UNIVERSITI PUTRA MALAYSIA

THE EFFECT OF INTERCROPPING ON SOIL STRUCTURE ATTRIBUTES AND SOIL EROSION ON SLOPING LAND

ADRINAL

FP 2002 31

THE EFFECT OF INTERCROPPING ON SOIL STRUCTURE ATTRIBUTES AND SOIL EROSION ON SLOPING LAND

By

ADRINAL

Thesis Submitted to The School of Graduate Studies, Universiti Putra Malaysia, in Fulfilment of the Requirement for the Degree of Doctor of Philosophy

May 2002

In the N arne of Allah.. Most Gracious, .. Most Merciful

(j)edication

rrFiis tfiesis is dedicated to:

5lfy 6eCoved parents fls6ir Sutan Saitfi (q>apa) fate (])arCis (:Mama) 1lj. NurCis fEte�

5lfy parents in Caw

1£ �uzar flk,..mam and 1lj. (])jawanis

5lfy ([)earest Wife 9rledia Sandra 1(asili

Our nice cliiUfren • Natfya I ntan 1(emafa fldrinaC • (]3erCian :NaufaC fldrinaC

P or tlieir everfasting Cove.

Abstract of the thesis submitted to the Senate of Universiti Putra Malaysia in fulfilment of the requirement for the degree of Doctor of Philosophy

THE EFFECT OF INTERCROPPING ON SOIL STRUCTURE ATTRIBUTES AND SOIL EROSION ON SLOPING LAND

By

ADRINAL

May 2002

Chairman Assoc. Prof. Dr. Jamal bin Talib

Faculty Agriculture

Soil erosion problems in Malaysia have been recognized for a long time. However,

management of upland area that is more exposed to soil erosion and soil

degradation risk through introduction of different cropping systems is still largely

unknown. Consequently, the current knowledge of rates of soil loss on upland

slopes is very limited. Therefore, the objectives of this study were to evaluate the

effect of intercropping on soil structure attributes and soil erosion, and to evaluate

effect of slope position on structural attributes and soil erosion.

Two experiments of intercropping of banana and pineapple and intercropping of

immature rubber with banana and pineapple consisting of standard erosion plot and

on farm research respectively were carried out for 40 months. In the first

experiment, four standard erosion plots of slopes 9% and length 22. 1 m were

prepared. Plot sizes were 22. 1 x 2.5 m, 22. 1 x 5.0 m, 22. 1 x 5.0 m, and 22. 1 x 2.5

m for bare plot, banana plot, banana-pineapple intercropped plot, and pineapple

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plot, respectively. In the second experiment a farmer's field of an area 1 1 ,250 m2

of intercropping was selected. The slope varied from 9 - 1 5 %. Both experiments

focused on evaluating some soil properties that were closely related to soil

structure such as bulk density, soil aggregate stability, soil organic matter, runoff,

and soil loss. The effect of root biomass on the above properties was also

evaluated.

Results from both experiments indicated that banana when intercropped with

pineapple showed optimum performance in improving soil structure attributes

particularly in increasing soil organic matter and aggregate stability. Due to better

and thicker canopy coverage and as well as the role of their root network in

building good soil structure, the combination of banana and pineapple is more

effective in reducing runoff since this system provided a better protection for soil

surface against impact of raindrops and improved soil infiltrability. It was found

that the least soil erosion occurred under pineapple, and banana-pineapple

intercropped whilst the most soil erosion occurred under rubber. Stepwise mUltiple

linear regressions demonstrated that soil loss was closely related to root biomass,

soil organic matter, and aggregate stability of the soil. In terms of slope position,

results showed that at depth of 0-1 5cm, middle slope had lowest bulk density and

highest soil organic matter content and percent soil aggregation indicating the

convex nature of the landscape. Due to higher deterioration of soil properties on the

upper slope compared to other slope positions the most soil erosion observed to be

on the upper slope position. Several future studies is needed especially on crop

suitability in relation to its physiological, morphological and economic values in an

intercropping system on the sloping lands.

IV

Abstrak tesis yang dikemukakan kepada Senat Universiti Putra Malaysia sebagai memenuhi syarat keperluan untuk mendapatkan Jjazah Doktor Falsafah

KESAN TANAMAN SELANG KE ATAS STRUKTUR TANAH DAN HAKISAN TANAH DI TANAH BERCERUN

Oleh

ADRINAL

Mei 2002

Pengerusi Prof. Madya Dr. Jamal bin Talib

Fakulti Pertanian

Masalah hakisan tanah di Malaysia telah dikenalpasti sejak dulu lagi.

Walaubagaimanapun, pengurusan kawasan tanah tinggi yang lebih terdedah

kepada hakisan tanah dan pencuraian tanah melalui kombinasi sistem penanaman

belum lagi dikenali secara luas. Oleh itu pengetahuan terkini mengenai kadar

kehilangan tanah pada tanah tinggi bercerun masih terhad. Oleh itu, objektif

kajian ini adalah untuk menilai kesan daripada sistem penanaman ke atas struktur

tanah dan hakisan tanah, dan juga untuk menilai kesan daripada kedudukan cerun

ke atas struktur tanah dan hakisan tanah.

Dua kajian tentang sistem tanaman selang antara pi sang dan nenas di atas plot

hakisan piawai, dan tanaman selang antara getah muda dengan pisang dan nenas

di lapangan telah dijalankan selama 40 bulan. Pada kajian pertama, empat petak

hakisan piawai yang mempunyai kecerunan 9% dan panjang 22.1 m telah

disiapkan. Saiz bagi setiap petak adalah 22.1 x 2.5 m, 22.1 x 5.0 m, 22.1 x 5.0 m

v

dan 22.1 x 2.5 m masing-masing untuk petak terdedah, petak pisang, petak

tanaman selang pisang dengan nenas dan petak nenas. Sedangkan kajian kedua

dijalankan di ladang tanaman selang petani yang meneakupi jumlah luas 11,250

m2• Keeerunan berjulat dari 9 hingga 15%. Kedua-dua kajian tertumpu untuk.

menilai beberapa sifat tanah yang berkait erat dengan perubahan kestabilan

struktur tanah seperti: ketumpatan pukal, kestabilan agregat tanah, kandungan

bahan organik, biomas akar, dan juga terhadap larian permukaan dan kehilangan

tanah yang disebabkan oleh sistem tanaman selang yang diamalkan.

Hasil dari kedua-dua kajian yang telah dijalankan menunjukkan bahawa tanaman

selang pi sang dengan nenas meningkatkan kestabilan struktur tanah terutama

sekali di dalam kandungan bahan organik dan kestabilan aggregat tanah.

Disebabkan oleh penutupan kanopi yang lebih baik, disamping juga peranan

jaringan akar dalam menciptakan struktur yang baik, kombinasi di antara pi sang

dan nenas adalah lebih efektif di dalam mengurangi larian permukaan kerana

sistem ini menyediakan perlindungan yang lebih baik terhadap permukaan tanah

dalam mengurangi kesan titisan hujan dan meningkatkan keupayaan resapan air

tanah. Didapati bahawa hakisan tanah yang terendah adalah di bawah kawasan

nenas, diikuti kemudian di bawah tanaman selang pisang-nenas, sedangkan tanah

yang paling banyak terhakis adalah di bawah kawasan pokok getah. Regresi linear

berganda mengikut kaidah berperingkat menunjukkan bahawa kehilangan tanah

berkait erat dengan biomas akar, kandungan bahan organik, dan kestabilan agregat

tanah. Dalam hal kedudukan eerun, hasil menunjukkan bahwa pada kedalaman 0-

15 em, eerun tengah mempunyai ketumpatan pukal yang paling rendah dan

kandungan bahan organik serta peratusan pengaggregatan tanah yang paling tinggi

VI

yang menunjukkan keadaan lansekap yang cembung. Kerana kerusakan sifat tanah

yang lebih tinggi di bahagian atas cerun dibandingkan dengan bahagian cerun lain,

maka hakisan tanah yang paling tinggi telah dijumpai di bahagian atas cerun.

Beberapa kajian lanjut adalah diperlukan mengenai kesesuaian tanaman dan

kaitannya dengan fisiologi, morfologi, dan nilai ekonomik di dalam sesebuah

sistem tanaman se1ang di tanah bercerun.

Vll

ACKNOWLEDGEMENTS

Foremost, I would like to express my most sincere appreciation and gratitude to

Associate Professor Dr. Jamal bin Talib, chairman of my supervisory committee

fot his constant valuable guidance, helpful advice, encouragement and

constructive criticisms throughout the study and in the preparation of manuscript.

My sincere appreciation is also extended to Professor Dr. Wan Sulaiman Wan

Harun, and Associate Professor Dr. Mohd. Fauzi Ramlan as committee members

for their very valuable suggestions and comments.

My sincere appreciation is also addressed to Associate Professor Dr. Mohd.

Mokhtaruddin Ab. Manan from Department of Land Management Universiti Putra

Malaysia and Dr. Zaino I Mohd. Eusof from The Malaysian Rubber Board who

gave constructive criticisms and very valuable comments during viva session and

in improving of manuscript in final stages.

I am deeply grateful for the financial assistance afforded by government of

Malaysia through Intensive Research for Priority Area (lRP A) Project, which

enables me to pursue the tertiary education in Universiti Putra Malaysia. I am also

grateful to the SEAMEO-SEARCA of Los Banos, Philippines for awarding thesis

grant on "The Effect of Intercropping System on Soil Structure Attributes and Soil

Erosion on Sloping Land"

Vlll

Grateful acknowledges are extended to Dean Faculty of Agriculture Universitas

Andalas and Rector of Universitas Andalas, Padang for encouraging and

providing me with leave in Malaysia to pursue Ph.D degree in Universiti Putra

Malaysia.

My thanks also go to the support staff of the soil physics laboratory UPM, Mr.

Mokhtar Mustapar, Mr. Ab. Aziz Abdullah, Mr. Arifin Abu Hassan, Mr. Mohd.

Hanif Arshad, and Mr. Mutuviren Alagoo for their cooperation in laboratory and

field works. I am also grateful to my colleagues Jalloh, Maswar, Osmanu, Mr. M.

Prama Yufdi, and Mr. Mohd. Jamil Hamzah, for their cooperation and friendship,

which made my stay in Malaysia a memorable and wonderful one. I am also

grateful to Mr. Muhammad Naseer who was kind enough to edit the whole text of

the thesis. Thanks is also extended to my colleague Dian Fiantis for her guidance

that paved the way for this postgraduate study at initial stages.

Above all, heartfelt appreciation is due to my beloved wife, Dr. Media Sandra

Kasih for her understanding, continued support, constant encouragement,

patience, and sacrifices expressed during the period of my studies in Malaysia,

and to my dearest children Nadya Intan Kemala Adrinal and Berlian Naufal

Adrinal for being an everlasting source of inspiration. To my father, Asbir Sutan

Saidi, my late mother Darlis, my mother Hj. Nurlis, my parent in law H. Yuzar

Akmam, and Hj. Djawanis, my sisters and brothers Nova, Ade, Ujang, Rudi, Am,

In, and Feri, and also my sister in law Des. I wish them every success in this

world and hereafter under the guidance of Allah the Almighty.

Adrinal

IX

I certify that an Examination Committee met on 2 1st May 2002 to conduct the final examination of Adrinal on his Doctor of Philosophy thesis entitled "The Effect of Intercropping on Soil Structure Attributes and Soil Erosion on Sloping Land" in accordance with Universiti Pertanian (Higher Degree) Act 1 980 and Universiti Pertanian (Higher Degree) Regulation1 98 1 . The Committee recommends that the candidate be awarded the relevant degree. Members of the Examination Committee are as follows:

MOHD. MOKHTARUDDIN AB. MANAN, Ph.D. Associate Professor, Faculty of Agriculture Universiti Putra Malaysia (Chairman)

JAMAL BIN TALm, Ph.D. Associate Professor, Faculty of Agriculture Universiti Putra Malaysia (Member)

WAN SULAIMAN WAN HARUN, Ph.D. Professor, Faculty of Agriculture Universiti Putra Malaysia (Member)

MOHD. FAUZI RAMLAN,Ph.D. Professor, Faculty of Agriculture Universiti Putra Malaysia (Member)

ZAINOL MOHD. EUSOF, Ph.D. Malaysian Rubber Board (Independent Examiner)

SHAMSHER MOHAMAD RAMADILI, Ph.D. Professor / Deputy Dean School of Graduate Studies Universiti Putra Malaysia

Date ::1 5 AUG 2002

x

This thesis submitted to the Senate of Universiti Putra Malaysia and has been accepted as fulfilment of the requirements for the degree of Doctor of Philosophy. The members of the Supervisory Committee are as follows:

JAMAL BIN T ALIB, Ph.D. Associate Professor, Faculty of Agriculture Universiti Putra Malaysia (Chairman)

WAN SULAIMAN WAN HARUN, Ph.D. Professor, Faculty of Agriculture Universiti Putra Malaysia (Member)

MOHD. FAUZI RAMLAN, Ph.D. Associate Professor, Faculty of Agriculture Universiti Putra Malaysia (Member)

Xl

AINI IDERIS, Ph.D. ProfessorlDean School of Graduate Studies, Universiti Putra Malaysia

Date:

DECLARATION

I hereby declare that the thesis is based on my original work except for quotations and citations, which have been duly acknowledged. I also declare that it has not been previously or concurrently submitted for any other degree at UPM or other institutions.

Date: 1 4/08/2002

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TABLE OF CONTENTS

Page

DEDICATION. . ... . . . . . ........... . .. . . . . .... .. . . .... . . .. ... . . .. . . . . . ..... . . . . . . . .. 11 ABSTRACT.. . . . . . .. .. . . . . . . . . . . .. . . ....... . . . . .. . . . . . . .. . .. . . . ..... . . . . . . .. . .. . . . ... 111 ABSTRAK. ..... .. . . . .......... . . . . . . . . . .... .. .. . . ..... . . . . . . . . . . ... .... . . . . . .. . .. . . . v ACKNOWLEDGEMENTS...... . . . . . . . .. .. . . . . .. ....... . .. . . ... . . .. .. . . . . . . . . .. . viii APPROVAL SHEETS�..... . . . ... .. . . . . . .. . .. . . . . . . . .... ..... . . . . . . ..... . . . .. .. . .. x DECLARATION FORM . .. .. . .... . . . .. ..... . . . .. ... . .... ..... . . . . ... .. . . . . .... .. xii LIST OF TABLES.... . ...... . .. . . . . . . . . . . . . . . ... . . . .. . . . . . . . . .... .. . . . . . . . . .. .. . . ... xv LIST OF FIGURES.. . . . . .. . . . ... . . .. . . . . . ... . . . . ..... . .. . . .. . . . . . . . .. . . . . . . . .... . . XVll LIST OF ABBREVIATIONS. .. . . . . . .. . . . . . . . . . .... .... . .. . . . . ..... . . . . .. ... . . .. xx

CHAPTER

I INTRODUCTION 1.1

II LITERATURE REVIEW 2.1 2 . 1 Soil Erosion Process 2. 1 2.2 Erosion Problem on Steep Land of Malaysia 2.3 2.3 Soil Physical Condition of Eroded Soil 2.4 2.4 Soil Structure and Its Effect on Soil Erosion 2.6 2.5 The Effect of Organic Matter on Soil Aggregates Stability 2.8 2.6 Banana Roots System 2.9 2.7 Pineapple Roots System 2. 1 3 2 . 8 Rubber Roots System 2. 1 4 2.9 The Role of Plant and Its Root in Controlling Soil Erosion 2 . 1 5 2 . 10 Slope Position and Its Relation to Soil Properties and Soil Erosion 2. 1 7 2. 1 1 Intercropping and Soil Erosion 2. 1 8

III SOIL PHYSICAL PROPERTIES, ROOT BIOMASS, AND SOIL EROSION UNDER BANANA-PINEAPPLE INTERCROPPING SYSTEMS 3.1 3 . 1 . Introduction 3 . 1

3 .2. Objectives 3.2 3 .3. Materials and Methods 3.3

3 .3 . 1 . Study Sites 3.3 3.3 .2. Experimental Plot Preparation 3.3 3.3.3. Crop Management 3.5 3 .3 .4. Soil Sampling for Characterization 3.7 3.3.5. Measurement of Root Biomass 3 . 1 2 3 .3 .6. Runoff and Soil Loss 3. 13 3.3 .7. Statistical Analysis 3.14

Xlll

3.4. Results and Discussions 3 . 1 5 3 .4. 1 . Rainfall Characteristic 3 . 1 5 3 .4.2. Soil Textures 3 . 16 3.4.3. Bulk Density 3 . 1 8 3 .4.4. Water Retention Characteristic 3.21 3.4.5 . Available Water Holding Capacity 3.25 3 .4.6. Aggregate Stability 3.29 3 .4.7. Soil Organic Matter 3 .34 3 .4.8. Root Biomass 3.37 3 .4.9. Relationship Between Soil Properties, Root Biomass and

Aggregate Stability 3.40 3 .4. 1 0. Runoff 3.42 3 .4. 1 1 . Soil Loss 3.44 3 .4. 1 2. Relationship Between Soil Properties and Root Biomass

with Soil Loss 3.46

IV. THE EFFECT OF UPLAND INTERCROPPING OF IMMATURE RUBBER WITH BANANA AND PINEAPPLE AND SLOPE POSITION ON SOIL STRUCTURE ATTRIBUTES AND SOIL EROSION 4.1 4. 1 . Introduction 4. 1 4.2. Objectives 4.3 4.3. Materials and Methods 4.3

4.3 . 1 . Study Site 4.3 4.3.2. Land Preparing and Planting 4.6 4.3 .3. Soil Sampling for Characterization 4.8 4.3 .4. Measurement of Root Biomass 4. 1 2 4.3.5. Measurement of Soil Erosion 4. 1 2

4.4. Results and Discussions 4. 1 6 4.4. 1 . Soil Physical Properties 4. 1 6 4.4.2. Effect of Slope Position on Soil Properties 4.40 4.4.3 Effect ofIntercropping and Slope Position on

Runoff and Soil Erosion 4.48

V. GENERAL DISCUSSION AND CONCLUSION 5 . 1 . General Discussion

5 . 1 . 1 . Standard Plot Experimentation in Puchong 5. 1 .2. On Farm Research in Bukit Nering

5.2. Conclusion 5.3 . Future Work

REFERENCES APPENDICES VITA

XIV

5.1 5. 1 5. 1 5.6

5 . 1 1 5 . 1 2

R.l A.l V.l

LIST OF TABLES

Table Page

2.1 Percentage distribution of active root in irrigated banana.................. 2.11

2.1 Percentage distribution of active root in rain-fed banana... ... ........ . . ... 2.11

3. 1 Particle size distribution of experimental plot before and 24 months after treatment at 0 -15 cm depth . . . . . . . .. . . . . , . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3 . 17

3 .2 The bulk densities of different cropping systems. ... .. . . . . . . ... . . . .. . . . . . . . . 3 . 19

3.3 Water retention characteristic at different pressures for depth of 0 - 1 5 cm under different cropping systems . ... . . . . . . . ... .. . . . . ... ... . . . . . . . 3.22

3 .4 Water retention characteristic at different pressures for depth of 1 5-30 cm under different cropping systems . . ... . . . . . . . . .. . . . . . . . . . .. . .. . . . . 3.23

3.5 Available water holding capacity under different cropping systems . .. . . . 3.26

3.6 Percent water stable aggregate under different cropping systems . . . . . . . 3.30

3.7 Percent soil organic matter as affected by different cropping systems . . .. 3.35

3.8 Root biomass under different cropping systems .... . . . . . . . . . . . . . . . . . . . . . . . ... 3.38

3.9 Relationship between soil properties and root biomass with water stable aggregates . . . .. . . . . . . . . . . . . . .. . . . . . . . . . . . . . .. . . . . . . . . . . . . . . . . . . . . . . 3.41

3 . 10 Runoff distribution, total runoff and its percentage of total rainfall . . . . . . 3.43

3. 1 1 Soil loss distribution under different cropping systems . . . . . . . . . . . . . . . .. . . . . 3.45

3 . 12 The relationship between soil properties and root biomass on soil loss under different cropping systems . . . . . . . . . .. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3.47

4. 1 Chemical properties of Batang Merbau series . . . . . .. . . . . . . . . .. . . . , . . . . . . . . . . 4.5

4.2 Particle size distribution of soil of experimental site. . . . . . . . . . . . . . .. . . . . . . . 4. 1 7

xv

4.3 Bulk density under different crops in an intercropping system on sloping land. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4.19

4.4 Percent soil aggregation under different crops in an intercropping system on sloping land . . . . . . . . . . . . . . . . . .. . . . . . . . . . . . . . . . . . . . . . . . ...... ... 4.22

4.5 Macroaggregate stability under different crops in an intercropping system on sloping land . . . ... ... ...... ......... ... ...... ... ... ... ... ... ... 4.26

4.6 Soil organic matter under different crops in an intercropping system on sloping land . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4.31

4. 7 Available water holding capacity under different crops in an intercropping system on sloping land . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4.34

4.8 Root biomass under different crops in an intercropping system on sloping land . . . . . . . . . . . . . . . . . . . . . . . . . .. . . . . . . . . . . . . . . . . . . . . . . . . .. . . . . . . . . . . . . . . 4.37

4.9 Soil moisture content and pore size distribution under different slope positions. . . ... . . . . . . ... .. . ... .. . . .. . .. ... ... . .. . . . .. . ... ... .. . .... .. .. . .. . . . . .. ... 4.46

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LIST OF FIGURES

2. 1 Root pattern of irrigated banana Var. Nendran. . . . . . .. . . . . . . . . . . . . . . . . . . . 2. 12

2.2 Root pattern of rain-fed banana Var. Nendran ... ...... . . . . . . . . . . . . . . . . . . 2.12

2.3 Root pattern of irrigated pineapple Var. Kew. . . . . . . . ................ .. .. . 2.14

3. 1 Layout of experimental plots. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3.4

3.2 Distribution of rainfall during 24 months ofthe experimental period. 3 . 16

3 .3 Changes in bulk density at 0 - 15 cm depth as affected by different cropping systems.. .. . . . . . . . . . . . . . . . . . . . . . .. . . .... ......... . . . . . . . . . . . . . . . . . . . 3.20

3 .4 Changes in bulk density at 15 - 30 cm depth as affected by different cropping systems. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. . . . . . . . . . . . . ... ... . . . . .... .. 3 .20

3 .5 Available water holding capacity at 0- 1 5 cm as affected by different cropping systems . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. . . . . . . . . . . . . . . . . . 3.27

3 .6 Available water holding capacity at 1 5-30 cm as affected by different cropping systems . . . . . . . . . . . . . . . . . . . . . . . . . . . .. . . . . . . . . . . . . . . . . . . . . . 3.27

3 .7 Changes in water stable aggregates under different cropping systems for 0- 15 cm depth . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3.3 1

3 .8 Changes in water stable aggregates under different cropping systems for 1 5-30 cm depth . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3.3 1

3 .9 Aggregate size distribution under different cropping systems for 0 - 1 5 cm depth . . . . . . . . , ... . .. .. .. . . . . . . . .. .... . . . . .... . . . ...... . . . . . . . . . . 3.32

3 . 1 0 Aggregate size distribution under different cropping systems for 1 5-30 cm depth. . . . . . . . . . . . . . . . . . . . . ... . .. . . . . . . . . . . . . . .. ... ... .... .. . . . 3.32

3 . 1 1 Dynamic of organic matter under different cropping systems for 0- 15 cm depth . . . . . . '.' ... ...... ...... .. .... .. . . ........ ..... .. .. ... . .. ... . . 3 .36

3.1 2 Dynamic of organic matter under different cropping systems at 1 5-30 cm depth . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3 .36

XVII

3 . 1 3 Dynamic of root biomass under different cropping systems at 0 - 1 5 cm depth. . . . . . . . . . . . . . . . . . . . . . . . . . . . .. . . . . . . . . . . . . . . . . . . . . . . . . . . 3 .39

3 . 14 Dynamic of root biomass under different cropping systems at 1 5-30 cm depth. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. . . . . . . . . . . . . . . . .. 3 .39

3. 1 5 Relationship between dry root and soil organic matter. . . . . . . . . . . . . . 3 .40

3 . 16 The distribution and total runoff during experimental period under different cropping systems. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3 .43

3 . 1 7 Amount of soil loss as affected by different cropping systems. . . . . . . . . . . . . . . . . . . . . . . . .. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3 .45

4. 1 Map of a part of Perak State showing the experimental site. . . . . . . . . 4.4

4.2 Section rubber-pineapple-banana intercropping along slope at TSB Bukit Nering . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . , . . . . . . . . . . . . . . . . . . 4.7

4.3 Portable rainfall simulator in the field. . .. . . . . ... . . . .... . . . . . . . .... .. . ... 4. 1 5

4.4 Changes of bulk density at depth of 0- 1 5 cm as affected by different crops in an intercropping system on sloping land . . . . . . 4.20

4.5 Changes of bulk density at depth of 1 5-30 cm as affected by different crops in an intercropping system on sloping land . . . . . . 4.20

4.6 Changes of percent aggregation at depth of 0- 1 5 cm as affected by different crops in an intercropping system on sloping land. . . . . . . 4.23

4.7 Changes of percent aggregation at depth of 1 5-30 cm as affected by different crops in an intercropping system on sloping land . . . . . . . 4.23

4.8 Changes of stability index at depth of 0- 1 5 cm as affected by different crops in an intercropping system on sloping land . . . . . . . 4.27

4.9 Changes of stability index at depth of 1 5-30 cm as affected by different crops in an intercropping system on sloping land . . . . . . . 4.27

4. 10 Changes of water stable aggregates at depth of 0- 1 5 cm as affected by different crops in an intercropping system on sloping land . . . . . .. 4.28

4. 1 1 Changes of water stable aggregates at depth of 1 5-30 cm as affected by different crops in an intercropping system on sloping land . .. . . .. 4.28

XVIII

4. 12 Dynamic of organic matter at depth of 0- 15 cm as affected by different crops in an intercropping system on sloping land . . . . . . . . 4.32

4. 1 3 Dynamic of organic matter at depth of 15-30 cm as affected by different crops in an intercropping system on sloping land . . . . . . . . 4.32

4. 14 Changes of available water holding capacity at depth 0- 1 5 cm as affected by different crops in an intercropping system on sloping land . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4.35

4. 1 5 Changes of available water holding capacity at depth of 1 5-30 cm as affected by different crops in an intercropping system on sloping land . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4.35

4. 16 The root biomass at 0- 15 cm depth for different crops in an intercropping system on sloping land. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4.38

4. 1 7 The root biomass at 1 5'-30 cm depth for different crops in an intercropping system on sloping land . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4.38

4. 1 8 Bulk density under different slope positions. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4.4 1

4. 1 9 Soil organic matter under different slope positions. . . . . . . . . . . . . . . . . . . . . 4.4 1

4.20 Soil aggregation under different slope positions. . . . . . . . . . . . . . . . . . . . . . . . . . 4.43

4.2 1 Soil stability index under different slope positions. . . . . . . . . . . . . . . . . . . . . . . . 4.43

4.22 Water stable aggregates under different slope positions. . . . . . . . . . . . . . . . . . 4.45

4.23 Available water holding capacity under different slope positions . . . . . . 4.45

4.24 Root biomass under different slope positions. . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4.47

4.25 RUlloff under different crops in an intercropping system on sloping land . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4.49

4.26 Amount of soil loss under different crops in an intercropping system on sloping land . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . , . . . . . . . . . . . . . . . . . . 4.50

4.27 Runoff following slope positions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4.52

4.28 Soil loss following slope positions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4.52

xix

LIST OF ABBREVIATIONS

Agg Aggregate

au auxiliary root

AWHC Available Water Holding Capacity

B Banana

B-P Banana-Pineapple

cm centimeter

cm-3 cubic centimeter

c.v cultivars

DMRT Duncan Multiple Range Test

FAO Food and Agriculture Organization

g gram

ha hectare

II Instability Index

kg kilo gram

km kilo meter

kPa kilo Pascal

L liter

m meter

MAP Months After Planting

mL mili liter

mm mili meter

MPa Mega Pascal

xx

MWD Mean Weight Diameter

MWDd Mean Weight Diameter dry

MWDw Mean Weight Diameter wet

N Normal

OM Organic Matter

P Pineapple

R Rubber

R-P Rubber - Pineapple

rpm rotation per minute

RRIM Rubber Research Institute of Malaysia

SI Stability Index

SL Soil Loss

SOM Soil Organic Matter

Sr Soil root

USA United Stated of America

USDA United States Department of Agriculture

Var. Variety

WSA Water Stable Aggregate

Wt. Weight

XXI

CHAPTER I

INTRODUCTION

Malaysia is located in the humid tropics where a large proportion of rain falls in

storms of high intensity (Wan Sulaiman et al. 1 990). The annual rainfall ranges

from 1 500 to 3000 mm and causes severe and widespread erosion (Jamal et al.

2000). The high rain intensity and erosivity increases the severity of the soil loss

problem. As pressure on land increases, more areas of rainforest are being

cleared, in particular, more steep land are being cultivated with high quality

croplands that need intensive management. Most of the development and land

clearings for agriculture and other purposes in Malaysia take place not only in

lowland but also increasingly on the foothills up to an elevation of 920 m. These

foothills are between 1 55 m to 465 m high and are in a belt of maximum rainfall;

therefore their potential for erosion is greater on this elevation (Goh, 1 982). As a

consequence of intensive farming on sloping land the high incidence of soil loss is

clue to erosion, thereby resulting in decline of soil fertility. It is estimated that

400,000 hectares of agricultural land are subjected to erosion and require urgent

soil conservation attention (lamil, 1 987). Another factor that could trigger soil

degradation in Malaysia is the unchecked loss of topsoil. This could happen on

hilly and steep terrain where proper conservation practices are not effectively

carried out (lamil, 2000).

1.2

Soil erosion on sloping land areas is a complex phenomenon involving

detachment and transport of soil particles, infiltration, storage and runoff of

rainwater (Romkens et aI., 1998). Excessive soil loss can lead to soil structure

deterioration, organic matter depletion, decrease of soil fertility and hence reduced

crop yield (Lal, 1984, 1988 b). In this situation, erosion control is indispensable

in the development of sloping land for agriculture purpose.

Resistance of soil to erosion (detachment and transport) is determined by the

properties of soil such as texture, aggregate stability, infiltrability, shear strength,

organic matter content and chemical status (Wan Sulaiman et al. 1983). The

structure of surface soil is usually given most attention in relation to soil erosion,

because it is most easily subjected to deterioration under raindrop impact, and

easily altered due to agricultural practices. Good soil structural stability resist

detachment, maintains high infiltration rate, reduces runoff and consequently

leads to low soil erosion. Various measures have been taken to control erosion

and conserve the fertile topsoil. They include various crop and soil management

practices on sloping land. Proper crop selection and good soil management

practices are important factors in controlling and reducing soil erosion. However

limited studies on the effect of management of fragile upland through c0111bination

of cropping systems in Malaysia.

Malaysian Agriculture has two major and distinct sectors namely, the estate or

plantation and the small holding sector (Rahim, 1986). About 1,267,094 hectares

(50.87%) of industrial crops are cultivated under smallholdings (Department of

1.3

Agriculture Malaysia, 1998). Most of the rubber small holders prefer planting

banana and pineapple as intercrops, instead of annual crops with young rubber for

economic sustainability, because these crops could generate better income

(Almas, 1998).

Besides the role of the canopy cover· of the plant, which provides a protection,

cover to soil against heavy rainstorms and run off on the soil surface, the plant's

root systems contribute a significant factor in the formation of good soil structure.

The effectiveness of plant for stabilizing soil structure depend on the extent to

which movement of particles or aggregates under the erosive influence of water

can be restricted (Goss, 1991), the growth stages of crop, the extent of their

foliage development, the density of ground cover, the root density and plant height

(Morgan, 1979; Benwale, 1986; Hashim and Wong, 1987).

Even though, soil erosion studies in Malaysia have been reported for a some time

(Jamal et aZ. , 1985), the current knowledge on erosion processes in upland steep

slopes is very limited. Aside from slope steepness, slope position and slope shape

also influence the extent of erosion because these parameters determine

transportation and depositional processes of soil sediment where eventually

affecting in situ soil properties and "oil erosion as well. Based on the above

reason, the study is focused on the effect of intercropping and slope positions on

soil structure attributes and soil erosion on sloping land.