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Soil compaction adversely affects nearly all physical, chemical and biological properties of the soil. In this research, effects of fertilizers that resulted in soil degradation and compaction were studied. Soil penetration resistance was measured by electronic penetrologger in 12 wheat fields at depth 0-30 cm (each farm is a treatment with 3 replications), and the randomized complete block design was applied. Having applied a variance analysis, the mean values of data were compared using Dun can's multiple range tests. Results indicated that bulk density changed from 1.34 to 1.80 Mg.m(-3), as well as, penetration resistance from 0.89 to 3.54 MPa in noncompacted and highly compacted soils, respectively. According to the results, soil compaction decreased permeability by 81.4 %, available water by 34 % and yields by 40 %. Therefore, usage of fertilizers more than the recommended amounts causes formation, accumulation and concentration of mineral salts of fertilizers which leads to compaction layer and soil degradation in the long-term. High compaction decreases porosity and aeration while increasing bulk density and soil penetration resistance. Furthermore, root development and plant growth will be limited by reducing water and nutrient uptake which decreases yields.
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AGRICULTURAL MECHANIZATION IN ASIA, AFRICA, AND LATIN AMERICA 2016 VOL.47 NO.144
Effect of Chemical Fertilizers on Soil Compaction
and Degradation
Abstract
Soil compaction adversely affects
nearly all physical, chemical and
biological properties of the soil. In
this research, effects of fertilizers
that resulted in soil degradation and
compaction were studied. Soil pen-
etration resistance was measured by
electronic penetrologger in 12 wheat
fields at depth 0-30 cm (each farm
is a treatment with 3 replications),
and the randomized complete block
design was applied. Having applied
a variance analysis, the mean values
of data were compared using Dun-
can’s multiple range tests. Results
indicated that bulk density changed
from 1.34 to 1.80 Mg.m-3, as well
as, penetration resistance from 0.89
to 3.54 MPa in noncompacted and
highly compacted soils, respectively.
According to the results, soil com-
paction decreased permeability by
81.4 %, available water by 34 % and
yields by 40 %. Therefore, usage
of fertilizers more than the recom-
mended amounts causes formation,
accumulation and concentration of
mineral salts of fertilizers which
leads to compaction layer and soil
degradation in the long-term. High
compaction decreases porosity and
aeration while increasing bulk den-
sity and soil penetration resistance.
Fu r thermore , root developme nt
and plant growth will be limited by
reducing water and nutrient uptake
which decreases yields.
Key words: bulk density; compac-
tion; degradation; penetration resis-
tance; permeability.
Introduction
Soil compaction is an important
co mponent of land deg r a dat ion
syndrome and is a signicant chal-
lenge facing advanced agriculture
th at adversely affects nearly all
soil properties: physical, chemical
and biological (Weisskopf, et al.,
2010). When soil is compacted, its
structure alters by crushing aggre-
gate units, reducing the size of pore
spaces between the soil particles,
reduction in soil volume and total
porosity that leads to increase in
soil bulk density and penetration
resistance. Soil compaction refers to
the formation of dense layers of well
lled that occurs on cultivated layer,
even more, the compressive forces
are applied to compressible soil
from wheels (Hamza and Anderson,
2005). Compaction is caused by the
use of heavy machinery, reduction
in use of organic fertilizer, frequent
use of che m ic a l fertili z e r s and
plowing at the same depth for many
years (Mari et al., 2008). One of the
principal causes of compaction is
over use of fertilizers (usage of fer-
tilizers more than the recommended
amount) for long periods and in-
tensive cropping. Soil compaction
causes problems including excessive
soil strength, limiting root growth,
poor aeration, poor drainage, run-
off, erosion and soil degradations
(Batey, 2009). These changes lead
to reduction in permeability, hy-
draulic conductivity and groundwa-
ter recharge (Blanco, et al., 2002).
Excessive soil compaction impedes
root growth and this can decrease
the plants uptake ability of nutri-
ents and water. If the bulk density
increases from 1.3 to 1.4 Mg.m-3 in
some sort of soil with loamy tex-
ture, infiltration rate and aeration
will reduce (Osunbitan et al., 2005).
Compaction reduces root growth,
as well as, the yield by more than
80 % (Rannik, 2009). When the soil
bulk density increases, nitrication
decreases by 50 % and plant absorbs
less nitrogen, phosphorus and zinc
from soil (Barzegar et al., 2006).
Reduction of biological activity due
to compaction is a great concern
(Beylich et al., 2010). Organic mat-
ter is the most important factor in
soil structure stability. Soil that has
high organic matter contents and
thrives with soil organisms is more
resistant to compactions and can
by
Jafar Massah
Assoc. Prof.,
Department of Agrotechnology,
College of Abouraihan, University of Tehran,
Tehran, IRAN
jmassah@ut.ac.ir
Behzad Azadegan
Assoc. Prof.,
Department of Irrigation and Drainage,
College of Abouraihan, University of Tehran,
Tehran, IRAN
bazad@ut.ac.ir
VOL.47 NO.1 2016 AGRICULTURAL MECHANIZATION IN ASIA, AFRICA, AND LATIN AMERICA 45
recuperate much better from slight
compaction damage (Dexter, 2008;
Celik et al., 2010). This research
aims to study the effects of over use
of fertilizers more than the recom-
mended amounts that cause com-
paction and soil degradation in long
term.
Materials and Methods
The soil studied in this research
had been planted with wheat for
over 50 years. This research was
carried out on 12 wheat farms (each
plot is a treatment) in Pakdasht re-
gions, station (35º37N, 35º37′ E;
1005 m above sea level) located 35
km southeast of Tehran. Average
annual precipitation at this site is
210 mm. The research procedure
was as follows:
Farms with different levels of soil
compaction were randomly selected.
After taking soil samples from each
farm (2 m × 1 m × 0.3 m), the neces-
sary analysis was performed in soil
laborator y using routine methods.
The experiment was a random-
ized complete block design with 3
replications. N-P-K fertilizers were
applied in the seedbed at average
rates of 405 kg N ha-1 (urea), 203 kg
P2O5 ha-1 (triple phosphate) and 120
kg K2O (Potassium sulfate) sulfate
ha-1. The average amounts of recom-
mended fertilizers were 178 kg N
ha-1, 85 kg P2O5 ha-1 and 50 kg K2O
ha-1 (Azadegan and Amiri, 2010).
Bulk density was determined from
undisturbed soil samples and was
measured by the core method. Soil
moisture content and penetration re-
sistance were measured at the same
time. In order to determine the soil
moisture content, undisturbed soil
samples were taken from each plot
using a steel cylinder of 100 cm-3
volume at depths of 0-15 and 15-30
cm. Soil gravimetric moisture con-
tent was calculated from the weight
difference between wet and oven-
dried samples (24 h at 105 ºC). The
volumetr ic moisture content was
calculated by dividing the gravi-
metric moisture content by the soil
volume of 100 cm3. Soil optimum
moisture was determined via stan-
dard proctor test (ASTM). Soil wa-
ter permeability was measured us-
ing double rings and aggregate sta-
bility was determined by measuring
the mean weight diameter (M.W.D)
of soil aggregates in a sieve under
run ning water. Soil bulk density
(ρb) was determined via volumetric
cylinder method and particle density
was measured using a Pycnometer.
In order to calculate soil porosity,
the relationship between bulk den-
sity and particle density was used.
Available water equals the differ-
ence between the water content at
field capacity (FC) and permanent
wilting point (PW P) which wa s
measured by the use of a pressure
membrane apparatus. Wheat net
water requirement was determined
using regional meteorological data
and Crop-wat software.
Soil penetration resistance was
det e r m in e d by a ha n d-pu shed
electronic cone penetrometer (Ei-
jkelkamp penetrologger, 06.15.SA)
following ASAE standard proce-
dures, using a cone with 2 cm2 base
area, 60º included angle, speed of 3
cm.s-1, 80 cm driving shaft; readings
were recorded at 10 mm intervals.
The measurements were performed
at 10 points in each plot. In order to
minimize the effect of compaction
caused by agricultural machinery
trafc in each plot, the soil from the
middle cultivation rows (between
the tractor tracks) was used for sam-
pling and testing. The penetration
resistance of 10 different points in
each plot was randomly measured at
depths of zero to 30 cm (at distance
is 5-10 m each of point). The average
penetration resistance of those 10
points represented the compaction
status of the soil in each plot. Values
of the average penetration resistance
of 12 t reatments (each plot was
considered as one treatment) were
compared. In order to compare the
average values of penetration resis-
tance, the normality of the data was
tested. Grain yield of each plot was
measured after harvest. Variance
analysis of data was done based
on the randomized complete block
design and mean comparison was
done using Duncan’s multiple range
test (P ≤ 0.05). The soil compaction
status was studied and conclusions
were made based on the results.
Results and Discussion
The experiment showed that the
studied soil contained 36 % clay, 33
% silt and 31 % sand at the depth
zero-30 cm. Soil texture was loam-
silt loam with 1-2 % slope. The soil
had a pH of 7.48-7.70, ECe of 1.15-
2.20 ds.m-1 and par ticle density
2.60-2.62 Mg.m-3. Soil bulk density
and pe netrat ion resistance were
used to characterize the compaction
and soil degradations.
The result of soil a nalysis of
physical properties (Table 1) shows
bulk density of 1.34-1.80 Mg m3-
and the mean aggregate diameter
(M.W.D) changes from 1.43 to 0.28
mm. The aggregates diameter in
non-compacted soil (plot, P2) is 5
times greater than the highly com-
pacted soil (plot, P4). The macro-
aggregates are disintegrated into
micro-aggregates that decrease the
size and proportion. The total pore
volume and porosity is decreased
17.4 % which slows down water and
air movement in the soil. Previous
studies revealed that the number
of small pores decreases, and so
does the amount of plant-available
oxygen. As a result, as soil density
increases, total porosity decreases
up to 17 % in the severe compac-
tion. The soil with aggregates about
5mm in diameter, has relatively low
volume of inaccessible water for
the highest crop yield (Jung, et al.,
2008; Kaufmann et al., 2005; Staw-
inski et al., 2010) and reduction in
nutrient uptake (Kuht and Reintam,
2004). These adverse effects may
be due to restriction in root depth,
AGRICULTURAL MECHANIZATION IN ASIA, AFRICA, AND LATIN AMERICA 2016 VOL.47 NO.146
where roots in compact soil are con-
ned to macro pores and the rate at
which they can extract water and
nutrients from the soil between the
macro pores may be considerably
slowed.
To achieve higher yield of crops, it
is essential to provide the optimum
level of nutrients requirement. In
Pakdasht regions, farmers applied
usually N, P and K fertilizers in the
seedbed at rates of 405 kg N ha-1,
203 kg P2O5 ha-1 and 120 kg K2O
ha-1 for wheat in each year. But fer-
tilizers were applied at average rates
of 227 kg N ha-1, 118 kg P2O5 ha-1
and 70 kg K2O ha-1 more than the
recommended amounts. However,
there were no significant increases
in yields. Results showed that cal-
cium carbonate content increased
from 12.24 % in non-compacted soil
to 24.8 % in highly compacted soil
(increased by 100 %). The calcium
carbonate concentrated and ac-
cumulated into sub soils with little
solubility, which created a com-
pressed layer that slows down the
water movement in the soil (Jung,
et al., 2008). Phosphorus and exces-
sive calcium in soil form insoluble
calcium phosphate which reduces
phosphorus absorption. Compaction
affects phosphorus uptake strongly
be cause the phosphorus is ver y
immobile in soil and the rate of re-
sidual phosphorus fertilizers in soils
is 75-80 % (Tisdale, et al., 1993).
Compaction also reduces penetra-
tion and growth of the roots because
phosphorus uptake is inhibited in
compacted soil. Therefore, extensive
root systems are necessary to enable
phosphorus uptake (Oussible, et al.,
1992). Potassium uptake is affected
the same way as phosphorus. The
rate of residual potassium fertilizer
is 30-40 % in the soils and gradu-
al ly forms carbon ate Pot a ssium
(Kaufmann, et al., 2010). Also, ni-
trication capacity decreases by 50
% while the rate of residual nitrogen
fertilizers is 30-35 % in the soils.
The result s show a reduction i n
absorption efficiency of fertilizers,
as well as, annual increase in fixa-
tion and concentration of insoluble
forms of nitrogen, phosphorus and
potassium in soils. This effect leads
to reduced uptake of nutrients in
return (Mari, et al., 2008). Over-
use of fertilizers in each year for
monoculture crop causes formation
and concentration of mineral salts
of fertilizers leading to compaction
layer and soil degradation in the
long-term. These results in increase
of physical properties of the soil,
such as, bulk density, penetration
resi st a n c e and soi l compaction
which in return decreases plants-
absorbable nutrients, crop yield and
increases the production cost. In
some soils dissolution of salts due to
irrigation causes dispersion of soil
particles. Once aggregates are dis-
persed, ne clay particles leach into
soil pores and block them. These
fine and structure-less substances
cover the soil surface which hinders
water penetration and forms a hard
and impermeable layer (Stawinski,
et al., 2011).
In this study, 20-40 ton.ha-1 of
cow manure was used in non-com-
pacted soil, and nothing in compact-
ed soil. Organic carbon was 0.58-
1.17 %, C/N decreased from 19.5 in
non-compacted soil to 8.28 in highly
compacted soil (42.5 % reduction).
Insufficient use of animal manure
causes organic matter deciency in
soil that contributes to its compac-
tion decelerates the organic carbon
mineralization. This consequently
disrupts the biotic activities of the
soil which decreases the absorb-
able nutrients, stunts plant growth
and limits the yield. With this loss
of organic fertilizer, soil aggregate
stability reduces. Total number of
bacteria and enzymatic activity in
soil under soybean decreased in
Fig. 1 Soil moisture versus soil bulk density
Plot Clay (%) ρb (Mg.m-3)M.W.D
(mm) Porosity
(%) Permeability
(mm.h-1)Avai la ble
Water (%)
P133 1.62 0.53 37.6 37 19
P232 1.34 1.43 48.2 71 24
P333 1.40 1.37 46.5 64 23
P435 1.79 0.30 30.8 12 16
P535 1.78 0.29 31. 5 25 17
P630 1.46 1.32 43.9 59 22
P736 1.55 1.25 41.3 48 21
P830 1.56 1.20 40.4 42 21
P935 1.68 0.32 35.5 33 18
P10 36 1.75 0.28 31.7 19 16
P11 34 1.80 0.28 31.0 15 16
P12 33 1.51 1.25 42.6 53 22
Table 1 Results of the soil physical analysis in Pakdasht County (0-35cm depth)
VOL.47 NO.1 2016 AGRICULTURAL MECHANIZATION IN ASIA, AFRICA, AND LATIN AMERICA 47
strongly compacted soil (Beylich,
et al., 2010; Siczek and Frac, 2012).
To optimize organic matter input in
the soil for maximum productivity,
one should reduce losses of organic
matter by preventing the soil ero-
sion (Bandyopadhyay, et al., 2011).
Structural stability of topsoil with
greater organic matter content was
considered as enhanced resistance
to compaction. Organic matter de-
composition is slower in compacted
soils, and less biological activity oc-
curs because the size and number of
macro pores in the soil, aeration and
microbial activity are reduced. Soil
with high organic matter content
that thrives with soil organisms is
resistant to compaction and can bet-
ter recuperate from degradation.
Fig. 1 shows soil moisture content
versus soil bulk density. Soil opti-
mum moisture was 13.2 %. Farmers
were usually tilling soil at moisture
content above the optimum level
(15-16 %) which contributes to soil
compaction. The compacted soil
often has higher soil moisture be-
cause soil water is unable to drain
away f reely and air movement in
the soil is restricted. Compaction of
soil pushes the soil particles closer
together, reduces the pore space and
so bulk density increases. That pro-
cess reduces porosity, permeability
and crop yield. A tractor of 75 HP
cannot easily till the farm due to its
highly compacted soil. Therefore,
heavy-duty tractor with more than
75 HP is needed, which results in
increasing the cost of production.
High penetration resistance and soil
compaction are f unctions of soil
moisture content. Each soil type
with a certain amount of moisture
(optimum moisture content) has
optimum penetration resistance,
bulk density, compression and com-
paction. When the soil rewets and
expands, the extra soil present in
the subsoil will induce compaction
(Kaufmann, et al., 2010; Jung, et
al., 2010). If tillage is done under
improper moisture conditions, big
clods are formed. The wetting of
clogged soil pores gradually after
irrigation reduces soil porosity and
permeability (Weisskopf, et al.,
2010). The effect of the plowing and
machineries traffic on yield can be
predicted by measuring of penetra-
tion resistance and soil compaction.
If soil is dry and f irm throughout
the prole, there may be no signi-
cant effect. If the surface layers are
moist and soft lying over dry soil,
the upper layers may be strongly
compressed. But if the surface lay-
ers are dry and rm with moist soil
below, the compre ssion may be
transmitted downwards to compress
the moisture in the more vulnerable
soil. Obviously, suitable moisture
content, during the cultivation, pre-
vents soil compaction.
Fig. 2 compares the mean values
of penetration resistance and soil
depth in non-compacted, low com-
pacted, moderate compacted and
highly compacted soils. Values of
soil bulk density were strongly cor-
related to soil penetration resistance.
Penetration resistance in non- com-
pacted soil at rst increased slightly
with depth but later changes were
insignificant because soil compac-
tion was within the normal range
due to stable aggregates and proper
soil structure. Penetration resistance
changes dramatically from the soil
surface to greater depths in highly
compacted soil as a result of com-
paction caused by the disintegration
of soil macro-aggregates and forma-
tion of micro-aggregates, reduction
in the aggregates diameter, total vol-
ume of soil pores, porosity percent-
age, the size and proportion of the
voids in it. An increase in soil bulk
density and penetration resistance
reduces soil permeability, air diffu-
sivity, rate of root development and
plant growth (Zhang, et al., 2006).
As noted, a moderate increase in
soil bulk density leads to an increase
in the cohesion among particles and
better adhesion between particles
and root surfaces by facilitating wa-
ter and nutrient absorption.
Table 2 shows the variance analy-
sis of soil compaction in order to
Fig. 2 Comparison the mean of penetration resistance
and soil depth
Variation
Source df Ms
Block 58 0.4189**
Treatment 12 6.1008**
Error 509 0.0499
C.V = 7.79 %
Table 2 Variance analysis of soil compaction
to compare 12 farms
Plot P4 P10 P11 P5 P9 P1
average 3.54a 2.73b 2 .72b 2.69b 2.00c 1.67d
Plot P8 P7 P12 P6 P3 P2
average 1.66de 1.60de 1.48ef 1.41fg 1.34g 0.89h
Table 3 Comparison of the mean values of soil compaction
in 12 farms using Duncan's multiple tests (P ≤ 0.05)
AGRICULTURAL MECHANIZATION IN ASIA, AFRICA, AND LATIN AMERICA 2016 VOL.47 NO.148
compare the 12 farms on the basis of
randomized complete block design.
The results have been signicant at
(P 0.01). Table 3 shows the com-
parison of mean soil compaction
amounts of 12 farms using Duncan’s
multiple range test (P ≤ 0.05). Table
1 shows that plot P4 has the penetra-
tion resistance 3.54 M Pa (highly
compacted), while plot P2 has 0.89
MPa (non-compacted). Soil penetra-
tion resistance in highly compacted
soil is 14 times greater than non-
compacted soil. Penetration resis-
tance is a better indicator of the
effects of soil compaction on root
growth because results can be inter-
preted independent of soil texture.
In Ta ble 1, the average bulk density
increases from 1.34 Mg.m-3 in non-
compacted soil to 1.80 Mg.m-3 in
highly compacted soil. It can be
observed that penetration resis-
tance increases as the bulk density
increases; this leads to an increase
in soil compaction which adversely
affects the indices of porosity and
available water. Highly compacted
soil constrains root penetration
and development, impedes plant
growth and reduces the yield. The
biggest differences between bulk
soil and the rhizosphere occurred in
heavily compacted soil, where soil
penetration resistance limited root
growth (Nosalewicz, 2011). When
soil penetration resistance is over 2
MPa (the critical level), root growth
in many plants will be restricted
and may stop due to soil compac-
tion (Henderson, 2005). Penetration
resistance index may individually
account for 50 % of the variations in
wheat growth and yields (Passioura,
2002; Rannik, 2009). Soil compac-
tion destroys soil st r uct u re and
leads to a more massive soil struc-
ture with fewer natural voids. When
penetration resistance changes from
0.4 to 4.2 MPa due to compaction,
the lengths of the primary root and
lateral roots are reduced by 71 and
31 %, respectively. Consequently,
the yield reduces by 20-40 % (Kuht
and Reintam, 2004; Jung, et al.,
2008). Compaction alters soil struc-
ture by increasing soil bulk density,
breaking down the soil aggregates,
decreasing soil porosity, aeration
and infiltration (Weisskopf, et al.,
2010).
Fig. 3 shows the relation between
soil bulk density and porosity. Po-
rosity was 48.2 % in non-compacted
soil and changed to 30.8 % in highly
compacted soil (reduced by 17.4
%); the bulk density also increased
from 1.34 Mg.m-3 normal to 1.80
Mg.m-3 in highly compacted soil.
Soil high compaction reduces the
pores diameter by disintegrating the
soil particles; therefore, increases
soil strength and decreases porosity.
High bulk density and low poros-
ity reduced the pore-spaces due
to which roots were incapable to
extract soil nutrients. Therefore, re-
duced nutrient uptake by plant and
also inadequate water may impede
and even stunt plant growth, result-
ing in decreased yields. Compaction
reduced air-lled porosity consider-
ably and caused more frequent and
pronounced conditions of low O2
concentration in soil air (Bassett, et
al., 2005). Soil compaction causes
other problems such as poor aera-
tion, limited root growth, excessive
runoff, erosion and a degradation
of soil structure. This degradation
is enforced when tillage is used to
break up compacted soils.
Fig. 4 shows the relation between
permeability and available water.
Permeability reduced from 71 mm/
h in non-compacted soil to 12 mm/
h in highly compacted soil (81.4
% reduction). The permeability in
highly compacted soil is 6 times
less tha n t hat in non-compacted
soil. Consequently, available wa-
ter is also reduced from 23.5 % in
non-compacted soil to 15.5 % in
highly compacted soil (34 % reduc-
tion). Plant suffers from nutrients
def iciency, physiological dryness
and water st r e ss. The occur red
water stress hinders plant growth
and re duces yield. Permeabilit y
and available water decreased by
21 and 49 % in moderately and
highly compacted soils, respec-
tively. In this study, average wheat
yield was 3,500 to 5,800 kg.ha-1
Fig. 3 Relation between the bulk density and soil porosity Fig. 4 Relation between permeability and available water
VOL.47 NO.1 2016 AGRICULTURAL MECHANIZATION IN ASIA, AFRICA, AND LATIN AMERICA 49
in highly compacted soil and non-
compacted soils, respectively. The
yield decreases 2,300 kg.ha-1 (40 %
reduction) due to high compaction
(Azadegan and Amiri, 2010). This
yield reduction not only reduces the
farmer income but also increases
the production cost. Reduction of
yield components was due to com-
paction and less supply of necessary
nutrients from soil because roots
were less proliferated, and were un-
able to supply the required material,
thus the yield decreased. Insuffi-
cient water and nutrients absorption,
as well as, increasing water stress in
plants reduced the yield (Kaufmann,
et al., 2010). With slow permeability
through the clay pan, soils saturate
quickly creating a high probability
of runoff (about 30 %), clay pan soil
reduced yields by 20-47 % (Blanco,
et al., 2002; Jung, et al., 2010)
High soil compaction substantial-
ly damages the physical, chemical
and biological properties of soil and
reduces the yield. In this research,
some operations like performing
tillage at optimum moisture condi-
tion, employing appropriate meth-
ods of irrigation, and observing
the technical tips of soil and water
management have been undertaken
in farms P4, P3, P6 and P12 under the
supervision of an expert, soil com-
paction had been within the normal
range. But in farms P2, P5, P10 and
P11 soil is highly compacted because
of the farmers’ excessive use of fer-
tilizers and not using organic mat-
ter. Also, there was mismanagement
of the soil and water and not observ-
ing crop rotation traditionally. Soil
compaction in farms P1, P7, P8 and
P9 had been moderate. High soil
compaction decreased absorbability
of water and nutrients, increased re-
sistance against root penetration and
development, stunted plant growth,
decreased available water, reduced
soil qualit y, yield s and f inally,
increased production costs. Soil
compaction affects signicantly the
soil structure, and nutrient uptake in
wheat plants (Mari et al., 2008).
Soil structure can be improved
by adding enough organic matter
to soil, reducing usage of chemical
fertilizers, observing crop rotation,
proper cultivation operation, us-
ing modern irrigation methods and
applying sub-soiler to shatter the
deep compact layers (Azadegan and
Amiri, 2010).
Conclusions
Over-use of fertilizers more than
the recom m e nded amou n t s fo r
continuous monoculture cropping
caused formation, accumulation of
mineral salts of fertilizers that lead
to compaction layer, compaction and
soil degradation in long-term. Soil
degradation affects signicantly the
soil structure and nutrient uptake.
Results showed that the size and
number of macro pores in the soil
reduced which lead to increase in
soil bulk density and penetration re-
sistance that degraded soil physical
properties. Soil bulk density values
were strongly correlated with soil
penetration resistance.
The plowing is performed mois-
ture content higher than the op-
timu m level. Conseque ntly soil
structure is damaged and caused
compaction because soil water is
unable to drain away freely and air
movement in the soil is restricted.
Not using organic fertilizers re-
duced C/N, organic carbon mineral-
ization, aggregate stability and po-
rosity which consequently disrupted
the biotic activities of soil, decreas-
ing the absorbable nutrients.
High soil compaction decreased
permeability, drainage, aeration,
water availability, absorption of
nutr ient, plant growth and yield.
It can be concluded that the major
cont r ibutor y factors to high soil
compaction are caused by the over-
use of fertilizers.
Acknowledgement
This project was funded by the
rese a rch de puty of Col lege of
Abouraihan, University of Tehran
which is really appreciated.
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The effect of fertilizer manage-
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... Soil compaction can lead to reductions in permeability, pore connectivity, water retention, root growth and nutrient uptake [4,[8][9][10][11][12]. Estimated yield losses due to compaction and its effects can reach as high as 40% of the potential yield [13], with more conservative estimates at 5% to 10% [14]. ...
... The percentual yield loss was estimated from the literature. Yield losses can range from of 5% to 40% [13,14], depending on the severity of the compaction. Therefore, we estimate that a reasonable yield loss is 10%. ...
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... Agriculture, now the most challenging field in human endeavour in the global perspective that require more robust attention (Nchuchuwe & Adejuwon, 2012). One of the challenges is the crop production and yield which defend on the agricultural input of chemicals like synthetic fertilizers and pesticides to improve the soil fertility for more production outcome and eventually, these processes of applying chemicals were found to have more detrimental effect to the environment and to the final consumers (Massah & Azadegan, 2016). The chemicals such as fertilizers, insecticides and pesticides which eventually lead to the environmental contamination in soil, air and water respectively. ...
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The recent use of heavy machinery combined with frequent disk tillage has created a subsurface compacted horizon in many of the irrigated soils of Morocco. The objective of this study was to evaluate the effect of subsurface compaction on the mot and shoot growth, grain yield, and grain yield components of wheat (Triticum aestivum L.). Field experiments were conducted in 1982 and 1983 on a Moroccan clay loam soil (typic Calcixerolls). Soil compaction was artificially created. The 0.10-111 surface layer was removed from all plots with a road scraper. The exposed subsurface layer was then packed by making four passes over the plots with a 7.5-ton tractor. The removed soil was then replaced and leveled. Control plots were tilled with a disk plow followed by hvo passes of a disk harrow. Both compacted and control plots were then roto-tilled for final seedbed preparation. The result of this compaction was a 12 to 23% decrease in grain yield and 9 to 20% decrease in straw yield. The decrease in yield was accompanied by a consistent reduction in the number of shoots per unit area. Number of kernels per spike and kernel weight were unaffected. Both root growth and distribution were markedly changed as a result of subsurface compaction. Wheat plants in compacted plots had a denser, finer, and shallower root system than wheat plants in control plots. Plant height, and leaf area and dry matter per shoot were also unaffected. The decrease in shoot number might be attributed to a limitation in the amount of available soil N to the roots. Joint contribution of the Institut Agronomique et Veterinaire Hassan II, and Univ. of Minnesota. Research supported in part by USAID project 608-0160. Paper no. 17790 of the Scientific Journal Series, Minn. Agric. Exp. Stn. Please view the pdf by using the Full Text (PDF) link under 'View' to the left. Copyright © . .
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The relationships between soil penetration resistance and the growth and yield of wheat were examined for a range of tillage and compaction experiments conducted on earthy sands near Geraldton, W.A. Overall, a single index of penetration resistance explained around 50% of the growth and yield variation, across sites and seasons. Equations using this index showed good potential for predicting the impact of various tillage and traffic practices on wheat yield.
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Soil compaction generally reduces crop performance because of degraded soil physical and biological properties, and possibly inappropriate soil nutritional status. The effects of varying compaction, and phosphorus (P) and zinc (Zn) supplies on the growth of Berseem or Egyptian clover (Trifolium alexandrimum), and accumulation of P and Zn in shoots and roots were investigated in a pot experiment using a surface layer of a Typic Torrifluvent (USDA), Calcaric Fluvisols (FAO) soil. Plants were treated with three soil compaction levels, three rates of P and three rates of Zn in a factorial combination. Phosphorus accumulation in shoots did not change up to bulk densities of 1.65Mgm−3 and declined at bulk density of 1.80Mgm−3. Increasing the levels of Zn and P resulted in a significant increase in shoot dry mass (from 0.3 to 0.8gpot−1), and root length (from 11.4 to 32.5mpot−1). Shoot and root growth were reduced by soil compaction particularly at low P and Zn application rates. Shoot dry mass was reduced from 0.8 to 0.3gpot−1, and root length from 43 to 5mpot−1 at bulk densities of 1.4 and 1.8Mgm−3, respectively. However, the accumulation of P (from 0.06 to 0.15gkg−1) and Zn per unit length of roots (from 0.8 to 1.8μgpot−1) increased as soil compaction increased. As the Zn supply increased, Zn accumulation per unit length of roots, and total Zn accumulation increased. Severe compaction reduced P and Zn accumulation in shoots and also decreased shoot dry mass, and root length compared to lower soil compaction levels. The present study suggests that Zn and P supply can moderate the adverse effect of soil compaction on clover performance.