Assessment of soil quality using soil organic carbon and total nitrogen and microbial properties in tropical agroecosystems

doi:10.4236/as.2011.21006

Paper Menu >>

Journal Menu >>

Vol.2, No.1, 34-40 (2011) Agricultural Sciences

doi:10.4236/as.2011.2 1006

Assessment of soil quality using soil organic carbon

and total nitrogen and microbial properties in tropical

agroecosystems

Maruf K. A. Adeboye*, Abdullahi Bala, Akim O. Osunde, Anthony O. Uzoma, Ayo J. Odofin,

Baba A. Lawal

Department of Soil Science, School of Agriculture and Agricultural Technology, Federal University of Technology, Minna, Nigeria.

*Corresponding Author: enilewu@yahoo.com

Received 12 December 2010; revised 6 February 2011; accepted 15 February 2011

ABSTRACT

Assessment of soil quality is an invaluable tool

in determining the sustainability and environ-

mental impact of agricultural ecosystems. The

study was conducted to assess the quality of

the soils under arable cultivation, locally irri-

gated and non-irrigated, forestry plantations of

teak (Tectona grandis Lin.) and gmelina (Gme-

lina arborea Roxb.), and cashew (Anacardium

occidentale Lin.) plantation agro ecosystems

using soil organic carbon (SOC), soil total ni-

trogen (STN) and soil microbial biomass C

(SMBC) and N (SMBN) at Minna in the southern

Guinea savanna of Nigeria. Soil samples were

collected from s oil depths of 0-5 cm a nd 5-10 cm

in all the agro ecosystems and analyzed for

physical, chemical and biological properties. All

the agro ecosystems had similar loamy soil

texture at both depths. The soils have high fer-

tility status in terms of available phosphorus

and exchangeable calcium, magnesium and po-

tassium. The irrigated arable land had signifi-

cantly (P < 0.05) higher SOC and STN in both

soil depths than all the other soils due to grea ter

C inputs into the soil and fertilizer application.

The cashew plantation soil had the lowest

SMBC value of 483 mg kg-1 while teak soil had

the highest value of 766 mg kg-1 which w as sig-

nificantly (P < 0.05) different from that of the

other soils at the surface layer. At both soil

depths, in all the soils, the SMBC/SMBN ratios

were >6.6 suggesting fungal domination in all

the agroecosystems. The forestry plantation

soils had higher SMBC and SMBN as a per-

centage of SOC and STN respectively than the

cultivated arable land soils. Burning for clearing

vegetation and poor stocking of forestry planta-

tions may impair the quality of the soil. The

study suggests that the locally irrigated agro-

ecosystem soil seems to be of better quality

than the other agroecosy stem soils.

Keywords: Agroecosystems; Microbial Biomass;

Soil Organic Carbon; Soil Total Nitrogen; Tropical

1. INTRODUCTION

Soil quality is the capacity of a soil to function within

ecosystem boundaries to sustain biological productivity,

maintain environmental quality and promote plant and

animal health and thus has a profound effect on the

health and productivity of a given ecosystem and the

environment related to it [1]. The soil organic carbon

(SOC), soil total nitrogen (STN) and soil microbial C

(SMBC) and N (SMBN) are some of the soil properties

that are used as basic indicators in assessing soil quality

[2].

The soil microbial biomass (SMB) is a small but key

component of the active soil organic matter (SOM) pool

and serves as a source and sink of soil nutrients [3]. It

has been used to understand soil nutrient dynamics and

as an ecological marker [4,5]. The SOM and STN are the

major determinants and indicators of soil quality and

fertility and are closely related to soil productivity in an

agricultural ecosystem [6,7]. The reduction of SOC and

STN will lead to adecrease in soil fertility, soil nutrient

supply, porosity and an increase in soil erosion [8].

The public concern about the issue of global climate

change has emphasized the need for developing and im-

plementing strategies of agroecosystem management

that will reduce carbon dioxide concentration in the at-

mosphere as well as improving soil fertility, SOC stor-

age and the dynamics of C stock change in agroecosys-

tems are important in evaluating the impact of agroeco-

system management on global climate change [9]. Soils

represent an important terrestrial stock of C and ap-

proximately two to three times as much as terrestrial

M. K. A. Adeboye et al. / Agricultural Sciences 2 (2011) 34-4 0

vegetation and atmosphere respectively and the C in the

SOM of agricultural land is composed of dominant ter-

restrial C stock [10,11]. Thus, the dynamics of SOC as

affected by agroecosystem to a large extent affects the

carbon dioxide concentration in the atmosphere as well

as even the global climate change [12,13].

Recent interest in evaluating soil quality has been

stimulated by increasing awareness that soil is a criti-

cally important component of the earth biosphere as it

functions not only in the production of food and fibre but

also in the maintenance of environmental quality as re-

lated to agroecosystem management and in formulating

and evaluating sustainable agricultural and land use poli-

cies [14]. In Nigeria, studies have been conducted on the

use of SOC, STN and SMB to evaluate effects of man-

agement practices such as legume rotation on soil fertil-

ity [15,16], but there is dearth of information on the as-

sessment of soil quality under different agroecosystems

using the SOC, STN, and SMB. The present study was

carried out to assess the quality of the soils under arable

cultivation, locally irrigated and non-irrigated, forestry

plantations of teak (Tectona grandis Lin.), and gmelina

(Gmelina arborea Roxb.) and cashew (Anacardium occi-

dentalis Lin.) plantation agroecosystems using the SOC,

STN and SMB contents of the soil in the southern

Guinea savanna of Nigeria.

2. MATERIALS AND METHODS

2.1. Site Description

The study site was Minna (9o 14’N, 6o 30’E) in the

southern Guinea savanna of Nigeria with a gently undu-

lating plain topography. The climate is sub-humid tropi-

cal with mean annual rainfall of about 1200 mm (90% of

the rainfall is between June and August). The mean daily

temperature rarely falls below 22 ˚C with peaks of 40 ˚C

and 36 ˚C between February to March and November to

December respectively. The soils of Minna are Alfisols

(USDA) developed from basement complex rocks rang-

ing from shallow to very deep soils overlying deeply

weathered gneisses and magmitites with some underlain

by ironpan to varying depths [17].

2.2. Agroecosystems

The agroecosystem sites were the forestry plantations

of teak and gmelina and cashew plantation established

about six years ago by the Federal University of Tech-

nology, Minna, Nigeria and the nearby locally irrigated

arable and non-irrigated arable lands. Each forestry and

cashew plantations are about six hectares in size with the

cashew plantation poorly stocked. The locally irrigated

field nearby had over the years been continuously culti-

vated both in the rainy season to maize (Zea mays), yam

(Dioscorea rotundata) with fertilizer application to the

maize and in the dry season to vegetables including, okra

(Hibiscus esculentus), garden egg (Solanum melongena)

and pepper (Capsicum annum) using a nearby stream as

the source of water for irrigation. The stream runs

through residential and automobile mechanic areas and

serves as the disposal site for domestic and automobile

repair wastes. The non-irrigated arable land also near the

plantations with few scattered trees of mango (Mangif-

era indica) had been under continuous mixed cropping

with maize, okra, yam and cassava (Manihot esculentus)

over the years with minimal fertilizer application during

the rainy season only. In the dry season, the land is oc-

cupied dominantly by speargrass (Imperata cylindrica).

2.3. Soil Sampling and Analysis

Ten soil samples were collected in June, 2009, at 0-5

cm and 5-10 cm depths underneath the canopies of the

trees (about 10 cm away from the tree base) and in the

arable lands, from within the planted rows and interrow

areas with a 5 cm2 soil coring tool. Each soil sample was

a composite of four soil cores collected at north, south,

east and west coordinates. After removing visible plant

residues and pebbles, the field fresh moist soil samples

were sieved with a 2 mm mesh sieve. Part of the sample

was stored in plastic bags at 4 ˚C for soil microbial bio-

mass (SMB) determinations. The remaining part was

air-dried for determination of soil physical and chemical

properties. All measurements were conducted within

seven days of sampling. Before determination of SMB C

and N, moisture content was determined and the results

are expressed on oven-dried basis.

The soil particle size distribution was determined by

the Bouyoucos hydrometer method. Soil pH was meas-

ured in 1:2.5 soil-water suspensions with glass electrode

pH meter. Organic C was determined using the Walkley-

Black wet oxidation method [18]. Total N was deter-

mined by the Kjeldahl digestion procedure [19]. Ex-

changeable bases were determined by extraction with

neutral 1N NH4OAc. Potassium in the extract was de-

termined with flame photometer while calcium (Ca) and

magnesium (Mg) were determined using the atomic ab-

sorption spectrophotometer. Available phosphorus (P)

was extracted by Bray P1 method. The P concentration

in the extract was determined colorimetrically using the

spectronic 70 spectrophotometer. Soil microbial biomass

C and N were determined by the chloroform- fumigation

method [20].

3. RESULTS AND DIS CUSSION

3.1. Soil Texture, Reaction and

Exchangeable Bases

Selected physical and chemical properties of the soils

are shown in Table 1. The soils of all the agroecosys

M. K. A. Adeboye et al. / Agricultural Sciences 2 (2011) 34-4 0

Table 1. Selected physical and chemical properties of the agroecosystems.

Agroecosystems Depth

(cm)

Sand

(g kg-1)

Silt

(g kg-1)

Clay

(g kg-1)Textural classpH

(H2O)

Available P

(mg kg-1)

Exchangeable bases

Ca K Mg

(cmol kg-1)

Arable Lands

Irrigated 0-5 681 170 149 Sandy loam6.6 27 1.57 0.30 0.23

5-10 642 193 165 Loam 6.6 26 1.83 0.36 0.20

Non-irrigated 0-5 461 300 239 Loam 5.0 21 2.61 0.15 0.35

5-10 475 285 240 Loam 5.0 22 2.63 0.64 0.33

Plantations

Teak 0-5 700 200 100 Sandy loam6.5 37 7.46 0.89 3.46

5-10 721 169 110 Sandy loam6.4 22 5.29 3.34 2.48

Gmelina 0-5 700 208 92 Sandy loam6.2 20 4.87 0.48 2.83

5-10 721 169 110 Sandy loam6.9 33 2.80 1.96 2.40

Cashew 0-5 710 171 119 Sandy loam6.3 33 7.44 0.49 2.84

5-10 720 140 140 Sandy loam5.8 24 7.60 0.34 1.80

tems have similar loamy texture in surface soil, 0-5 cm

and 5-10 cm depths. This reflects the origin of the soils

from the same parent material and suggests that differ-

ences in the soils chemical and microbial properties are

due to management rather than inherent differences. The

soils reaction were slightly to moderately acidic at both

soil depths [21]. The soil of the non-irrigated arable land

had the lowest soil pH of 5.0 which was significantly (P

≤ 0.05) lower at both soil depths than that of the other

agroecosystem soils. Continuous cropping of tropical

soils with or without fertilizer application results in

acidification of the soil [22,23].

The plantation soils had significantly (P ≤ 0.05) higher

exchangeable bases (Ca, Mg, K) at both 0-5 cm and 5-10

cm soil depths compared to the arable land soils. These

results may be partly attributed to lower leaching losses

of the bases due to the litter under the trees and the recy-

cling of plant nutrients by the deep roots of the trees.

The occasional burning of the under storey vegetation in

the plantations can also cause liming effect of the ashes

of the burned vegetation with corresponding increase in

the exchangeable bases [24].

3.2. Soil Organic Carbon and Total Nitrogen

There was no stratification of soil organic C (SOC)

and soil total N (STN) as a function of depth in all the

soils except in the irrigated soil where the STN at 0-5 cm

depth is significantly (P ≤ 0.05) higher compared to that

of the 5-10 cm depth (Table 4) indicating that the

agroecosystem induced effect on SOC and STN extend

as far as the 15 cm soil depth which can be considered as

the surface soil. The SOC and STN values were rela-

tively high in both depths in all the soils and had the

pattern suggesting that they are intimately connected. A

significant (P < 0.01) positive relationship have been

reported between SOC and STN in different tropical

agroecosystems [15,25]. In both 0-5 cm and 5-10 cm soil

depths, the irrigated arable soil had significantly (P ≤

0.05) higher amounts of SOC and STN than the other

soils (Tables 3 and 4). The increased plant biomass pro-

duced with fertilizer application, all year round cultiva-

tion and increased nutrient input through irrigation water

have probably resulted in increased returns of organic

materials to the soil in the form of decaying roots, litter

and crop residues [26,27], thus the highest SOC in the

irrigated soil. Higher SOC have been obtained with fer-

tilizer application in a savanna Alfisol in Nigeria [28].

Annual cropping reduces C loss from soils [29].

The arable agroecosystem soils at both soil depths had

higher STN than the plantation agroecosystems with

concomitant lower C/N ratio (Ta b le s 2 and 3) which is

an indication of higher degree of humification and easy

mineralization of organic N [30]. The availability of wa-

ter-soluble organic C from rhizodeposition products

which are the main energy sources for microorganisms

and enhances their activity [31] may be partly responsi-

ble for the lower C/N ratios obtained in the arable soils.

The application of inorganic fertilizers which is a ready

source of N for the microorganisms may also be respon-

sible in the low C/N ratio. Rhizodeposition is the release

of organic materials from growing roots including exu-

dates, lysates, mucigels, sloughed root cap cells and de-

caying roots [32].

3.3. Soil Microbial Properties

Values of the soil microbial biomass C (SMBC) and N

(SMBN) in all 153 the agroecosystems were signifi-

cantly (P ≤ 0.05) higher in the surface soil than at the

5-10 cm depth except SMBN in the soil under gmelina

(Table 4). These indicate the importance of this surface soil

M. K. A. Adeboye et al. / Agricultural Sciences 2 (2011) 34-4 0

Table 2. Soil organic carbon, total nitrogen and microbial properties at 0-5 cm depth of the agroecosystems.

Agroecosystems Depth

(cm)

Org. C

(g kg-1)

Total N

(g kg-1) C/N ratioSMBC

(mg kg-1)

SMBN

(mg kg-1)SMBC/SMBN SMBC/Org.C

(%)

SMBN/Total N

(%)

Arable Lands

0-5 21.00*a 13.78a 1.5 693b 47.40a 14.6 3.3 0.3

Irrigated 5-10 22.40*a 14.70a 1.5 182d 27.53b 6.6 0.8 0.2

0-5 13.50c 7.09b 1.9 640c 22.71d 28.2 4.7 0.3

Non-irrigated 5-10 14.45b 6.80b 2.1 240c 18.59e 12.9 1.7 0.3

Plantations

Teak 0-5 13.71c 6.28c 2.2 766a 29.25c 26.2 5.6 0.5

5-10 12.50e 5.69c 2.2 244c 23.07c 10.6 2.0 0.4

Gmelina 0-5 15.46b 6.45c 2.4 690b 40.92b 16.9 4.5 0.6

5-10 15.46b 6.45c 2.4 690b 40.92b 16.9 4.5 1.0

Gmelina 0-5 13.46c 6.45c 2.1 483d 41.28b 11.7 3.6 0.6

5-10 13.60c 5.20d 2.6 315b 21.14d 14.9 2.3 0.4

*Means in the same column that are followed by the same letter are not significantly different at P ≤ 0.05 (n = 50).

Table 3. Soil organic carbon, total nitrogen and microbial properties at 5-10 cm depth of the agroecosystems

Agroecosystems Org. C

(g kg-1)

Total N

(g kg-1)

C/N ratio SMBC

(mg kg-1)

SMBN

(mg kg-1)

SMBC/SMBN

SMBC/Org.C

(%)

SMBN/Total N

(%)

Arable Lands

Irrigated 22.40*a 14.70a 1.5 182d 27.53b 6.6 0.8 0.2

Non-irrigated 14.45b 6.80b 2.1 240c 18.59e 12.9 1.7 0.3

Plantations

Teak 12.50e 5.69c 2.2 244c 23.07c 10.6 2.0 0.4

Gmelina 15.46b 6.45c 2.4 690b 40.92b 16.9 4.5 1.0

Cashew 13.60c 5.20d 2.6 315b 21.14d 14.9 2.3 0.4

*Means in the same column that are followed by the same letter are not significantly different at P ≤ 0.05 (n = 50).

Table 4. Comparison of soil chemical and microbial properties between 0-5 cm and 5-10 cm depths in the agroecosystems.

Agroecosystems Depth

(cm)

Org. C

(g kg-1)

Total N

(g kg-1)

SMBC

(mg kg-1)

SMBN

(mg kg-1)

Arable Lands

Irrigated 0-5 21.00a* 13.78a 693a 47.40a

5-10 22.40a 6.80b 240b 27.53b

Non-irrigated 0-5 13.50a 7.09a 640a 22.71a

5-10 14.45a 6.80a 240b 18.59b

Plantations

Teak 0-5 13.71a 6.28a 766 29.25a

5-10 12.50a 5.69a 244b 23.07a

Gmelina 0-5 15.40a 6.45a 690a 40.92b

5-10 12.60a 4.71a 580b 44.78a

Cashew 0-5 13.46a 6.45a 483a 41.28a

5-10 13.60a 5.20a 315b 21.14b

*Means followed by the same letter in the same column of each agroecosystem are not significantly different at P ≤ 0.05 (n = 50)

layer, 0-5 cm depth, for microbial meditated processes

such as nutrient cycling and decomposition. Loss of this

surface soil through human or natural disturbances

would be detrimental to the functioning of these ecosys-

tems [33]. The SMBC values ranged from 483-766 mg

kg-1 at the 0-5 cm and 182-580 mg kg-1 at 5-10 cm soil

depths (Ta b l e s 2 and 3). These values are in the middle

of values of 115-1231 mg kg-1 reported by [34] and [35]

and 61-1620 mg kg-1 by [36] in other terrestrial ecosys-

tems. The values are lower than the values of 1000-

M. K. A. Adeboye et al. / Agricultural Sciences 2 (2011) 34-4 0

2000 mg kg-1 recorded in humid tropical forest in Ama-

zonia [37,38]. The soil under the cashew plantation had

the lowest value of SMBC, 483 mg kg-1, at the 0-5 cm

soil depth. The poor stocking of the plantation and the

clearing of the undergrowth by burning which resulted in

relatively low SOC, 13.60 g kg-1 may be the reason for

this result. This finding support that of [29] and [39] that

SOC loss increases and microbial biomass declines

when residues are removed by burning. The size of the

microbial biomass is mainly potentially related to C in-

puts [3].

The SMBN values obtained in this present study,

22.71-47.40 mg kg-1 at 0-5 cm and 18.59-44.78 mg kg-1

at 5-10 cm soil depths (Ta b l e s 2 and 3) are comparable

with the ranges, 25.6 --42.2 mg kg-1 reported by [40] and

20-46 mg kg-1 by [41]. At the 0-5 cm soil depth, the irri-

gated arable agroecosystem which had the highest SOC

and STN also had the highest SMBN value of 47.40 mg

kg-1 which was significantly (P ≤ 0.05) higher compared

to the other agroecosystems. The relatively higher amounts

of residues produced due to cultivation in both the rainy

and dry seasons and inorganic fertilization may be re-

sponsible for the high SMBN values. The application of

inorganic fertilizer and increased C inputs into the soil

result in increased SMBN [42,43].

The SMBC/SMBN ratio has often been used to de-

scribe the structure of the microbial community [44]. A

low SMBC/SMBN ratio indicates that the microbial

biomass contains a higher proportion of bacteria whereas

a high value suggests that fungi predominate in the mi-

crobial population [45]. The SMBC/SMBN ratios ob-

tained in this study were relatively high, >11.7 in the 0-5

cm depth and >6.6 in the 5-10 cm depths (Tables 3 and 4)

indicating the predominance of fungi in these soils. Ref-

erence [46] reported SMBC/SMBN ratios varying from

5.2 in an arable soil to 20.8 in a forest soil. The surface

soil had relatively higher ratios than the lower depth in

all the agroecosystem soils. The decline in SMBC/

SMBN ratio from the 0-5 cm to 5-10 cm soil depth may

be an indication of a shift from fungal to bacteria popu-

lation at the lower depth [47].

The SMBC and SMBN when expressed as percent-

ages of SOC and STN respectively give an estimation of

the quantities of nutrients in the microbial biomass, or-

ganic matter dynamics and substrate availability in soils

[48,44]. From available studies, [3] estimated that SMBC

accounted for 2%-5% of SOC and SMBN for 1%-5% of

STN. In both 0-5 cm and 5-10 cm soil depths, the SMBC

accounted for between 0.8%-5.6% of SOC while SMBN

was 0.2%-1.0% of STN (Ta b l e s 2 an d 3). The range of

SMBC as a percentage of SOC obtained in this study is

comparable to the range of 0.99%-4.30% reported for

some New Zealand soils by [48]. The SMBN as a per-

centage of STN obtained are lower than the ranges re-

ported in literature by other workers for arable, pasture

and forest agroecosystems [40,44,46]. These low values

indicate that the microbial biomass is not important as a

sink for N in these agroecosystems [46]. The SMBC as a

percentage of SOC were higher in the surface soil, 0-5

cm than 5-10 cm soil depth in all the soils. These results

may be due to greater C and N inputs, which are of a

quality stimulating greater soil microbial biomass pro-

duction, into the surface soil [48].

3.4. Correlation of Soil Organic Carbon and

Total Nitrogen and Microbial Properties

Correlation analysis of SOC, STN and SMB meas-

urements at both 0-5 cm and 5-19 cm soil depths re-

vealed significant and non-significant correlations be-

tween the variables assayed (Tabl es 5 and 6). At the 0-5

cm soil depth, SOC was strongly related (P ≤ 0.0001) to

STN (r = 0.96) and SMBN (r = 0.68) while STN was

strongly related to SMBN (r = 0.56, P ≤ 0.0001). These

results indicate that SMBN levels in the soils were de-

termined by SOC and STN at the surface soil. Numerous

other studies in terrestrial ecosystems have found strong

correlations between SMBN and STN [33,44,49,50].

Reference [33] has reported close relationship between

SMBN and SOC in shrub-steppe agroecosystem in

North America. SMBN was highly related (r = 0.84, P ≤

0.0001) to SMBC at the 5-10 cm soil depth. These re-

sults suggest that both SMBC and SMBN are influenced

by the same factors at this soil depth. Highly significant

correlations have been reported for different terrestrial

agroecosystems by other workers [16,44,46,51]. The

SMBC had a highly significant (P ≤ 0.0001) negative

Table 5. Matrix of correlation coefficients for soil chemical

and microbial properties at 0-5 cm depth of the agroecosys-

tems.

Variables Org. C Total N SMBC SMBN

Org. C. -

Total N 0.96*** -

SMBC 0.27NS 0.18NS

SMBN 0.68*** 0.56*** −0.20NS

***Significant at P ≤ 0.0001, NS—Not significant

Table 6. Matrix of correlation coefficients for soil chemical

and microbial properties at 5-10 cm depth of the agroecosys-

tems.

Variables Org. C Total N SMBC SMBN

Org. C. -

Total N 0.99*** -

SMBC −0.53 *** −0.58***

SMBN −0.09NS −0.11NS 0.84***

***Significant at P ≤ 0.0001, NS—Not significant

M. K. A. Adeboye et al. / Agricultural Sciences 2 (2011) 34-4 0

relationship with SOC (r = −0.53) and STN (r = −0.58)

at the 5-10 cm soil depth. The microorganisms at this

lower depth are possibly subjected to stress factor of

oxygen availability. Another possible stress factor that

the microorganisms can be subjected to at this depth

could be substrate availability as a result of the higher

proportion of the soil organic matter being in the form of

humified C and inactive N that are not substrate for mi-

croorganisms. Imposition of stress factors on the micro-

bial biomass will increase its maintenance energy re-

quirement which may reduce the yield efficiency of the

biomass and increase the death rate of the biomass [51,

52].

4. CONCLUSIONS

Arable crop cultivation in both rainy and dry seasons

with fertilizer application was a good measure in im-

proving the quality of the soil especially in terms of SOC

and STN. The surface soil, 0-5 cm, was the main site for

microbial meditated processes of nutrient cycling and

decomposition in all the agroecosystems. The clearing of

the forest undergrowth by burning and poor stocking of

plantations may impair the quality of the soil. There was

no discernable effect of the agroecosystems on the soil

microbial biomass. The microorganisms were more ac-

tive in the plantation soils due to their having more C

and N immobilized in their microbial biomass. Generally,

from this study, the SOC, STN, biomass C and N in SOC

and STN respectively all seem to be suitable diagnostic

indicator of the quality of the soil of these agroecosys-

tems.

REFERENCES

[1] Doran, J.W., Sarrantonio, M. and Janke, R. (1994) Strate-

gies to promote soil quality and health. Proceedings of

the OECD Co-operative Research project on Biological

Resource Management, 1, 230-237.

[2] Doran, J.W. and Parkin, T.B. (1994) Defining and as-

sessing soil quality. Special Publication of the Soil Sci-

ence Society of America, 35, 3-21.

[3] Smith, J.L. and Paul, E.A. (1990) The significance of soil

microbial biomass estimation. Publication of Soil Biol-

ogy and Soil Biochemistry, 6, 357-396.

[4] Paul, E.A. and Voroney, R.P. (1980) Nutrient and energy

flows through soil microbial biomass. Contemporary

Microbial Ecology, 1, 215-237.

[5] Parton, W.J., Sandford, R.L., Sanchez, P.A. and Stewart,

K.W.B. (1989) Modelling soil organic matter dynamics

in tropical soils. Publication of the University of Hawaii,

240, 153-171.

[6] Reeves, D.W. (1997) The role of soil organic manure in

maintaining soil quality in continuous cropping systems.

Soil Tillage Research, 43, 131-167.

doi:10.1016/S0167-1987(97)00038-X

[7] Al-Kaisi, M.M., Yin, X.H. and Licht, M.A. (2005) Soil

carbon and nitrogen changes as influenced by tillage and

cropping systems in some Iowa soils. Agriculture, Eco-

system and Environment, 105, 635-647.

[8] Gray, L.C. and Morant, P. (2003) Reconciling indige-

nous knowledge with scientific assessment of soil fertil-

ity changes in southwestern Burkina Faso. Geoderma,

111, 425-437. doi:10.1016/S0016-7061(02)00275-6

[9] Smith, P., Martimo, D., Cal, Z., Gwary, D., Janzen, H.H.,

Kumar, P., McCarl, B., Ogle, S., O’Maria, F., Rice, C.,

Scholes, R.J., Sirotenko, O., Howden, M., McAllister, T.,

Pan, G., Romanenkov, V., Schneider, U., Towprayoon,

S., Wattenbach, M. and Smith, J.U. (2008) Greenhouse

gas mitigation in agriculture. Philosophical Transactions

of the Royal Society B, 363, 789-813.

[10] Davdson, E.A., Trumbore, S. and Amundson, R. (2000)

Biogeochemistry; soil warming and organic carbon con-

tent. Nature, 408, 789-790. doi:10.1038/35048672

[11] Janzen, H.H., Campbell, C.A. and Ellert, B.H. (1997) Sol

organic matter dynamics and relationship to soil quality.

Publication of Elsevier Scientific Company, 25, 277-292.

[12] Tan, Z.X. and Lal, R. (2005) Carbon sequestration po-

tential estimates with changes in land use and tillage

practice in Ohio, USA. Agriculture, Ecosystem and En-

vironment, 111, 140-152.

[13] Huang, B., Sun, W., Zhao, Y., Zhu, J., Yang, R., Zou, Z.,

Ding, F. and Su, J. (2007) Temporal and spatial variabil-

ity of soil organic matter and total nitrogen in an agricul-

tural ecosystem as affected by farming practices. Ge-

oderma, 139, 336-345.

[14] Granatstein, D. and Bezdicek, D.F. (1992). The need for

a soil quality index: Local and regional perspectives.

American Journal of Alternati ve Ag ricultur e, 17, 12-16.

[15] Adeboye, M.K.A., Iwuafor, E.N.O. and Agbenin, J.O.

(2006) The effects of crop rotation and nitrogen fertiliza-

tion on soil chemical and microbial properties in a

Guinea savanna Alfisol of Nigeria. Plant and Soil, 281,

97-107. doi:10.1007/s11104-005-3828-5

[16] Yusuf, A.A., Abaidoo, R.C., Iwuafor, E.N.O., Olufajo,

O.O. and Sanginga, N. (2009) Rotation effects of grain

legumes and fallow on maize yield, microbial biomass

and chemical properties of an Alfisol in the Nigerian sa-

vanna. Agriculture, Ecosystem and Environment, 129,

325-331.

[17] FDALR (1990) Literature review of soil fertility investi-

gation in Nigeria. Publication of the Federal Department

of Agriculture and Land Resources, Lagos, Nigeria, 2,

116-158.

[18] Nelson, D.W. and Sommers, L.E. (1982) Total carbon,

organic carbon and organic matter. Publication of the

American Society of Agronomy, 9, 539-579.

[19] Bremner, J.S. and Mulvaney, C.S. (1982) Nitrogen-total.

Publication of the American Society of Agronomy, 9, 580

623.

[20] Anderson, J.M. and Ingram, J.S.I. (1993) Tropical Soil

Biology and Fertility: A Handbook of Methods. Publica-

tion of CABI, Wallingford, UK, 2, 68-70.

[21] Brady, N.C. and Weil, R.R. (1999) The nature and prop-

erties 279 of soils. Publication of Prentice Hall Inc., New

Jersey, USA, 12, 343-376.

[22] Kang, B.T. (1993) Changes in soil chemical properties

and crop performance with continuous cropping on an

Entisol in the humid tropics. Publication of IITA/K.U.,

Leuven, 1, 297-305.

M. K. A. Adeboye et al. / Agricultural Sciences 2 (2011) 34-4 0

[23] Kang, B.T. and Balasubramanian, V. (1990) Long term

fertilizer trials on Alfisols in West Africa. Transactions

of XIV International Soil Science Society Congress,

Kyoto, Japan, 4, 25-68.

[24] Nounamo, L., Yemefack, M., Tchienkoua, M. and Njo-

mgang, R. (2002) Impacts of natural fallow duration on

topsoils characteristics of a Ferralsol in sduthern Camer-

oon. Nigerian Journal of Soil Research, 3, 52-57.

[25] Haron, K., Brookes, P.C., Anderson, J.M. and Zakaria,

Z.Z. (1998) Microbial biomass and soil organic matter

dynamics in oil palm (Elaeis guineensis Jacq.) planta-

tions in West Malaysia. Soil Biology and Biochemistry,

30, 547-552. doi:10.1016/S0038-0717(97)00217-4

[26] Haynes, R.J. and Naidu, R. (1998) Influence of lime,

fertilizer and manure application on soil organic matter

content and soil physical conditions: A review. Nutrient

Cycling in Agroecosystem, 51, 123-137.

[27] Bi, L., Zhang, B., Liu, G., Li, Z., Liu, Y., Ye, C., Yu, X.,

Lai, T., Zhang, J., Yin, J. and Liang, Y. (2009) Long

term effects of organic amendments on the rice yields for

double rice cropping systems in subtropical China. Agri-

culture, Ecosystem and Environment, 129, 534-541.

doi:10.1016/j.agee.2008.11.007

[28] Ogunwole, J.O. (2005). Changes in an Alfisol under

long-term application of manure and inorganic fertilizer.

Soil Use and Management, 21, 260-261.

[29] Collins, H.P., Rasmussen, P.E. and Douglas, Jr., C.L.

(1992) Crop 300 rotation and residue management ef-

fects on soil carbon and microbial dynamics. Soil Science

Society of America Journal, 56, 783-788.

[30] Bai, J.H., Ouyang, H., Deng, W., Zhu, Y.M., Zhang, X.L.

and Wang, Q.G. (2005) Spatial distribution characteris-

tics of organic matter and total nitrogen of marsh soils in

river marginal wetlands. Geoderma, 124, 181-192.

[31] Theng, B.K.G., Tate, K.R. and Sollins, P. (1989) Con-

stituents of organic matter in temperate and tropical soils.

Publication of the University of Hawaii, 3, 5-32.

[32] Whipps, J.M. (1990) Carbon economy. Publication of

John Wiley and Sons, New York, 1, 59-97.

[33] Bolton, Jr., H., Smith, J.L. and Link, S.O. (1993) Soil

microbial biomass and activity of a disturbed and undis-

turbed shrub-steppe ecosystem. Soil Biology and Bio-

chemistry, 25, 545-552.

doi:10.1016/0038-0717(93)90192-E

[34] Anderson, T.-H. and Domsch, K.H. (1989) Ratio of mi-

crobial biomass carbon to total organic carbon in arable

soils. Australian Journal of Soil Research, 30, 195-207.

[35] Insam, H., Parkinson, D. and Domsch, K.H. (1989) In-

fluence of macroclimate in soil microbial biomass. Soil

Biology and Biochemistry, 21, 211-221.

[36] Srivastava, S.C. and Singh, J.S. (1988) Carbon and

phosphorus in the soil biomass of some tropical soils of

India. Soil Biology and Biochemistry, 20, 743-747.

[37] Luizao, R.C.C., Bonde, T.A. and Rosswall, T. (1992)

Seasonal variation of soil microbial biomass—The ef-

fects of clear felling a tropical rainforest and establish-

ment of pasture in the Central Amazon. Soil Biology and

Biochemistry, 24, 805-813.

doi:10.1016/0038-0717(92)90256-W

[38] Henrot, J. and Robertson, J.P. (1994) Vegetation removal

in two soils of the humid tropics—Effect on microbial

biomass. Soil Biology and Biochemistry, 26, 111-116.

[39] Biederbeck, V.O., Campbell, C.A., Bowren, K.E., Schnitzer,

M. and McIver, R.N. (1980) Effect of burning cereal

straw on soil properties and grain yields in Saskatchewan.

Soil Society of America Journal, 44, 103-111.

[40] Singh, H. and Singh, K.P. (1993) Effect of residue

placement and chemical fertilizer on soil microbial bio-

mass under tropical dryland cultivation. Boilogy and

Fertility of Soils, 16, 275-281.

[41] Srivastava, S.C. and Singh, J.S. (1989). Effect of cultiva-

tion on microbial carbon and nitrogen in the tropical for-

est soil. Bioogy and Fertility of Soils, 8, 343-348.

[42] Ocio, J.A., Brookes, P.C. and Jenkinson, D.S. (1991)

Field incorporation of straw and its effects on soil micro-

bial biomass and soil inorganic N. Soil Biology and Bio-

chemistry, 23, 171-176.

[43] Singh, J.S. and Singh, V.K. (1992) Phenology of season-

ally dry tropical forest. Curre n t Scienc e, 63, 684-688.

[44] Moore, J.M., Klose, S. and Tabatabai, M.A. (2000) Soil

microbial biomass carbon and nitrogen as affected by

cropping systems. Biology and Fertility of Soils, 31,

200-210. doi:10.1007/s003740050646

[45] Campbell, C.A., Biederbeck, V.O., Zentner, R.P. and

Lafond, G.P. (1991) Effect of crop rotations and cultural

practices on soil organic matter, microbial biomass and

respiration in a thin black Chernozem. Canadian Journal

of Soil Science, 71, 363-376.

[46] Joergensen, R.G. (1995) Die quantitative bestimmung

der mikrobiellen 340 biomasse in boden mit der chlor

fom-fumigations-extraktions-methode. Gottinger Boden-

kundliche Berichte, Justus von Liebig, Gottingen, 104,

1-229.

[47] Wheatley, R., Ritz, K. and Griffiths, B. (1990) Microbial

biomass and mineral N transformations in soil planted

with barley, ryegrass, pea, or turnip. Plant and Soil, 17,

157-167. doi:10.1007/BF00014422

[48] Sparling, G.P. (1992) Ratio of microbial biomass carbon

to soil organic carbon as a sensitive indicator of changes

in soil organic matter. Australian Journal of Soil Re-

search, 30, 195-207.

[49] McCarthy, G.W., Meisinger, J.J. and Jenniskens, F.M.M.

(1995) Relationships between total-N, biomass-N and

active-N in soil under different tillage and N fertilizer

treatments. Soil Biology and Biochemistry, 27, 1245-

1250. doi:10.1016/0038-0717(95)00060-R

[50] Singh, S. and Singh, J.S. (1995) Microbial biomass asso-

ciated with water-stable aggregates in forest, savanna and

cropland soils of a seasonally dry tropical region, India.

Soil Biology and Biochemistry, 27, 1027-1023.

[51] Franzluebbers, A.J., Hons, F.M. and Zuberer, D.A. (1995)

Soil organic carbon, microbial biomass, and mineraliz-

able carbon and nitrogen in sorghum. Soil Science Soci-

ety of America Journal, 56, 460-466.

doi:10.2136/sssaj1995.03615995005900020027x

[52] Witter, E., Marttensson, A.M. and Garcia, F.V. (1993)

Size of the soil microbial biomass in a long-term field

experiment as affected by different N-fertilizers and or-

ganic manures. Soil Biology and Biochemistry, 25, 659-

669. doi:10.1016/0038-0717(93)90105-K