IJERD – International Journal of Environmental and Rural Development (2015) 6-2

Research articleerd

Evaluation on Agro-forestry System in Salt Affected andNon-salt Affected Areas
JEERANUCH SAKKHAMDUANG
Institute of Environmental Rehabilitation and Conservation, Southeast Asia Office, Thailand
Email: j.sakkhamduang@gmail.com

MACHITO MIHARA*
Faculty of Regional Environment Science, Tokyo University of Agriculture, Tokyo, Japan /Institute of Environmental Rehabilitation and Conservation, Tokyo, Japan
Received 22 December 2014

Accepted 20 May 2015(*Corresponding Author)

Abstract Low economical return is the main constraint that makes farmers not grow more trees
in salt affected areas. So, the research interest was paid to the applicable agro-forestry system
combining advantages of trees and crops for rehabilitating salt affected soils and increasing
local farmers’ income. Accordingly, existing agro-forestry systems in salt affected and non-salt
affected areas in Khon Kaen province were investigated and evaluated. For the evaluation, theplant profile of each system was described in the investigation plot at 20m x 20m. In addition,
Simpson and Shannon indexes were used to evaluate plant diversity of each investigation plot.
Agro-forestry systems on salt affected areas could be categorized into five types: patch forests
in farmlands, trees on paddy bunds, tree plantations associated with animal husbandry, homegardens, and trees in vegetable gardens. On the other hand, agro-forestry systems in non-salt
affected areas could be categorized into seven types: trees in farm boundaries, trees on paddybunds, tree plantations associated with animal husbandry, trees in home gardens, trees invegetable gardens, trees in fruit orchards, and trees and aquaculture. The results of the twoindexes revealed that the diversity of plants in agro-forestry systems in non-salt affected areas
was higher than that in salt affected areas, except in the systems of tree plantations associatedwith animal husbandry and of trees in home gardens. It was considered that as the plant
diversity in salt affected areas was lower than that in non-salt affected areas due to soil salinity;
local people in salt affected areas kept higher plant diversity in the systems of tree plantations
associated with animal husbandry and of trees in home gardens for their livelihoods.
Keywords agro-forestry system, salt affected and non-salt affected areas,
Simpson diversity index, Shannon diversity index

INTRODUCTION
Reforestation by fast growing trees for lowering saline groundwater level is one of practices that can beapplied by local people for rehabilitating salt affected soil in northeast, Thailand (Yamklee et al, 1995;
Wada, 1998; Yuwaniyama, 2011). Several organizations in Thailand and overseas introduced theutilization of salt-tolerant trees and plants to solve or to mitigate salinization problem. However, local
farmers have not adapted planting trees, as it takes long time to gain the profit (Vittayakorn et al.,1994). Thus, the applicable practice that combines the advantage of growing trees for mitigating salt
affected soils along with generating income should be considered to introduce to local people.
Agro-forestry is an interface between agriculture and forestry and encompassed mixed land use
practices. Agro-forestry practices are ranging from simple forms of shifting cultivation to complex
hedgerow intercropping systems. All agro-forestry systems have the purposeful growing trees withⒸISERD54

IJERD – International Journal of Environmental and Rural Development (2015) 6-2

crops and/or animals for multiple products or benefits from the same management unit. Agro-forestry
also has three attributes: productivity, sustainability, and adoptability (Nair, 1993).
Agro-forestry systems for rehabilitating salt affected soils are widely applied in several countries
such as Australia, Bangladesh, and China, and India (Singh et al., 2002; Zang et al., 2004; Ahmed,1991; Eastham et al., 1993).
Agro-forestry in Thailand has been practiced for a long time since the Forest Village Scheme wasintroduced by the Forest Industries Organisation of Thailand (FIO) in 1967 as an attempt to stop
further spreading of the fast shifting cultivation and deforestation in the country (Boonkird et al., 1984).
In Nakorn Ratchasima province, Im-Erb et al. (2004) reported that an agro-forestry system being
promoted in recharge area of the province for mitigating salt affected soils was well accepted by
farmers according to their additional income. In 2007, Ruaysoongern studied about agro-forestry
systems in the northeast of Thailand and categorized into 25 systems.
While there were some researches regarding agro-forestry systems in Thailand, there were a few
investigations focusing on agro-forestry practices in salt affected areas. The objectives of this study
were to categorize and evaluate the existing agro-forestry systems in salt affected and non-salt affectedareas in Khon Kaen province.
Salt affected and non-salt affected areas are defined by the salinity level of soils. Salinity level in
Thailand is defined by percentage of salt crust on soil surface in dry season. The area that salt crust
covers more than 50% is defined as very severely affected class, and the salt crust covers 10-50% isdefined as severely affected class, and for the 1-10% as moderately affected class and non-salt crust is
defined as non-salt affected area (Arunin, 1998).
METHODOLOGY
Field investigation on existing agro-forestry practices in salt affected areas and non-salt affected area
were conducted in September, 2009 and March 2013 in Khon Kaen province, Thailand. Aerial maps
were used for identifying the land utilization. After the land utilization was identified, agro-forestry
practices were categorized based on the studies of Ruaysoonngern (2007) and Nair (1993). Thesampling plots of 20m x 20m were made for observing plant profiles of each practice. For thecomparison of agro-forestry in salt affected and non-salt affected areas, Simpson diversity index andShannon diversity index were employed in this research. The Simpson diversity index is theprobability of any two individuals drawn at random from an infinitely large community belonging tosame species. The Shannon diversity index assumes that individuals are randomly sampled from anindefinitely large population and also assumes that all species are represented in the sample.
Simpson diversity index (1949)

𝑠(𝑃𝑖 2 )𝐷=

where𝑖=1

and Shannon’s index (1949)

𝑠′

𝐻 =−
𝑖=1

where(1)

D = Value of Simpson’s diversity index
Pi = proportion of individuals in the ith speciess = number of species𝑛𝑖𝑛𝑖{( ) ∙ ln( )}𝑁𝑁H’ = Value of Shannon’s diversity index
Pi = proportion of individuals in the ith species
ln = natural logarithms = number of species in communityⒸISERD55(2)IJERD – International Journal of Environmental and Rural Development (2015) 6-2

The indexes were used for calculating diversity index of each sampling plot. Moreover, hearing
survey to farmers regarding their land utilization were also conducted.
Research Sites
Salt affected areas: Phra Yun district is one of the salt affected areas of Khon Kaen province.
According to Regional Environment Office 10, Khon Kaen reported that salt affected areas cover 6,095
hectare or around 35 percent of the district area (REO 10, 2003). Agriculture is the main occupation ofpeople in the district while paddy rice and sugarcane are the main agricultural products (Phra YunCommunity Development Office, 2012).
Non-salt affected areas: Nong Rue district is one of the non-salt affected areas of Khon Kaen
province. Agriculture is the main occupation of the people in the district while paddy rice, cassava, veg
etable, and sugarcane are main agricultural products (Nong Rue Community Development Office, 2012).

Non salt affected area
Salt affected area

Fig. 1 Study areas
RESULTS AND DISCUSSION
Salt Affected Areas
Land uses in the salt affected areas were classified into paddy field, upland field, patch forest along thestream, settlement area, and bare area. Five agro-forestry systems were found in salt affected areas.
Patch forest in farmland was a small area of natural forest surrounded by naked land or farmland, as thenatural Dipterocarp trees were kept in farmland for collecting fuelwood and being source of timber, as
well as food such as leaves, flowers, shoots, and mushrooms. The samples of tree from patch forests
were Sindora siamensis, Dipterocarpus obtusifolius, Xylia xylocarpa, and Lannea coromandelica.

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IJERD – International Journal of Environmental and Rural Development (2015) 6-2

Farmers in the northeast of Thailand preferred to keep trees in their paddy bunds formultipurposes. Trees found in the paddy bunds were considered important due to their commercialvalue. Shorea obtusa was the dominant tree found in the paddy bunds. Farmers with large areas plantedtrees and let their cows graze in the plantation for weed control. The cows also provided naturalfertilizer for trees in the plantations. The samples of trees from the plantation were Eucalyptus
camaldulensis, Tectona grandis, and Pterocarpus macrocarpus.
20 m

20 m

2211555355535555113355200

5112555554500
20 m
21125Fig. 2 Trees in home gardens

20 m

As shown in Fig. 3, farmers planted several kinds of tree in their home garden. The examples oftree in the home gardens were Bambusa bambos, and Thyrsostachys siamensis, S. siamensis andAzadirachta indica. Fast-growing Anthocephalus chinensis was found to be used for temporaryconstruction materials and Pennisetum purpureum for fodder. In vegetable gardens, farmers planted
several kinds of tree together with vegetables. The trees of Mangifera indica, Cocos nucifera, Musasapientum,and Anthocephalus chinensis were used as edible fruits and temporary construction
materials.
Non-salt Affected Areas
Land uses in the non-salt affected areas were classified into paddy field, upland field, trees plantation, water
bodies, fruit orchards, and settlement area. Agro-forestry systems in non-salt affected area could be
categorized into seven types.
Farmers often grew trees for indicating farm boundary because it was cheaper than construct farmfence. Trees that mainly grew for indicating farm boundary were valuable trees or fast growing ones
such as E. camaldulensis, A. indica, and Bambusa sp. In the sampling plot, P. marcrocarpus weregrown for indicating boundary of sugarcane farm.
20 m20 m

020 m

020 mFig. 3 Trees in home gardenⒸISERD57

IJERD – International Journal of Environmental and Rural Development (2015) 6-2

Trees on paddy bunds were kept for several purposes. Aside from natural trees, in non-salt
affected area farmers also grew fast growing trees for economical purpose. In the sampling plot, E.
camaldulensis and A. indica were grown on the paddy bund for economical purpose. Farmers who had
enough farmland grew commercial trees in large area and let their cows graze in the plantation forweed control. Besides weed control, cows also provided natural fertilizer for the trees in the plantations.
The sample of the tree from the plantation was E. camaldulensis.
As shown in Fig. 3, home gardens consisted of various kinds of tree for foods, construction
materials, fuel wood, and material for handicraft. The samples of trees in the home gardens were B.
bambos for construction and handicraft, garden fences; Cocos nuciferus and Musa sapientum for food;and Cyperus alternifolius for weaving mat. In vegetable gardens, several kinds of trees were planted
together with vegetables. For this agro-forestry practice, 18 species of plants were found included trees
such as fruits trees and timber trees for construction materials.
Farmers grew trees and mixed them with fruit trees for several purposes. In fruit orchard, trees
were grown and resulted in multi-storey pattern, the highest tree P. macrocarpus and Tamarindus
indica provided shade to Annona squamosa and Dimocarpus longan while B. bambos was the middle
storey. Two of agro-forestry practices that commonly applied in non-salt affected areas were trees andaquaculture. In this practice, several kinds of trees were grown around fish pond for fruit, construction
material, and shadow. Moreover, trees around fish pond also provided shade that decreased
evaporation. Trees found in this practice included; P. macrocarpus, Mangifera indica, A. indica,Borassus flabellifer, Leucaena leucocephala and Erythophleum succirubrum.
Trees found on the paddy bund in salt affected areas were the trees surviving from the forest whiletrees found on paddy bund in non-salt affected area were domesticated or new introduced trees. The
result was similar to Vityakon (1993) finding that surviving trees were once a part of dry Dipterocarp
forest while the domesticated or new introduced trees were grown intentionally.
Comparison of Agro-forestry System in Salt Affected and Non-salt Affected Areas
The results of the field investigation of agro-forestry systems in salt affected and non-salt affectedareas in Khon Kaen province indicated that the agro-forestry systems as well as plant varieties in salt
affected areas had a lower variety than that in non-salt affected areas.
Table 1 Simpson and Shannon diversity indexes of plant species found in each agro-forestry
system in salt affected and non-salt affected area
Salt affected area

Non-salt affected area

Practice

1/D

ShannonDiversityindex

1. Patch forests in farmland

2.666

1.165

nonobserved
1.001

nonobserved
0.004

4. Tree plantation associatedwith animal husbandry

1.134

0.279

4. Tree plantation associatedwith animal husbandry

5. Trees in home garden

2.909

1.098

6. Trees in vegetable garden

3.111
nonobserved
nonobserved

1.174
nonobserved
nonobserved

2. Trees on farm boundary
3. Trees on paddy bunds

7. Trees in fruit orchard
8. Trees and aquarculture

1. Patch forests in farmland

nonobserved

ShannonDiversity
index
nonobserved

2. Trees on farm boundary

1.04

0.097

3. Trees on paddy bund

1.002

0.01

10

5. Trees in home garden

1.006

0.024

6. Trees in vegetable garden

34.7350.512

7. Trees in fruit orchard

3.459

1.284

8. Trees and aquarculture

9.142

1.126

PracticeⒸISERD58

1/D

IJERD – International Journal of Environmental and Rural Development (2015) 6-2

Moreover, total plant species, as well as plant numbers that were found in agro-forestry systems insalt affected area were lower than that in non-salt affected area. The results of Simpson diversity index
and Shannon’s index revealed that the diversity of plants in agro-forestry systems in non-salt affected area
were higher than that of in salt affected area except in the practices of tree plantation associate with animalhusbandry and trees in home garden (Tables 1).
CONCLUSION
The agro-forestry systems found in salt affected areas consisted of five practices while in non-salt
affected areas consisted of seven practices. Simpson diversity index and Shannon’s index revealed thatthe diversity of plants in agro-forestry systems in non-salt affected area were higher than that of in salt
affected area except in the systems of tree plantation associate with animal husbandry and trees in homegarden. Based on the investigated results, it was suggested that the suitable agro-forestry system withhigher varieties of plant be introduced in salt affected area.
It was suggested that farmers in salt affected area increase the diversity of tree species especiallysalt tolerant tree together with salt tolerant or halophyte vegetable or field crop in each agro-forestry
practice in salt affected areas for increasing plants diversity and income, as well as rehabilitating salt
affected soil.
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