effect of different tillage methods on bulk density

EFFECT OF DIFFERENT TILLAGE METHODS
ON BULK DENSITY, PENETRABILITY AND
AGGREGATE SIZE DISTRIBUTION ON A CLAY SOIL.
KACEMI M.
(1)
H. HILALI
(1)
AND G. MONROE
(1)
RESUME
EFFET DE DIFFERENTS TYPES DE
TRA VAUX DU SOL SUR LA DENSITE
APPARENTE, LA RESISTANCE A LA
PENETRATION, ET LA DISTRIBUTION
DE LA TAILLE DES AGREGATS DANS
UN SOL ARGILEUX
ABSTRACT
The present study was conducted to evaluate the effect
of different tillage methods on sorne soil physical parameters.
Tillage treatments involved the blade implcment "Dutzi" (D),
the paraplow "Culti-vie" (CU), the stubble plow (SP), the disk
plow (CD),
the moldboard
plow (CS) and
no-till (NL).
Secondary tillage consisted of zero (CCO), two (CC2) and three
(CC3) offset disk passes. Measurements
density, penetration
were taken for bulk
resistance, aggregate size distribution, and
moisture. Bulk density values were signilicantly different among
tillage methods at the 15 cm depth. The Dutzi maintained
a
constant and smaller Bd in the upper 20 cm compared to that
of the other tillage implements, for which the Bd was b~sically
identical. Beyond the 15-cm depth, SP and NL tended to
present
higher
Bd than
the other
tillage methods.
TIle
secondary tillage effect on Bd was confined to the upper 10 cm.
Cone index values from the 0 to 10 cm, and 40 to 50 cm depths
were not significant among tillage methods. Howevcr, between
the 5 and 35 cm soil depths
the differences
were highly
significant. On the average NL, SP and D had consistently
higher cone index values than CU, CS and CD. TIle reported
cone index differences between these two groups is related to
the depth of the primary tillage, and suggests the persistence of
the high zone strength with D and S below 15 cm depth. The
moldboard
plow
(CS)
maintaincd
consistently
lower
CI,
whereas NL had consistently higher CI over the 0 to 50 cm
depth. Dry-mean weight diameter was not signilicant among
tested tillage systems.
(1) Institut National de Recherche Agronomique - Settat.
La présente étude avait comme objectif d'évaluer
l'effet de différents types de labour sur quelques propriétés
physiques du sol. Les outils de travail du sol testés étaient
comme suit: un outil il lame dit "Dutzi" (D), un outil à dent
courbées dit "Cul ti-vie" (CU), le stubble plow (SP), la charrue
à disques (CD), la charrue à soc, et le non-labour (NL). Les
travaux de reprises consista'ent en: zéro (CCO), deux (CC2) et
trois (CC3) passages au "covercrop". Les mesures entreprises
consistaient en la densité apparente (Bd), la résistance à la
pénétration (CI), la distribution de la taille des agrégats du sol
(MWD), et l'humidité du sol. Les densités apparentes différaient singnificativement d'un travail de sol à un autre au
niveau de 15 cm de profondeur.
Le D a maintenu une Bd constante au niveau des 20
premiers cm du sol par comparaison aux autres types de
labour. Au delà de 15 cm de profondeur, le SP, et le NL
tendaient à présenter des valeurs élevées de Bd par rapport au
reste des types de travaux du sol. L'effet des labours de reprise
sur Bd était limité au 10 premiers cm du sol, sans toutefois qu'il
y ait une différence entre deux et trois passages au covercrop.
La résistance à la pénétration (CI) était significativement
différente entre les types de travaux du sol testés, dans
l'interval de profondeur 10 et 40 cm. Ces différences n'étaient
pas significatives au niveau des profondeurs 0 - 10 et 40 - 50
cm. En moyenne, le NL, SP et D avaient constamment des
valeurs de CI élevés par comparaison il ceux observés pour
CU, CD et CU. Les différences en terme de CI entre ces deux
groupes de types de travaux du sol étaient liées essentiellement
à la profondeur à laquelle le sol était travaillé, et suggèrent que
le SP et D seraient incapables d'affecter la densité de la couche
du sol en deçà de 15 cm. Le travail du sol secondaire avait un
effet significatif sur CI au niveau des premiers 10 cm de la
surface du sol. Deux et trois passages de covercrop, pour
lesquels CI étaient le même, ont significativement réduit la
résistance à la pénétration par rapport il la situation où il n'y a
pas eu de passage de covercrop. Les résultats relatifs il la
distribution de la taille des agrégats du sol inférieurs à 10 mm,
mesurées en terme de diamètre pondéré moyen (MWD), n'a
pas révélé de différences significatives entre les types de
travaux du sol testés.
INTRODUCTION
Tillage generally improves soil conditions for
plant growth, especially under the circumstances
where the soil presents zones of high strength and
compaction. However, tillage may also exert adverse
effect on soil conditions when it is performed in less
than adequate soil moisture, or when inadequate
tillage implements are used. Campbell et al (1974)
found that the chisel was the most effective at
disrupting soils with localized high strength, such as
plow pans. Bauder et al. (1981) indicated that
inversion plowing provided the most effective way
to remove compaction of soils with initially uniform
strength.
They reported
that under
such
circumstances moldboard plowing yielded lower
mechanical resistance than the chisel plowing. Disk
tillage while effective in removing soil crust, tends
to compact the soil (Taylor and Burnett, 1964),
which results in zones with high soil strength. Bulk
density and penetration resistance are the widely
used soil physical parameters to assess soil
loosening or compaction in tillage studies. The
difficulty in using bulk density to investigate soil
strength or detect tillage depth is related to the fact
that it is a tedious and time consuming method.
Second, several reports have indicated contrasting
results as to the effect of tillage on bulk density.
Blevins et al. (1983a) reported that tillage had~no
effect on bulk density after a 10-year period of
tillage treatments on a medium textured soil.
However, other studies have reported a drastic
increase in bulk density with no-till compared to
moldboard plowing of a clay loam soil (Griffith et
al. 1977; Gantzer and Black, 1978). Blevins et al.
(1983b) found similar bulk density values with
conventional and no-till systems and smaller bulk
density with chisel tillage on a poody drained soil.
Resistance ta penetration was, however, much more
effective in detecting zones of soil strength, depth of
tillage and the extent of tillage induced soil
loosening or compaction and the degree of their
persistence over time. Carter (1988) measured
mechanical resistance in a tillage study and found
that moldboard plowing produced more soil
loosening than chisel plowing in a loam ta sandy
loam sail. He reported that the depth of tillage
declined over a period of five months by 30 and 60
%, respectively for the moldboard and the paraplow.
Pelgrin et al. (1990) reported that bulk
densities, measured three weeks after tillage
application, were similar in the upper 20 cm of a
sandy clay loam where tillage was done with disk
plow, moldboard plow, cultivator, disk harrow, and
no-till. He indicated that bulk density values
increased with time and were significantly higher in
no-till, dise plow, and cultivator than moldboard
plow and disc harrow. He also, reported that sail
penetration resistance, measured immediately after
tillage application, was identical among tillage
treatments in the upper 15 cm , and significantly
different between 15 and 40 cm depth. Dorenko
(1924) and Kvasnikov (1928), cited by Braunack and
Dexter (1990), reported maximum wheat yields with
seedbeds of 2-3 mm aggregates. Jaggi (1972)
concluded that a seedbed of 1-2 mm aggregates with
a dry bulk density of 1.2-1.3 glcm3 would give the
best wheat grain yield on a clay soil. Braunack and
Dexter (1988) found that intermediate
size
aggregates (2-3 mm) resulted in earHer emergence
and higher wheat yields than with larger aggregates
(> 4mm) on a loam soil. Piner aggregates « Imm)
tend to restrict aeration and reduce emergence
under more wet soil conditions, but result in earlier
emergence in drier years (Braunack and Dexter
1988).
The objective of the present study was ta
evaluate the effect of contrasting tillage treatments
on soil bulk density, mechanical resistance and
aggregate size distribution measured as mean weight
diameter, and also to identify the tillage treatments
that are more likely ta affect favorably the soil
loosening condition of this clay soil.
MATERIALS AND METHODS
The study was initiated in 1990-91 at the
experiment station of Allal Tazi (340 TN, 50 8'W),
Morocco. The soil, of clay type, is poorly drained
and experiences a lot of compaction that would
hinder the growth of root crops like sugarbeet. The
particle size analysis shows that it has 12 % sand,
30 % silt, and 58 % clay. The experiment was laid
97
out as a split plot design with three replications.
Tillage methods were assigned to the subplots, and
include the blade tillage implement "DUTZI" (0),
paraplow caIled "Culti-vie" (CU), moldboard plow
(CS), three-disk plow (CD), stubble plow (SP),
along with the no-till system (NL). Secondary
tillage, applied to the whole plots, consisted in zero
(CCO), two (CC2) and three (CC3) offset disk
passes. The size of the whole plot and subplot was
20 X 74 m and 20 x 9 m, respectively. Tillage depth
was 15 to 20 cm with the stubble plow, 30 to 35 cm
with the moldboard plow and Culti-vie, 20 to 25 cm
with the Dutzi and the disk plow. Secondary tillage
depth was 10 to 15 cm and was accomplished with
the offset disk. The measurements of bulk density,
resistance to penetration and mean weight diameter
were done two months after tiIlage application,
period during which the weather was unusuaIly dry.
Bulk density was measured at 10, 20, 30 and 40 cm
depths along a transect perpendicular to the tillage
direction with a double-eylinder, hammer-driven
sampler. Soil moisture to 40-cm depth was
determined at the same time. Soil resistance to
penetration was measured from 0 to 50 cm depths
in a 5-cm Increment along a transect perpendicular
to the tillage direction by means of a hand-held
penetrometer
manufactured by HCH Inc. in
Russelville, Kentucky, USA The cone had a
standard 1.3 cm2 base area, and the penetrometer
rod aIlowed a maximum depth of measurement into
the soil of about 50 cm. The penetrometer gauge
had a scale in bars, and cone index values were
obtained using the multiplication factor of 77 found
after the calibration
of the penetrometer,
calibration which was performed using an accurate
platform scale. Mean weight diameter (MWD) was
measured to evaluate the aggregate size distribution.
Soil samples, taken from 0 to 5, 5 to 10, and 10 to
15 cm depths using a shovel, were air dried, passed
through a 1O-mm sieve, and then subjected to a
5-minute sieving period through a 5, 4, 2, 1, and
0.25 mm series of sieves, mounted on, a portable
sieve shaker. AlI measurements were undertaken in
two repli cations and data were analyzed using the
analysis of variance procedure and the least
significant difference method available in the SAS
program.
RESULTS AND DISCUSSION
Bulk density data as affected by tillage
methods are reported in table 1. The same data are
depicted in figure 1. There were significant
differences in bulk density values among tillage
treatments at the 15 cm depth. The Dutzi
maintained a constant and smaIler Bd in the upper
20 cm compared to the bulk density values of the
other tillage implements or notill treatment. At the
35 cm depth CS and CD had the lowest Bd
compared to aIl other tillage treatments. SP had
higher Bd than NL from 10 to 35 cm depth, but the
difference between these two tillage methods was
not significant. Such a result was not expected,
because of the high compaction this clay soil
undergoes when left untilled. There may be more
hardpan formation with SP than any of the tillage
methods that were tested. Secondary tillage had a
significant effect on Bd at the 5 to 10 cm depth
layer, which is in agreement with the depth of
secondary tillage using the harrow disk. There was
no effect on Bd between 2 or 3 passes of the harrow
disk for the preparation of seedbed.
Table 1 : Bulk density as affected by tillage
on a clay soil at Allal Tazi, Morocco.
•
CS
1.44
1.23
1.27
1.22
1.40
1.41
1.49
1.37
1.42
CUSP
CD
1.36
1.28
NL 1.24
NS
1.52
1.57
1.45
1.55
1.57
Depth (cm)
Tillage methods
•--.---.--------------------
D=Dutzi, CU=Culti-vie,
SP=Stubble plow, CS=Moldboard
plow CD=Disk plow, NL=No-till
NS means not significant; • means significant at the probability level of 0.05.
Bt:ilk denslty ( g/cm3)
~c
5
t
l'~
20 1.2
15
0 (l
5
35 25
30
40
10
1.3
••.
.
1.4
•. '0,,"
- -,,~- ,,\
....
.
1.5
1.6
,
...
-- .•.. ~ '-; ....
---~,~
:.\:--,
:'
1\
.
~Q.
1 \
\
1 \
. ,,~
l
1
"1
.
.....
....
\
...•
"
" \'
'\ \ ",
\.
..,
~"
\
'0
"\''\~ ", \.\
}.
"8
Figure 1. Effeet of different tiIIage methods on bulk density
of a clay soil al Allal Tazi, Morocco, (0 •• Outzi, CU •• Culti-vie
SP •• Stubble plow, CS •• Moldboard plow, CD •• Disk plow
and NL •• No-till).
c
i
lJ 0 (l
20
30 0
Cone Index (!<Pa)
1000
2000
3000
4000
5000
50
60 40
l: 10
Figure 2. Effeet of
resislance of a clay
SP •• Slubble plow,
CU •• Cultivle, and
different tillage methods on penetration
soil al Allal Tazl, Morocco. (D •• Ou1zl,
CS •• Moldboard plow, CD •• Disk plow
NL •• No-lill ).
Observed
cone index values under tested
tillage methods are reported in table 2. The data are
depicted in figure 2.
The resistance to penetration trom 0 to lü
cm, and trom 40 to 50 cm depths were not
significant among tillage methods. However,
between the 5 and 35 cm soil depths, the differences
were highly significant. On the average, NL, SP and
had consistently higher cone index values than
CU, CS, and CO. The difference between these two
groups in term of cone index values, is related to
the depth of the primary tillage, and not to the
differences in soil moisture because soil water
o
content under aIl the tillage methods was identical
in the upper 50 cm depth.
Similar results from a study conducted on a
clay loam soil were reported by Bauder et al. (1981).
They found small CI in the moldboard tilled plots,
intermediate CI in chisel plowed plots, and finally
high resistance in the no-till plots or disk tilled
plots.
Aggregate size distribution data, measured in
term of MWD (mm) for aggregates less than 10
mm, are reported in table 3. There were no
differences among tillage methods for MWD. Such a
result was not expected. It may be due to bad
sampling method and/or to the way aggregates were
hand broken prior to the lü-mm samples sieving, or
simply due to the short history of tillage treatments.
Bulk density data do not seem to agree
totaUy with the resistance to penetration data.
However, mechanical resistance appears to reflect a
genuine picture in term of soil loosening and
strength conditions
th an the observed bulk
densities. The high cone index values observed in
plots tilled with the stubble plow, values that are
not significantly different from those of no-till,
suggest the presence of a plow pan at 15 cm depth
with this tillage method. These data are in
agreement with the tillage history at Allal Tazi
station, where the stubble plow was the common
primary tillage implement in use for several years.
Soil compaction is commonly induced by disk tillage
implements (Taylor and Burnett, 1964), especially
when tillage is do ne under moist soil conditions.
Soil structure of the upper 20 cm depth of the plots
tilledwith the Outzi was better compared to that of
aU other plots tilled with any of the tested tillage
implements. Field observations of wheat stand
Table 2 : Resistance to penetration as affected
by tiIIage on a clay soil at Allal Tazi, Morocco~
.
• ••••
•• cu
••• 2316
NS
3869
2352
2568
3228
4071
3914
1736
4055
2660
3648
1409
1906
4014
NS
250
1262
CS
212
2076
170
404
391
504
1222
1604
1206
SP
583882
1348
484
199
3751
3683
3911
4347
3446
3702
3844
2987
1402
3770
4193
3334
3632
4649
4129
4209
3635
3356
3532
3789
4238
690
3298
555
446
1014
3526
1226
905
2528
574
CD
263
815
472
NL
167
Tillage
methods
Depth
(cm)
------------------------
D=Dutzi,
NS
100
CU=Culti-vie,
SP=Stubble
plow, CS = Moldboard
plow, CD=Disk
plow, NL=No-till.
= not significant,• = significantat 0.05, •• and ••• = highly significantat 0.01 and 0.001 probabilities,respectively.
1
60
CCO
0
10
' ......
.
0......
,
0.
~
.. ---,{;,--_
CC3
1000
2000
<
CC2
El
( kPa)
30
20
Cl
.13>.
~Ç>"
<.. ...
Q),', ....
~J
"
(,)
"
5000
Cone index
E
1
40
50 ~
Figure 3. Effect of offset disk passes on penetration
resistance of a clay soil at Allal Tazi. Morocco. (CCO = Zero passe.
CC2 = Two offset disk passes. CC3 = Three offset disk passes).
Table 3.
Dry-mean weight diameter (MWD)of aggregates
tillage
on a clay soil at Allal Tazi, Morocco.
Ti}lage
Depth
(cm)
D
cu
10 mm as affected
by
methods
cs
SP
<
CD
NL
mm
not
means
3.4
3.6
3.2
3.6
SP=Stubble
0-5
3.1
3.3
2.9
NS
3.3
3.5
3.8
3.7
3.9
CS=Moldboard
CD=Disk
NS
CU=Culti-vie,
plow,
significant.
plow
plow,
101
indicated better crop establishment with the Dutzi
than with any other implement. However, the data
indicated that such an implement was unable to
reduce soil strength below the 20 cm depth
(figure 2). Root growth could be hindered below
this depth when using either the Stubble plow or
the Dutzi. When considering the cloddy rough
surface generally created when this soil is tilled with
the moldboard plow or the disk plow, rough surface
which requires more passes with the disk harrow to
break the clods and level the soil, thus increasing
the chances of more compaction due to traffic, the
paraplow appears to be the appropriate implement
to use in any similar high strength clay soil. The
main disadvantage of using the paraplow is that it
requires a lot of traction power.
CONCLUSION
The
penetration
data
show
that
the
resistance
to
is a much more accurate method than
the bulk density measurement in the assesqment of
soil loosening induced by different tillage methods.
ln such a high clay content soil, the moldboard
plow, the three disk plow, and the paraplow
provided better soil loosening conditions up to 35
cm depth than the Dutzi and the stubble plow.
However, when other considerations are taken into
account, espeeially the high risk of soil compaction
as a result of more traffic to break the clods
generated with the moldboard and disk plow, the
paraplow seems to be the appropriate tillage
implement because it does not invert the soil.
REFERENCES
BAUDER, J.W., G.W. RANDALL, AND J.B. SWANN. 1981.
Effect of four continuous tillage systems on mechanical impedance of a clay loam
soil. Soil Sci. soc. Am. J. 45:802-806.
BLEVINS, RL., SMITH, M.S., THOMAS, GW. AND FRYE, W.W. 1983a.
Influence of conservation
38:301-305.
tillage on soil properties.
J. Soil Water
Conserv.
BLEVINS, RL., SMITH, M.S., THOMAS, GYV., FRYE, W.W, AND CORNELIUS. 1983b.
Changes in soil properties after 10 years continuous non-tilled and conventionally
tilled corn. Soil tillage Res. 3:135-146.
BRAUNACK, M.V. AND DEXTER, AR
1988.
The effect of aggregate size in the seedbed on surface crusting and growth of yield of
wheat (Triticum eastivum, L. ev. Halberd) under dryland conditions. Soil Tillage Res.
11:133-145.
BRAUNACK, M. V. AND DEXTER, AR 1990.
Soil aggregation in the seedbed: A review. Sail Tillage Res. 14:281-298.
CAMPBELL, RB., B.e. REICOSKY, AND e.W. DOTY. 1974.
Physical properties and tillage of Paleudilts in the eastern Costal Plains. J. Soil
Conserv. 29:220-224.
CASSEL, D.K, RD. BOWEN, AND L.A NELSON. 1978.
An evaluation of mechanical impedance for three tillage treatments
sandy loam. Sail Sei. Soc. Am. J. 42 : 116-120.
102
on Norf0lk
GANTZER, c.J. AND BLACKE, G.R. 1978.
Physical characteristics of le Sueur clay loam soil following no-till and conventional
tillage. Agron. J. 70:853-857.
GRIFFITH, D.R., J.V. MANNERING, AND W.c. MOLDEHAUER.
1977.
Conservation tillage in the eastern Corn Bell. J. Soil Conserv. 32:20-28.
JAGGI, I.K. GORANTIW AR, S.M. AND RHANNA, S.S. 1972.
Effect of bulk density and aggregate size on wheat growth. J. Indian Soc. Soil Sei.,
20:421-423.
TAYLOR, H. M., AND E. BURNETT. 1964.
Influence of soil strength on the root-growth habits of plants. Soil Sei. 98:174-180.
PELGRIN, F. F. MORENO, J. MARTIN-ARANDA AND M. CAMPS. 1990.
The influence of tillage methods on soil physical properties and water balance for a
typical crop rotation in SW Spain. Soil Tillage Res. 16:345-358.
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