ＳＤＧs 人材育成特別コース

ＳＤＧs プロジェクト実習成果報告書
令和元年度

岡山大学大学院環境生命科学研究科
GRADUATE SCHOOL OF ENVIRONMENTAL AND LIFE SCIENCE,OKAYAMA UNIVERSITY

ＳＤＧｓ人材育成特別コース
令和元年度 ＳＤＧｓプロジェクト実習 成果報告書

目次（１）SDGs Fieldwork in Rural Vietnam and Japan・・・・・・・・・・・・・・・・・・・ 1～12
指導教員：キムドウチュル

履修者：MAI Thi Khanh Van，立石翼（２）Farm Practices and Soil Environment Survey in Ifugao, the Philippines towards Sustainable Rice
Terrace Farming ・・・・・・・・・・・・・・・・・・・・・・・・・・・・ 13～73

指導教員：森也寸志

履修者：黒住知代

凡例実習グループ毎
・指導教員による実習概要の報告
・学生（グループ）による実習成果報告及び感想
・学生による英文での概要報告

SDGs fieldwork in rural Vietnam and Japan
岡山大学・環境生命科学研究科
教授

金

枓哲

1．全体の概要「SDGs プロジェクト実習」の一環として、ベトナムと日本の農村部を対象に国内および国際実習を行った。参加学生は社会基盤環境学専攻・農村環境創成学講座のの立石

翼君と MAI Thi

Khanh Van さんの２名であった。国際実習は担当教員と２名の学生が現地研究者の協力を得ながら共同で行い、海外学際共同研究の醍醐味を学生自ら体験できるよう様々な工夫を行った。国内
実習は担当教員と MAI Thi Khanh Van さんのみが参加し、岡山県鏡野町を対象に中山間地域における観光開発と地域の活性化をテーマに行った。
なお、国際実習および国内実習の前後に、学内実習として準備会、予備発表会等を行った。
2．国際実習の日程と主な内容

調査期間は 2019 年 8 月 27 日（火）から 9 月 1 日（日）の 6 日間であり、主に中部ベトナムのフエ省、クァンチ省およびクァンビン省の農村地域を訪れて聞き取り調査を行った。なお、具体的な日程と主な内容は以下のとおりである。
8 月 27 日（火）：フエ市内集合。フエ農林大学の Quy 博士と日程等の確認
8 月 28 日（水）～29 日（木）：クァンチ省カウニ村にて、ベトナムの伝統的な農村社会構造（地縁組織、血縁組織それぞれの成り立ちとその関係）と地域開発に関する調査実習
8 月 30（金）：フエ省フォンヒエン村にて農地の再集積に関する調査実習
8 月 31 日（土）～9 月 1 日（日）：クァンビン省ソンチャク村にて観光開発と住民生業の変化、

地域内格差に関する調査実習
3．国内実習の日程と主な内容

調査期間は 2019 年 10 月 24 日（木）から 26 日（土）の 3 日間であり、岡山県鏡野町を対象に中山間地域における観光開発と地域の活性化に関する調査実習を行った。
4．全体を通して今回の実習は全学で推し進めている SDGs を共通言語として、ベトナムと日本の農村地域を対象にそれぞれの地域が抱えている問題と潜在力を総合的に理解する力を養うことを目的として行った。とりわけ、クァンチ省カウニ村とフエ省フォンヒエン村における実習では SDGs の 9 番目
（産業と技術革新の基盤をつくろう）と 11 番目の目標（住み続けられるまちづくりを）を、ク
ァンビン省ソンチャク村では 8 番目（働きがいも経済成長も）と 12 番目（つくる責任つかう責任）の目標を、さらに岡山県鏡野町での国内実習では SDGs の 12 番目の目標を、それぞれ念頭
1

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に置きながら調査実習を行った。また、これらの過程で 2 名の学生がそれぞれの専門を活かしながら調査結果をまとめ上げるプロセスは極めて教育的効果が高く、今後さらに拡大させていきた
い。

写真１.

写真 2.

クァンチ省カウニ村における調査実習の様子

クァンビン省ソンチャク村での調査実習中の食事
2

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II. Overseas fieldtrips (Vietnam)
2.1. Cau Nhi Village
48501155

Tsubasa Tateishi

2.1.1. Introduction
Clan system, a social unit, has been important and necessary for farming society
in Vietnam since the past. It is related with production activity, which is related with
development of farming villages. On this research, we focused on the function andstructure of clan system in a farming village in Vietnam.
2.1.2. Fundamental information of Cau Nhi Village
Cau Nhi Village in Hai Tan Commune is located on the northwest of Hue City,
the center of Vietnam. It takes 1 hour from Hue City by car. Cau Nhi Village wasfounded in 1417. There are historical and traditional buildings in the village, thus it
was registered as the first Cultural Village of Quang Tri Province. 550 households livein 8 hamlets of the village. There are no industrial estates around the village, thus the

Source : Google Maps

villagers are almost full-time farmers.
Figure 1. Location of

Table 1. Number of family clans in Cau Nhi Village
Original family clans since founding

Disappeared

4

Exist now

8

Family clans that came later

Cau Nhi Village

18

2.1.3. Methodology
We conducted interview to 7 original family clans written on the Table 2 and asked some questions likethe below.
Careers of each interviewee

Anniversary days of each family clan and the

Number of households of each family clanvillage

Branches of each family clan

Role of family clans in the village council

Table 2. Timetable of interview in Cau Nhi Village
Date

Time

th

Interviewee (Family clan)

28 AugustAM

Mr. Le Chi Ca (Le)Mr. Tran Dang Thoi (Tran)

2019

PM

Mr. Nguyen Van Cam (Nguyen)

Mr. Bui Xuan Kha (Bui)29th AugustAM

Mr. Pham Huu Hoa (Pham)Mr. Hoang Tan Lap (Hoang)

2019

PM

Mr. Dao Ba Hong (Dao)

3

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2.1.4. Findings
Communication of policies: Government → Local authority → Clan leaders → Villagers
Family clans have their own anniversary days, facilities and organizations as well as those of the village
like the Table 3. As for the village council, all 26 family clans belong to it. However, 4 original familyclans: Bui, Hoang, Nguyen and Pham have priorities in making decisions.
Table 3. Comparison between family clan and village
Family clan

Village

Anniversary days

Death days of some ancestors

Praying days

Facilities

Ancestral houses

Communal house
Worship hall
Cultural village executive board
Village steering committee

Organizations

Executive committee

Hamlet executive committee
Village council
Cooperatives

Cau Nhi Village Council

Priority

Original family clans (8)

Bui
Tran

Hoang

Nguyen

Pham

Le

Dao

Do

Family clans that came later (18)Figure 2. Cau Nhi Village Council
Clan system is divided into some branches. People have close

Figure 3. Family clan tree

relationship with other members at least in their own branches.
2.1.5. Our view
Family clans that have priority in the village council are likely to influence the development of farming
villages.
Ties of clan system seem strong as well as those of local community or stronger than them.
Regarding comparison between Vietnam and Japan, both clan system and local community establish
their own anniversary days, facilities and organizations that is peculiar to Vietnam. On the other hand,
only the latter is true of Japan.

4

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2.2. Phong Hien Commune
48501155

Tsubasa Tateishi

2.2.1. Introduction
The fieldwork in Phong Hien Commune was to understand the land consolidation and its effect.
2.2.2. Fundamental information of Phong Hien Commune
Phong Hien Commune is located on the northwest of Hue City, thecenter of Vietnam. It takes 30 minutes from Hue City by car. Phong
Hien Commune have agricultural land areas with 2,400 ha: paddy fields
Hue(16%), farmland for annual crops (13%) and others (71%). The averagearea of farmland is 0.5 ha/household. In the commune, farmers growSource : Google Maps

crops for 2 times per year. Between 2003 and 2004 and in 2017, theFigure 4. Location of Phongland consolidation was conducted.

Hien Commune

2.2.3. Methodology
We conducted interview about land consolidation, for instance, condition of farmland before and afterland consolidation, how to divide farmland after land consolidation and production system in landconsolidation areas.
Table 4. Timetable of interview in Phong Hien Commune
Date

Time

Activities
Interview to vice chairman of Phong Hien CPC

30th August
2019

Interview to director of An Lo Cooperative
AMInterview to an organic farmer
Visit to a land consolidation area

Figure 5. Interview in Phong

Figure 6. Interview to an

Figure 7. Visit to a land

Hien CPC

organic farmer

consolidation area

5

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2.2.4. Findings
Farms after land consolidation were graded and divided by lottery among farmers.
Phong Hien Commune has its own production process of land consolidation areas like the Figure 8.

Figure 8. Production process of land consolidation areas in Phong Hien Commune
2.2.5. Our viewAfter the land consolidation, situations of farmers became not only better but also worse than before
like the below. This difference might be a bigger and bigger problem to affect their incomes.
As for higher graded land, the enhancement of productivity can be expected. And
organic farming is successful, thus it may lead to the creation of added value.
As for lower graded land, farmers suffer from inconvenient cultivation.

↓
Phong Hien Commune and the cooperative should settle measures to support farmers who
have lower graded land or correct unfairness.
Regarding production process, the cooperative assists farmers by provisions and mediates sale ofproducts that meet organic standard. That makes the agricultural production process much easier for farmers.

6

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2.3. Son Trach commune
48430167

MAI Thi Khanh Van

2.3.1. Location

Figure 9. Map of Son Trach commune

Source : Ziegler et al. (20171) & Son Trach CPC (20192)
Son Trach commune located in buffer zone of Phong Nha Ke Bang National Park (PNKB NP), Quang
Binh province.

The acreage of this commune is 10,138.71ha with the population is 3,060 households /12,475 people. From figure 9, there is the list of villages in Son Trach commune: 1) Xuan Son; 2) Gia Tinh;3) Na ; 4) Ha Loi; 5) Xuan Tien; 6) Cu Lac 1; 7) Tram Me; 8) Phong Nha; 9) Cu Lac 2; 10) Rao Con.
2.3.2. Timetable of fieldtrip and Methodology
Table 5. Timetable of interview in Son Trach Commune
Date

Activities

31st August

Visiting Paradise cave and interviewing local employees

2019Interviewing the leader of Xuan Tien village
1st September

Visiting Mooc spring and interviewing local employees

2019Interviewing the owner of local restaurant and staffs in local hotel

In two days at Son Trach commune, we met the local tourism employees and local residents, (Table 5)
and interviewed them about: Socio-economic background; Status of tourism development; Changes to local

livelihoods induced by tourism; Issues and concerns and suggestions for the future.

1

Ziegler, T., Hendrix, R., Vu, N. T., Vogt, M., Forster, B., & Dang, N. K. (2007). The diversity of a snake community in a karst forest ecosystem in the central

Truong Son, Vietnam, with an identification key. Zootaxa, 1493(21), 1-40.
2

Son Trach Commune People's Committee (2019). Census map

7

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2.3.3. Findings
Figure 10 showed the increaseover the years of the number oftourists and the number of tourism
destinations. Tourism activities here
have existed for a long time andflourished from 2013 to the present.
Due to the tourism development,
the local livelihoods also changed
fromagriculture-based

tourism-based

incomelives

toactivities.

(Table 6)

Figure 10. Status of tourism development in PNKB NP

Source: People’s committee of Quang Binh province (2010)3; Nguyen T.T.H.
(2018)4; PNKB NP Management Board (2019)5

Table 6. Changes in livelihoods of local people
Time

Agriculture

Forestry

1975 - 1997

- paddy field- illegal forest logging (wood andTourism

non-wood products)
1997 - 2013

- paddy field- illegal forest logging (wood and- tour boat

- cattle raising

non-wood products)- employees for tourism companies- acacia planting- tour boat

- illegal forest logging (non-wood- employees

products)- owners (hotel, motel, restaurant, ...)- aquaculture
2013 - now- aquaculture- photographer

Source: Field survey in 2019
2.3.4. Our view
- The local livelihoods in center of Son Trach commune were greatly affected by tourism. Tourism andtourism-related activities became main income-generating activities.
- However, because tourism was majorly dependent on nature, local people had to find alternative jobs
during unfavorable weather period each year. Local government has been endeavoring to design more typesof tourism activities, adapted to the local real situation.

3

People’s committee of Quang Binh province (2010). Sustainable Tourism Development Plan 2010 to 2020 PNKB NP Region. As part of the Nature Conservationand Sustainable Management of Natural Resources in the PNKB NP Region Project4

Nguyen, T.T.H. (2018). Participation and the Role of Stakeholders in Tourism Development in the World Natural Heritage Area - Case study of Phong Nha - Ke

Bang (Chapter 8). In “Monograph SCG-ASEAN Initiative Conference 2018”. Institute of Asian Students,Chulalongkorn University.
5

PNKB NP Management Board (2019). Number of tourists and total revenue from 2009 - 2019 in PNKB NP

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III. Domestic fieldtrip (Japan)
3.1. Kagamino town
48430167

MAI Thi Khanh Van

3.1.1. Location

Figure 11. Map of Kagamino town
Source: Tourism association of Kagamino town (2019)6
Kagamino town located in Tomata District, Okayama Prefecture, Japan. The acreage of this town is419.68 km2 with the population is 12,245 people.
3.1.2. Timetable of fieldtrip and Methodology
In three days in Kagamino town,we met the local tourism employees and local residents, (Table 7) andinterviewed them about: Socio-economic background; Status of tourism development; Local issues in
tourism; Plan for developing tourism and solving with issues.
Table 7. Timetable of interview in Kagamino town
Time
October 24th

Interviewee
Staffs of Kagamino town officeSenior manager of Industry Tourism Division, Kagamino town office
Maganer of Okutsu lake general information center

October 25th

Employee of Furusato Shiitake village - Shiitake tour
General manager of Okutsu lake general information center
Staffs of Tourism Research Association

October 26th

Host of Tomisanso HotelManager of Utatane-no-Sato Ippuku-Tei Restaurant
Host of Satoyama restaurant Aelu

6 Tourism association of Kagamino town (2019) http://www.kanko-kagamino.jp/access/Dated: December 28th 2019

9

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3.1.3. Findings
8000004000

6000003000

4000002000

2000001000

002005 2010 2015 2018
Domestic

Table 8. Development process of tourist activities
in Kagamino town
Period of time
Main

type

of

tourism1940 - 1989

After 1989 - now

big group tourism

individual tourism(company scale)small group tourism(family scale)International
Activities

Figure 12. Number of visitors visited

enjoying

hotspring (onsen)sightseeing;

Kagamino town

takingphotos

Source: Field survey in 2019

Table 8 showed the change intrekking; walking to

Source: Field survey in 2019

Table 9. Number of labors in tourism sector of Kagamino town

main type and activities of tourism

Types of tourism

Number of

Number of laborsthat took place before and after 1989.

destinations

destinations

Total

Next, the data in Figure 12 also

The scenery anddemonstrated the change in types of
tourist to Kagamino town. While thenumber of domestic tourists has
decreased, the rapid increase ofinternational visitors has been a
promising sign. The role of tourism
in

this

town'seconomy

was

7

113

43

Hot spring and Lodging

11

57

30

Local specialty

5

40

29

Restaurants

8

25

19

Experience history and

4

5

2

35

240

123

(100%)(51.25%)experience

products/souvenirs

undeniable. In the changing process

cultureof tourism, the creating new tourist

Total

destinations

have

Femaleprovided

employment opportunities for many

Source: Field survey in 2019local residents. (Table 9)
3.1.4. Our view
Tourism in Kagamino town has a lots of potential for development, especially for rural tourism andnature-based tourism.

However, the decline in number of tourists in recent years makes hardly to maintainand develop tourist businesses.

Another problem is that the small scale of the business and the fact thatmost of the workers are part-time workers constitute the unprofessional business, arduous to compete withother localities to attract tourists. In order to improve the situation, the local government focuses on creating
new types of tourism, suitable to the needs of tourists. These efforts are proving its success, especially withattracting international visitors.

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Essay through SDGs Project Research48501155

Tsubasa Tateishi

SDGs Project Research was introduced in the course “Introduction to Social Environment.” By thetime I knew SDGs Project Research, I had been some foreign countries for the training course to study
English or traveling. However, I had never participated in the program for academic research then, thus I
found a good chance to do so. The project that I enrolled in was going to be conducted in Vietnam. I had
never been to Vietnam, so I had just a little background knowledge about Vietnam. I took the course“Sustainability of Rural System” which was taught by Prof. Kim and read a book about agriculture andfarming villages in Vietnam during the period of rapid economic growth to acquire fundamental information
about that.
On 27th August 2019, I arrived at Hue City. In the evening, I ate pho for the first time. It was quitedelicious and gave me the energy to participate in the research motivationally. I participated in the researchfrom 28th August to 1st September. The first study area was Cau Nhi Village. In the village, our project teamvisited houses of each interviewee. I thought if I was traveling individually, I would not have the chance tovisit houses of Vietnamese ordinary citizens and face to portraits of Mr. Ho Chi Minh in each house.
Regarding the main subject, a lot of Vietnamese proper nouns and lack of background knowledge disturbed
me in my understanding about the interview. Although I got information which was not enough, I could
compare the differences of community between in Vietnam and in Japan because I had grown up in a farming
town in Japan. I thought ties of family clans in Vietnamese farming villages were wider and more firmly thanthose in Japanese ones. I found this kind of differences between two countries, which was my harvest. As forthe second study area: Phong Hien Commune, I got to know the farming system in land consolidation areas.
Not only that, I saw the plot-to-plot irrigation at the paddy field our project team visited, which was rare tosee if we were in Japan. Regarding the third study area: Son Trach Commune, the difference between
domestic travelers’ taste and foreign one was impressive.
Through this project research, I could understand the sense to research in foreign study area. It was
the first time to participate in this kind of project, so I could also understand my situation without enoughknowledge and technique. I wish I could have a chance to work abroad after graduation from master course,
thus I need more effort to polish my grounding to active abroad.
For the ending of this essay, I want to appreciate to Prof. Kim, Ms. Mai Thi Khanh Van and otherparticipants in the project research in Vietnam. Especially Prof. Kim gave me the supplementary explanation
clearly during the research and Ms. Mai Thi Khanh Van gave me a lot of information and advice to prepare
for the debriefing session and colloquium. Thank you so much for their helpful support to me.

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Essay through SDGs Project Research48430167

MAI Thi Khanh Van

The first time when my supervisor - Prof. Kim suggested that I should join SDGs Project Research, I
had no idea about its purposes. Next time, I learned regarding it and started to plan my field trips. The researchsites located in both Vietnam and Japan. I have learned that there are the differences between villages in Vietnam
and Japan. However, my personal view was not established until I came to each of these places.
The first field trips of SDGs Project Research started in late August, 2019 in Cau Nhi village. The first
visit took only a few hours, and my impression of this village was only the surprising modern of a rural area in thecentral of Vietnam. Coming back this time, I studied more, and I found the cause of that development. It camefrom the deep connection between members of a clan family and each family clans in the village. That made Cau
Nhi be easier to implement effectively the policies issued by the Vietnamese government.
The second site was Phong Hien commune. Although the theme still related to the rural development, I
learned about a completely different issue on this trip - land consolidation. At that time, I not only gained at theknowledge in the new field, but also surprised by the understanding each other between the neighbors.
The third one - Son Trach commune was also the study site of my master's thesis. Because of coming
here many times, I became the guide on that trip. From the questions of my supervisor and the rest of the members,
I was capable to consider familiar issues from a new perspective. This provided me the opportunity to moreconsiderably improve my thesis.
The last trip was Kagamino town in late October 2019. Although I spent a lot of time preparing, I still
worried. My Japanese has been not good enough to conduct interviews. However, both my supervisor and cosupervisor translated to me in these interviews, helping me break down the language barrier. The information I
have collected during the 3 days in this town was extremely diverse and fascinating. In addition, the other memberson the trip selected various issues. That allowed me an opportunity to know more about Kagamino. I undoubtedly
experienced a memorable time in this town.
While preparing a report and remembering what happened, I realized how lucky I was to participate inthis program. The knowledge and memories I have received, the ideas and plans that I am working on, all started
from SDGs Research Project.
Because of every great thing, I would like to thank all the members who joined me on field trips inVietnam and Japan. After that, I truly appreciate Mr. Tsubasa Tateishi, my project partner. We spent many times
discussing ideas, preparing reports and presenting presentations together. This program helped me to have a goodfriend. At the end, from the bottom of my heart, my deepest appreciation goes to Prof. Kim. Whether in Vietnam
or Japan, talking with him and answering his questions allowed me to investigate the issues in many alternative
ways. Thanks to the guidance of my supervisor, all journeys ended well.
Hopefully, in the future, on new trips, I will have the opportunities to collect more wonderfulexperiences. At the same time, I will be able to create back the meaningful things, appropriating to the content of
SDGs.

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Farm Practices and Soil Environment Survey in Ifugao, the Philippines towards
Sustainable Rice Terrace Farming

フィリピン・イフガオの棚田の営農と土壌環境の調査

岡山大学大学院環境生命科学研究科
社会基盤環境学専攻
教授

森 也寸志

1． はじめに
フィリピン・ルソン島にある棚田群は，世界遺産であるコルディリェーラの棚田群を含み，フィリピンの生産基盤のひとつであると共にイフガオ族の伝統水稲耕作文化として非常に貴重な存在である．その一方で，経済的に大きな発展をとげるフィリピンにあって，若い労働力は山を下り，都市部へと移動してしまう問題がある．今回対象とする地域には 2000ha の棚田があり，そのうち 600ha が崩壊の危機にある．コルディリエー
ラについては 2001 年に危機遺産登録され，2012 年に危機遺産解除となっているが，棚田崩壊の危機が去ったわけではなく遺産の自然科学的危機は依然として進行している．
つまり，危機遺産指定の解除は，棚田を巡る社会学的，文化的条件からやや安易になされており，自然科学的に危機が去ったことが証明された結果ではない．従って，今，現地調査を行い，その課題と解決策を模索することは将来に向けた環境保全となる．
棚田は傾斜地に水をためて営農を行うと言うことで，文化的な遺産と言うだけでなく，自然の物質循環の中で，斜面のままであれば表面流の発生と有機物の流亡が発生するところを，水源涵養と有機物の保全に変え，自然環境の一部を担っている．今回調査する
フィリピン・バナウェーの棚田では，事前調査によって，亀裂発生防止のために年間を通じて湛水状態を維持することがわかっている．一方で灌漑・排水路が系統立っておらず，下水が混入する状況で有機物が多い棚田が認められ，一部では，浸透抑制はされても棚田の構造基盤となる硬盤は発達していない棚田が認められた．つまり硬盤形成ではなく目詰まりによる浸透抑制が行われており，それによって湛水を維持している棚田が存在すると推測された．
今回は，このような状況にある棚田ではどのような営農が行われており，土壌環境としてどのような状態にあるのか，その解決策はどのようなものであるのかを模索することを目的に調査・分析を行った．なお，調査・分析そのものの内容については学生の報告を参照されたい．
2． 実習の概要
国内に於ける事前準備として，調査手法，分析手法の学習を行った．まず，日本棚田百選に選ばれている岡山県久米郡美咲町の棚田で調査演習を行った．日本の棚田も同様- 13 -

に人口減による管理不全が報告されており，棚田の保全については課題を抱えている．
土壌サンプリングを行い，土壌物理性として，透水・保水実験，粒度分析を行い，土壌化学性として，ICP 発光分析，全炭素・全窒素分析を行った．特にリン・窒素について
は抽出方法について検討し，現状を最もよくあらわす分析手法を模索した．
次いで，フィリピン現地については教員が事前に訪問し，概要がわかっている棚田について，学生が主に訪問・調査することで実習を行った．調査に対しては，フィリピン
大学ロスバニョス校に留学し，土壌科学を専門とする研究室に在籍し，必要に応じて調査に出るという体制を取った．当該大学には指導教員と学生で事前に訪問し，研究施設の概要，受け入れ体制を把握した上でその留学を行っている．
調査後の試料の分析や考察については，Skype を活用してリアルタイムで議論をし，調査計画，現地調査，土壌試料分析計画，実試料分析，考察と進めた．
3． 主な成果
これまでの調査から，棚田の浸透性は概ね適切に保たれていること，それは耕盤という水田が水をためるために必要とする構造の発達の有無にかかわらず維持されていることがわかっていた．水資源の保全としては良好であるが，耕盤による湛水の維持というよりは目詰まりによる湛水の維持が疑われていた．また，有機物が多い水田においては，栄養塩の洗脱と思われる肥料分の不足が発生しており，有機物の取り扱いに課題があるであろう事が推測されていた．
今回の調査により，科学的な分析に加えて，現地農家に対するインタビューも行ったため，彼等の棚田管理に対する意識が明らかになり，いくつか新たな考察項目が加わった．すなわち，多くの棚田で肥料が足りていないこと，肥料に対する知識の欠如，営農手法の改善に対する抵抗感，などが明らかになった．化学肥料は悪いものであるといった印象を持っており，適切な使用も見られないこと，逆に排水路に下水が混ざることに
よって下流部では有機物過多となる水田があることがわかってきた．有機物過多である
棚田の場合，肥料成分としての効用より，栄養塩の洗脱が起こりやすくなり，これがこれまでの分析から観察されていた事柄であると考えられた．さらに，硫化水素の発生と思われる現地報告があり，この場合，根腐れの危険性があり，早めの対処が望まれる．
4． おわりに
傾斜地に作られた農地は，雨の多い東南アジアにおいては棚田というひとつの景観を形作っている．また自然の水循環という立場からも非常に重要な位置づけにある．今回の調査から，自然科学的な分析事項に併せて，農家のインタビューを行ったため，普段とは違った視点からの調査ができたと考えている．学生の現地留学と調査という，理想的な体制での調査・分析が実施でき実りの多い実習になった．今回の調査内容を踏まえて，農家や自治体に対する提案ができればそれが望ましい成果の形では無いかと考える．

- 14 -

Assessment of Soil Quality as Affected by Topography
and Farming Practices in Banaue Rice Terraces,
Ifugao Province

Division of Social Engineering and Environmental Management
48501154

Tomoyo Kurozumi

February, 2020

- 15 -

1. Introduction ............................................................................................................................................... 3
1.1 Background history of the Ifugao Rice Terraces ................................................................. 3
1.2 Objectives ............................................................................................................................................ 5

2. Methodology .............................................................................................................................................. 6
2.1 Study area ....................................................................................................................................... 6
2.2 Interview ......................................................................................................................................... 8
2.3 Soil sampling and field investigation ............................................................................... 10
2.4 Analysis........................................................................................................................................ 13

3. Results and Discussion ..................................................................................................................... 14
3.1 Interview ........................................................................................................................................... 14
Farmers Characteristic ................................................................................................................... 15
Water management.......................................................................................................................... 15
Stone works ........................................................................................................................................ 16
Rice variety ........................................................................................................................................ 16
Cropping calendar ........................................................................................................................... 19
Pests and pest control ..................................................................................................................... 21
Perception of climate ...................................................................................................................... 24
Soil character ..................................................................................................................................... 24
Azolla and Blue green algae ........................................................................................................ 25
Perception of soil fertility ............................................................................................................. 25
Soil sampling and analysis ........................................................................................................... 25

4. Conclusion and recommendation .................................................................................................. 36
Future task .......................................................................................................................................... 37

References ................................................................................................................................................... 38- 16 -

1. Introduction
1.1 Background history of the Ifugao Rice Terraces
The Ifugao Rice Terraces (IRT) is well known as the world cultural heritage site. The riceterraces were constructed manually, and they have more than 2000-year history(Acabado.S, 2015). As the world heritage, it includes five clusters; the Nagacadan terrace
cluster in the municipality of Kiangan, the Hungduan terraces cluster, the central
Mayoyao terraces cluster, the Bangaan terrace cluster in the municipality of Banaue thatbackdrops a typical Ifugao traditional village, and the Batad terrace cluster of themunicipality of Banaue that is nestled in amphitheater-like semi-circular terraces with avillage at its base (UNESCO, 2019).
However, the rice terraces face their change such as collapse, and soil degradationconsidered to be serious nowadays. On the background, social and other environmental
changes, decrease of the farm population, shortage of the indigenous knowledge (IK), useof chemical products and climate change, greatly affect the rice terrace destruction(Sekiguchi, 2014).
In previous studies, which were mainly based on interviews from farmers, they assured
the crisis of rice farming in IRT. Mainly in 2000s, some studies were conducted to raise
the awareness of its vulnerability to social and environmental changes since the site waslisted as endangered world cultural heritage by World Heritage Committee. In 2012, it
was formally removed from the list. However, it did not mean that terraces degradationends. UNESCO (2019) reported that storms and other climate change impacts affected
greatly on the rice terraces as they are vulnerable to natural disaster.
Moreover, it should be noted that there is still limitation of scientific data, especiallywith regard to soil and water environment in IRT. Few studies assess and ensure thesustainability of IRT from agricultural and environmental aspects.

- 17 -

Soil quality and sustainable agriculture

Soil quality is the capacity of a specific kind of soil to function, within natural or managed
ecosystem boundaries, to sustain plant and animal productivity, maintain or enhancewater and air quality, and support human health and habitation. (NRCS Colorado, USDA,
2019)
Soil quality now occupies a pivotal position in this concept, alternative agriculture to theultimate goal of sustainable agriculture, and many would agree that soil quality is the"key" to agricultural sustainability as shown in Figure.1. Further research is needed toquantify the indicators or attributes of soil quality into indexes that can accurately andreliably characterize the relative state of soil quality as affected by management practices
and environmental stresses. (J.F.Parr, 1992)

Figure.1 A conceptual diagram that illustrates how they attributes of soil quality provide
a link between the strategy of alternative agriculture and ultimate goalof sustainableagriculture.
Soil and water environment are hardly recognized since few changes are visible.
Sustainable agriculture and agricultural management should be encouraged all over theworld, to achieve the Sustainable Development Goals (United Nations, 2015)- 18 -

1.2 Objectives
In Banaue Rice Terraces as a pivotal part of IRT, the scientific data is limited as well asother areas in IRT. Therefore, the assessment should be more specific to utilize theinformation by farmers. Soil quality and affected factors were examined and discussed inthis paper.
The objectives of my study are to assess the soil quality and to clarify the effects of the
farming practices and topography on the soil quality in Banaue Rice Terraces
Specific objectives are:•to assess the soil quality•

to determine the effects of the farming practices and topography on
the soil quality *•to identify the farmer’s knowledge in soil and land management•

to propose better farming and land managementin Banaue Rice Terraces, Ifugao- 19 -

2. Methodology
2.1 Study area

Bangaan and Batad, Banaue, Ifugao Province shown in Figure.2 were selected as study
areas considered the worse soil condition and the terraces collapse that was shown inprevious paragraph . One researcher revealed that the destruction of the rice terraces
dikes in certain area in Banaue was nine times larger than those in Kiangan.

● Batad● Bangaan

Figure.2 Map of Banaue (cited from Google Map)

Outline of field survey

Survey was done following the schedule on Table.1 and Table.2 Table.3 and Table.4
show sampling schedules.

- 20 -

Table.1 Schedule of survey in Bangaan
Date and time

Activity

October 1

Interview with questionnaire, field
investigation

October 2

soil sampling, field investigation

October 3

Soil sampling, field investigation,and interview

October 4

Soil sampling, field investigationand interview

October 5

Soil sampling, field investigationand interview

December 27

Additional interview

Table.2 Schedule of survey in Batad
Date and time

Activities

October 28

Interview, and field investigation

October 29

Soilsampling,

and

field

investigation
October 30

Soil sampling, field investigation,and interview,

October 31

Soil sampling, field investigation,and interview

December 26

Additional interview- 21 -

Table.3 Schedule of soil sampling in Bangaan
Date and time

Sampling site (owner name_ number of one’s fields)

October 2

Bato_01, Bato_02, James_01, Bato_03, Virginia_01, Virginia_02

October 3

Conchita_01, Leticia_01, Lucas_01, Leticia_02, Ester_01

October 4

Virginia_03, Christina_01

October 5

Jose_01, Maribel_01

October 26

Bato_04, Pio_01

Table.4 Schedule of soil sampling in Batad
Date and time

Sampling site (owner name_ number of one’s fields)

October 29

Joseph_01, Madelyn_01, Ana2_01, Elizabeth_01, Tessie_01,
Collapse_01(Tessie), Abandoned_01

October 30

Rodolfo_01,

Moises_01,

Ana1_01,

Moises_02,

Linda_01,

Moises_03, Hilda_01
October 31

Ana1_02, Collapse_02, Nancy_01, Abandoned_02

All field survey was approved by municipal office of Banaue and barangay captain of
Bangaan and barangay office of Batad.

2.2 Interview

In order to collect necessary data, Interview to the farmers was conducted before andduring the soil sampling. Oral and written interview were done.
17 farmers were interviewed in each Barangay, Bangaan and Batad.
Gathering for interview was in October1 in Bangaan and October 28 in Batad as shownin Figure.3- 22 -

Figure.3 Interview to the farmers in Bangaan
Additional interview was done at the same venue or at famers houses after the gathering
Paper questionnaire includes original questions in English, distributed to each farmer
individually.
The questionnaire has 5 sections as follows:
1.

General farm household characteristics

2.

Products description

3.

Crop cultivation

4.

Characteristic and practices unique to the area5.

Supply chain and facilities

Some farmers could fill up the questionnaire in English, sometimes using their dialect
and pictures while others who could not understand English or do not know how to writein English was supported by a translator who can use both their dialect and English. He
wrote the answer on the questionnaires instead of them.
In oral interview，concept of soil and soil management were also mentioned.

- 23 -

2.3 Soil sampling and field investigation

17 fields were selected in Bangaan and 16 fields in Batad considering with the differencein farming practices and elevation and location shown as Figure.4 and Table5 in Bangaan,
and Figure.5 and Table.6 in Batad, respectively.

Figure.4 sampling sites in Bangaan, Banaue

Figure.5 sampling sites in Batad, Banaue(cited from Google Earth Pro version7.3.2.5776)- 24 -

Table.5 Elevation of each sampling site in BangaanGroup

Elevation (m)A

950 aboveB

900 – 949

CD

850 – 899

800 – 849

Sampling site
1039

Maribel_01

1010

Pio_01

940

Jose_01

891

Christina_01

886

Bato_03

874

Verginia_02

873

Verginia_01

870

Bato_02

867

Leticia_02

865

Bato_01

859

Ester_01855

James_01

851

Verginia_03

847

Bato_04

840

Lucas_01

833

Leticia_01

828Conchita_01- 25 -

Table.6 Elevation of each sampling site in Bangaan
Group
A

B

C

D

E

Elevation (m)950 above

900-949

850-899

800-849

750-799

Sampling site

987

Ana2_01

972

Joseph_01

935

Elizabeth_01

923

Madelyn_01

900

Rodolfo_01

868

Tessie_01

828

Moises_01

822

Ana1_01802

Moises_02794

Linda_01

785

Hilda_01

774

Moises_03

772

Ana1_02759

Nancy_01- 26 -

Sampling procedure

Soil was taken from three depths: 0 to 10cm, 10 to 20cm depths, using shovel and trowel.
two points were chosen in each field. When the field is small enough, one point in thecenter was a representative. Soil was mixed in the plastic bag after the soil sampling.
In addition to soil sampling, information about irrigation facilities, soil condition, otherland use condition was recorded.

2.4 Analysis

The soil brought back were kept air-dried for 7 days to 10 days in soil chemistrylaboratory, pounded and sieved at 2mm.
Following items shown in Table 7 were measured.
Table 7 List of analysis item and used methods
Analysis

Methods

Moisture content
Soil pH(1:1=soil:water)

Organic Matter

Walkley and Black Method

Total Nitrogen

Kjekdahl method

Available Phosphorus contents

Bray No.2 method

Exchangeable K, Ca, Mg

Quick methods

Available micronutrient

DTPA extraction, ICP-OAS(Cu, Zn, Mn, Fe)
Cation Exchange Capacity (CEC)

Ammonium acetate methods- 27 -

3. Results and Discussion
3.1 Interview
Farmers profiles was shown in Table 8. Part of farmers response was shown in Table9.
In Bangaan, the interview was announced by Barangay Captain, in Batad, announced by
Barangay officer in advance and on the morning of the day through radio in the area.

Table 8 Farmers profile
Bangaan (n=17)
Average farming
experience (years)
female respondents (%)

36.1

37.8

64.7

82.4

3

2.2

52.9

52.9

number of family member(person)non-farm income (%)

Batad (n=17)

Table 9 Farmers response about field and farming practices (selected basic question)
Bangaan (n=17)

Batad (n=17)

Irrigation (%)

70.1

94.1

Rainfed (%)

29.4

17.6

Stone wall (%)

100

100

Machine use (%)

52.9

29.4

5.9

11.7

Pesticide use (%)

35.3

35.3

Herbicide use (%)

0

11.8

Sign before collapse (%)

35.3

58.8

Double cropping (%)

5.9

5.9

Commercial fertilizer use(%)- 28 -

Farmers Characteristic

Women tended to join interview since their husband worked in the fields. In Batad, some
farmers have more than 20 fields, and they also play an major role in an organization or
their traditional role such as “tonaong” who leads the rice planting in the area. Those whohave many fields hire many labors to maintain all fields and they can afford to do thatsince they have rice to sell or give to the labor instead of money.

Water management

There are 5 irrigation ways in Bangaan and Batad according to the interview.
1. irrigation from river
2. water from mountain
3. water from spring outside/ inside their fields
4. water from upper fields
5. rainfed
As shown in Table.11, both areas have irrigation. The irrigation from a river in Bangaan
was established few years ago.
In both areas, everyone prefers to keep the water however, upper area in Bangaan which
no irrigation maintained and rely on rainfed and water from the mountain, often
experience shortage of water and cracking soil.
According to previous research, in November or December, farmers distribute water toeach rice terraces, harrow and puddle the field in Ifugao (IFSU,2011). However, interview
revealed that people in Batad and Bangaan seldom drain the water and always keep waterflowing from up to downstream preventing cracking on the soil surface. In Batad, someof them drain the water only for plowing period while A few those who in Bangaan thathave fields in specific area (just below the village) drain the water before planting because- 29 -

the soil is too soft and rice cannot be grown if they don’t drain the water Sowing starts
simultaneously and the seedling are transplanted in December or January.

Stone works

There are two types of the rice terraces in Ifugao, the stonewalled and unstonewalled.
Prior to the introduction of mortar and plasters, stone wall is purely made of stones.
Nowadays, the farmers make the wall with not only the stones, but with mortar that used
for fillers or on the top layer that is expected to be footpath. (IFSU, 2011)
In Bangaan and Batad, almost all the rice fields have stone wall. Some fields which
experienced collapse before, the owner had difficulty to bring needed stones, the wall
would be incomplete.
Only one farmer in Bangaan and two farmers in Batad use commercial fertilizer. The
farmer in Bangaan mentioned that she does not have enough time to take care the rice, so
she thinks better to use chemical to grow rice easily.
Also, it is noted that farmers who have fields not in main portion of the area have different
practices. It seems the indigenous knowledge comes from different person or not inherited
well.

Rice variety

The rice variety grown in two areas are shown in Figure.6 and Figure.7.

- 30 -

12

Number

10
8
6
4
2
0
california

intan

glutinous

red

white

other
varieties

Rice variety
Figure6 Rice variety in Bangaan“California rice” is commercial rice as they recognized.
“Intan rice” seems also commercial rice originated in India, that is included in “othervarieties”. As well as Intan rice, there is one farmer who produces C4 rice developed by
IRRI.
“Tinawon” as general term referring to their native rice varieties which are produced oncea year, included in “white rice” in this paper.
“Chayaot” and “bino’gong/ binuhgon/ binuhgpa” included in “sticky rice”, “minnang/minaangan rice” were included in “red rice”, respectively.
The characteristics of “ninhgon”, “sipor”, “mayoyao rice”, “inten red rice”, and “inten
white rice” included in “other varieties” were not well identified.

- 31 -

16
14

Number

12
10
8
6
4
2
0
california

glutinous

red
Rice variety

white

other

Figure7 Rice variety in Batad“California rice” seems only one commercial variety produced in Batad.
“Tinalbok/ tinalbo”, ”pinkitan/pawikan”, “inguna”, ”dayakot”, and “tinwon” areincluded in “white rice”,“binugon/ inugon”, “chaga’od”, “dikket/dicket/diket”, and ”buyabuy/ pujapuy /puyapuy”
are categorized in “sticky rice”.
“Ingngoppot” is native “red rice”.
They have other varieties “linawang”, “injula”, “tukayan”, “imbu-u”, ”latong”, and“migapas”. Migaspas was brought from Viscaya and Isabela, stunted variety to be tolerant
to extreme weather.

The main reason why they plant heirloom rice is the accessibility of rice seeds.
Traditionally farmers plant the rice variety and still inherit them.
A part of their testimony is consistent with previous research noted as below.

- 32 -

According to previous research conducted by IFSU (2011), heirloom rice is preferred by
farmers because of the characteristics: aroma, taste, resistance to pests, disease, andextreme weather condition, and less fertilizer requirement.
So, it has short height, low yield, and long maturity. Also, the cost, accessibility toirrigation, and its value as inheritance from ancestor that encourage unity are the reason
why they grow the heirloom rice.
On the other hands, in order to meet increasing food demands, it’s inevitable to cultivatecommercial rice that has high yields and short maturity that enables the farmers tocultivate the rice twice a year. (Sekiguchi, 2014)

Respondents

Cropping calendar
14
12
10
8
6
4
2
0

Month
seedingtransplanting

cleaning/land fixing

Figure 8 Cropping calendar in Bangaam (n=17)- 33 -

harvestRespondents

18
16
14
12
10
8
6
4
2
0

Month
seedingtransplanting

clean and landfixing

harvestFigure 9 Cropping calendar in Batad (n=17)

As shown in Fig.8 and 9 there is a similar trend of both cropping schedule in Bangaan
and Batad.
There is a slight difference in transplanting season. It peaks in February in Bangaan while
in January in Bangaan. Besides transplanting, harvesting period also varies widely sincemore varieties of rice are produced in Batad. Most of the farmers in Bangaan and Batad
grow rice only once in a year. It’s somewhat correspondent with previous study; some
farmers cultivate rice twice a year, however, once is still dominant because of theselection of rice variety, water capacity (IFSU,2011).
Farmers in Batad pointed that few decades ago, they could plant rice twice in a year, but
now due to climate change, double cropping is impossible. More details should be
examined.

- 34 -

After the rice harvest, the rice straws are left in the fields. Farmers bury them into the soil
and make them rotten as fertilizer for the next cultivation. Some farmers mentioned thatthey burn the rice straw if it’s dried.

Pests and pest control
Bangaan

1. rat (dongo/dango ,gehing for smaller,cho’oh for bigger)
Present throughout the year, especially the ripeness period. They often burrow thehole from inside to the stone wall, which can be water path. In planting season, theyalso eat the young rice plants and the damaged plants would be dead.
Control: Farmers make feed mixed with poison and put it on the path way or theirnests. Rice, camote, weeds, or golden kohol are used as their feed.
2. maya bird (red bird, pujang/fujang)
They eat rice fruits.
Control: Farmers hang something on the line to make noise keeping the birds away.
Scarecrows also can be substitutes for the farmers monitoring birds.
3. white bird (terob)
They eat rice fruits.
Control: Farmers hang something (called idro) on the line to make noise keeping thebirds away. Scarecrows also can be substitutes for the farmers monitoring birds.
4. earthworm (kiwit)
Present throughout a year in the moist soil, appear if the soil gets dried. The length isfrom 5 to 30 cm. They eat rice and dig the hole into deeper soil (bottom) that makewater comes out from the fields and cause terrace collapse.
Control: Electric apparatus is effective for earthworm (according to one farmer).

- 35 -

5. eel (o’lang)
Active during night time.They eat rice and dig the hole as well as earthworm.
Conrtol: Kill with knife during at night.
6. cricket
They seems damage the rice. Some farmers argue that it also dig some hole in the rice
fields.
7. fly (change) :Evrey year appear in ripneness period.The number increase rapidly for few weeks,
8. golden kohol (biskol)
Eat young rice plants.
Control: Drain the water from the fields

For those pests, some farmers use insecticides, Cymbush (Cypermethrin 25%) and karate(2.5g/L Lambda-cyhalothrin) which is a synthetic pyrethroid. Also, changing rice
planting season is effective to avoid flies like change.
Some farmers also mentioned that animal variety including pests are changing from what
they used to be.

Batad

1.

rat (pu-at /mahulatan)
Present from February to May (ripeness period).They burrow the holes.
Control: Same as in Bangaan, put the poisoned feed (called at-tib/binin) to the stone
wall (their nests).

2.

maya birds (red birds, pujang(fujang) billit tukeng)
Present in ripeness period. They eat rice.
Control: Use lanet to keep them away.

- 36 -

3.

white birds (terob)

4.

earthworm (kiwit)
They burrow the hole in the rice fields that caused terrace collapse.
Control: Kill manually when farmers drain the water to plow the soil/

5.

long earthworm (o’lang)
1-foot-length earthworm. They distinguish regular earth worm and longer earth
worm. In Bangaan, O’lang is considered as an eel, however, People in Batad insisted
that o’lang is big earthworm not an eel.

6.

fly (chango)
insects that eat rice. Some farmers insist it is present every ripeness period while othersay throughout a year.

7.

Golden kohol (biskol)Present from February to March. It damages rice panicle.
Control: Use insecticides or pick up manually.

8.

ground breath cricket (gwelet/ kol’le/ kul’la )Present throughout a year, especially February and Murch.Dig holes in the soil.

9.

white butterfly

10. fly (pho-ew)
Like butterfly.
11. bag or fly (bu-aw/ puchien,bucheng)
12. worm (bigis/ peeke/ peleckel)
Present throughout a year especially February, March, May.

Some farmers spray insecticides, Cymbush (Cypermethrin 25%), Karate (2.5g/L
Lambda-cyhalothrin), and Solomon (Beta-Cyfluthrin + Imidacloprid 300 OD(8.49 + 19.81 % w/w)).

- 37 -

Perception of climate

Interesting to note that, Farmers in Bangaan regard summer as March and April, while
those who in Batad regard it as during September to November.
Statistically, lowest temperature is recorded in January and highest recorded in May
generally (world weather online, 2019))

Soil character
Cracking

During the field trip, the situation water went into the big crack （can be called rill） was
observed ( groupB, Jose_01), farmers argued that is a cause of terrace collapse.

Dark soil

In both areas, Dark colored soil was observed below the village.
In Bangaan, some farmers argued that soil below the village are different from others;
rice cannot be grown due to the softness of soil. They drain the water before planting
and also, they experienced their skin turned red and many leeches living there and biting
farmers.
In Batad, one farmer mentioned the soil beside the village is easily cracking. white
those below the village are soft, black and the terraces are very deep.
They have some fields but they did not change their farming practices between eachfield. The size of the field, direction, rice variety, and altitude are not significantly
different from other fields, so that water quality might affect the soil. In both areas thatkind of soil was observed only below the village, so it’s considered that wasted waterfrom the village containing a lot of organic material and Phosphorous derived fromdetergent and soap they use come into downstream and cause the soil too fertile andmake it suitable for leeches to live.

- 38 -

Azolla and Blue green algae

Roger.A.P (1986) mentioned that Azolla and Blue green algae are seen on the surface
water in Banaue Rice Terraces. Azolla is a genus of seven species of aquatic ferns in thefamily Salviniaceae while Blue-green algae is a type of bacteria called cyanobacteria.
Both have ability of nitrogen fixation but azolla is more available as a fertilizer. Bluegreen algae is often considered as a problem caused by eutrophication and takes more
oxygen for other plants and animals in the water.

According to interview and field observation, Azolla was observed in Bangaan and
Batad and Blue green algae was observed in Batad.
Some farmers remove them and others leave them in the fields.
Why some farmers remove them is because it sticks with rice plants and prevent growing
rice plants.

Perception of soil fertility

The farmers judge fertile fields by the amount of fertilizer, yields, accessibility ofirrigation, but not the actual soil condition.
One answered that brown soil in the upper mountain is an example of a fertile soil,
while the other answered, black soil in the lower.
From this, it is said that they do not share a common knowledge, nor do they have aconcrete idea about soil quality.
Also, most of them assumed that any commercial fertilizer and pesticides do harm tosoil physical properties.

Soil sampling and analysis

Characteristics of analyzed soil were shown in Table 10 and 11.

- 39 -

Table 10 Analyzed soil samples in Bangaan with their charactersGroup

Elevation (m)A

950 aboveB

900-949C

850-899D

800 - 849

Sampling site

Character

Maribel_01

DL-1, CF

Pio_01DL-1, OF

Jose_01

OF

Christina_01

OF

Bato_01

OF

Ester_01

DL-2, OFJames_01

OF, DC

Verginia_03

OF, BS

Leticia_01

DL-2, OF

Conchita_01

OF

Table 11 Analyzed soil samples in Batad with their characters
Elevation(m)Sampling site

CharacterA

950 aboveAna2_01OFB

900-949

Rodolfo_01

OFC

850-899

Tessie_01

OFD

800-849

Moises_01

CF

Ana1_01OFE

750-799

Hilda_01

OF, BS

Nancy_01

DL-1, OF

OF: Organic fertilizer CF: Chemical fertilizer BS: Black color soil DC: Double cropping
DL: Different location considered a watershed surrounding a village as a center. (samenumber refers to same watershed that separated by river or road) Results of soil analysis- 40 -

were shown in Table 12 to Table 17. In discussion, coefficient of determination (R2) todiscuss correlation. C/N ratio was cariculated as OM contains 58% of organic carbon.
Table12 Soil PH, Organic matter, Total Nitrogen in Bangaan
sample
depth

OM

TN

C/N ratioGroupsample site

(cm)

pH

（％）

（％）

A

Maribel_01

0-10

4.5

3.03

0.11

10.58

A

Maribel_01

10-20

4.8

1.37

0.10

10.20

A

Pio_01

0-10

5.0

3.50

0.18

10.74

A

Pio_01

10-20

5.1

3.27

0.16

6.62

B

Jose_01

0-10

5.6

2.91

0.15

19.26

B

Jose_01

10-20

5.7

0.44

0.06

14.59

C

Christina_01 0-10

5.5

2.90

0.16

14.97

C

Christina_01 10-20

5.4

1.12

0.10

14.53

C

Bato_01

0-10

5

3.25

0.18

11.06

C

Bato_01

10-20

5.2

2.98

0.17

10.87

C

Ester_01

0-10

5.5

7.38

0.29

11.40

C

Ester_01

10-20

5.5

6.89

0.27

4.28

C

James_01

0-10

6.2

3.82

0.20

12.34

C

James_01

10-20

5.8

3.45

0.18

12.35

C

Verginia_03

0-10

5.2

8.31

0.42

16.09

C

Verginia_03

10-20

5

7.54

0.34

8.08

D

Leticia_01

0-10

5.6

5.44

0.26

11.45

D

Leticia_01

10-20

5.4

4.31

0.20

12.86

D

Conchita_01 0-10

5.5

6.14

0.18

11.59

D

Conchita_01 10-20

6.1

5.42

0.22

12.24

- 41 -

Table 13 Soil PH, Organic matter, Total Nitrogen in Batad
sample
depth

OM

TN

C/N
ratio

Group

sample site

(cm)

pH

（％）

（％）

A

Ana2_01

0-10

5.4

4.08

0.20

11.82

A

Ana2_01

10-20

5.5

2.11

0.08

14.47

B

Rodolfo_01 0-10

5.3

2.79

0.13

12.44

B

Rodolfo_01 10-20

5.5

1.88

0.12

9.29

C

Tessie_01

0-10

5.6

3.90

0.14

16.56

C

Tessie_01

10-20

5.6

2.43

0.14

10.44

D

Moises_01

0-10

5.8

3.72

0.17

12.84

D

Moises_01

10-20

6.0

1.52

0.11

7.70

D

Ana1_01

0-10

5.8

5.44

0.21

14.83

D

Ana1_01

10-20

5.4

2.11

0.14

8.90

E

Hilda_01

0-10

5.8

6.34

0.41

8.91

E

Hilda_01

10-20

6.0

8.01

0.35

13.10

E

Nancy_01

0-10

5.4

2.01

0.17

6.76

E

Nancy_01

10-20

5.3

0.85

0.08

6.32

As shown in Table12 and 13, pH of the fields with chemical fertilizer (Maribel_01 is
lower than organic one in Bangaan. However, no significant difference was observed in
Batad (Moises_01).
OM showed similar trends as TN (Figure 10 and 11) that is consistent with the results ofWang (2011). However, unlike the previous study, elevation and these two elements arenegatively correlated (R2 = 0.3 in both). This shows that the source of OM and TN are thesame, leaching occurred and they were accumulated at lower.
Black color soil (Verginia_03 in Bangaan and Hilda_01 in Batad) have twice or threetimes as much as OM and TN than other fields at the same elevation. It’s probably because- 42 -

the effects of wasted water from the village.
In different location, one field in Bangaan (Ester_01) have more OM. It might be because
the field is closest to the mountain and the humus from the mountain easily come andaccumulate into the field.
Compared with different elevation, same watershed, and organic fertilizer application in
Bangaan, (Jose_01, Chiristina_01, Bato_01, James_01, Conchita_01), organic matter
content and average total Nitrogen are relatively higher at higher elevation, while there isno significant difference in Batad.
Average pH was lower in Bangaan (5.4) than that in Batad (5.6) and generally categorized
0.50 acidic”. Average OM was higher in Bangaan
0.50(4.2) than that in Batad (3.4). TN“slightly
0.40
0.40
0.0433x + 0.0297
y = different
0.036x + 0.0479
value
was not
from each (0.2 for each), thatarey =generally
low compared to
R² = 0.8695

0.30

TN

TN

standard shown in Appx.1.
0.20

R² = 0.7945

0.30
0.20

pH in Bangaan was negatively correlated with elevation (R2 0.37) and consistent with
0.10

0.10

previous study (Roger,1984).

0.00

0.00

0.00

5.00

0.00

10.00

5.00

10.00

OM

OM

Figure 10 OM-TN in Bangaan

Figure 11 OM-TN in Batad- 43 -

Table14 Soil macro nutrients, CEC, and Base saturated percentage in Bangaan
sampleGroup sample site

Base

depth

AP

Ca

Mg

K

CEC

saturation(cm)(mg/kg)(cmol/kg)(cmol/kg)(mg/kg)(cmol/kg)(%)

A

Maribel_01

0-10

4.63

14.50

6.87

2.19

29.28

80.46

A

Maribel_01

10-20

3.00

14.25

5.01

1.68

29.83

70.21

A

Pio_01

0-10

4.93

18.12

13.02

3.70

41.30

84.36

A

Pio_01

10-20

4.28

17.23

15.27

2.69

35.02

100.49B

Jose_01

0-10

12.02

24.61

11.78

2.19

40.84

94.47

B

Jose_01

10-20

7.53

23.95

15.58

3.20

43.34

98.59

C

Christina_01 0-10

5.02

21.54

10.89

2.69

35.51

98.94

C

Christina_01 10-20

3.42

20.97

14.46

4.21

36.30

109.19C

Bato_01

0-10

5.15

22.47

15.80

5.22

37.13

117.14C

Bato_01

10-20

5.07

22.50

13.86

3.20

41.95

94.30

C

Ester_01

0-10

21.95

19.35

11.18

2.19

44.88

72.90

C

Ester_01

10-20

18.56

21.62

11.81

1.68

41.92

83.78

C

James_01

0-10

21.81

23.89

14.66

18.86

40.37

142.20CJames_01

10-20

16.44

22.87

15.97

14.81

41.35

129.77

C

Verginia_03

0-10

19.51

18.97

13.35

3.20

32.13

110.52

C

Verginia_03

10-20

20.81

20.99

9.79

2.19

35.46

92.99

D

Leticia_01

0-10

14.14

21.09

8.62

5.72

36.40

97.36

D

Leticia_01

10-20

11.92

20.56

9.34

1.68

35.74

88.37

D

Conchita_01 0-10

14.31

21.01

11.32

2.69

39.23

89.26

D

Conchita_01 10-20

10.62

24.09

10.58

2.19

28.01

131.62- 44 -

Table15 Soil macro nutrients, CEC, and Base saturated percentage in Bangaan

sample

Base

depth

AP

Ca

Mg

K

CEC

saturationGroupsample site(cm)

(mg/kg)(cmol/kg)(cmol/kg)(mg/kg)(cmol/kg)(%)

A

Ana2_01

0-10

20.87

17.03

3.81

12.79

27.95

120.37A

Ana2_01

10-20

16.79

14.22

2.12

13.30

20.78

142.62B

Rodolfo_01

0-10

10.37

15.03

3.39

2.69

25.81

81.79

B

Rodolfo_01

10-20

10.37

14.80

5.43

2.69

25.64

89.40

C

Tessie_01

0-10

10.72

16.58

4.77

4.21

26.37

96.94

C

Tessie_01

10-20

6.74

14.72

4.67

1.68

27.22

77.40

D

Moises_01

0-10

13.48

16.39

7.06

8.25

28.50

111.22

D

Moises_01

10-20

10.72

14.54

5.96

2.69

25.23

91.91

D

Ana1_01

0-10

18.94

17.25

7.55

10.77

29.77

119.50D

Ana1_01

10-20

15.33

18.08

5.74

4.71

27.96

102.05

E

Hilda_01

0-10

10.88

17.35

5.98

4.21

37.45

73.53

E

Hilda_01

10-20

13.09

16.28

6.34

1.68

30.41

79.89

E

Nancy_01

0-10

6.01

16.05

6.56

7.24

28.25

105.65E

Nancy_01

10-20

5.96

15.20

4.33

3.20

26.95

84.34

As shown in Table 14 and 15, topsoil (0 -10cm) are richer in macro nutrient in general.
Macro nutrients in the fields with chemical fertilizer are relatively lower than organic
farming even they have higher CEC. (Maribel_01 and Pio_01 in Bangaan, Moises_01
and Tessie_01 in Batad).
Field with double cropping in Bangaan (James_01) have relatively larger amount of
nutrient compared to one cropping field (Christina_01 and Bato_01). However, the owner,
James complained that the rice yield is not good at second harvest, so more data areneeded to identify the nutrient change in whole year.

- 45 -

Fields in different watershed in both areas have certain difference from other fields,
however no consistent trend with them.
Elevation do not affect the trend of macro nutrient on soil in both areas.
Compared with average value, Mg, Ca, and CEC value were higher in Bangaan. CEC
contributes to store more Ca and Mg in Bangaan, mainly decided by parent smaterial.
Based on previous studies shown in Appx.1 (Sigari, A.T, 2005), most fields in both areas
contain larger nutrient than the standard level in the Philippines.
P-deficiency is 34.8％， and 7.14％, Bangaan and Batad repectively. Upper terraces in
Bangaan have less Available P than those of lower, probably upper one was washed awaywith soil particle and accumulate them at lower.
K-deficiency is 78.3% and 71.4％, Bangaan and Batad respectively, is almost same asprevious study (Sigari,2003) and high rate. Some There is no trend in K flow in the areas,so the reason should be identified.

- 46 -

Table 16 Soil micronutrients in Bangaan
sample
depth

Fe

Mn

Cu

Ni

(mg/L)(mg/L)(mg/L)(mg/L)

Group

sample site

(cm)

A

Maribel_01

0-10

403.98

42.64

39.31

1.35

A

Maribel_01

10-20

395.47

74.10

68.95

1.55

A

Pio_010-10

272.75

79.70

74.03

3.02

A

Pio_01

10-20

317.17120.52113.81

3.03

B

Jose_010-10

144.41

12.76

12.78

0.15

B

Jose_01

10-20

150.04

21.17

20.28

0.25

C

Christina_01 0-10

168.46

5.93

6.76

0.42

C

Christina_01 10-20

120.23

9.37

9.86

0.70

C

Bato_010-10275.30

32.86

31.08

0.83

C

Bato_01

10-20

274.73

32.49

30.70

0.86

C

Ester_01

0-10

165.19

9.38

9.75

0.87

C

Ester_01

10-20

148.86

8.57

9.00

1.26

C

James_01

0-10

119.42

17.91

17.37

0.98

C

James_01

10-20

81.74

21.25

20.09

1.02

C

Verginia_03

0-10

192.04

20.60

19.65

0.06

C

Verginia_03

10-20

235.89

34.03

31.62

0.03

D

Leticia_01

0-10

144.88

18.92

18.20

0.93

D

Leticia_01

10-20

225.54

26.13

24.61

0.84

D

Conchita_01 0-10

131.456

13.887

13.9125

1.05

DConchita_01 10-20

133.2205

4.76855.7765

1.12- 47 -

Table17 Soil micronutrients in Batad
sample
depth

Fe

Mn

Cu

Ni

(mg/L)(mg/L)(mg/L)(mg/L)

Group

sample site

(cm)

A

Ana2_010-10

249.48

44.79

41.41

0.55

A

Ana2_01

10-20

324.64

90.75

84.52

0.25

B

Rodolfo_01 0-10

319.58

54.94

50.68

0.29

B

Rodolfo_01 10-20275.09

56.23

51.64

0.43

C

Tessie_01

0-10274.46

74.40

69.13

0.48

C

Tessie_01

10-20

337.52

71.91

66.37

0.26

D

Moises_01

0-10

57.23

7.11

7.62

0.46

D

Moises_01

10-20

95.16

8.26

8.54

0.03

D

Ana1_01

0-10

91.16

2.91

3.97

0.20

D

Ana1_0110-20

101.02

3.78

4.72

0.15

E

Hilda_01

0-10

283.27

55.20

50.85

0.30

E

Hilda_01

10-20

220.51

96.64

90.28

0.29

E

Nancy_01

0-10

364.58

28.16

26.07

0.90

E

Nancy_01

10-20

441.48

29.58

27.24

1.19

As shown in Table 16 and 17, General trend that subsoil (10 -20) have more micronutrient
than topsoil (0-10) was observed in both areas. Elevation does not affect the micronutrient
trend so much.
Zn content was also very low in both areas so that ICP could not measure the Zn amount( resulted in less than 0mg/L).
Some fields in different watershed/location showed different contents if seen eachelement (e.g. Maribel _01 and Pio_01 which in fferent location in Bangaan, have more
Fe than other fields.)- 48 -

Also, farming practices or irrigation water quality might affect the micronutrient (e.g. In
Verginia_03 in Bangaan, there is few Ni compared to others.)
Excess Cu content can be a pollutant if it’s constantly high, so needed to figure out thesource of Cu for proper and possible management. (Appx.1)
There is no specific trend in each element based on elevation, location and farming
practices. However, these results probably illustrate that Parents material mainly affectthe micronutrient contents. also Fe is strongly correlated with pH because pH contributeto these metal elements mobile (Figure 12)350.00300.00250.00Fe

200.00150.00100.00y = -153.04x + 1019.1
R² = 0.6378

50.00
0.00
0.0

2.0

4.0

6.0

pH

Figure 12 pH-Fe in Bangaan- 49 -

8.0

4. Conclusion and recommendation
This study aimed at figuring out the soil quality in Banaue and how affected byenvironment and human activities. Even the number of data was not sufficient, theanalysis had potential to figure out the soil quality at local scale and how they can improvetheir farming based on scientific data.
it was confirmed that chemical fertilizer affects the soil pH in Bangaan while double
cropping does not affect the soil properties. Also, it is found that different watershed has
different soil quality, but there is a trend of accumulation of OM, N and P in lower fields.
They increased as the elevation decreased significantly.
Most fields are applied only weeds, sunflowers and rice straw as fertilizer, however, thenutrient is not enough especially N and K that has high deficient rate. K and N should be
added more. For example, mixing Azolla and Blue green algae with soil is a way toincrease soil nutrient. Also, in order to decompose the rice straw before the seedlings neednutrient, it is recommended to drain some water and keep the rice straw buried into thesoil so that it decompose easily and make Nitrogen available to the plants.
Some farmers left the rice straw on the fields and clean them before sowing. It mightcause immediate reduction of soil and less nutrient supply to seedlings.
Each area has unique black color soil below villages and the soil was rich in OM and TN.
H2S might be produced that damage rice growth. In Bangaan the black soil was
distributed in small area so if waste water made the soil fertile, proper management ofwasted water can be addtitional fertilizer of the area and also the soil can be a buffer forcontaminated water from households. The temporary solution for this is also to drain thewater sometimes.
Lastly, farming plan should be improved reflecting the trend of the present soil quality.
From the results obtained, certain tendencies were found such as; movement of soil
nutrients downstream, effect of chemical fertilizer on the soil quality, and nutrient- 50 -

deficiency of a large portion of the area. Based on these results, farmers can know which
fields to prioritize.
In this way, from soil environment’s perspective, farming in the rice terraces are gonna
be more productive and sustainable.

Future task

To develop sustainable farming, more data gathering is strongly recommended to assess
the environment properly for crop production and conserve the land.
Interview was not enough to figure out yields and amount of organic fertilizer application.
Soil fertility would change easily during the fallow period influenced by fertilization
practices during plant seeding and growth periods in the plains (Li 1992). Further data
gathering, field survey during specific period such as planting season, harvest season,
typhoon season are necessary.

- 51 -

References
Acabado.S, 2015 Antiquity, Archaeological Processes, and highkand Adaptation The
Ifugao Rice Terraces
CUI Baoshan, 2010: Temporal and spatial distributions of soil nutrients in Hani terraced
paddy fields, Southwestern China, nternational Society for Environmental Information
Sciences 2010 Annual Conference (ISEIS), Procedia Environmental Sciences 2 (2010)
1032–1042
farmguru: Insecticides/Pesticides, Syngenta Insecticide Cymbush –https://www.store.farmguru.in/products/agro-chemicals-crop-protectioninsecticidespesticides/syngenta/syngenta-insecticide-cymbush/pid-11552122.aspx
Gomez,A.R, et al., 2005 Survey of the Damage in the Ifugao Rice Terraces and Its
Environmental Dynamics, The Philippine agricultural scientist , vol88, No.1, 133-137
IFSU, 2011; Ifugao Indigineous Knowledge (IK) Workbook
J.F. Parr, R.I et al, 1992 :Soil quality: Attributes and relationship to alternative andsustainable agriculture, America Journal of alternative agriculture, Volume 7, Numbers
1 and 2,
IRRI, Science of C4rice (http://photosynthome.irri.org/C4rice/index.php/19-about/57science-of-c4-rice , https://c4rice.com/the-project-2/ )Ngidlo,T.R (2014) Modern Farming Technologies: Impact on Farm Productivity andFood Security in the Rice Terraces of the Cordillera Region, Northern Philippines
American Journal of Experimental Agriculture, ISSN: 2231-0606,Vol.: 4, Issue.: 8 , 913921
NRCS Colorado, USDA, 2019https://www.nrcs.usda.gov/wps/portal/nrcs/detailfull/co/home/?cid=nrcs144p2_0630
20 (Visit October 15, 2019)
Roger.A.P ,1986, NlTROGEN-FIXlNG'PHOTOTROPHS IN THE IFUGA0 RICE

- 52 -TERRACES (PHILIPPINES) Phil Agri 69, 599-609
science india,
https://www.cropscience.bayer.in/en/Products-H/Brands/Crop-Protection/InsecticideSolomon.aspx (Insecticide-Solomon - Crop Science Indiacrop)
Sekiguchi Hirotaka, 2014:世界遺産を守る民の知識 フィリピン・イフガオの棚田と地域の学び
Sigari. A.T. et al., 2005: Soil Fertility Limitations of Ifugao Rice Terraces , Crop science28(1) 39-48, Crop Science Society of the Philipines.
UNESCO, Rice Terraces of the Philippine Cordilleras(https://whc.unesco.org/en/list/722/ ) Visit on September 3
United Nations,2015: A/RES/70/1 - Transforming our world: the 2030 Agenda for
Sustainable Development
Wang.Q ,2011: Soil Nutrient Distribution in Two Typical Paddy Terrace Wetlands Alongan Elevation Gradient During the Fallow Period, J. Mt. Sci. (2011) 8: 476-483 DOI:
10.1007/s11629-011-1122-yworld weather online: Banaue weather
https://www.worldweatheronline.com/banaue-weather-averages/ifugao/ph.aspx- 53 -

- 54 -

持続可能な営農を目的としたフィリピン・イフガオの棚田における営農と土壌環境の調査

環境生命科学研究科社会基盤環境学専攻
48501154 黒住知代

- 55 -

1.調査背景フィリピン・イフガオの棚田は世界遺産としても有名で 2000 年以上の歴史を持つとされている。しかしながら昨今，棚田の崩壊や，土壌劣化が深刻化していると考えられている。社会科学的アプローチを中心に行われてきた棚田の保全だが，土壌の観点からそれに言及した先行研究は少ない。そこで今回は，土壌の質をキーワードに現地での営農と土壌の環境について詳細に調査し整理した。また，調査結果をもとに持続可能な営農について提言することを目指した。
土壌の質とは，「特定の種類の土壌が自然または管理された生態系の境界内で機能する能力で，植物と動物の生産性を維持し，水と大気の質を維持または向上させ、人間の健康と居住をサポートする能力のことを指す。
（NRCS Colorado、USDA、2019）
土壌の質は現在、持続可能な農業の達成において極めて重要な位置を占めている。図 1 に示すように、土壌の質が農業の持続可能性の「鍵」である。土壌の質の指標または属性を、パラメータを選択して正確に評価する研究が今までにも数多く行われてきている。(J.F.Parr, 1992)

図.1 土壌の質が代替農業の戦略と持続可能な農業の橋渡しをする概念図

よって，以下の目的で今回の調査を実施した。
・Batad、Batad における土壌の化学物理性の評価
・どのような（営農要因・環境要因）が Bangaan、Batad における土壌の化学物
理性に影響を及ぼしているのかの考察- 56 -

・Bangaan、Batad の棚田における営農、営農管理方法の提案

2. 調査地概要と調査方法
調査地は，フィリピンにあるイフガオ州のバナウェ市，Bangaan と Batad で調査を行った。
これらの調査地の特徴は主に以下の 3 つである。
・有機農業が多い。
・村の土地利用が類似している（上流から森林，棚田，居住区，棚田）
・集落が棚田群内に存在しているため生活排水の影響が考えられる。

2.1 調査に用いたアンケートとインタビュー
インタビューには、筆者自作のアンケートを用いた。このアンケートは（1）農家の基本情報、（2）作物の基本情報、（3）営農に関する情報、（4）農地の特徴と、地域特有の取組に関する情報（5）サプライチェーンと設備の 5 つの大項目で構成され、質問に応じて、選択式の回答欄と自由記述欄を設けている。
また，追加で土壌に対する認識やその他現地で気になったことについてグルー
プディスカッションと個別の口頭インタビューを行なっている。

2.2 現地踏査、土壌サンプリング
図 2 に Bangaan の土壌サンプリング地点，図 3 に Batad の土壌サンプリング地
点を示す。

- 57 -

図2

Bangaan の土壌サンプリング地点

図3

Batad の土壌サンプリング地点

サンプリングのほか、灌漑設備の見学や、土壌の様子、サンプリングを実施しなかった他の圃場の様子についても観察を行った。調査中に村内で会った農家の方からもお話を伺い、営農・営農管理・農地管理・灌漑設備・地形、営農以外の土地利用に関する追加の情報を得た。

- 58 -

土壌は、2 深度（表層〜10cm、10〜20cm）に分けてサンプリングを実施した。0〜20cm が稲の根群域で作土層と考えられているためである。
また、圃場内の不均一性を平均化するため、各圃場では基本的に 2 地点から土壌を採取し、混ぜ合わせたのちに１試料とした。

2.3 土壌分析
土壌分析は表 1 に示す項目を実施した。
表 1 土壌分析項目と用いた手法
Analysis

Methods

含水比
土壌ｐH(1:1=土：水)

有機物

Walkley and Black 法

全窒素

Kjekdahl 法

可給態 P

Bray No.2 法

交換態 K, Ca, Mg

Quick 法可給態 Cu, Zn, Mn, Fe

DTPA 抽出 ICP-OAS

陽イオン交換容量(CEC)

Ammonium acetate 法

3. 調査結果と考察
表 2，3 に，各土壌の特徴を示す。
表 2 Bangaan の土壌情報
Group

Elevation (m)A

950 above- 59 -

Sampling site

Character

Maribel_01

DL-1, CFB

900-949C

850-899D

800 - 849

Pio_01DL-1, OF

Jose_01

OF

Christina_01

OF

Bato_01

OF

Ester_01

DL-2, OFJames_01

OF, DC

Verginia_03

OF, BS

Leticia_01

DL-2, OF

Conchita_01

OF

表 3 Batad の土壌情報
Elevation(m)Sampling site

CharacterA

950 aboveAna2_01OFB

900-949

Rodolfo_01

OFC

850-899

Tessie_01

OFD

800-849

Moises_01

CF

Ana1_01OFE

750-799

Hilda_01

OF, BS

Nancy_01

DL-1, OF

OF: Organic fertilizer CF: Chemical fertilizer BS: Black color soil DC: Double cropping
DL: Different location considered a watershed surrounding a village as a center. (samenumber refers to same watershed that separated by river or road)

次に，ｐH，OM，T N，C N 比を示す。C N 比に用いた有機炭素量は有機物の 58％と仮定して計算した。(Sparks,1996)

表4

土壌の基本特性 （ Bangaan）- 60 -

sample
depth

OM

TN

C/N
ratio

Group

sample site

(cm)

pH

（％）

（％）

A

Maribel_01

0-10

4.5

3.03

0.11

10.58

A

Maribel_01

10-20

4.8

1.37

0.10

10.20

A

Pio_01

0-10

5.0

3.50

0.18

10.74

A

Pio_01

10-20

5.1

3.27

0.16

6.62

B

Jose_01

0-10

5.6

2.91

0.15

19.26

B

Jose_01

10-20

5.7

0.44

0.06

14.59

C

Christina_01 0-10

5.5

2.90

0.16

14.97

C

Christina_01 10-20

5.4

1.12

0.10

14.53

C

Bato_01

0-10

5

3.25

0.18

11.06

C

Bato_01

10-20

5.2

2.98

0.17

10.87

C

Ester_01

0-10

5.5

7.38

0.29

11.40

C

Ester_01

10-20

5.5

6.89

0.27

4.28

C

James_01

0-10

6.2

3.82

0.20

12.34

C

James_01

10-20

5.8

3.45

0.18

12.35

C

Verginia_03

0-10

5.2

8.31

0.42

16.09

C

Verginia_03

10-20

5

7.54

0.34

8.08

D

Leticia_01

0-10

5.6

5.44

0.26

11.45

D

Leticia_01

10-20

5.4

4.31

0.20

12.86

D

Conchita_01 0-10

5.5

6.14

0.18

11.59

D

Conchita_01 10-20

6.1

5.42

0.22

12.24

- 61 -

表 5 土壌の基本特性（Batad）
sample
depth

OM

TN

C/N
ratio

sample site (cm)

pH

（％）

（％）

A

Ana2_01

0-10

5.4

4.08

0.20

11.82

A

Ana2_01

10-20

5.5

2.11

0.08

14.47

B

Rodolfo_01 0-10

5.3

2.79

0.13

12.44

B

Rodolfo_01 10-20

5.5

1.88

0.12

9.29

C

Tessie_01

0-10

5.6

3.90

0.14

16.56

C

Tessie_01

10-20

5.6

2.43

0.14

10.44

D

Moises_01

0-10

5.8

3.72

0.17

12.84

D

Moises_01

10-20

6.0

1.52

0.11

7.70

D

Ana1_01

0-10

5.8

5.44

0.21

14.83

D

Ana1_01

10-20

5.4

2.11

0.14

8.90

E

Hilda_01

0-10

5.8

6.34

0.41

8.91

E

Hilda_01

10-20

6.0

8.01

0.35

13.10

E

Nancy_01

0-10

5.4

2.01

0.17

6.76

E

Nancy_01

10-20

5.3

0.85

0.08

6.32

Group

- 62 -

表 6 土壌に含まれる元素（Bangaan）
sampleGroup sample site

Base

depth

AP

(cm)

(mg/kg)Ca

Mg(cmol/kg) (cmol/kg)

K

CEC

saturation(mg/kg)(cmol/kg)(%)

A

Maribel_01

0-10

4.63

14.50

6.87

2.19

29.28

80.46

A

Maribel_01

10-20

3.00

14.25

5.01

1.68

29.83

70.21

A

Pio_01

0-10

4.93

18.12

13.02

3.70

41.30

84.36

A

Pio_01

10-20

4.28

17.23

15.27

2.69

35.02

100.49B

Jose_01

0-10

12.02

24.61

11.78

2.19

40.84

94.47

B

Jose_01

10-20

7.53

23.95

15.58

3.20

43.34

98.59

C

Christina_01 0-10

5.02

21.54

10.89

2.69

35.51

98.94

C

Christina_01 10-20

3.42

20.97

14.46

4.21

36.30

109.19C

Bato_01

0-10

5.15

22.47

15.80

5.22

37.13

117.14C

Bato_01

10-20

5.07

22.50

13.86

3.20

41.95

94.30

C

Ester_01

0-10

21.95

19.35

11.18

2.19

44.88

72.90

C

Ester_01

10-20

18.56

21.62

11.81

1.68

41.92

83.78

C

James_01

0-10

21.81

23.89

14.66

18.86

40.37

142.20CJames_01

10-20

16.44

22.87

15.97

14.81

41.35

129.77

C

Verginia_03

0-10

19.51

18.97

13.35

3.20

32.13

110.52

C

Verginia_03

10-20

20.81

20.99

9.79

2.19

35.46

92.99

D

Leticia_01

0-10

14.14

21.09

8.62

5.72

36.40

97.36

D

Leticia_01

10-20

11.92

20.56

9.34

1.68

35.74

88.37

D

Conchita_01 0-10

14.31

21.01

11.32

2.69

39.23

89.26

D

Conchita_01 10-20

10.62

24.09

10.58

2.19

28.01

131.62- 63 -

表 7 土壌に含まれる元素（Batad）

sample
depth

Base
AP

Ca

Mg

K

CEC

saturationGroupsample site(cm)

(mg/kg) (cmol/kg) (cmol/kg) (mg/kg) (cmol/kg)(%)

A

Ana2_01

0-10

20.87

17.03

3.81

12.79

27.95

120.37A

Ana2_01

10-20

16.79

14.22

2.12

13.30

20.78

142.62B

Rodolfo_01

0-10

10.37

15.03

3.39

2.69

25.81

81.79

B

Rodolfo_01

10-20

10.37

14.80

5.43

2.69

25.64

89.40

C

Tessie_01

0-10

10.72

16.58

4.77

4.21

26.37

96.94

C

Tessie_01

10-20

6.74

14.72

4.67

1.68

27.22

77.40

D

Moises_01

0-10

13.48

16.39

7.06

8.25

28.50

111.22

D

Moises_01

10-20

10.72

14.54

5.96

2.69

25.23

91.91

D

Ana1_01

0-10

18.94

17.25

7.55

10.77

29.77

119.50D

Ana1_01

10-20

15.33

18.08

5.74

4.71

27.96

102.05

E

Hilda_01

0-10

10.88

17.35

5.98

4.21

37.45

73.53

E

Hilda_01

10-20

13.09

16.28

6.34

1.68

30.41

79.89

E

Nancy_01

0-10

6.01

16.05

6.56

7.24

28.25

105.65E

Nancy_01

10-20

5.96

15.20

4.33

3.20

26.95

84.34

- 64 -

表 8 土壌に含まれる微量元素（Bangaan）
sampleGroup sample site

depth

Fe

Mn

Cu

Ni

(cm)

(mg/L)(mg/L)(mg/L)(mg/L)A

Maribel_01

0-10

403.98

42.64

39.31

1.35

A

Maribel_01

10-20

395.47

74.10

68.95

1.55

A

Pio_010-10

272.75

79.70

74.03

3.02

A

Pio_01

10-20

317.17120.52113.81

3.03

B

Jose_010-10

144.41

12.76

12.78

0.15

B

Jose_01

10-20

150.04

21.17

20.28

0.25

C

Christina_01 0-10

168.46

5.93

6.76

0.42

C

Christina_01 10-20

120.23

9.37

9.86

0.70

C

Bato_010-10275.30

32.86

31.08

0.83

C

Bato_01

10-20

274.73

32.49

30.70

0.86

C

Ester_01

0-10

165.19

9.38

9.75

0.87

C

Ester_01

10-20

148.86

8.57

9.00

1.26

C

James_01

0-10

119.42

17.91

17.37

0.98

C

James_01

10-20

81.74

21.25

20.09

1.02

C

Verginia_03

0-10

192.04

20.60

19.65

0.06

C

Verginia_03

10-20

235.89

34.03

31.62

0.03

D

Leticia_01

0-10

144.88

18.92

18.20

0.93

D

Leticia_01

10-20

225.54

26.13

24.61

0.84

D

Conchita_01 0-10

131.456

13.887

13.9125

1.05

DConchita_01 10-20

133.2205

4.76855.7765

1.12- 65 -

表 9 土壌に含まれる微量元素（ Batad）
sampledepth
Groupsample site (cm)

Fe

Mn

Cu

Ni

(mg/L)(mg/L)(mg/L)(mg/L)

A

Ana2_010-10

249.48

44.79

41.41

0.55

A

Ana2_01

10-20

324.64

90.75

84.52

0.25

B

Rodolfo_01 0-10

319.58

54.94

50.68

0.29

B

Rodolfo_01 10-20275.09

56.23

51.64

0.43

C

Tessie_01

0-10274.46

74.40

69.13

0.48

C

Tessie_01

10-20

337.52

71.91

66.37

0.26

D

Moises_01

0-10

57.23

7.11

7.62

0.46

D

Moises_01

10-20

95.16

8.26

8.54

0.03

D

Ana1_01

0-10

91.16

2.91

3.97

0.20

D

Ana1_0110-20

101.02

3.78

4.72

0.15

E

Hilda_01

0-10

283.27

55.20

50.85

0.30

E

Hilda_01

10-20

220.51

96.64

90.28

0.29

E

Nancy_01

0-10

364.58

28.16

26.07

0.90

E

Nancy_01

10-20

441.48

29.58

27.24

1.19

＊Zｎは 0 に近い値をとり I C P での測定が不可能だったので，1 月に再測定のためデータなし。
以下に，特筆すべき結果を整理する。
Bangaan では，OM が 8.70%，TN が 52.2％，P が 34.8％，K が 78.3％，CEC が0％，Batad では OM が 14.29%，TN が 71.43％，P が 7.14％，K が 71.43％，CECが０％割合で適正範囲外の値をとった。
C E C は全域で基準値を満たしており，土壌栄養を保持する能力が高いことがわ

かる。C E C が高いのは粘土鉱物の組成と O M と T N，そして P は流域ごとに見ると，下流ほど表層有機物が増加する傾向が見られた。Batad では特に傾向が- 66 -

見られなかった。OM が８％を超えたのは，どちらの地域でも⿊⾊の下流部の土壌であった。灌漑水の違いあるいは管理の頻度（圃場にいくまでが遠い）が関与していると考えられた。
次に，ｐH について見る。
湛水下では，酸性土壌におけるｐH の上昇が起きる（Sigari，2003）。植物が取り込む炭酸水素イオンが，光合成のために二酸化炭素と水酸化物イオンに分解され，葉の上部より放出されることが原因の一つである。
（臼井，2013）
また Roger（1984）は Banaue での研究で標高とｐH には負の相関があることを明らかにしている。今回も標高とｐH の負の相関は，Bangaan では多少見られた。
決定係数は Bangaan で０.37，Batad で 0.07 であった。
また，Ngidlo（2014）などの主張した化学肥料の使用による土壌ｐH の低下は，今回も確認された。しかしながら，Gomez の主張よる伝統農法で P とＯM が有意に多いという傾向は，確認されず，OM の大小は農法よりも地域と標高による違いが顕著であった。

0.50

0.50

0.30

y = 0.036x + 0.0479

0.40

y = 0.0433x + 0.0297

R² = 0.8695

0.30

R² = 0.7945

TN

TN

0.40

0.20
0.10

0.20
0.10
0.00

0.00
0.00

5.00

10.00

0.00

5.00

10.00

OM

OM

図 4 OM-TN （ Bangaan）

図 5 OM-TN （ Batad ）- 67 -

インタビュー・現地調査での観察
インタビュー
アンケート結果については，今回特筆すべき内容以外を省略する。ここでは，グループディスカッションと，口頭でのインタビューで得られた知見について簡単に整理する。
土壌と営農の認識について調査を行ったところ，肥沃な土壌についての認識は農家によってまちまちであり，共有されていない，あるいは体系的な知識となっていないことが明らかになった。
また，化学肥料の利用については，土壌劣化，生物多様性の損失につながるという考え方が一般的であった。
一方で，収量が少なく自分たちの食べるコメも賄えていない現状があること，出稼ぎでマメな管理ができないことから化成肥料を使用している農家も 34 人中３名見られた。
現地調査での観察
特徴的な土壌としては、⿊っぽい土壌が農村の直下部にどちらの地域でもみられた。特に Batad は最下流までに棚⽥が多く、広範囲で⿊っぽい土壌が見られた。これは灌漑水に生活排水が混合している可能性が高く，土壌が排水に含まれる物質を吸着していると考えられる。また，このような土壌では，耕盤と考えられる水⽥の底（足がつくところ）が深いところにあり，ある圃場では，礫を敷き詰めていることもあった。
（なぜ敷き詰めているのか聞く必要あり）下水施設が整っていない分，汚水に含まれる物質が土壌の栄養の供給源となっていることが考えられた。物質循環の視点で見ればサステイナブルともいえるが，それが原因で営農がしにくい，硫化水素の発生でイネ が育たないなどの問題になっているという問題もみられることから適切な管理を行うことにより，域内での物質循環をより効率的に営農に活用できる可能性がある。
その他，9 月，10 月の調査時には，代かきしている棚⽥もあれば，まだ収穫後のイネの株がそのままになっているところもあった。この作業のスピードは圃場
と農家の家の距離に多少依存しているようであった。種まきの直前に代かきを行っても，イネ藁が急激に分解され過還元になったり，分解されずに苗に栄養が十分供給されないことがあったりするので，収穫後のイネ藁は迅速に処理する- 68 -

必要がある。日本では，⽥から水を抜き，気温の高い秋のうちにイネわらのすき込みを行う。またコンバインを使うことでイネわらを細かく裁断することも可能である。Banaue でも，⽥植えに向かうに従って気温が低下するので，収穫直後に，イネわらのすき込みを行うのが望ましいと考えられる。また，どちらの地域でも，「土壌表面の乾燥を防ぐために湛水している，あるいは，湛水したいが，水がないのでできない」という課題を伺った。⻲裂を防ぐために必要な水を供給する，あるいは，土壌の乾燥を防ぐ手段があるといい。尚，湛水を止めると雑草が繁茂する。⽥植えまでに雑草をきれいにしなければならないので手間はかかるが緑肥として施肥することが可能である。一方雑草の繁茂している圃場では⻲裂が見られ，湛水している土壌より大きな⻲裂が⼊り，そこへ水が流れ込んでいるのが確認できた。雑草が繁茂していてもマルチの代用として土壌表面からの蒸発を防ぐことはならないようだ。

4. 結論と提言
今回は，営農と地形的要因を踏まえて Banaue の土壌の質について，どのような分布を示すか，そしてどのような課題が見られるかを明らかにしようとした。土
壌の質は，作物の生産性だけでなく，環境保全機能など土壌が持つ機能がどの程度働いているのかを示すものであり，その中でも今回は土壌の化学性に焦点を当てて，分析を行い先行研究との比較を中心に考察を行った。その結果データ数は少なかったものの，化学肥料の使用による土壌の性質変化に関しては概ね先行研究と同様の結果が得られたが，先行研究にない新たな傾向は見られなかった。
今回の 2 地域で特徴的だったのは，O M が総じて多いことほとんどの土壌が酸性を示していること，N と K が少ないこと，C EC が高いことが挙げられる。また OM，T N，P は下流に行くに従い増加する傾向が見られたことから土粒子とともに移動している，あるいはリーチングが起きていると考えられた。
土壌栄養の飢餓を改善するためには，域内で未活用の資源を利用することも考えるべきであり，現地踏査の結果から Azolla と Blue green algae のすき込みは効果的であると考えられた。また，稲ワラは C N 比の高いこと，生活排水による影響か有機物が村直下の棚⽥で過剰であることが確認され，土壌が⿊っぽくな- 69 -

っていることから，排水を定期的に行うことで，可給態の窒素量を増やす，有機物量を適量にし，過還元を防ぐといった対策ができるだろう。今回分析したのは化学性のデータのみのため，土壌中での元素の動態，化学反応については勉強不
足の部分が多く，研究方針によっては更なる文献調査が必要である。
さらに営農の記録と細かなサンプリングを行う必要が出てきた場合は，農家の協力を得るのが望ましい。

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引用・参考文献
Acabado.S, 2015 Antiquity, Archaeological Processes, and highkand Adaptation The
Ifugao Rice Terraces
CUI Baoshan, 2010: Temporal and spatial distributions of soil nutrients in Hani terraced
paddy fields, Southwestern China, nternational Society for Environmental Information
Sciences 2010 Annual Conference (ISEIS), Procedia Environmental Sciences 2 (2010)
1032–1042
farmguru: Insecticides/Pesticides, Syngenta Insecticide Cymbush –https://www.store.farmguru.in/products/agro-chemicals-crop-protectioninsecticidespesticides/syngenta/syngenta-insecticide-cymbush/pid-11552122.aspx
Gomez,A.R, et al., 2005 Survey of the Damage in the Ifugao Rice Terraces and Its
Environmental Dynamics, The Philippine agricultural scientist , vol88, No.1, 133-137
IFSU, 2011; Ifugao Indigineous Knowledge (IK) Workbook
J.F. Parr, R.I et al, 1992 :Soil quality: Attributes and relationship to alternative andsustainable agriculture, America Journal of alternative agriculture, Volume 7, Numbers
1 and 2,
IRRI, Science of C4rice (http://photosynthome.irri.org/C4rice/index.php/19-about/57science-of-c4-rice , https://c4rice.com/the-project-2/ )Ngidlo,T.R (2014) Modern Farming Technologies: Impact on Farm Productivity andFood Security in the Rice Terraces of the Cordillera Region, Northern Philippines
American Journal of Experimental Agriculture, ISSN: 2231-0606,Vol.: 4, Issue.: 8 , 913921
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0 (Visit October 15, 2019)
Roger.A.P ,1986, NlTROGEN-FIXlNG'PHOTOTROPHS IN THE IFUGA0 RICE

- 71 -TERRACES (PHILIPPINES) Phil Agri 69, 599-609
science india,
https://www.cropscience.bayer.in/en/Products-H/Brands/Crop-Protection/InsecticideSolomon.aspx (Insecticide-Solomon - Crop Science Indiacrop)
Sekiguchi Hirotaka, 2014:世界遺産を守る民の知識 フィリピン・イフガオの棚田と地域の学びSigari. A.T. et al., 2005: Soil Fertility Limitations of Ifugao Rice Terraces , Crop science28(1) 39-48, Crop Science Society of the Philipines.
UNESCO, Rice Terraces of the Philippine Cordilleras(https://whc.unesco.org/en/list/722/ ) Visit on September 3
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Sustainable Development
Wang.Q ,2011: Soil Nutrient Distribution in Two Typical Paddy Terrace Wetlands Alongan Elevation Gradient During the Fallow Period, J. Mt. Sci. (2011) 8: 476-483 DOI:
10.1007/s11629-011-1122-yworld weather online: Banaue weather
https://www.worldweatheronline.com/banaue-weather-averages/ifugao/ph.aspx- 72 -

感想
今回の調査を通じて，海外で研究に必要なプロセスを一通り体験することができた。
まずは問題の発見，そしてそれに取り組むための手段を模索した。次に，どのような情報が必要かを精査すること，そして必要な情報をいかに正確に効率的に取得するかということを計画し，実践的に学ぶことができた。また，現地でしかわからないことを整理しどのように分析や考察につなげていくかという筋道を立てていく発表や報告書作成までの過程も，大変であったが，やりがいもあった。
現地では，電気や水が途切れやすい不自由な生活，そして土壌サンプリングなどの力仕事もあり，身体的・精神的疲労も多く，自己管理と現地の方の協力を得る
ことは非常に重要だと感じた。実際，アンケートやインタビューなどは現地の方に通訳をしてもらいながらデータをとっており，労力はかかったが，その分貴重なデータが得られたと思う。
また，今回は自分が今まで行ったことのないアンケート調査や分析なども実施している。これにはフィリピン大学ロスバニョス校の先生，技官の方々に大変お世話になった。皆様がいなければ自分が今回データを得ることもできなかった。
日本で発表を来てくださった方々の協力もありがたい。この授業を通してそういった手法であったり得られた結果を多くの方に見ていただけたりしたこと，
そして専門分野の異なる各先生から有益な助言をいただけたことは非常に有益であったと思う。
今回の調査で改めて，国際研究を行う際にどのように研究を進めていくべきか，また，国境をこえて研究をすることで得られるものを実感することができた。
この経験を，これから自分の修士研究を進めてまとめ上げていく上でも，卒業後の就職でも役立てていきたいと考えている。
ひとまずは今回の調査を生かして，自分の修士研究をさらにより良いものに，そして社会と現地のニーズにあったものになるようにこれからも研究に邁進していきたい。

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