Directory UMM :Data Elmu:jurnal:S:Soil & Tillage Research:Vol54.Issue1-2.Mar2000:

Soil & Tillage Research 54 (2000) 11±19

Effect of deep-tillage and nitrogen fertilization interactions
on dryland corn (Zea mays L.) productivity
M. DõÂaz-Zorita*
EEA INTA Gral.Villegas, CC 153 (6230) Gral.Villegas, Argentina and University of Kentucky,
Department of Agronomy, N-122 Agric. Sci. Center North, Lexington, KY 40546-0091, USA
Received 3 June 1999; received in revised form 12 October 1999; accepted 3 November 1999

Abstract
Subsoiling a compacted soil should loosen it, improve the physical conditions, and increase nutrient availability and crop
yields. The aim of this work is to compare the effects of different tillage and fertility treatments in a loamy Typic Hapludoll
soil, and to determine the interactions of N fertilization with several soil properties and dryland corn (Zea mays L.)
productivity. The experiment, conducted in 1995 and in 1997, had a split-plot design consisting of three tillage systems
(MBˆmoldboard plowing, CHˆchisel plowing or NTˆno-tillage) in a corn±soybean (Glycine max (L.) Merrill) rotation since
1991 as main treatments. Four subtreatments: (i) subsoil (paratill subsoiler to 40 cm depth in fallow 1995)‡N fertilization
(100 kg haÿ1 N as ammonium nitrate, at the V6 development stage of corn), (ii) subsoil‡no N fertilization, (iii) no
subsoiling‡N fertilization, and (iv) no subsoiling‡no N fertilization. Chemical and physical properties in the top layer of the
soils were determined at seeding in 1995. Penetration resistance was measured at seeding, ¯owering and at harvest in 1995 and
at seeding in 1997. Corn shoot dry matter during vegetative stages and grain yield components were also determined. The
preparation of seedbed using either moldboard or chisel plowing with or without deep-tillage, increased the vegetative biomass

by 27% and the grain yield of the corn crops by 9% over the no-tillage system. Subsoiling no-till plots improved the vegetative
growth of the crops, but the effect of the deep-tillage did not modify the corn grain yields. Grain yields were strongly related to
the N fertilization treatments. Although bulk density values (BD) ranged between 1.05 and 1.33 Mg mÿ3 differences in crop
yields were attributed to differences in the BD and the N fertilization. In the western Pampas Region of Argentina, the
production of high yielding corn crops, under no water stress conditions, is independent of the tillage systems but negatively
related with the soil BD values, and positively dependent on N fertilization. # 2000 Elsevier Science B.V. All rights reserved.
Keywords: No-tillage; Paratill subsoiler; Loamy soil; Compaction; Bulk density

1. Introduction
The cropped soils of the western Pampas Region of
Argentina (34±368S; 61±638W) are loam to sandy*
Tel.: ‡1-606-257-3655; fax: ‡1-606-257-2185.
E-mail address: mdzori2@pop.uky.edu (M. DõÂaz-Zorita).

loam Hapludolls that are affected by physical degradation processes (crusting, compaction, etc.) due to
intensive agricultural use. Genetic causes have been
attributed to the origin of low macroporosity in the ®ne
loamy soils of the Pampas Region of Argentina
(Taboada et al., 1998). Water de®cits are the main
climatic constraints and, in corn crops, they can be

0167-1987/00/$ ± see front matter # 2000 Elsevier Science B.V. All rights reserved.
PII: S 0 1 6 7 - 1 9 8 7 ( 9 9 ) 0 0 1 0 0 - 2

12

M. DõÂaz-Zorita / Soil & Tillage Research 54 (2000) 11±19

expected in 3 out of 4 years. Minimum and no-tillage
practices have been widely adopted in this region for
the purpose of controlling erosion processes, increasing water use ef®ciency of summer crops and improving crop productivity (Senigagliesi and Ferrari, 1993;
Buschiazzo et al., 1998). Compaction of the topsoils
under tillage systems that do not disturb the soil has
been described in several studies in the Pampean
region (Andriulo and Rosell, 1988; Kruger, 1996a;
Buschiazzo et al., 1998). Not only are soil bulk density
and soil penetration resistance values higher in the
topsoil of no-tilled soils than in tilled soils, but nutrients and organic carbon accumulations have been
observed in the topsoil of no-tilled soils (Kruger,
1996b; Chagas et al., 1994; Scheiner and Lavado,

1998).
Mechanical impedance to root growth has been
shown to limit root elongation and is related with
the reduction of plant shoot and grain yields. The
effect of compaction on crop yields depends on
weather conditions interacting with soil properties
(Lowery and Schuler, 1994; Vepraskas, 1994). A
compacted soil layer, because of its high strength
and low porosity, con®nes the crop roots in the top
layer and reduces the volume of soil that can be
explored by the plant for nutrients and water (Hammel, 1994). Where no-till systems are practiced poor
early vegetative growth, resulting from the hardness of
the soil, can be a major factor limiting the ability of
crops to fully utilize soil moisture at depth during the
critical grain ®lling stage (Mead and Chan, 1988).
Reductions in leaf nutrient concentrations that apparently affected crop yields in compacted soils have
been described (Lowery and Schuler, 1994; Bennie
and Krynauw, 1985). Compaction also reduces plant
growth and yields by affecting water in®ltration,
aeration and disease pressure (Unger and Kaspar,

1994). Bulk density and penetrometer resistance are
two of the most common parameters used to determine
the presence of compacted soil layers in agricultural
soils. The interpretation of penetrometer resistance
values in terms of root growth depends on soil particle
size distribution and soil structure. Penetration resistance lacks a clearly de®ned theoretical basis with
which to extrapolate results to different soils but it is
usually considered that soil strength is a problem for
crop growth in the ®eld if penetrometer values (cone
index) are greater than 2±3 MPa (Ehlers et al., 1983;

Gupta and Allmaras, 1987; Boone et al., 1986). Other
authors suggested that instead of focusing on soil
strength, it may be easier to use bulk density values
to determine the presence of root impedance problems. Cone index and bulk density values that
impede root growth vary with texture increasing as
the sand content increases (Gerard et al., 1982; Jones,
1983; Vepraskas, 1994).
Tillage pans occur in many sandy-loam agricultural
soils due to repeated tillage practices and hardening in

no-tilled soils, and must be ripped by using a form of
deep-tillage to maximize yields. Deep-tillage break up
high density soil layers, improves water in®ltration
and movement in the soil, enhances root growth and
development, and increases crop production (Bennie
and Botha, 1986). Sene et al. (1985) concluded that
increments in corn yield due to subsoiling are highly
related to the soil texture and the soil structure. Many
farmers and researchers from the Pampean Region of
Argentina have speculated that the use of deep-tillage
practices may improve crop yields in some compacted
soils. Nevertheless, the effects of deep soil loosening
on crop yields are not well documented. Studies that
show bene®ts of deep-tillage practices on wheat (Triticum aestivum L.) or soybean (Glycine max (L.)
Merrill) crops conclude that the increments in grain
yields in the deep-tilled soils are related to soil types
and weather conditions (Scotta and Herrera, 1991;
Ripoll and Kruger, 1996).
In soils under no-till practices, the subsequent
tillage of the soil redistributes soil nutrients within

the plow layer and stimulates the mineralization and
availability of nitrogen (Pierce et al., 1994). Subsoiling a compacted soil should loosen it and improve its
physical condition and nutrient availability. Consequently, the nitrogen fertilization requirements could
be reduced and the grain yields increased. For these
reasons, the aim of this work was to compare the
effects of deep-tillage practices using a subsoiler in a
sandy-loam soil under different tillage systems and to
determine their interactions with nitrogen availability
on dryland corn (Zea mays L.) productivity.

2. Materials and methods
This study was conducted during 1995±1996 and
1997±1998 at the Agricultural Experimental Station

M. DõÂaz-Zorita / Soil & Tillage Research 54 (2000) 11±19

``General Villegas'', Instituto Nacional de TecnologõÂa
Agropecuaria (INTA) in Drabble (34854'S and
63844'W, Buenos Aires, Argentina) on a sandy-loam
and

Typic
Hapludoll
(clayˆ145 g kgÿ1
ÿ1
siltˆ385 g kg ). 63 000 viable seeds haÿ1 of Corn
(``Pionner 3456'') were planted on 18 October 1995
and on 15 October 1997. 60 kg of triple superphosphate per hectare were broadcast before planting in
1995.
The experiment was a three-factor study in a splitplot design with three replications. Main plots
(2040 m2) consisted of three tillage management
treatments (MBˆmoldboard plowing, CHˆchisel
plowing or NTˆno-tillage) in a corn±soybean rotation
since 1991. Subplots (1020 m2) were (a) deep-tillage (DT) treatments with or without paratill subsoiler
to 40 cm depth, in August 1995, and (b) with or
without N fertilization (100 kg haÿ1 of N as ammonium nitrate) applied 30 days after corn seeding (V6
development stage).
At seeding in 1995, composite soil samples were
taken from the 3 to 20 cm soil layer in each subplot.
Soil samples were air dried and passed through a
2 mm sieve. The following determinations were carried out on each soil sample: total organic carbon

(TOC) by wet combustion (Nelson and Sommers,
1982), total nitrogen (Nt) by the Kjeldahl semimicro
method (Bremner and Mulvaney, 1982), NO3-N
extracted with 2.0 N KCl (Keeney and Nelson,
1982) and available phosphorus (Pa) extracted with
an acid±¯uoride solution (Bray and Kurtz, 1945). The
BD, in the 3±20 cm layer, was determined with core
samples (244 cm3). The residue cover was measured
at seeding in 1995 using a 10 m rope with 30 knots
(0.30 m apart) and counting the number of knots that
have residues greater than 0.005 m long under them.
The rope was stretched diagonally across the rows and
the procedure was repeated three times in different
areas of each plot.
Soil mechanical impedance to root growth from the
soil surface to 0.40 m depth was measured at intervals
of 0.05 m down using a hammer-driven cone penetrometer with a 308 right circular cone point of
4.22 cm2 lateral area. Five penetration resistance measurements at every 0.30 m were obtained per subplot
(O'Sullivan et al., 1987) at seeding, ¯owering and
harvest in the 1995±1996 crop and only at seeding in

the 1997±1998 crop. These measurements were done

13

48 h after rainfall events, when the soil water content
(gravimetric method) was approximately 80% of the
®eld capacity.
For shoot dry matter (DM) production in 1995, two
middle corn rows (1.53 m2) were hand harvested at
41, 48 and 68 days after seeding (V10, V11 and r1
growth stages). The daily crop DM production was
calculated from the dry matter levels according to
Eq. (1).
CGR ˆ …DM2 ÿ DM1 †…t2 ÿ t1 †ÿ1

(1)

where CGR is the crop growth rate in kg haÿ1 per day,
DM2 the dry matter production at the date 2 (t2) and
DM1 the dry matter production in the previous sampling date (t1).

For grain yield, in both periods, four corn rows
(33 m2) were hand harvested and grain weights
adjusted to 140 g kgÿ1 moisture content. Plant density
and individual grain weight were also determined in
each plot.
Crop and soil results were subjected to analysis of
variance as a three factor (main tillage system, deeptillage and N fertilization) experiment and signi®cant
means separated by the LSD (T) test. Multiple regression analysis (stepwise method) between grain yield
and soil properties was also considered including the
deep-tillage and nitrogen subtreatments as class variables (Analytical Software, 1998).

3. Results and discussion
3.1. Soil properties
Soil mechanical impedance, using the soil penetration resistance as a function of depth and tillage
treatments, is given in Fig. 1. The nitrogen fertilization
treatment did not interact signi®cantly with the tillage
effects on this property so the average across fertilized
and non-fertilized plots were considered. Only in the
no-tilled soils without deep-tillage (subsoiler) treatment the penetration resistance values were above 2±
3 MPa, critical value for normal root and shoot growth

(Vepraskas, 1994). A reduction in the penetration
resistance values was observed in this treatment during the study. Several studies have pointed out that
roots can perforate compact layers, create easily
accessible pathways for the roots of succeeding crops,

14

M. DõÂaz-Zorita / Soil & Tillage Research 54 (2000) 11±19

Fig. 1. Soil penetration resistance (PR) of a Typic Hapludoll from the western Pampas Region of Argentina during the growing season of corn
crops in three tillage systems in the ®rst (1995±1996) and the beginning of the third (1997±1998) period after applying deep-tillage treatments
with paratill subsoiler. Average across N fertilization treatments. MBˆmoldboard plowing, CHˆchisel plowing, NTˆno-tillage. Open
symbols at the same depth, sampling date and tillage system are signi®cantly different at the 5% level by the LSD (T) test.

and leave biopores which may increase water movement and gaseous diffusion (Unger and Kaspar, 1994).
Penetration of plant roots into compact soils has been
described to be a possible natural process which may
ameliorate compacted soils (Dexter, 1991). In the
1995±1996 season subsoiling signi®cantly decreased
the penetration resistance of the 10±20 cm layer of the

tilled soils at seeding stage. After the measurement at
seeding in 1995, no differences due to this treatment
were observed in the soil resistance pro®les. In the notilled soil deep-tillage decreased signi®cantly the
penetration resistance in the 3±35 cm layer at seeding
in 1995. This effect was also observed in the 10±25 cm
layer during the remainder of the 1995±1996 season

15

M. DõÂaz-Zorita / Soil & Tillage Research 54 (2000) 11±19

Table 1
Effect of three tillage systems and the deep-tillage on the crop residue cover and several soil properties in the 3±20 cm layer of a Typic
Hapludoll from the western Pampas Region of Argentinaa
Deeptillage

Tillage

BDb
(Mg mÿ3)

TOC
(g kgÿ1)

Nt
(g kgÿ1)

NO3-N
(mg kgÿ1)

P
(mg kgÿ1)

Residue
cover (%)

NO

NT
CH
MB

1.33c (c)
1.20d (c)
1.14e (c)

18.4c (c)
17.4d (c)
15.9e (c)

1.55c (c)
1.45d (c)
1.42d (c)

1.5c (c)
13.4d (c)
16.0e (c)

24.8c
24.0c
25.7c

(c)

97.8c (c)
24.0d (c)
2.2e (c)

NT
CH
MB

1.27c (d)
1.17d (c)
1.10e (c)

17.2c (c)
16.4d (c)
16.1d (c)

1.50c (c)
1.45d (c)
1.43d (c)

5.9c (c)
12.6d (c)
15.0d (c)

24.3c
24.2c
25.2c

(c)

YES

(c)
(c)

(c)
(c)

78.3c (d)
16.3d (d)
1.3e (d)

a
TOCˆtotal organic carbon, Ntˆtotal nitrogen, NO3-Nˆnitrate nitrogen, Pˆavailable phosphorus, BDˆbulk density, NTˆno-tillage,
CHˆchisel plowing and MBˆmoldboard plowing.
b
Means in the same column within each deep-tillage subtreatment followed by different superscripts are signi®cantly different at the 5%
level by the LSD (T) test. Means followed by different superscripts between parentheses within each tillage treatment are signi®cantly
different at the 5% level by the LSD (T) test.

but not 2 years after the deep-tillage treatment application (Fig. 1).
The bulk density in the 3±20 cm layer of the soils
was signi®cantly increased when the intensity of the
tillage system decreased (Table 1). The deep-tillage
treatment signi®cantly decreased the bulk density in
the no-tilled soils, but not in the tilled soils (Table 1).
Another consequence of the subsoiling was the
promotion of mineralization observed from the
increment in the NO3-N levels in the soils under no
tillage practices and the reduction in the soil residue
cover at seeding in 1995 for all the main tillage
systems (Table 1). These soils, mainly under no-till
practices, present greater amounts of available P in
the topsoil layers than in the subsoil layers (DõÂazZorita, 1999). The absence of differences in the
available P values observed between tilled soils or
due to the subsoiling practice (Table 1) suggests
that little vertical mixing between subsoil and
topsoil layers took place due to the deep-tillage
treatment.
3.2. Corn shoot dry matter and grain production
The effects of the deep-tillage and the N fertilization treatments on the dry weight of the corn shoot
were analyzed separately between tilled and non-tilled
soils because of signi®cant interactions due to tillage
practices (Table 2). In general, the shoot dry matter
was signi®cantly higher in the tilled treatments than in
those under no-tillage. Between tilled systems, the

largest dry matter production was observed in the
treatment with moldboard plow only 41 days after
seeding. The deep-tillage treatment increased shoot
dry weight only in the no-till treatments. Differences
in the shoot dry matter accumulation due to the
nitrogen fertilization were observed only in the notill treatments at ¯owering.
The crop growth rate (CGR) between planting and
the V10 growth stage showed a signi®cant interaction
between the main tillage systems and the subsoiling
treatment. The deep-tillage practices enhanced the
CGR of the crop only in the system under continuous
no tillage (Table 3). By decreasing the intensity of the
tillage the initial crop growth was signi®cantly
reduced. This behavior can be partially explained
by the lower soil NO3-N levels in the NT than in
CH or MB systems (Table 1). When the CGR between
V10 and V11 or V11 and R1 growing stages were
considered, there were no signi®cant interactions or
differences between N fertilization, deep-tillage and
the main tillage systems (Table 3).
The corn grain yield components in both periods did
not present signi®cant interactions between the three
factors (main tillage system, deep-tillage and nitrogen
fertilization). No signi®cant differences between any
of the treatments were observed in the plant density
and in the weight of the grains (Table 4). The main
tillage system and the nitrogen fertilization treatment
signi®cantly increased the grain yields in both periods.
The highest corn grain yields were observed in the
tilled soils and when the nitrogen fertilizer was

16

M. DõÂaz-Zorita / Soil & Tillage Research 54 (2000) 11±19

Table 2
Effect of nitrogen fertilization (N fert.) or deep-tillage (DT) on corn dry matter (kg haÿ1) in a Typic Hapludoll from the western Pampas
Region of Argentina under no-tillage (NT) and tillage (chisel (CH) or moldboard (MB) plowing) systems
Dry matter yield (kg haÿ1)a
41 days after seeding

48 days after seeding

62 days after seeding

NT

No N fert.
With N fert.
Without DT
With DT

1481.7
1493.3
1236.7b
1738.3c

2011.7
1966.7
1680.0b
2298.3c

3033.3b
3225.0c
2770.0b
3488.3c

Tilled

CH
MB
No N fert.
With N fert.
Without DT
With DT

1989.2b
2129.2c
2111.7
2006.7
2024.2
2094.2

2455.8
2630.8
2426.7
2660.0
2514.2
2572.5

4071.7
3867.5
3890.8
4048.3
3972.5
3966.7

a

Means in the same column within each subtreatment followed by the same superscript or the absence of superscripts are not signi®cantly
different at the 5% level by the LSD (T) test.

applied. No differences were detected due to the deeptillage treatment (Table 4).
The enhancement of the corn shoot dry matter
production because of subsoiling indurate soil layers,
and the lack differences on the corn grain weights and
yields can be explained by considering the rainfall
during the growing season (Table 5). Varsa et al.
(1997) indicated that adequate rainfall events minimize the bene®ts derived from deep-tillage practices.
In this study the rainfall during grain ®lling stages (end

of January and February) was above the normal values
(DõÂaz-Zorita et al., 1998) and potential rainfall de®cits
were only detected during vegetative stages (October±
December) in the 1995±1996 period.
Although the observed bulk density values can be
considered non-limiting for the normal crop growth
(Daddow and Warrington, 1983; Vepraskas, 1994),
differences in crop yields were related to differences
in the soil BD of the 0±20 cm layer at seeding and
the nitrogen fertilization (Fig. 2). In both periods,

Table 3
Effect of nitrogen fertilization or deep-tillage on CGR of corn crops cultivated in a Typic Hapludoll from the western Pampas Region of
Argentina under NT and tillage (chisel (CH) or moldboard (MB) plowing) systems
Tillage

Deep-tillage

CGR (kg haÿ1 per day)a
Without N fertilization
0±41 days
after seeding

41±48 days
after seeding

With N fertilization
48±62 days
after seeding

0±41 days
after seeding

41±48 days
after seeding

48±62 days
after seeding

NT

No
Yes
Mean (NT)

31.9b
40.4c
36.1

93.3
86.7
90.0

38.3
93.3
65.8

28.5
44.4
36.4

28.5
44.4
36.4

33.3
73.3
53.3

CH

No
Yes
Mean (CH)

48.9
50.1
49.5

66.7
83.3
75.0

113.3
78.3
95.8

45.0
50.1
47.5

45.0
50.1
47.5

70.0
46.7
58.3

MB

No
Yes
Mean (MB)

54.6
52.4
53.5

70.0
93.3
81.7

105.0
100.0
102.5

48.9
51.8
50.4

48.9
51.8
50.4

73.3
50.0
61.7

a
Means in the same column within each tillage or means by tillage within each N fertilization treatment followed by the same superscript
or the absence of superscripts are not signi®cantly different at the 5% level by the LSD (T) test.

17

M. DõÂaz-Zorita / Soil & Tillage Research 54 (2000) 11±19

Table 4
Effect of tillage systems, nitrogen fertilization (N fert.) or deep-tillage (DT) treatments on the yield components of corn crops cultivated in a
Typic Hapludoll from the western Pampas Region of Argentinaa
1995±1996

1997±1998

Stand (plants
per m2)

Grain weight
(mg per grain)

Grain yieldb
(kg haÿ1)

Stand (plants
per m2)

Grain weight
(mg per grain)

Grain yield
(kg haÿ1)

MB
CH
NT

6.05
5.83
5.92

245.9
243.7
241.5

5236.9c
5048.3c
4709.6d

5.98
6.02
5.93

247.5
248.1
245.9

10089.3c
10015.3c
8294.3d

No N fert.
With N fert.

5.93
5.93

242.5
244.9

3916.2c
6080.3d

5.99
5.97

243.3
250.9

8929.3c
10003.2d

Without DT
With DT

5.96
5.90

240.5
247.0

4941.5
5055.0

5.98
5.91

248.1
246.3

9184.3
9748.2

a

CHˆchisel plowing; MBˆmoldboard plowing; NTˆno-tillage.
Means in the same column within each subtreatment followed by the same superscript or the absence of superscripts are not signi®cantly
different at the 5% level by the LSD (T) test.
b

Table 5
Normal, 1995±1996, and 1997±1998 monthly rainfall at Drabble (Buenos Aires, Argentina) during the corn growing season
Rainfall (mm)

1995±1996
1997±1998
Normala
a

October

November

December

January

February

64
155
92

78
92
101

69
401
114

93
118
130

108
159
90

Source: DõÂaz-Zorita et al. (1998).

Fig. 2. Effect of soil BD and N fertilization on corn yields in a Typic Hapludoll from the western Pampas Region of Argentina. In the
equations, Nˆ0 in treatments without N fertilization and Nˆ1 in treatments with N fertilization.

18

M. DõÂaz-Zorita / Soil & Tillage Research 54 (2000) 11±19

increasing the soil BD reduced the grain yields
independent of the N fertilization treatment. The
negative effect of increasing levels of BD on corn
yields could be because of limitations in the available
soil for root development in soils with low water
holding capacity and moderate to low nitrogen availability. In these soils, DõÂaz-Zorita (1996) found
that corn grain yields decreased from 8190 to
2490 kg haÿ1 when the thickness of the soil above
an endured layer diminished from 65 to 45 cm. No
other soil properties (e.g. penetration resistance
per layer or cumulated in the 0±20 cm layer) or
management practices (e.g. tillage system) were
related to the yields.
In the absence of cultivation, this soil tends to
set hard resulting in high bulk density and high
soil penetration resistance in surface layers. A deeptillage operation is an effective method for overcoming soil physical limitations under no-tillage
systems in soils with similar characteristics to the
studied soil. This may be a suitable strategy for
improving the early shoot growth of corn crops in
the initial stages of the adoption of the no-tillage
system. Nitrogen fertilization requirements must
also be considered in order to achieve high crop
productivity.

4. Conclusions
The preparation of seedbed using either moldboard
or chisel plowing with or without deep-tillage
increased the vegetative and grain yield of the crops
when compared with the no-tillage system. The poor
vegetative growth of the no-tilled plots was improved
by deep-tillage. Subsoiling did not modify the corn
grain yields of the crops which were independent of
the tillage practice. Soil bulk density and nitrogen
fertilization control the grain yields of corn crops in
agricultural production systems in the western Pampas
Region of Argentina.

Acknowledgements
I express my thanks to Dr. Edmund Perfect who
critically reviewed the manuscript. The ®nancial support by INTA Gral. Villegas is greatly appreciated.

References
Analytical Software, 1998. Statistix for windows, Version 2.0.
Analytical software, Tallahassee, FL, USA.
Andriulo, A.E., Rosell, R.A., 1988. Propiedades eda®cas en dos
sistemas de labranza (Soil properties in two tillage systems).
Turrialba 38, 365±375.
Bennie, A.T.P., Botha, F.J.P., 1986. Effect of deep tillage and
controlled traf®c on root growth, water-use ef®ciency and yield
of irrigated maize and wheat. Soil Tillage Res. 7, 85±95.
Bennie, A.T.P., Krynauw, G.N., 1985. Causes, adverse effects and
control of soil compaction. S. Afr. J. Plant Soil 2, 109±114.
Boone, F.R., van der Werft, H.M.G., Kroesbergen, B., ten Hag,
B.A., Boers, A., 1986. The effect of compaction of the arable
layer in sandy soils on the growth of maize for silage 1: critical
matric water potentials in relation to soil aeration and
mechanical impedance. Neth. J. Agric. Sci. 34, 155±171.
Bray, R.H., Kurtz, L.T., 1945. Determination of total, organic, and
available forms of phosphorus in soils. Soil Sci. 59, 39±45.
Bremner, J.M., Mulvaney, C.S., 1982. Nitrogen-total. In: Page,
A.L., Miller, R.H., Miller, D.R. (Eds.), Methods of Soil
Analysis II. Chemical and Microbiological Properties. American Society of Agronomy, Madison, WI, pp. 595±624.
Buschiazzo, D.E., Panigatti, J.L., Unger, P.W., 1998. Tillage effects
on soil properties and crop production in the subhumid and
semiarid Argentinean Pampas. Soil Tillage Res. 49, 105±116.
Chagas, C.L., Marelli, H.J., Santanatoglia, O.J., 1994. Propiedades
®sicas y contenido hidrico de un Argiudol Tipico bajo tres
sistemas de labranzas (Soil physical properties and water
content of a Typic Argiudoll under three tillage systems).
Ciencia del Suelo 12, 11±16.
Daddow, R.L., Warrington, G.E., 1983. Growth-limiting soil bulk
densities as in¯uenced by soil texture. USDA Forest Serv. Rep.
WSDG-TN-00005, Fort Collins, USA, p. 9.
Dexter, A.R., 1991. Amelioration of soil by natural processes. Soil
Tillage Res. 20, 87±100.
DõÂaz-Zorita, M., 1996. Labranzas en la regioÂn semiaÂrida-subhuÂmeda bonaerense noroeste (Tillage practices in the semiaridsubhumid region of the northwestern of Buenos Aires). In:
Buschiazzo, D.E., Panigatti, J.L., Babinec, F. (Eds.), Labranzas
en la RegioÂn SemiaÂrida Argentina. INTA y SAPyA, Santa Rosa,
Argentina, pp. 39±48.
DõÂaz-Zorita, M., 1999. Efecto de 6 anÄos de labranzas en un
Hapludol del noroeste bonaerense, Argentina (Effects of six
years of tillage systems in a Hapludoll from the northwestern
part of Buenos Aires, Argentina). Ciencia del Suelo 17, 31±
36.
DõÂaz-Zorita, M., Pepi, M.L., Grosso, G.A., 1998. Estudio de las
precipitaciones en el oeste bonerense (Rainfall studies in the
western part of Buenos Aires). EEA INTA ``General Villegas'',
Publ. TeÂcnica No. 23, 15 pp.
Ehlers, W., Popke, V., Hesse, F., Bohm, W., 1983. Penetration
resistance and root growth of oats in tilled and untilled loam
soil. Soil Tillage Res. 3, 261±275.
Gerard, C.J., Sexton, P., Shaw, G., 1982. Physical factors
in¯uencing soil strength and root growth. Agron. J. 74, 875±
879.

M. DõÂaz-Zorita / Soil & Tillage Research 54 (2000) 11±19
Gupta, S.C., Allmaras, R.R., 1987. Models to assess the
susceptibility of soils to excessive compaction. Adv. Soil Sci.
6, 65±100.
Hammel, J.E., 1994. Effect of high-axle load traf®c on subsoil
physical properties and crop yields in the Paci®c Northwest
USA. Soil Tillage Res. 29, 159±203.
Jones, C., 1983. Effects of soil texture on critical bulk density for
root growth. Soil Sci. Soc. Am. J. 47, 1208±1211.
Keeney, D.R., Nelson, D.W., 1982. Nitrogen-inorganic. In: Page,
A.L., Miller, R.H., Miller, D.R. (Eds.), Methods of Soil
Analysis II. Chemical and Microbiological Properties. American Society of Agronomy, Madison, WI, pp. 643±658.
Kruger, H.R., 1996a. CompactacioÂn en Haplustoles del sudoeste
bonaerense (Argentina) bajo cuatro sistemas de labranza (Soil
compaction in Haplustolls from the southwest of Buenos Aires
(Argentina) under four tillage systems). Ciencia del Suelo 14,
104±106.
Kruger, H.R., 1996b. Sistemas de labranza y variacion de
propiedades quõÂmicas en un Haplustol eÂntico (Tillage systems
and changes in chemical properties in an Entic Haplustoll).
Ciencia del Suelo 14, 53±55.
Lowery, B., Schuler, R.T., 1994. Duration and effects of
compaction on soil and plant growth in Wisconsin. Soil Tillage
Res. 29, 205±210.
Mead, J.A., Chan, K.J., 1988. Effect of deep tillage and seedbed
preparation on the growth and yield of wheat on a hard-setting
soil. Aust. J. Exp. Agric. 28, 491±498.
Nelson, D.W., Sommers, L.E., 1982. Total carbon, organic carbon,
and organic matter. In: Page, A.L., Miller, R.H., Miller, D.R.
(Eds.), Methods of Soil Analysis II. Chemical and Microbiological Properties. American Society of Agronomy, Madison, WI, pp. 539±579.
O'Sullivan, M., Dickson, J., Campbell, D., 1987. Interpretation and
presentation of cone resistance data in tillage and traf®c studies.
J. Soil Sci. 38, 137±148.

19

Pierce, F.J., Fortin, M.C., Staton, M.J., 1994. Periodic plowing
effects on soil properties in a no-till farming system. Soil Sci.
Soc. Am. J. 58, 1782±1787.
Ripoll, M., Kruger, H., 1996. Labranza vertical en el S.O. de la
Prov. de Bs.As. Efectos sobre la resistencia a la penetracioÂn, el
sistema radical y los rendimientos de trigo (Vertical tillage in
the southwest of Buenos Aires province. Effects on the soil
penetration resistance, root systems and wheat yields).
Memorias IV Cong. Argentino y II Internacional de IngenierõÂa
Rural (CADIR 96), NeuqueÂn, Argentina, I, pp. 383±388.
Scheiner, J.D., Lavado, R.S., 1998. The role of fertilization on
phosphorus strati®cation in no-till soils. Commun. Soil Sci.
Plant Anal. 29, 2705±2711.
Scotta, E.S., Herrera, D., 1991. Rendimiento de trigo y soja con y
sin arado subsolador (Wheat and soybean yields with and
without paraplowing). In: INTA (Ed.), Jornada de InformacioÂn
TeÂcnica Para Productores. ParanaÂ, Argentina.
Sene, M., Vepraskas, M.J., Naderman, G.C., Denton, H.P., 1985.
Relationships of soil texture and structure to corn yield
response to subsoiling. Soil Sci. Soc. Am. J. 49, 422±427.
Senigagliesi, C., Ferrari, M., 1993. Soil and crop responses to
alternative tillage practices. Int. Crop Sci. I, 27±35.
Taboada, M.A., Micucci, F.G., Cosentino, D.J., Lavado, R.S., 1998.
Comparison of compaction induced by conventional and zero
tillage in two soils of the rolling Pampa of Argentina. Soil
Tillage Res. 49, 57±63.
Unger, P.W., Kaspar, T.C., 1994. Soil compaction and root growth:
a review. Agron. J. 86, 759±766.
Varsa, E.C., Chong, S.K., Abolaji, J.O., Farquhar, D.A., Olsen, F.J.,
1997. Effect of deep tillage on soil physical characteristics and
corn (Zea mays L.) root growth and production. Soil Tillage
Res. 43, 219±228.
Vepraskas, M.J., 1994. Plant response mechanisms to soil
compaction. In: Wilkinson, R.E. (Ed.), Plant-Environment
Interactions. Marcel Dekker, New York, USA, pp. 263±287.