Soil organic matter and water-stable aggregates under different tillage and residue conditions in a...

8/18/2019 Soil organic matter and water-stable aggregates under different tillage and residue conditions in a tropical dryland…

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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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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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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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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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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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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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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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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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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.


13/13


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.

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