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230 C.P. Kushwaha et al. / Applied Soil Ecology 16 (2001) 229–241
practices has increased from 15 to 38million ha
over the last decade (CTIC, 1994) because of the
potential of this practice to reduce soil erosion, con-
serve soil moisture and improve soil structure. In
semi-arid conditions conservation tillage may reduce
evaporative water loss and increase crop biomass
thereby favouring organic matter accumulation from
the higher input of residues (Campbell and Janzen,
1995).
Soil structure plays a key role in the ability of soil
to store organic matter (Balabane, 1996). Soil organic
matter can be physically protected from microbial
attack within soil aggregates, and contributes to the
productivity and physical well-being of soils (Camp-
bell et al., 1996). The proportions of water-stable
aggregates in a soil often change very rapidly when
tillage practices and crop rotations are modified
(Angers et al., 1992). In addition to soil type and
climatic variables, the magnitude of these effects de-
pends on the intensity of cultivation, in particular, thetype and frequency of tillage and the quantity and
quality of fertilizers and organic residues returned to
the soil (Rasmussen and Collins, 1991). Conventional
tillage practices disrupt soil aggregates, exposing
more organic matter to microbial attack (Beare et al.,
1994). Organic matter can be protected from mi-
crobial attack by adsorption to clay minerals (Ladd
et al., 1985) and the formation of microaggregates
(Gregorich et al., 1989), by isolation in micropores
(Foster, 1981) and by physical protection within sta-
ble macroaggregates (Elliott, 1986; Gupta and Ger-
mida, 1988). In conventional agricultural production
practices, tillage and residue removal increase theloss of soil organic matter (Dalal and Mayer, 1986),
and reduce the proportion of macroaggregates (Tis-
dall and Oades, 1980). This is mainly due to loss
of the labile organic matter (i.e. microbial biomass)
which is responsible for the formation of macroaggre-
gates. In cultivated soils, the organic matter content
of macroaggregates is considerably greater than that
of microaggregates. Application of organic matter in
the form of crop residues has long been known to
improve the properties of soils (Blevins and Frye,
1993). The only shortcoming of residue application
is the immobilization of nutrients during the early
phase of decomposition because of its wider C/Nratio. This can be overcome by the use of chemical
fertilizers in addition to crop residue. It has been
reported that straw incorporation may increase the
formation and stability of soil aggregates (Smith and
Elliott, 1990).
The role of conservational tillage and residue re-
tention in aggregate formation is poorly documented
in tropical agroecosystems. Such information is lack-
ing from dryland (rainfed) agroecosystems of India
which account for ca. 70% of the cultivated land in
the country. An understanding of the effect of various
management practices on the soil aggregation may
help develop sustainable crop production systems in
dryland agroecosystems. The main aim of this study
was to determine the changes in both soil organic
matter (organic and microbial C) and water-stable
aggregates under different tillage systems and residue
retention/removal conditions. This study addresses the
following questions with respect to tropical dryland
agroecosystems:
1. What is the impact of tillage reduction and residue
manipulation on the physico-chemical properties of soil?
2. Are the changes in water-stable soil aggregates
associated with the levels of soil organic mat-
ter under different tillage and residue retention
practices?
3. To what extent do macro- and microaggregates dif-
fer with respect to their organic C and total N ac-
cumulations?
4. What is the relationship between soil microbial
biomass and water-stable soil aggregates under dif-
ferent tillage systems and residue conditions?
2. Materials and methods
2.1. Study site
These experiments were conducted on the dry-
land farm of the Institute of Agricultural Sciences,
Banaras Hindu University at Varanasi (at 25◦18N
latitude and 83◦1E longitude, 76 m above the msl).
The region has a tropical moist subhumid climate,
characterized by strong seasonality with respect to
temperature and precipitation. The year is divisi-
ble into a warm rainy season (July–September), acool winter (November–February), and a hot sum-
mer (April–June). October and March constitute
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C.P. Kushwaha et al. / Applied Soil Ecology 16 (2001) 229–241 231
Fig. 1. Temperature and rainfall data for the study site.
transitional months between seasons. The summer is
dry and hot with temperatures ranging between 35
and 45◦C during the day. Warm conditions (25–35◦C)
and high relative humidity (70–91%) prevail dur-
ing the rainy season. The rainy season starts with
the onset of heavy monsoons in the end of June
and continues till mid-October, over 85% of the an-
nual rainfall being received within 4 months. The
long-term average annual rainfall is about 1100 mm.
During the study period (1997–1998), annual rainfallwas 1287mm with 60 rainy days and an extended
dry period of about 9 months. During the winter sea-
son, day temperature falls to between 10 and 25◦C
with occasional light rain received from the retreating
western monsoon. Mean monthly values of temper-
ature and rainfall are plotted in Fig. 1. The rainy
and winter seasons are the major cropping seasons
in this region. Rice was selected as the rainy sea-
son test crop and barley as the winter season test
crop.
The soil of the Banaras Hindu University campus
which includes the agriculture farm is characterized
as Banaras type III by Agarwal and Mehrotra (1952).It is an inceptisol with a flat topography, pale brown
colour, and sandy loam texture.
2.2. Experimental design
The experiment was designed to vary the degree
of soil disturbance using different tillage practices
(such as conventional tillage, minimum tillage and
zero tillage), and the amount of organic input through
residue retention from the previous crop to the next
crop. Rice was grown during the rainy season in 1997
in a conventionally tilled field of ca. 3000 m2. When
rice matured (November 1997), six treatments withthree replicate 9 m × 10 m plots were established in a
randomized block design. A 1 m uncultivated strip was
left to separate the treatment blocks. An assessment of
the initial soil fertility status, carried out in November
1997, showed that the differences in organic C and
total N contents between different replication blocks
were not significant; the means(±S.E.) for the three
blocks were: organic C 7.85 ± 0.08gkg−1, total N
0.872 ± 0.008gkg−1.
The treatments were: (1) conventional tillage
(disked twice, cultivated once to 20 cm depth), and
residues removed (CT − R); (2) conventional tillage
(as above), and residues retained (CT + R); (3) min-imum tillage (disked once, cultivated once to 10 cm
depth), and residues removed (MT−R); (4) minimum
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232 C.P. Kushwaha et al. / Applied Soil Ecology 16 (2001) 229–241
Table 1
Chemical composition and quantities of crop residues retained in different treatments; values are means ± S.E.
Crop residue Carbon (gkg−1)a Nitrogen (g kg−1)b C/N ratio Quantity of residue (kg ha−1)
Rice 491 ± 5.2 6.02 ± 0.25 81.56 6825 ± 358 (in all residue retained treatments)
Barley 489 ± 5.3 6.22 ± 0.20 78.61 5831 ± 495 (in CT + R), 6687 ± 308
(in MT + R), 3750 ± 508 (in ZT + R)
a Determined as: loss in ignition/2 (McBrayer and Cromack, 1980).b Micro-Kjeldahl method (Jackson, 1958).
tillage (as above), and residues retained (MT+R); (5)
zero tillage (no cultivation other than the disturbance
caused by the planting tines), and residues removed
(ZT − R); (6) zero tillage (as above), and residues
retained (ZT +R). In residue removed plots, harvest-
ing of rice was done at the ground level, leaving no
standing aboveground rice residues. In the residue re-
tained plots, harvesting of rice was done 20 cm above
the ground, leaving a portion of the rice aboveground
residue standing in the plot. This was incorporated
into the soil during the tillage operations (either
conventional or minimum tillage) carried out before
sowing of barley (October 1997). In the case of zero
tillage plots, the standing rice residue was chopped at
the ground level and left on the soil surface at the time
of first tillage operation in conventional and minimum
tillage plots. When barley matured (April 1998), it
was harvested in the same way as the preceding rice
and the same six treatments with barley aboveground
residue were again established for the succeeding
rice crop. The chemical composition and the amounts
of rice and barley residues retained are given in
Table 1.NPK chemical fertilizers (80 kg N ha−1, 40 kg
P ha−1 and 30kgKha−1 for rice and 60kgNha−1,
40kgPha−1 and 30kgKha−1 for barley) were ap-
plied in all treatments.
2.3. Soil sampling
Soil samples were collected once after the rice har-
vest (November 1998) for physico-chemical and ag-
gregate analyses. Three sub-samples from the upper
10 cm depth were collected by using 10×10×10cm3
monoliths from each replicate plot, and field moist
samples were gently crumbled manually and sieved(4.75, 2.0–4.75, 0.5–2.0, 0.3–0.5,
0.053–0.3, and 0.3 mm were bulked as macroaggre-
gates and those
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C.P. Kushwaha et al. / Applied Soil Ecology 16 (2001) 229–241 233
2.6. Estimation of soil microbial biomass
Microbial biomass C (MBC) was measured by de-
termining the organic C in chloroform fumigated and
non-fumigated samples by dichromate digestion as de-
scribed by Vance et al. (1987). Soil MBC was then
estimated from the equation: MBC = 2.64EC (Vance
et al., 1987), where E C is the difference between C
extracted from the K2SO4 extract of fumigated and
non-fumigated soils. With the same K2SO4 soil ex-
tracts, microbial biomass N (MBN) was determined as
total N using Kjeldahl digestion procedure (Brookes
et al., 1985). The flush of total N (K2SO4 extractable
N from non-fumigated soil subtracted from that of fu-
migated soil) was divided by a K N (fraction of biomass
N extracted after chloroform fumigation) value of 0.54
(Brookes et al., 1985). All the results are expressed on
oven dry soil (105◦C) basis.
2.7. Data analysis
Statistical analysis was carried out using the SPSS
package. Significance of differences between treat-
ment means was examined by an LSD range test pro-
cedure at the 5% level of significance. Data were anal-
ysed by correlation and regression analysis to evaluate
relationships between the different soil parameters.
Table 2
Changes in soil properties following various treatments; the values are means ± S.E.; treatment codes: CT − R, conventional tillage and
residues removed; CT+R, conventional tillage and residues retained; MT−R, minimum tillage and residues removed; MT+R, minimum
tillage and residues retained; ZT − R, zero tillage and residues removed; ZT + R, zero tillage and residues retained
Soil properties Treatments LSD
CT − R CT + R MT − R MT + R ZT − R ZT + R
pH 6.85 ± 0.018 6.76 ± 0.014 6.84 ± 0.016 6.75 ± 0.016 6.75 ± 0.007 6.72 ± 0.008 0.04
Bulk density
(gcm−3) 1.27 ± 0.006 1.24 ± 0.007 1.29 ± 0.007 1.25 ± 0.006 1.42 ± 0.004 1.40 ± 0.004 0.04
WHC
(gkg−1) 412 ± 2.6 423 ± 1.9 416 ± 3.2 431 ± 0.9 410 ± 0.6 414 ± 2.4 9.10
Organic C
(gkg−1 soil) 7.8 ± 0.21 9.8 ± 0.23 8.2 ± 0.15 11.1 ± 0.17 8.1 ± 0.15 8.6 ± 0.15 0.68
(kgha−1)a 9906 ± 264 12152 ± 286 10578 ± 197 13875 ± 216 11502 ± 217 12040 ± 214 885
Total N
(gkg−1 soil) 0.87 ± 0.017 1.18 ± 0.013 0.92 ± 0.006 1.33 ± 0.017 0.89 ± 0.005 0.98 ± 0.019 0.05
(kgha
−1
)
a
1105±
22 1461±
18 1180±
7 1663±
22 1262±
7 1367±
26 70C/N ratio 8.96 8.30 8.95 8.34 9.10 8.80
a 0–10cm depth.
3. Results
3.1. Physico-chemical properties
The soil was almost neutral in reaction (pH 6.8 in
CT−R, which can be regarded as the control, Table 2).
The maximum tillage reduction along with residue re-tention (ZT+R) decreased the pH slightly. The tillage
practices affected the bulk density considerably (for
instance, it increased from 1.27 g cm−3 in CT − R to
1.40gcm−3 in ZT + R) and the effect of residue re-
tention alone was small. The water holding capacity
increased marginally (5%) in the MT + R treatment
compared to the CT − R treatment.
Within a short time, tillage reduction in association
with residue retention (MT+R, ZT + R) significantly
increased soil organic C and total N contents in the
0–10 cm soil layer compared to the CT −R treatment
(Table 2). Compared to CT − R, the maximum in-
crease occurred in the MT + R treatment (organic C42% and total N 53%). Residue retention alone also
increased organic C (by 26%) and total N (by 36%)
in the CT + R treatment. The minimum increases of
organic C (10%) and total N (12%) were recorded in
the ZT + R treatment. In the residue removed treat-
ments, the changes in the concentrations of organic
C and total N were relatively small. The amounts of
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234 C.P. Kushwaha et al. / Applied Soil Ecology 16 (2001) 229–241
Table 3
Per cent soil distribution in aggregate size classes and their MWD in different treatments, values are means ± S.E.; treatment codes as in
Table 2
Treatments Size classes (mm) MWD (mm)
>4.75 2.0–4.75 0.5–2.0 0.3–0.5 0.053–0.3 4.75 mm size class in all treat-
ments (Table 3). The maximum increase was recorded
in the MT + R treatment, and less marked increase
in the 2.0–4.75 mm size class. However, the propor-
tion of soil in the lower size classes (
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Fig. 2. Distribution of water-stable soil macroaggregates (>0.3 mm) and microaggregates (
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236 C.P. Kushwaha et al. / Applied Soil Ecology 16 (2001) 229–241
Fig. 4. Amount of total N in macro- and microaggregates under different treatments in a tropical dryland agroecosystem; values are means,
LSD is shown at p
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C.P. Kushwaha et al. / Applied Soil Ecology 16 (2001) 229–241 237
Table 6
Correlation and regression parameters ( A, intercept; B, regression coefficient; r , correlation coefficient) reflecting relationships between
different soil parameters and micro- and macroaggregates (n = 18); MBC, microbial biomass carbon; MBN, microbial biomass nitrogen;
SOC, soil organic carbon; STN, soil total nitrogen
Parameters A B S.E. of B r 2a
y x
Macroaggregatesb
vs. MBCc
24.93 0.080 0.012 0.73Macroaggregatesb vs. MBNc 32.76 0.530 0.110 0.59
Macroaggregatesb vs. SOCd 18.35 0.004 0.001 0.52
Macroaggregatesb vs. STNd 25.42 0.024 0.006 0.50
Microaggregatesb vs. MBCc 75.25 −0.080 0.012 0.70
Microaggregatesb vs. MBNc 67.34 −0.526 0.115 0.57
Microaggregatesb vs. SOCd 82.32 −0.004 0.001 0.52
Microaggregatesb vs. STNd 74.91 −0.024 0.006 0.49
a All values for r 2 are significant at p
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238 C.P. Kushwaha et al. / Applied Soil Ecology 16 (2001) 229–241
reduction) in combination may prove better than either
practice used alone to elevate the soil nutrient levels.
Varying reports are available with respect to the
fraction of C in organic input conserved as soil or-
ganic C. For instance, Vandermeer (1995) reported
the incorporation of 20–40% of plant residue C into
soil biological material and release of the rest as CO2,
and Jenkinson (1988) approximated 70% respiratory
loss during residue decomposition (the remaining con-
served in soil). In contrast, low incorporation of only
4–7% of crop residue C in soil organic C was reported
in Danish soils by Powlson et al. (1987), and slightly
higher retention of ca. 14% of plant residue was re-
ported by Saffigna et al. (1989). In the present case,
a large fraction of the C contained in crop residues
in different treatments (ca. 36–41%, computed from
Tables 1 and 2) was reflected by an increase in soil
organic C 1 year after the setting up of the experi-
ment. Such high incorporation of the residue C in soil
may be related to the high decomposition rate of thecrop residues in dry tropical agroecosystems (Singh
and Shekhar, 1989a,b). In a tropical grassland (under
similar climatic conditions), where litter decomposi-
tion was rapid, Gupta and Singh (1982a,b) showed that
ca. 35% of the decomposed plant debris was annually
conserved as new soil organic matter.
In different treatments, expected results were ob-
tained with soil pH, bulk density and water hold-
ing capacity. In the present study, soil pH decreased
slightly in zero tillage, similar to that observed by
Blevins et al. (1977). Elimination of soil mechanical
loosening caused by tillage operations is responsible
for the increase in soil bulk density in zero tillagealone (ZT − R) and in combination with residue re-
tention (ZT + R). Similar to this study, Genter and
Blake (1978) in Minnesota found higher bulk den-
sity in zero tillage treatments than in ploughed treat-
ments. Lal (1989) also reported that upland soils in the
tropics may be more susceptible to compaction than
equivalent soils in the temperate zone, due to the an-
tecedent low level of organic matter, lack of ameliora-
tive effect of freezing and thawing, and predominance
of low-activity clays. Tillage reduction in association
with residue retention significantly increased the wa-
ter holding capacity in the present study, mainly due
to large increase in soil organic C in residue retainedtreatments (MT+R, CT+R and ZT+R). The nature
and quantity of soil organic C has been shown to con-
trol water holding capacity (Piper, 1966). Similarly,
Singh and Singh (1993) reported significant increase
in water holding capacity in straw treated plots in the
dryland agroecosystem of Indian tropics.
Cultivation tends to increase the rate of organic
matter loss in soils primarily by accelerated micro-
bial decomposition (Seybold et al., 1999), and alters
structural stability of soil and reduces the amount of
soil organic matter (van Veen and Paul, 1981). Loss
of organic matter reduces the proportion of macroag-
gregates in cultivated soils (Tisdall and Oades, 1980).
Cultivation also reduces the proportion of water-stable
macroaggregates and increases the proportion of mi-
croaggregates (Monreal and Kodama, 1997). Further,
it has been reported that the reduction in tillage will
improve the stability of soil aggregates and the in-
creased amount of organic matter is responsible for
improved soil structure. Residue retention in associa-
tion with tillage reduction (MT+R and ZT+R) in the
present study considerably increased the proportion of macroaggregates in the soil. The enhanced level of or-
ganic matter in residue retained treatments and reduc-
tion in soil mechanical disturbance are responsible for
increases in the proportion of water-stable macroag-
gregates.
In the agroecosystem studied tillage reduction and
residue retention both increased aggregate stability
(MWD), the effect of the latter being greater than
the former. The greatest increase in MWD was in the
MT+R treatment followed by the ZT+R and CT+R
treatments. This may be due to increases in organic
C and microbial biomass in these treatments, as both
of these play significant roles in aggregate stability(Chaney and Swift, 1984). Studies performed under
green house conditions have shown that the stability
of soil aggregates can be modified after only a few
months of plant growth (Dufey et al., 1986; Monroe
and Klavidko, 1987). Angers and Mehuys (1988), in
a field experiment, reported that within two growing
seasons the aggregate content of a marine clay soil
was increased by up to 50% under barley and alfalfa
compared to a fallow control or corn. They concluded
that the growth of barley and alfalfa for a short period
significantly increased both the macroaggregates size
and stability of clay soil compared to a fallow control
and to initial conditions.Microbial management through residue manage-
ment and conservation tillage has great potential for
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C.P. Kushwaha et al. / Applied Soil Ecology 16 (2001) 229–241 239
the management of organic matter and nutrients in
dryland agroecosystems (Singh and Singh, 1993).
Conservation tillage is reported to lead to greater and
better quality soil organic matter and higher micro-
bial biomass (Elliott and Coleman, 1988) through
increased number and diversity of soil organisms and
their interactions among biota. Generally, the growth
and functioning of microbial biomass is limited by C
(Smith and Paul, 1990; Singh and Singh, 1993). When
flushes of C are supplied to the soil in the form of
crop residues, the microbial biomass increases in size
until the substrate is depleted. In the present study,
residue retention and tillage reduction both increased
the level of soil microbial biomass, the maximum ef-
fect on microbial biomass being recorded in MT +R,
either alone or in combination. It has been reported
that use of minimum and zero tillage retained more
crop residue C as soil organic C and soil MBC com-
pared to conventional tillage (Salinas-Gracia et al.,
1997). Singh and Singh (1993) stated that microbialgrowth due to the application of organic matter such
as straw is mainly dependent on the availability of
C in the soil; they reported 77% increases for MBC
and MBN under straw + fertilizer, and 51 and 84%
increases under straw treatment for MBC and MBN,
respectively. Saffigna et al. (1989) reported smaller
increases in soil MBC and MBN (10–23%) following
the incorporation of straw into Australian soils. Al-
though the quantity of microbial biomass is mainly
related to C inputs, other mitigating factors can reg-
ulate the growth and activity of the native microflora
(Smith and Paul, 1990).
Soil aggregate disruption by tillage may be coun-tered by an increase in the stability of aggregates due
to enhanced microbial activity by the addition of crop
residues following cultivation (Molope et al., 1987;
Beare et al., 1994). Incorporation of organic materials
into soil promotes the aggregation of soil particles
(Smith and Elliott, 1990). Cultivation results in loss
of labile organic matter which binds microaggregates
into macroaggregates and the inter-microaggregates
organic matter is responsible for the long-term fertil-
ity of native soils. In general, the stability of aggre-
gates increases with increased soil microbial biomass
(Lynch, 1984), although the relationship between
microbial biomass and stabilizing effect depends onthe microbial species. Since the most labile fraction
of soil organic matter is reflected in soil microbial
biomass, the negative impact of cultivation on the
microbial content was one of the reasons for reduced
macroaggregation in cultivated soil (Gupta and Ger-
mida, 1988). Because the microbial biomass plays an
important role in the metabolism of transient binding
organic matter, such as plant and microbial derived
polysaccharides, the increase in microbial biomass
will positively affect the soil aggregation in agro-
ecosystems. Although the increases in organic C,
MBC and MBN were higher in CT+R treatment than
in ZT + R treatment, the percentage of macroaggre-
gates was higher in the ZT +R, which may be due to
the combined effect of soil organic matter enrichment
and complete elimination of soil disturbances in the
zero tillage. Several studies have shown that reduced
tillage practices can result in greater aggregation and
higher standing stocks of soil organic matter compared
with conventional tillage practices (Doran, 1980;
Lamb et al., 1985; Bruce et al., 1990; Havlin et al.,
1990).In the present study, the concentration of organic C
and total N were the highest in the minimum tillage
residue retained treatment for both macro- and mi-
croaggregates. In all treatments, concentration of or-
ganic C and total N were higher in the macroag-
gregates than the microaggregates. Since macro- and
microaggregates of the residue retained treatment in
the present study had more organic C and total N
than macro- and microaggregates from residue re-
moved treatment, they were more stable. This is be-
cause of the role of soil organic matter in the stabiliza-
tion of soil structure as exhibited by significant posi-
tive correlation between organic C and aggregate sta-bility (Chaney and Swift, 1984). Greater susceptibility
of macroaggregates compared to microaggregates has
been reported to the disruptive forces of cultivation
and to the dispersion that results from rapid wetting
or raindrop impact (Tisdall and Oades, 1980, 1982;
Beare et al., 1994). Some reports suggest that fungi are
dominant in macroaggregates and bacteria dominate in
microaggregate (Tisdall and Oades, 1982; Gupta and
Germida, 1988). In the present study, the C/N ratio
of macroaggregates was greater than that of microag-
gregates. Since fungi have a considerably greater C/N
ratio than bacteria, it is possible that macroaggregates
may have greater C/N ratios than microaggregates dueto the dominance of fungi in the former and bacteria
in the latter.
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240 C.P. Kushwaha et al. / Applied Soil Ecology 16 (2001) 229–241
We found strong positive correlations of soil mi-
crobial biomass, total N and organic C with macroag-
gregates, and strong negative correlations between the
above soil parameters with microaggregates (Table 6).
This suggests a strong influence of organic matter
addition through residue manipulation on MBC level
in the soil. The microbial biomass and its metabolite
products bind microaggregates which subsequently in-
creases the proportion of macroaggregates in the soil.
Better correlations of MBC with macroaggregates than
microaggregates suggest a strong effect of MBC on
the formation of macroaggregates in soil. Thus, it may
be suggested that decrease in the mechanical disrup-
tion of the soil aggregates by tillage reduction along
with an increase in active and labile soil organic matter
may prove more effective in improving aggregation
than changes in total soil organic matter. Water-stable
aggregates are responsible for maintaining the soil
structure and organic matter (Table 6). Besides several
beneficial effects, tillage practices generally decreasesoil aggregation. For sustained crop production, we
recommend retention of 25–40% post-harvest above-
ground crop residue from the previous crop and its in-
corporation into soil through minimum tillage before
sowing the next crop. In low organic matter containing
soils in tropical dryland agroecosystems, management
practices involving manipulation of crop residues
and optimum tillage reduction can improve and sus-
tain soil fertility by increasing soil organic matter,
water-stable soil aggregates and microbial biomass.
Acknowledgements
We thank the Head and the Programme Co-ordinator
CAS in Botany for providing laboratory facilities and
Prof. S.R. Singh, Institute of Agricultural Sciences,
Banaras Hindu University for providing experimental
plots and other field facilities in the dryland farm.
References
Agarwal, R.R., Mehrotra, C.L., 1952. Soil Survey and Soil Work
in Uttar Pradesh, Vol. II. Department of Agriculture, Uttar
Pradesh.
Angers, D.A., Mehuys, G.R., 1988. Effect of cropping on
macroaggregation of a marine clay soil. Can. J. Soil Sci. 68,
723–732.
Angers, D.A., Prasant, A., Vignoux, J., 1992. Early cropping
changes in soil aggregation, organic matter and microbial
biomass. Soil Sci. Soc. Am. J. 56, 115–119.
Arshad, M.A., Schnitzer, M., Angers, D.A., Ripmeester, J.A., 1990.
Effect of till vs no-till on the quality of soil organic matter.
Soil Biol. Biochem. 22 (5), 595–599.
Balabane, M., 1996. Turnover of clay associated organic nitrogen
in the different aggregate size classes of a cultivated silty loam.
Eur. J. Soil Sci. 47, 285–291.Beare, M.H., Hendrix, P.F., Coleman, D.C., 1994. Water stable
aggregates and organic matter fractions in conventional and
no-tillage soils. Soil Sci. Soc. Am. J. 58, 777–786.
Blevins, R.L., Frye, W.W., 1993. Conservation tillage: an
ecological approach to soil management. Adv. Agron. 51, 33–
78.
Blevins, R.L., Thomas, G.W., Cornelius, P.L., 1977. Influence of
no-tillage and nitrogen fertilization on certain soil properties
after five years of continuous corn. Agron. J. 69, 383–386.
Brookes, P.C., Landman, A., Pruden, G., Jenkinson, D.S., 1985.
Chloroform fumigation and the release of soil N: a rapid direct
extraction-method to measure microbial biomass nitrogen in
soil. Soil Biol. Biochem. 17, 837–842.
Bruce, R.R., Langdale, G.W., Dillard, A.L., 1990. Tillage and crop
rotation effect on characteristics of sandy surface soil. Soil Sci.Soc. Am. J. 54, 1744–1747.
Campbell, C.A., Janzen, H.H., 1995. Effect of tillage on soil
organic matter. In: Farming for a Better Environment. Soil and
Water Conservation Society, Ankeny, IA, pp. 9–11.
Campbell, C.A., McConkey, G., Zentner, R.P., Selles, F., Curtin,
D., 1996. Long term effects of tillage and crop rotations on
soil organic C and total N in a clay soil in south-western
Saskatchewan. Can. J. Soil Sci. 76, 395–401.
Chaney, K., Swift, R.S., 1984. The influence of organic matter
on aggregate stability in some British soils. J. Soil Sci. 35,
223–230.
CTIC, 1994. Reducing Herbicide Runoff: Role of Best
Management Practices. Conservation Technology Information
Centre, West Lafayette, IN, 16 pp.
Dalal, R.C., Mayer, R.J., 1986. Long-term trends in fertility of soilsunder continuous cultivation and cereal cropping in southern
Queensland. III. Distribution and kinetics of soil organic carbon
in particle size fractions. Aust. J. Soil Res. 24, 293–300.
Doran, J.W., 1980. Soil microbial and biochemical changes
associated with reduced tillage. Soil Sci. Soc. Am. J. 44, 765–
771.
Dormaar, J.F., Carefoot, J.M., 1996. Implications of crop residue
management and conservation tillage on soil organic matter.
Can. J. Plant Sci. 76, 627–634.
Dufey, J.E., Halen, H., Frankart, R., 1986. Evolution de la stabilite
structurale de sol sous l’influence des recines de trefle et de
ray-grass. Observations pendant et apres culture. Agronomie 6,
811–817.
Elliott, E.T., 1986. Aggregate structure and carbon, nitrogen and
phosphorus in native and cultivated soils. Soil Sci. Soc. Am.
J. 50, 627–633.
Elliott, E.T., Coleman, D.C., 1988. Let the soil work for us. Ecol.
Bull. 39, 23–32.
-
8/18/2019 Soil organic matter and water-stable aggregates under different tillage and residue conditions in a tropical dryland…
13/13
C.P. Kushwaha et al. / Applied Soil Ecology 16 (2001) 229–241 241
Foster, R.C., 1981. The ultrastructure and histochemistry of the
rhizosphere. New Phytol. 89, 263–273.
Genter, C.J., Blake, G.R., 1978. Physical characteristics of a Le
Sueur clay loam following no-till and conventional tillage.
Agron. J. 70, 853–857.
Gregorich, E.G., Kachanoski, R.G., Voroney, R.P., 1989. Carbon
mineralization in soil size fractions after various amounts of
aggregate disruption. J. Soil Sci. 40, 649–659.
Gupta, V.V.S.R., Germida, J.J., 1988. Distribution of microbialbiomass and its activity in different soil aggregate size classes
as affected by cultivation. Soil Biol. Biochem. 20, 777–786.
Gupta, S.R., Singh, J.S., 1982a. Carbon balance of a tropical
successional grassland. Oecol. Gener. 3 (4), 459–467.
Gupta, S.R., Singh, J.S., 1982b. Influence of floristic composition
on the net primary production and dry matter turnover in a
tropical grassland. Aust. J. Ecol. 7, 363–374.
Havlin, J.L., Kissel, D.E., Moddux, L.D., Classen, M.M., Long,
J.H., 1990. Crop rotation and tillage effects on soil organic
carbon and nitrogen. Soil Sci. Soc. Am. J. 54, 448–452.
Jackson, M.L., 1958. Soil Chemical Analysis. Prentice-Hall,
Englewood Cliffs, NJ.
Jenkinson, D.S., 1988. Soil organic matter and its dynamics. In:
Wild, A. (Ed.), Russell’s Soil Conditions and Plant Growth.
Wiley, New York, pp. 564–607.Kalembasa, S.J., Jenkinson, D.S., 1973. A comparative study of
titrimetric and gravimetric methods for the determination of
organic carbon in soil. J. Sci. Food Agric. 24, 1085–1090.
Ladd, J.N., Amato, M., Oades, J.M., 1985. Decomposition of
plant material in Australian soils. III. Residual organic and
microbial biomass C and N from isotope labeled plant material
and organic matter decomposing under field conditions. Aust.
J. Soil Res. 23, 603–611.
Lal, R., 1989. Conservation tillage for sustainable agriculture:
tropics versus temperate environments. Adv. Agron. 42, 85–197.
Lamb, J.A., Peterson, G.A., Fenster, C.R., 1985. Wheat fallow
tillage systems effect on a newly cultivated grassland soils
nitrogen budget. Soil Sci. Soc. Am. J. 49, 352–356.
Lynch, J.M., 1984. Interaction between biological process,
cultivation and soil structure. Plant Soil 76, 307–318.
McBrayer, J.F., Cromack Jr., K., 1980. Effect of snow-pack on
oak-litter breakdown and nutrient release in a Minnesota forest.
Pedobiologia 20, 47–54.
Molope, M.B., Grieve, I.C., Page, E.R., 1987. Contribution of
micro-organisms to aggregate stability. J. Soil Sci. 38, 71–77.
Monreal, C.M., Kodama, H., 1997. Influence of aggregate
architecture and minerals on living habitats and soil organic
matter. Can. J. Soil Sci. 77, 367–377.
Monroe, C.D., Klavidko, E.J., 1987. Aggregate stability of a silt
loam soil as affected by roots of corn, soybean and wheat.
Commun. Soil Sci. Plant Anal. 18, 1077–1097.
Oldeman, L.R., 1994. The global extent of soil degradation.
In: Greenland, D.J., Szaboles, I. (Eds.), Soil Resilience
and Sustainable Land Use. CAB International, Wallingford,
pp. 99–118.
Piper, C.S., 1966. Soil and Plant Analysis. Hans Publisher,
Bombay, 366 pp.
Powlson, D.S., Brookes, P.C., Cristensen, B.T., 1987. Measurement
of soil microbial biomass provides an early indication of
changes in total soil organic matter due to straw incorporation.
Soil Biol. Biochem. 19, 159–164.
Rasmussen, P.E., Collins, H.P., 1991. Long-term impacts of tillage,fertilizer, and crop residue on soil organic matter in temperate
semiarid regions. Adv. Agron. 45, 93–134.
Saffigna, P.G., Powlson, D.S., Brookes, P.C., Thomas, G.A., 1989.
Influence of Sorghum residues and tillage on soil organic matter
and soil microbial biomass in an Australian Vertisol. Soil Biol.
Biochem. 21 (6), 759–765.
Salinas-Gracia, J.R., Hons, F.M., Motocha, J.E., 1997. Long
term effects of tillage and fertilization on soil organic matter
dynamics. Soil Sci. Soc. Am. J. 61, 152–159.
Seybold, C.A., Herrick, J.E., Brejda, J.J., 1999. Soil resilience: a
fundamental component of soil quality. Soil Sci. 165 (4), 224–
234.
Singh, K.P., Shekhar, C., 1989a. Weight loss in relation to
environmental factors during the decomposition of maize and
wheat roots in a seasonally dry tropical region. Soil Biol.Biochem. 21, 73–80.
Singh, K.P., Shekhar, C., 1989b. Concentration and release patterns
of nutrients (N, P and K) during decomposition of maize and
wheat roots in a seasonally dry tropical region. Soil Biol.
Biochem. 21, 81–85.
Singh, H., Singh, K.P., 1993. Effect of residue placement and
chemical fertilizer on soil microbial biomass under tropical
dryland cultivation. Biol. Fert. Soils 16, 275–281.
Smith, J.L., Elliott, L.F., 1990. In: Singh, R.P., Parr, J.F.,
Stewart, B.A. (Eds.), Dryland Agriculture — Strategies for
Sustainability. Springer, New York, pp. 68–88.
Smith, J.L., Paul, E.A., 1990. The significance of soil microbial
biomass estimation. In: Bollag, J.M., Stotzky, G. (Eds.), Soil
Biochemistry, Vol. 6. Marcel Dekker, New York, pp. 357–
396.
Tisdall, J.M., Oades, J.M., 1980. The effect of crop rotation on
aggregation in a red-brown earth. Aust. J. Soil Res. 18, 423–
434.
Tisdall, J.M., Oades, J.M., 1982. Organic matter and water stable
aggregates in soils. J. Soil Sci. 33, 141–163.
Vance, E.D., Brookes, P.C., Jenkinson, D.S., 1987. An extraction
method for measuring soil microbial biomass carbon. Soil Biol.
Biochem. 19, 703–707.
Vandermeer, J., 1995. The ecological basis of alternative
agriculture. Annu. Rev. Ecol. Syst. 26, 201–224.
van Veen, J.A., Paul, E.A., 1981. Organic carbon dynamics
in grassland soils. I. Background information and computer
simulation. Can. J. Soil Sci. 61, 185–201.