effects of nutrient and pest management on soil microorganism in hybrid rice double‐annual...

14
This article was downloaded by: [University of Auckland Library] On: 06 December 2014, At: 06:13 Publisher: Taylor & Francis Informa Ltd Registered in England and Wales Registered Number: 1072954 Registered office: Mortimer House, 37-41 Mortimer Street, London W1T 3JH, UK Communications in Soil Science and Plant Analysis Publication details, including instructions for authors and subscription information: http://www.tandfonline.com/loi/lcss20 Effects of Nutrient and Pest Management on Soil Microorganism in Hybrid Rice DoubleAnnual Cropping System Zeng Lu Sheng a , Liao Min a , Huang Chang Yong a & Subhani Abid a a Department of Resources Science , College of Environmental and Resource Sciences, Zhejiang University , Hangzhou, P.R. China Published online: 05 Feb 2007. To cite this article: Zeng Lu Sheng , Liao Min , Huang Chang Yong & Subhani Abid (2005) Effects of Nutrient and Pest Management on Soil Microorganism in Hybrid Rice DoubleAnnual Cropping System , Communications in Soil Science and Plant Analysis, 36:11-12, 1525-1536, DOI: 10.1081/CSS-200058508 To link to this article: http://dx.doi.org/10.1081/CSS-200058508 PLEASE SCROLL DOWN FOR ARTICLE Taylor & Francis makes every effort to ensure the accuracy of all the information (the “Content”) contained in the publications on our platform. However, Taylor & Francis, our agents, and our licensors make no representations or warranties whatsoever as to the accuracy, completeness, or suitability for any purpose of the Content. Any opinions and views expressed in this publication are the opinions and views of the authors, and are not the views of or endorsed by Taylor & Francis. The accuracy of the Content should not be relied upon and should be independently verified with

Upload: subhani

Post on 07-Apr-2017

214 views

Category:

Documents


0 download

TRANSCRIPT

Page 1: Effects of Nutrient and Pest Management on Soil Microorganism in Hybrid Rice Double‐Annual Cropping System*

This article was downloaded by: [University of Auckland Library]On: 06 December 2014, At: 06:13Publisher: Taylor & FrancisInforma Ltd Registered in England and Wales Registered Number: 1072954Registered office: Mortimer House, 37-41 Mortimer Street, London W1T 3JH,UK

Communications in Soil Scienceand Plant AnalysisPublication details, including instructions forauthors and subscription information:http://www.tandfonline.com/loi/lcss20

Effects of Nutrient andPest Management on SoilMicroorganism in HybridRice Double‐Annual CroppingSystemZeng Lu Sheng a , Liao Min a , Huang Chang Yong a &Subhani Abid aa Department of Resources Science , College ofEnvironmental and Resource Sciences, ZhejiangUniversity , Hangzhou, P.R. ChinaPublished online: 05 Feb 2007.

To cite this article: Zeng Lu Sheng , Liao Min , Huang Chang Yong & Subhani Abid(2005) Effects of Nutrient and Pest Management on Soil Microorganism in Hybrid RiceDouble‐Annual Cropping System , Communications in Soil Science and Plant Analysis,36:11-12, 1525-1536, DOI: 10.1081/CSS-200058508

To link to this article: http://dx.doi.org/10.1081/CSS-200058508

PLEASE SCROLL DOWN FOR ARTICLE

Taylor & Francis makes every effort to ensure the accuracy of all theinformation (the “Content”) contained in the publications on our platform.However, Taylor & Francis, our agents, and our licensors make norepresentations or warranties whatsoever as to the accuracy, completeness,or suitability for any purpose of the Content. Any opinions and viewsexpressed in this publication are the opinions and views of the authors, andare not the views of or endorsed by Taylor & Francis. The accuracy of theContent should not be relied upon and should be independently verified with

Page 2: Effects of Nutrient and Pest Management on Soil Microorganism in Hybrid Rice Double‐Annual Cropping System*

primary sources of information. Taylor and Francis shall not be liable for anylosses, actions, claims, proceedings, demands, costs, expenses, damages,and other liabilities whatsoever or howsoever caused arising directly orindirectly in connection with, in relation to or arising out of the use of theContent.

This article may be used for research, teaching, and private study purposes.Any substantial or systematic reproduction, redistribution, reselling, loan,sub-licensing, systematic supply, or distribution in any form to anyone isexpressly forbidden. Terms & Conditions of access and use can be found athttp://www.tandfonline.com/page/terms-and-conditions

Dow

nloa

ded

by [

Uni

vers

ity o

f A

uckl

and

Lib

rary

] at

06:

13 0

6 D

ecem

ber

2014

Page 3: Effects of Nutrient and Pest Management on Soil Microorganism in Hybrid Rice Double‐Annual Cropping System*

Effects of Nutrient and Pest Managementon Soil Microorganism in Hybrid Rice

Double-Annual Cropping System

Zeng Lu Sheng, Liao Min, Huang Chang Yong, and Subhani Abid

Department of Resources Science, College of Environmental and

Resource Sciences, Zhejiang University, Hangzhou, P.R. China

Abstract: Combined effects on soil microbial activity of nutrient and pest management

in hybrid rice double-annual cropping system were studied. The results of a field experi-

ment demonstrated significant changes in soil phospholipid content, heterotrophic

bacteria, proteolytic bacteria, and electron transport system (ETS)/dehydrogenase

activity studied with different management practices and at different growth stages.

Marked depletions in the soil microbial biomass phospholipid contents were found

with the advancement of crop growth stages, while the incorporation of fertilizers

and/or pesticides also produced slight changes, lowest microbial biomass phospholipid

content was found with pesticides-alone application. A decline in the bacterial

abundance of heterotrophic bacteria and proteolytic bacteria was observed with the

continuance of crop growth, while lowest abundance of heterotrophic bacteria and pro-

teolytic bacteria were found with pesticides-alone application, which coincided with

the similar decline of soil microbial biomass. A consistent increase in ETS activity

was measured during the different crop growth stages of rice. The use of fertilizers

(NPK) alone or fertilizers and pesticides increased it, while a decline was noticed

with pesticides-alone application as compared with the control.

Keywords: Phospholipid content, heterotrophic bacteria, proteolytic bacteria, electron

transport system

Received 26 April 2004, Accepted 3 November 2004

Sino-Germany Cooperation Project on Agricultural Science and Technology, No.

2001-47.

Address correspondence to Liao Min, Department of Resources Science, College

of Environmental and Resource Sciences, Zhejiang University, Hangzhou 310029,

P.R. China. Fax: 86-571-86971955; E-mail: [email protected]

Communications in Soil Science and Plant Analysis, 36: 1525–1536, 2005

Copyright # Taylor & Francis, Inc.

ISSN 0010-3624 print/1532-2416 online

DOI: 10.1081/CSS-200058508

1525

Dow

nloa

ded

by [

Uni

vers

ity o

f A

uckl

and

Lib

rary

] at

06:

13 0

6 D

ecem

ber

2014

Page 4: Effects of Nutrient and Pest Management on Soil Microorganism in Hybrid Rice Double‐Annual Cropping System*

INTRODUCTION

Rice is the staple diet for approximately 30% of the world population and

for approximately 60% of the Asian population. This crop is preferentially

or generally cultivated under submerged soil conditions for better yields

and topographical situations (Sethunathan, Singh, and Raghu 1999). Soil

microorganisms constitute a large dynamic source and sink of nutrients in

all ecosystems and play a major role in plant-litter decomposition and

nutrient cycling (Collins, Rasmussen, and Douglas 1992), soil structure,

nitrogen fixation, mycorrhizal associations, reduction in plant pathogens,

and other alterations in soil properties influencing plant growth (Kennedy

and Smith 1995).

As intensively farmed agroecosystems that stay flooded for most of the

crop season, irrigated rice soils are unique in microbial ecology. Yet, a satis-

factory inventory of the microbial biomass in rice fields is still lacking. The

effects of submergence, crop stage, root environment, and agronomic

practices on the rice soil microbial community with its impact on nutrient

cycling have hardly been studied.

Evidence suggests that a distinct shift to the dominance of pesticide-

degrading aerobes after intensive use of a pesticide (diazinon and HCH

isomers) in flooded soil occurs due to the ability of the aerobes to utilize

the pesticide for growth as an energy source vis-a-vis cometabolism during

anaerobic transformation (Bhuyan et al. 1993). Thus, flooded soil serves as

an excellent medium for isolation of microorganisms, bacteria in particular,

with pesticide-degrading capabilities.

Studies of biodiversity and its relation to ecosystem structure and function

have focused primarily on macroorganisms, with little consideration of micro-

organisms, even though the latter perform key ecological roles (Parkinson and

Coleman 1991). Decomposition is dominated by microbial activities and is as

fundamental as primary production to the long-term functioning of ecosys-

tems. In addition, microorganisms are primarily responsible for the degra-

dation and detoxification of many environmental contaminants (Lamar and

Dietrich 1990). For these reasons, changes in the composition or activity of

microbial communities might have immediate or lasting effects on

ecosystem functioning (Perry et al. 1989).

Soil microorganisms are one of the most sensitive biological markers

available and are the most useful for classifying disturbed or contaminated

systems, since soil microbial activity can be affected by minute changes in

the ecosystem. The use of soil microbial activity for examination of

environmental stress and declining biological diversity needs to be investi-

gated more fully. In the present study, we studied the changes occurring in

soil microbial biomass, heterotrophic bacteria (copiotrophs and oligotrophs),

proteolytic bacteria, and their activity parameters in a paddy soil with

different nutrient and pest management in hybrid rice double-annual

cropping system.

Z. L. Sheng et al.1526

Dow

nloa

ded

by [

Uni

vers

ity o

f A

uckl

and

Lib

rary

] at

06:

13 0

6 D

ecem

ber

2014

Page 5: Effects of Nutrient and Pest Management on Soil Microorganism in Hybrid Rice Double‐Annual Cropping System*

MATERIALS AND METHODS

Field Experiment

The experimental site was located around Jinhua city (29850 N, 1198470 E) in

the center of Zhejiang Province. This area has a subtropical climate with

annual rainfall of 1300–1500 mm and an annual mean temperature of

16.6–17.78C. The selected soil properties are listed in Table 1.

The treatments were control (without fertilizer and pesticides), NPK fer-

tilizers application (no pesticide), pesticides application (no fertilizer), appli-

cation of NPK fertilizers, and pesticides. The mineral fertilizer urea, calcium

perphosphate, and KCl were used at the rate of 100:25:100 kg/ha, respect-

ively. Pesticides included herbicides (butachlor and bensulfuron-methylþ

metsulfuron-methyl at field rate [FR] 4 days after transplanting [DAT]), insec-

ticides (triazophos, bisuta, and louprofezin at FR applied four times depending

upon pest occurrence), and fungicide (validamycin applied twice at FR). The

experiment was laid out according to randomized complete block design

(RCBD) with a plot size of 25 m2. All the treatments were replicated three

times, and the values appeared in the tables are their mean values expressed

on oven-dry-weight basis (1058C, 24 h).

Soil Sampling

The soil samples were taken at different growth stages of the rice crop (at

tillering, panicle initiation, and physiological maturity) in the standing

water or wet soil. Between rows and hills, 15 cm long cores were taken

using a (6 cm diameter � 20 cm length) rubber stoppered Plexiglass tube

equipped with a valve (6–8 cores/replicate), which was brought immediately

to the laboratory and used on the same day for the measurements of various

parameters.

Soil Analyses

Soil microbial biomass/total phospholipids (polar lipid fraction in lipids

extracted from soil) were determined by means of its phosphate content.

Table 1. Characteristics of the soil used

pH (H2O) 4.74 Cation exchange

capacity (cmolc kg21)

7.33

Water-holding capacity (g kg21) 510 Sand (g kg21) 278

Total organic carbon (g kg21) 15.25 Silt (g kg21) 562

Available N (mg kg21) 106.40 Clay (g kg21) 160

Available P (mg kg21) 13.34 Textural class Silt loam

Effects of Nutrient and Pest Management on Soil Microorganism 1527

Dow

nloa

ded

by [

Uni

vers

ity o

f A

uckl

and

Lib

rary

] at

06:

13 0

6 D

ecem

ber

2014

Page 6: Effects of Nutrient and Pest Management on Soil Microorganism in Hybrid Rice Double‐Annual Cropping System*

Inorganic O-phosphate is released by digestion of the lipid extract with

potassium persulfate, and color is developed by reaction of phosphate with

ammonium molybdate and malachite green and measured the absorbance at

610 nm (Frostegard, Tunlid, and Baath 1991). Viable counts of cultivable

heterotrophic bacteria were determined as colony forming units (CFUs) on

agar plates by the dilution plate method (James 1958; Reichardt 1978). Two

nutritional types, copiotrophs (heterotrophic bacteria adapted to high

nutrient concentration, “R-strategists”) and oligotrophs (with adaptation to

low nutrient concentrations, “k-strategists”) can be distinguished. For the enu-

meration of the copiotrophs, casein-peptone-starch (CPS) agar was used as the

plating medium (James 1958; Reichardt 1978). For the enumeration of the oli-

gotrophs, water-soil extract agar (SEA) was used as the plating medium

(James 1958). The samples were further serially diluted and suspensions

(150mL) spread in triplicate on to the CPS agar medium or SEA agar

medium. The plates were incubated at 308C, and copiotrophs were counted

after 4 days and oligotrophs after 4 weeks. Viable counts (CFUs) of

protein-degrading bacteria were done in the same way as previously

mentioned for heterotrophic bacteria. The suspensions (150mL) were spread

in triplicate onto the Gelatin-agar medium. The plates were incubated at

308C for 2 days and counted bacterial colonies with zones of clearing

(hydrolysis) that indicates proteolytic activity (Pitt and Dey 1970). Electron

transport system (ETS)/dehydrogenase activity was measured using

the reduction of 2-(p-iodophenyl-3-(p-nitrophenyl)-5-phenyl tetrazolium

chloride (INT) to iodonitrotetrazolium formazan (INT-formazan/INTF)

(Benefield, Howard, and Howard 1977). The absorbance values obtained

photometrically (480 nm) were converted to nmoles INT-formazan min21 g21

(dry soil) using a standard curve of INT-formazan (INTF).

Statistical Analyses

The experimental data were analyzed statistically according to completely

randomized design using CoStat Software. All measurements in this study

are the mean analysis of triplicate soil samples (CoStat 1990).

RESULTS

Effect of Nutrient and Pest Management on Soil Microbial

Biomass/Phospholipid Contents

The pesticides-alone application exerted a marked deleterious effect on the

soil microbial biomass phospholipid contents of the submerged paddy soil

as compared to the control, measured at different growth stages in both rice

crops (Table 2). A consistent and unambiguous decreasing tendency in the

Z. L. Sheng et al.1528

Dow

nloa

ded

by [

Uni

vers

ity o

f A

uckl

and

Lib

rary

] at

06:

13 0

6 D

ecem

ber

2014

Page 7: Effects of Nutrient and Pest Management on Soil Microorganism in Hybrid Rice Double‐Annual Cropping System*

Table 2. Changes in microbial biomass phospholipid contents at various growth stages of rice under different treatments

Treatments

Crop I: Growth stages Crop II: Growth stages

Tillering Panicle Maturity Tillering Panicle Maturity

nmol phosphates g21 soil nmol phosphates g21 soil

Control 110.15 Aa 45.54 C 40.67 CD 50.64 B 33.26 C 19.53 EF

Fertilizer only 120.15 A 47.55 C 42.64 C 63.45 A 33.97 C 20.17 EF

Pesticide only 92.17 B 38.48 CD 29.97 D 31.24 CD 25.02 DE 16.71 F

Fertilizer and pesticide 114.69 A 42.04 C 39.58 CD 60.18 A 30.98 CD 19.81 EF

aMean values followed by the same letter (s) are not significantly different at P ¼ 0.01 based on Duncan’s Multiple Range Test.

Effects

of

Nu

trient

an

dP

estM

an

ag

emen

to

nS

oil

Micro

org

an

ism1

52

9

Dow

nloa

ded

by [

Uni

vers

ity o

f A

uckl

and

Lib

rary

] at

06:

13 0

6 D

ecem

ber

2014

Page 8: Effects of Nutrient and Pest Management on Soil Microorganism in Hybrid Rice Double‐Annual Cropping System*

phospholipid contents was noticed with the passage of time at different growth

stages in both crops. The addition of fertilizer alone caused a slight and in most

cases nonsignificant improvement in the phospholipid contents as compared

with the control in all growth stages of both crops. Whereas, the combined

application of fertilizer and pesticide displayed mixed responses at different

growth stages probably due to variation in moisture status or input addition.

Comparatively lower phospholipid contents were estimated during all

growth stages of second crop than the first crop. The maximum quantities

of phospholipids that were recorded at tillering stage, in all the treatments

in both the crops, were gradually decreased in the next growth stage, and

the minimum phospholipid contents were observed in the last measured

stage. The submergence or anoxic soil condition caused marked depletion

in the microbial biomass phospholipid contents, which declined with time.

Effect of Nutrient and Pest Management on Soil Heterotrophic

Bacteria and Proteolytic Bacteria

Variations in bacterial counts at different growth stages of rice (proteolytic

bacteria for Crop I was not determined) were influenced by different treat-

ments (Table 3). An overall decrease in bacterial count was observed from

Crop I to Crop II and also in growth stages of both crops. The numbers of

colony-forming units in the submerged paddy soil were the highest at

tillering stage, which declined with progression of growth stage. Slight incre-

ments in few treatments were observed in heterotrophic bacteria at panicle

stage, against the tillering stage, which afterwards declined at maturity

stage. A distinct decreasing inclination in the proteolytic bacteria was

observed with the advancement of rice growth stage in various treatments.

Notable changes in the CFUs were also produced by the different treatments.

The maximum reduction in CFU counts was recorded with the application of

pesticides alone, while combined addition of fertilizer and pesticide and ferti-

lizer alone produced lesser depletions as compared to the control. The decline

in bacterial abundance (copiotrophs, oligotrophs, proteolytic bacteria) in the

field (Table 3) coincided with the similar decline of soil biomass as

measured by total phospholipids during a single cropping system.

Effect of Nutrient and Pest Management on ETS Activity

The ETS activity responded differently with different treatments at various

growth stages (Table 4). An overall increase in the ETS activity was

observed with the progression of growth stage in both crops of early and

late rice. The minimum ETS activity was recorded at the time of tillering in

all the treatments, which enhanced significantly (in few cases there was non-

significant increase) at panicle and maturity stages in both the rice crops taken

Z. L. Sheng et al.1530

Dow

nloa

ded

by [

Uni

vers

ity o

f A

uckl

and

Lib

rary

] at

06:

13 0

6 D

ecem

ber

2014

Page 9: Effects of Nutrient and Pest Management on Soil Microorganism in Hybrid Rice Double‐Annual Cropping System*

Table 3. Changes in soil heterotrophic bacteria and proteolytic bacteria at various growth stages of rice under different treatments

Bacteria type Treatments

Crop I: Growth stages Crop II: Growth stages

Tillering Panicle Maturity Tillering Panicle Maturity

Copiotrophsb Control 6.1Aa 4.8C 4.2C 4.3A 4.0C 3.5B

Fertilizer only 4.6A 4.3C 4.1C 4.2A 3.9C 3.3B

Pesticide only 3.8B 3.4CD 2.8D 3.0B 3.5C 3.1BC

Fertilizer and pesticide 4.7A 4.0C 3.9CD 4.9A 3.8CD 3.5B

Oligotrophsc Control 4.8BC 4.7B 4.4C 4.5BC 4.3C 4.1CD

Fertilizer only 4.5BC 4.0BC 3.9BC 3.9BC 3.8CD 3.9CD

Pesticide only 4.0B 3.5C 3.4BC 3.4C 3.6CD 3.5D

Fertilizer and pesticide 4.8BC 4.4B 5.1C 5.0B 4.3CD 4.1CD

Proteolytic bacteriad Control 4.8A 4.5C 3.8CD 4.1B 3.8C 3.6C

Fertilizer only 4.6A 4.3C 3.9C 4.0B 3.8C 3.4C

Pesticide only 3.5B 3.1CD 2.8D 3.4C 3.2D 2.5D

Fertilizer and pesticide 3.9A 3.5C 3.2CD 3.7B 3.5CD 3.1CD

aMean values followed by the same letter (s) are not significantly different at P ¼ 0.01 based on Duncan’s Multiple Range Test.bCopiotrophs � 105.cOligotrophs � 104.dProteolytic bacteria � 103.

Effects

of

Nu

trient

an

dP

estM

an

ag

emen

to

nS

oil

Micro

org

an

ism1

53

1

Dow

nloa

ded

by [

Uni

vers

ity o

f A

uckl

and

Lib

rary

] at

06:

13 0

6 D

ecem

ber

2014

Page 10: Effects of Nutrient and Pest Management on Soil Microorganism in Hybrid Rice Double‐Annual Cropping System*

Table 4. Changes in ETS activity at various growth stages of rice under different treatments

Treatments

Crop I: Growth stages Crop II: Growth stages

Tillering Panicle Maturity Tillering Panicle Maturity

nmol INTF min21 g21 soil nmol INTF min21 g21 soil

Control 135.8 EFa 220.4 D 358.5 B 123.6 D 129.3 D 307.4 B

Fertilizer only 159.6 E 266.1 C 450.9 A 154.2 D 237.2 BCD 421.7 A

Pesticide only 115.2 F 163.5 E 243.8 CD 112.8 D 134.1 D 170.1 D

Fertilizer and pesticide 142.7 EF 253.8 CD 414.2 A 133.6 D 183.6 CD 300.3 BC

aMean values followed by the same letter (s) are not significantly different at P ¼ 0.01 based on Duncan’s Multiple Range Test.

Z.

L.

Sh

eng

eta

l.1

53

2

Dow

nloa

ded

by [

Uni

vers

ity o

f A

uckl

and

Lib

rary

] at

06:

13 0

6 D

ecem

ber

2014

Page 11: Effects of Nutrient and Pest Management on Soil Microorganism in Hybrid Rice Double‐Annual Cropping System*

(growth-stage effect). The different treatments also produced marked changes

in the ETS activity in both crops (treatment effect). Nearly similar responses

were recorded due to different inputs (fertilizers and/or pesticides) in two rice

crops. The application of fertilizers applied singly or in combination with pes-

ticides caused an increase in the ETS activity, while the addition of pesticides

alone declined it as compared to the control. The incorporation of fertilizers

alone and with pesticides at tillering stage enhanced the ETS activity by

17.5% and 5.1%, respectively, over the control. On the other hand, addition

of pesticides alone resulted in its depletion by 15.2% over control in

Crop I. The corresponding ETS values for panicle stage were found to be

20.7% and 15.1% higher (in fertilizer only and fertilizer and pesticide) and

25.8% lower (in pesticide), respectively, relative to the control. While at

maturity stage, these values further improved to 25.5 and 15.5 (increase),

and 32.0% (decrease), respectively, with reference to the control in Crop

I. Almost similar treatment response at various growth stages was recorded

in the second rice crop. Here, tillering and panicle stages, the difference

among treatments was found to be nonsignificant, while at maturity stage sig-

nificant changes were recorded. The pesticide used alone tended to decrease

ETS activity, while fertilizers alone or together with pesticides increased it

as compared to the control.

DISCUSSION

The wide range in soil microbial biomass, counts of bacteria, potential

activity, and biochemical parameters studied in the present investigation rep-

resents variations in soil microbial populations as a result of differences in

crop management.

Marked differences in the phospholipid contents of soil microbial biomass

were recorded at different crop growth stages, while incorporation of fertilizer

and/or pesticide also produced some changes. Phospholipids occur in the cell

membranes of all living cells and are not used as storage products (Petersen

et al. 1991). They are rapidly transformed into glycolipids after cell death.

Total phospholipids are therefore considered as an accurate measure of total

biomass of living microorganisms (Inubushi, Brookes, and Jenkinson 1991).

Earlier it has been observed that soil under aerobic condition contains larger

amounts of phospholipids than under facultative-anaerobic and anaerobic con-

ditions (Wingfield, Davies, and Greaves 1977). Slightly lower quantities of

phospholipids in pesticide-treated soils than in control soil might be due to

their toxicity (Wingfield et al. 1977). A notable depletion in biomass phospho-

lipid contents was also noticed by Reichardt et al. (1997) due to reduced

(anoxic) conditions in continuously cropped irrigated rice fields. The results

of the present field study are similar to the findings of the laboratory experi-

ments conducted under almost similar but controlled conditions (Subhani

et al. 2001). The slight fluctuations in the present field study at some places

Effects of Nutrient and Pest Management on Soil Microorganism 1533

Dow

nloa

ded

by [

Uni

vers

ity o

f A

uckl

and

Lib

rary

] at

06:

13 0

6 D

ecem

ber

2014

Page 12: Effects of Nutrient and Pest Management on Soil Microorganism in Hybrid Rice Double‐Annual Cropping System*

might be due to fluctuations in moisture, temperature, and additions of

different inputs during the crop growth.

The decline in bacterial abundance (copiotrophs, oligotrophs, proteolytic

bacteria) in the field coincided with the similar decline of soil biomass (as

measured by total phospholipids) during a single cropping system (rice

Crops I and II). This reduction can be explained by an exhaustion of energy

and nutrient carriers, a sudden increase of grazers (Clarholm 1994), a

drastic change in the redox regime, or a combination of these. The develop-

ment of microbial populations in soils grown to rice has scarcely been inves-

tigated. Nevertheless, a steep decline from the seedling to the flowering stage

has already been observed before, although field conditions and methodology

were different (Goshal and Singh 1995). Oxygen concentrations and diffusion

rates significantly affect the growth and respiration of soil bacteria. They may

have pronounced effects on the specific growth rate, maximum growth rate,

respiration, numbers and types of bacteria isolated from soil (Nagatsuka and

Furusaka 1980). Similar declines in direct microscopic count of bacteria,

and fungi were observed by investigators in a long-term intensive cropping

field experiment at the International Rice Research Institute farm and in

a greenhouse experiment employing the submergence-tolerant variety

(Subhani et al. 2000). They further reported that this decline in total

bacterial abundance in the field was matched with a similar decline of total

soil biomass (total phospholipids) (Reichardt et al. 1996). Conversely,

Reichardt et al. (1997) found an increase in viable counts of sulfate-

reducing bacteria, of total heterotrophic copiotrophs, and in concentrations

of diether lipids as fingerprints of methanogenic bacteria toward physiological

maturity of the rice crop. This finding contrasts with the general declining

trend, but they interpreted it as a gradual adaptation to the anoxic conditions

prevailing in the waterlogged crop soil. On the other hand, they observed that

proteolytic bacteria declined from the beginning of the cropping cycle on, as

was observed in the present study (Reichardt et al. 1997). They concluded that

the organic matter drives the buildup of microbial biomass pool by “copio-

trophic producers,” which is available as energy and as a carbon source in

the soil. Decline in the heterotrophic bacteria in the present study might be

due to the inadequate supply of energy and carbon source through organic

matter in the soil and due to some stress from different inputs that were

applied at different times during the crop cycle.

Most studies of soil enzymes have been confined to arable agricultural

and forest soils. But a flooded rice soil is predominantly anaerobic and as a

result differs from a nonflooded soil in several physical, chemical, and biologi-

cal characteristics. It has been reported that dehydrogenase/ETS activity is

higher in anaerobically or flooded incubated soil than aerobically incubated

soil (Orten and Neuhaus 1970). One of the important consequences of

flooding soil is a marked shift in favor of anaerobic microorganisms, the

increased ETS activity was related to the increase in the population of

anaerobic microorganisms in flooded soils as most dehydrogenases are of

Z. L. Sheng et al.1534

Dow

nloa

ded

by [

Uni

vers

ity o

f A

uckl

and

Lib

rary

] at

06:

13 0

6 D

ecem

ber

2014

Page 13: Effects of Nutrient and Pest Management on Soil Microorganism in Hybrid Rice Double‐Annual Cropping System*

anaerobic origin (Orten and Neuhaus 1970). Tate (1979) observed a signifi-

cant increase in the dehydrogenase activity of soil under anaerobic conditions

though no change in the microbial numbers was detected. This, he suggested,

might be due to an increased role for the facultative and anaerobic bacteria. A

positive correlation was also observed between dehydrogenase activity and

soil moisture, and it was concluded that moisture was generally limiting to

the microbial activity (Tate and Terry 1980). Comparatively higher ETS

values in Crop I than in Crop II were observed particularly at the maturity

stage. It might be due to higher temperature at the time of sampling in Crop

I as soil sampling for Crop I was done in mid-July, while for Crop II, the

same stage was done in late October. Trevors observed that an increase in

temperature from 10 to 208C and from 20 to 308C caused increases in dehy-

drogenase activity by factors of 3.2 and 3.9, respectively (Trevors 1984). So,

the results are in full agreement with the previous findings. In the present

study, a consistent increase in the ETS activity was also observed, like

previous studies, during the different growth stages of rice as the rice crop

remained under anoxic (reduced) condition throughout its life cycle. Fluctu-

ations in the activity in some treatments/growth stages may be attributed to

the changes in the moisture, temperature, and inputs (fertilizers, pesticides),

as these conditions were changed from time to time during the study period.

In the field, of course, some conditions are beyond the control, specifically,

the main difference was the standing rice crop, which had influenced the

soil environment. In the planted soil, continuous addition of enzymes could

be expected from plant roots and associated microorganisms (Speir et al.

1980).

REFERENCES

Benefield, C.B., Howard, P.J.A., and Howard, D.M. (1977) The estimation of dehydro-genase activity in soil. Soil Biol. Biochem., 9: 67–70.

Bhuyan, S., Sreedharan, B., Adhya, T.K., and Sethunathan, N. (1993) Enhanced degra-dation of g-hexachlorocyclohexane (g-HCH) in HCH (commercial) acclimatizedflooded soil: Factors affecting its development and persistence. Pestic. Sci., 38:49–55.

Clarholm, M. (1994) The microbial loop. In Beyond the Biomass; Ritz, K., Dighton, J.,and Giller, K.E., eds.; J. Wiley and Sons: Chichester, United Kingdom, 221–230.

Collins, H.P., Rasmussen, P.E., and Douglas, C.L.J. (1992) Crop rotation and residuemanagement effects on soil carbon and microbial dynamics. Soil Sci. Soc. Am. J., 56:783–788.

CoStat. In CoStat statistical software; Manual revision 4.2., CoHort Software:Berkeley, California, 1990.

Frostegard, A., Tunlid, A., and Baath, E. (1991) Microbial biomass measured as totallipid phosphate in soils of different organic content. Microbiol. Meth., 14: 151–163.

Goshal, N. and Singh, P.K. (1995) Effects of farmyard manure and inorganic fertilizerson the dynamics of soil microbial biomass in a tropical dry land agroecosystem. Biol.Fertil. Soils, 19: 231–238.

Effects of Nutrient and Pest Management on Soil Microorganism 1535

Dow

nloa

ded

by [

Uni

vers

ity o

f A

uckl

and

Lib

rary

] at

06:

13 0

6 D

ecem

ber

2014

Page 14: Effects of Nutrient and Pest Management on Soil Microorganism in Hybrid Rice Double‐Annual Cropping System*

Inubushi, K., Brookes, P.C., and Jenkinson, D.S. (1991) Soil microbial biomass C, N,and ninhydrin-N in aerobic and anaerobic soils measured by the fumigation-extraction method. Soil Biol. Biochem., 23: 737–741.

James, N. (1958) Soil extract in soil microbiology. Can. J. Microbiol., 4: 363–370.Kennedy, A.C. and Smith, K.L. (1995) Soil microbial diversity and the sustainability of

agricultural soils. Plant Soil, 170: 75–86.Lamar, R.T. and Dietrich, D.M. (1990) In-situ depletion of pentachlorophenol from

contaminated soil by phanerochaete spp. Appl. Environ. Microbiol., 56: 3093–3100.Nagatsuka, T. and Furusaka, C. (1980) Effects of oxygen tension on growth, respir-

ation, and types of bacteria isolated from soil suspensions. Soil Biol. Biochem.,12: 397–403.

Orten, J.M. and Neuhaus, O.O. (1970) Biochemistry, 8th Ed.; Mosby: St. Louis, Missouri.Parkinson, D. and Coleman, D.C. (1991) Microbial communities, activity, and

biomass. Agric. Ecosys. Environ., 34: 3–33.Perry, A.D.M., Amaranthus, M.P., Borchers, J.G., Borchers, S.L., and Brainerd, R.E.

(1989) Bootstrapping in ecosystems. BioScience, 39: 230–237.Petersen, S.O., Henriksen, K., Blackburn, T., Blackburn, H., and King, G.M. (1991) A

comparison of phospholipid and chloroform fumigation analyses for biomass in soil:Potentials and limitations. FEMS Microbiol. Ecol., 85: 257–268.

Pitt, T.C. and Dey, D. (1970) A method for the detection of gelatinase production bybacteria. J. Appl. Bacteriol., 42: 687–691.

Reichardt, W. (1978) Methods in Aquatic Microbiology; Fisher-Verlag G: New York.Reichardt, W., Briones, A., Padre, B., Dejesus, R., and Mascarina, G. (1996) Dynamics

of soil microbial communities and sustainable nutrient supply in highly intensified ricecultivation. In Proceedings of International Symposium on Maximizing SustainableRice Yields Through Improved Soil and Environmental Management, Nov. 11–17;Funny Publishing Limited Partnership: Khon Kaen, Thailand, 887–891.

Reichardt, W., Mascarina, G., Padre, B., and Doll, J. (1997) Microbial communities ofcontinuously cropped, irrigated rice fields. Appl. Environ. Microbiol., 63: 233–238.

Sethunathan, N., Singh, N., and Raghu, K. (1999) Rice ecosystem: An excellentmedium for detoxification of pesticides. Paper presented in 2nd International Con-ference on Contaminants in Soil Environment in the Australasia-Pacific Region.Dec. 12–17; Indian Network for Soil Contamination Research: New Delhi, India.

Speir, T.W., Lee, R., Pansier, E.A., and Cairns, A. (1980) A comparison of sulphatase,urease, and protease activities in planted and fallow soils. Soil Biol. Biochem., 12:281–291.

Subhani, A., Liao, M., Huang, C.Y., and Xie, Z.M. (2000) Effects of some managementpractices on electron transport system (ETS) activity in paddy soil. Pedosphere, 10:257–264.

Subhani, A., Liao, M., Huang, C.Y., and Xie, Z.M. (2001) Ecological effects of insec-ticide under different moisture levels in paddy soil. Chinese J. Rice Sci., 15:137–141.

Tate, R.L. (1979) Effect of flooding on microbial activities in organic soils: Carbonmetabolism. Soil Sci., 128: 267–273.

Tate, R.L. and Terry, R.E. (1980) Variation in microbial activity in histosols and itsrelationship to soil moisture. Appl. Environ. Microbiol., 40: 313–317.

Trevors, J.T. (1984) Effect of substrate concentration, inorganic nitrogen, O2 concen-tration, temperature and pH on dehydrogenase activity in soil. Plant Soil, 77:285–293.

Wingfield, G.I., Davies, H.A., and Greaves, M.P. (1977) The effect of soil treatment onthe response of the herbicide dalapon. J. Appl. Bacteriol., 43: 39–46.

Z. L. Sheng et al.1536

Dow

nloa

ded

by [

Uni

vers

ity o

f A

uckl

and

Lib

rary

] at

06:

13 0

6 D

ecem

ber

2014