 to 2002
Year Tillage � residue
NTNR (Mg ha�1) RTNR (Mg ha�1) CTNR (Mg ha
1991 7.2 7.3 7.3
1992 7.6 ab 7.9 a 7.1 b
1993 7.3 8.0 7.9
1994 8.5 a 8.2 a 8.1 a
1995 10.0 10.4 10.2
1996 8.9 9.1 9.6
1997 6.5 5.6 5.9
1998 9.3 9.0 9.1
1999 12.6 12.1 11.7
2000 7.7 6.9 6.4
2001 1.3 2.3 1.3
2002 3.3 3.1 4.6
Averagea 7.5 7.5 7.4
Within a given year, treatments with the same letter or no letter did nota Average value of grain yields from 1992 to 2002. NTNR: no-till
conventional tillage without residue; NTR: no-till with residue; RTR: red
3.3. Grain yield
The long-term average grain yield from 1992 to
2002 indicated that R had a significantly lower grain
yield than NR: 7.1 and 7.5 Mg ha�1, respectively. Two
out of the 11 years showed significant tilla-
ge � residue interactions: 1992 and 1994. In 1992,
RTNR had significantly higher grain yields than
CTNR, NTR and RTR (7.9, 7.1, 6.1 and 6.5 Mg ha�1,
respectively). Also in 1992, NTR and RTR had
significantly lower grain yields than the other tillage
practices (6.1 and 6.5 Mg ha�1, respectively)
(Table 4). In 1994, NTR (5.5 Mg ha�1) had sig-
nificantly lower grain yields than all other treatments
(ranging from 8.1 to 8.5 Mg ha�1).
There was a fluctuation in grain yields over the
course of the study (Table 4). Grain yield from 1991 to
1994 stayed somewhat consistent, after which grain
yield increased in 1995 and 1996, then decreased in
1997 (Table 4). Grain yields then increased to a
maximum in 1999 whereafter they declined to a low in
2001 and increased slightly in 2002. Spring of 1997
was the fourth coolest on record, and this may have
hindered growth by lowering soil water evaporation
and kept soil temperatures cool through the spring.
The spring and summer of 2000 were amongst the
wettest on record (Meteorological Service of Canada,
2002) thus, the wet conditions probably hindered
�1) NTR (Mg ha�1) RTR (Mg ha�1) CTR (Mg ha�1)
7.4 6.9 6.8
6.1 c 6.5 c 7.3 ab
7.4 7.2 7.8
5.5 b 8.4 a 8.3 a
9.3 9.2 10.0
10.0 8.5 9.1
5.8 5.3 5.9
9.4 8.1 9.5
11.5 11.7 11.5
5.8 7.1 7.5
1.2 1.5 0.8
3.6 3.6 3.6
6.9 7.0 7.4
differ significantly at p � 0.05.
without residue; RTNR: reduced tillage without residue; CTNR:
uced tillage with residue; CTR: conventional tillage with residue.
R.F. Dam et al. / Soil & Tillage Research 84 (2005) 41–5350
growth by lowering soil temperatures due to the higher
soil water. Summer 2001 was the driest summer
experienced in the St. Lawrence–Great Lakes corridor
in 54 years (Phillips, 2002). There were 35 con-
secutive days during July and August 2001 with no
measurable precipitation. Due to these drought
conditions, cobs and kernels did not develop
sufficiently. The low values in 2001 were also
attributed to extensive raccoon damage sustained at
the site. Raccoon damage was also encountered at the
site in 2002, but the damage was not as extensive. The
more extreme weather over the last 5 years of this
study seem to have had a much greater effect on grain
yields rather than treatment effects.
Another factor taken into consideration was the
long-term continuous monocropping of corn at the
site. There was a fairly dramatic decline in grain yield
in the last 3 years of this study (attributable to climatic
and rodent problems). In addition, changes in soil
chemistry and biological properties related to long-
term monoculture may also be a reason for the decline
in yields. As corn residues were returned to the soil to
decompose, P and K in the residues are incorporated in
the soil. The long-term application of corn residues
may lead to increased levels of P and K in the soil.
During testing of the soil for P and K in 2001, it was
found that several plots at the site (particularly the R
plots) exceeded Quebec fertilization recommenda-
tions for K and P at a continuous corn site (Conseil des
productions vegetales du Quebec, 1996). High
concentrations of K and P (over 501 kg K ha�1 and
251 kg P ha�1) may hinder plant growth rather than
enhance it. In Quebec, over 60% of soils used for
monoculture grain corn have excessive phosphorus
levels (MacKenzie and Zhang, 1997). This may have
contributed to the decline of grain yields at this site.
Continuous corn monoculture is not a recommended
agronomic practice for the above reason, in addition to
the fact that it degrades soil quality.
Considering the differences in inter-annual climate
variation, it would be expected that NT treatments
would have the most variable yields due to the fact that
residues maintain higher soil water content and lower
soil temperatures. Dwyer and Ma (2001) studied grain
yields in 1996 and 1997 in Eastern Ontario on a sandy
loam site and found that 1997 yields were lower due to
limited rainfall and uneven precipitation distribution
over the season. Assuming that soil water content was
influenced by bulk density, higher bulk density in NT
was not reflected in lower grain yield from this site.
Al-Darby and Lowery (1986) also found that grain
yields were not significantly different among tillage
systems (moldboard plowing, chisel plow, ridge tillage
planting and no-till) in any of the 3 years of their study.
The inter-seasonal variability in grain yields found in
this study was most likely due to the climatic
differences experienced during each season, espe-
cially since there was no indication of any statistical
trend due to the treatment effects. Despite the
influence of ambient temperature and precipitation
on grain yields at this site, NT did not reduce yields
over the long-term on this site. No-till (NT) grain
yields from 1992 to 2002 were 7.2 Mg ha�1, while CT
and RT were 7.4 and 7.3 Mg ha�1, respectively.
Though NT grain yield was 0.2 Mg ha�1 lower than
CT, the values were still comparable and show that NT
can have comparable yields to conventional and
minimally tilled sites.
3.4. Dry matter yields (grain and stover yields)
In 1992, NTR and RTR (13.0 and 13.2 Mg ha�1,
respectively) had significantly lower yields than all
other treatments (Table 5). In 1994, NTR
(11.0 Mg ha�1) had a significantly lower dry matter
yield than the other treatments (ranging from 15.2 to
16.2 Mg ha�1).
Average dry matter yields per year were consistent
from 1991 (14.4 Mg ha�1) and reached a peak in 1999
(21.1 Mg ha�1), after which yields declined until 2002
(7.9 Mg ha�1) (Table 5). The combination of no-till and
residue consistently had the highest total dry matter
yield. The lowest yield in 6 of the 11 years was RTR
(15.2 Mg ha�1). Within each individual plot at the site,
there is variability in soil texture and soil drainage. Soil
textural differences in the RTR plots could have
contributed to the lower overall total dry matter yield.
Lower emergence rates did not translate into lower
yields in 1993, 1996 and 1997. In 1992, there was a
significant tillage � residue interaction where NTR
and RTR had a significantly lower total dry matter
yield than CTR, CTNR, RTNR and NTNR (Table 5).
The climatic conditions of 1992 were wetter than
normal (Fig. 1); thus, less warming and evaporation of
water from these R sites may have contributed to their
lower yield. In 1994, NTR (11.0 Mg ha�1) was found
R.F. Dam et al. / Soil & Tillage Research 84 (2005) 41–53 51
Table 5
Dry matter yield by tillage � residue combination for 1991 to 2002
Year Tillage � residue CTR (Mg ha�1)
NTNR (Mg ha�1) RTNR (Mg ha�1) CTNR (Mg ha�1) NTR (Mg ha�1) RTR (Mg ha�1)
1991 14.5 14.9 14.6 15.2 13.5 13.6
1992 15.6 a 15.6 a 14.4 a 13.0 b 13.2 b 15.0 a
1993 13.1 14.8 14.6 13.9 13.1 15.2
1994 15.9 a 15.2 a 15.5 a 11.0 b 15.8 a 16.2 a
1995 15.9 17.3 16.6 16.4 14.8 17.1
1996 15.2 15.7 16.3 16.6 14.4 15.4
1997 14.9 13.6 13.2 13.4 13.4 4.2
1998 16.7 16.6 17.2 17.1 15.2 17.8
1999 22.1 21.4 20.8 21.5 19.9 20.5
2000 15.8 14.2 13.4 12.1 14.5 15.3
2001 10.0 10.3 11.3 8.2 11.5 9.4
2002 8.1 6.2 8.8 8.2 8.1 8.2
Averagea 14.8 14.6 14.7 13.8 14.0 14.9
Within a given year, treatments with the same letter or no letter did not differ significantly at p � 0.05.a Average value of grain yields from 1992 to 2002. NTNR: no-till without residue; RTNR: reduced tillage without residue; CTNR:
conventional tillage without residue; NTR: no-till with residue; RTR: reduced tillage with residue; CTR: conventional tillage with residue.
to have a significantly smaller total dry matter yield
than both CTR and RTR (16.2 and 15.8 Mg ha�1,
respectively). This was attributed to difficulty in
seeding through residue from the previous year, and
the large amount of precipitation received 2–3 days
before planting, creating a poor seedbed (Burgess et
al., 1996). Cox et al. (1990) found that on a corn site in
northern New York State, with a silt loam soil, slow
emergence in NT did not affect final grain yields
significantly. Our research produced similar findings.
Emergence differences on this site did not
necessarily translate into lower total dry matter yield,
but climatic conditions over the entire season could
have affected total yield. Under drier than average
conditions during a 20-year study, Kapusta et al.
(1996) noticed that NT corn yields were greater than
CT, probably because of the higher amount of soil
moisture held in NT plots compared to CT. Currie and
Norwood (1996) found that NT yields increased by
100% in the driest year, while CT had lower yields in a
4-year study. We did not find this at our site: in those
years, which were particularly dry (2001 and 2002),
NT yields were comparable to CT in 2002, but lower
than CT in 2001. The low yields in 2001 in all
treatments were attributed to a combination of
extremely dry, hot weather and severe raccoon
damage. With average precipitation and warmer than
average temperatures in 1999, total dry matter yields
at this site exceeded those of all other years. In 1999,
NT had the highest total dry matter yield
(21.8 Mg ha�1) compared to CT and RT, which had
the same total dry matter yield (20.7 Mg ha�1). No-till
(NT) also had the highest bulk density in the 0–0.10 m
depth in 1999. Considering the higher bulk density,
warmer temperatures and average precipitation in
1999, this could imply that NT held soil water more
effectively, which led to higher total dry matter yields.
This was confirmed by Callum (2001) who measured
soil moisture on August 23, 1999 at this site and NT
was found to have significantly higher soil moisture
than CT and RT treatments (14.2, 12.3 and 11.2%
volumetric water content, respectively).
In nine of the 11 years of study, average
temperatures from May to September have been
warmer than the 30-year average (Fig. 1). Greater than
average precipitation during May occurred in 9 of the
11 years. Over the rest of the growing season (June to
September), 4 of the 11 years had above-average
precipitation. As a result, the precipitation in the latter
part of the growing season of most years of the study
was below average (Fig. 1). The considerable variation
in temperature and precipitation was reflected in the
variations in total dry matter yield. Thus, differences
in total dry matter yield from year to year were due to
climatic differences rather than to variations in soil
properties, since the long-term average of total dry
R.F. Dam et al. / Soil & Tillage Research 84 (2005) 41–5352
matter produced were similar for all tillage and residue
practices in most years.
4. Conclusions
The following conclusions were drawn from this
study:
i. B
ulk density was affected by tillage practices, butonly within the first 0.10 m. Both CT and RT
reduced bulk density relative to NT. Residues did
not affect bulk density nor was there any temporal
trend in bulk density over the 11 years.
ii. T
illage � residue interactions affected corn emer-gence in most years. Poorer emergence found with
NTR was attributed to cooler soil temperatures
and higher soil moisture associated with the
residues remaining on the soil surface from the
previous year.
iii. N
o distinct long-term tillage or residue trend wasfound in grain yields. Differences in grain yields
over 11 years betweenCT,RTandNTwereminimal
(7.4, 7.3 and 7.2 Mg ha�1, respectively). The year-
to-year fluctuation in grain yields was attributed to
extreme conditions, particularly from 1997 to 2002.
iv. T
here was no long-term tillage or residue effect ondry matter yields over the 11 years. As with the
grain yield, the differences in dry matter yield
between tillage practices over 11 years was
minimal (NT: 14.3 Mg ha�1; RT: 14.3 Mg ha�1;
CT: 14.8 Mg ha�1) and year-to-year differences
were attributed to climatic variation over the 11
years.
v. H
igher bulk density and residue cover in sometreatments (NTR and RTR) may have increased
the ability of the soil to retain water during seasons
with less than average precipitation, which may
have contributed to higher grain and dry matter
yields in those seasons.
vi. N
o-till is recommended as a sustainable tillagepractice on a sandy loam soil in a temperate climate.
Acknowledgements
This study was funded by the Fonds quebecois de
recherche sur la nature et les technologies du Quebec
(FQRNT). The authors would like to thank Peter
Kirby, Department of Natural Resource Sciences,
McGill University, for his assistance with the field
work.
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