Geoderma 136 (2006) 64 – 74
www.elsevier.com/locate/geoderma
Farmers' knowledge of soils in relation to cropping practices:
A case study of farmers in upland rice based slash-and-burn
systems of northern Laos
Kazuki Saito a,⁎, Bruce Linquist b , Bounthanh Keobualapha c ,
Tatsuhiko Shiraiwa a , Takeshi Horie a
a
b
c
Graduate school of Agriculture, Kyoto University, Kyoto 606-6502, Japan
Department of Plant Sciences, University of California, Davis, 95616, USA
Provincial Agriculture and Forestry Office, Luang Prabang, Lao PDR, Laos
Received 21 February 2005; received in revised form 8 February 2006; accepted 10 February 2006
Available online 19 April 2006
Abstract
Understanding indigenous knowledge of soils has come to be seen as essential in understanding the local realities of farmer and
may be critical for the success or failure of agricultural development. However, little effort has been made to capture the indigenous
knowledge of upland farmers in northern Laos where many projects are working to develop sustainable crop production systems as
alternatives to slash-and-burn systems. This paper discusses the indigenous knowledge of Loum and Khamu slash-and-burn
farmers in relation to soil quality and cropping practices. Most farmers interviewed distinguished two or more soils in their field.
When farmers were asked to describe their soils, farmers took a holistic view and not only discussed the soil (primarily color or
texture) but also the occurrence of weeds on the soil and the quality of burn. Glutinous rice, their staple food, tended to be planted
on good soils, while non-glutinous rice and cash crops (i.e. Job's tears and sesame) were planted on poor soils. Farmers'
classification of soils showed good correlation with soil chemical and physical analysis and agronomic performance. For example,
color was the most common descriptor of soils. Black soils, which farmers ranked highest in preference, had higher pH, total N,
total C and CEC levels than the other color soils. Also, upland rice yields were significantly higher on black soils compared to other
soils. Such information can facilitate collaboration between farmers, extension workers and researchers to improve crop production
systems and the use of soil and natural resources.
© 2006 Elsevier B.V. All rights reserved.
Keywords: Upland rice; Indigenous knowledge; Laos; Slash-and-burn; Soil
1. Introduction
Indigenous knowledge of soils is defined as “the
knowledge of soil properties and management pos⁎ Corresponding author. Present address: Africa Rice Center
(WARDA), 01 B.P. 2031, Cotonou, Benin. Tel.: +229 21 35 01 88.
E-mail address: [email protected] (K. Saito).
0016-7061/$ - see front matter © 2006 Elsevier B.V. All rights reserved.
doi:10.1016/j.geoderma.2006.02.003
sessed by people living in a particular environment for
some period of time” (WinklerPrins, 1999). Local
farmers have acquired knowledge from generations of
experience and experimentation, as they have had to
adapt their agricultural systems using limited resources
under harsh and insecure conditions. Understanding
such knowledge is essential to understand the local
realities of farmers and can be critical for the success or
K. Saito et al. / Geoderma 136 (2006) 64–74
failure of agricultural development (WinklerPrins and
Sandor, 2003). Recent research has shown that there are
significant similarities and complementarities between
indigenous knowledge of soils and scientific understanding of soils in Africa (Birmingham, 2003; Gray and
Morant, 2003) and Asia (Tamang, 1993; Shah, 1995;
Hirai et al., 2000, 2003) indicating potential synergism,
especially for solving problems related to soil and land
management (Barrera-Bassols and Zinck, 2003). Some
researchers have found that use of indigenous knowledge facilitates soil survey and land evaluation for
agricultural development and increases the probability
that resulting projects will meet community needs and
respect cultural values (i.e. Furbee, 1989; Gonzalez,
1995; Habarurema and Steiner, 1997; Steiner, 1998;
Gandah et al., 2000; Barrios and Trejo, 2003).
Little effort has been made to capture the acquired
knowledge of upland farmers in northern Laos where
upland rice has been grown for centuries in slash-andburn systems. Upland rice accounts for about half of the
total rice area in northern Laos (National Statistical
Center, 2004). Farmers do not apply fertilizer to upland
rice but have traditionally relied on extended fallows to
restore soil fertility and to reduce problems from insects
and weeds as slash-and-burn farmers have done in other
tropical agricultural systems (Nye and Greenland,
1960). However, rapid population growth and the
government policies of land allocation (limiting farmers
to three or four parcels of land) to protect forests from
slash-and-burn are resulting in shorter fallows and the
need to change management practices in order to ensure
sustainability. Roder et al. (1997) reported that fallows
decreased from 38 years during the 1950s to 5 years in
1992. In a 2002 survey, farmers reported fallows of only
2 or 3 years, which is in line with current land allocation
policies (Trosch, 2003). Shortened fallow periods have
rendered these systems unsustainable as soil quality
(due to nutrient depletion and erosion) is declining,
weed pressure and labor inputs are increasing, and
yields are declining with the end results being lower
returns on productivity and increased poverty (Asian
Development Bank, 2001; Linquist et al., 2005; Saito,
2005). The major soil fertility constraints in the Lao
uplands are low N and P supply (George et al., 2001;
Roder, 2001; Saito et al., 2006a,b).
Soil characteristics, rainfall and temperature vary
considerably, over short distances in the hilly region of
northern Laos. The scale of most soil maps is too coarse
to take these variations into consideration, thus limiting
their usefulness for soil and crop management options.
Extension recommendations are only relevant for farmers
if they take into account site specific environmental
65
factors. Thus, understanding and using farmer knowledge
can improve the quality of extension recommendations.
The objectives of this study were to (1) describe the
current upland rice slash-and-burn systems in northern
Laos, (2) describe how upland farmers name, describe
and evaluate their soils, (3) determine how farmers
manage their cropping systems in relation to their soils,
(4) test whether their description of soils is related to the
soil chemical and physical properties, and (5) test the
relationship between farmers description of soils and
upland rice productivity. The study was conducted with
Loum and Khamu ethnic groups in Luang Prabang
province in 2001 and 2002 and used a combination of
farmer surveys, soil tests and crop cuts (measuring yield
from a specified area at harvest).
2. Materials and methods
2.1. Description of study area
The study area was 30 to 60 km north of Luang
Prabang city in Pak Ou district, Luang Prabang province
in northern Laos (Fig. 1). This province has the highest
proportion of slash-and-burn upland rice cultivation in
Laos (National Statistical Center, 2004).
The climate is intermediate between tropical and subtropical wet and dry, and rainfall is erratic with an
average of 1300 mm year− 1. Rainfall in 2001 and 2002
was adequate with no extended dry spells. The amount
of rainfall recorded in one of the study villages
(Houayluang) between May and October was 1362
and 1261 mm in 2001 and 2002, respectively.
The land allocation process was started in this area in
2000. Under this government program, farmers are
generally allocated three or four parcels of land. Since
farmers are restricted to these parcels, the maximum
fallow duration can only be 2 or 3 years. During the
study period, villages were in different stages of the land
allocation process and some of them had not yet begun.
Upland farmers in these villages are mostly Loum or
Khamu in ethnicity, the most common ethnic groups in
Luang Prabang province. The major upland crop in
northern Laos (and also for these ethnic groups) is rice,
which has been grown for generations under slash-andburn systems. Loum and Khamu farmers grow primarily
glutinous rice, which is used for household consumption. In these systems, farmers begin land preparation by
slashing fallow vegetation in January and February and
burning it in March and April. Following burning, there
is no further land preparation. Rice is planted in late
April through May. Seed is dibble planted by planting
seeds into cone shaped holes made in the soil using a
66
K. Saito et al. / Geoderma 136 (2006) 64–74
Fig. 1. Location of the study site in Pak Ou district, Luang Prabang province, Lao PDR.
sharp stick (dibble stick). Each of these holes is referred
to as a “hill” of rice. In general, 10 to 20 rice seeds are
planted in each hill and there is 4 to 15 hills m− 2.
Farmers generally weed two to four times a season. Rice
is harvested from early September through October.
The study involved interviews and fieldwork in 10
villages in 2001 and 2002. Loum villages were Hatxua,
Latthahai, Pakchack and Phathung, and Khamu villages
were Hatmat, Houaylat, Houaykhaw, Houayluang,
Houaytham and Somusanuk. Survey and field studies
were conducted in collaboration with staff from the
District Agriculture and Forestry Office. The language
used was mainly Lao and a farmer having good
knowledge of Lao served as a translator when necessary.
In field study, fallow length in the fields ranged from 2 to
15 years and the fields lie at altitudes of 300 to 550 m asl.
2.2. Survey on farmers knowledge of soils in relation to
cropping pattern
A survey to gather information on farmers' knowledge of upland soils and crops was conducted with 233
K. Saito et al. / Geoderma 136 (2006) 64–74
randomly chosen households (Loum: 138 and Khamu:
95 households). Of the informants 180 were men and 53
were women. In most households, the man is considered
the head of the household. Where women informants
were surveyed no distinction was made as to whether or
not they were the head of the household (women become
the head of the household in cases such as when her
husband dies). The questionnaire focused on the major
crops grown by farmers and the soils that these crops
were grown on. Minor crops and crops that were
intercropped with upland rice or grown along pathways
were not discussed. For the major crops, the area planted
to each crop was determined by the amount of seed
planted. Farmers were generally unsure about units of
area but knew precisely the amount of seed they planted.
While plant density varies, this estimate of area was
adequate for the purposes of this study. Since upland rice
is the most common crop and the crop for which the
farmers had the greatest knowledge, a greater amount of
detail was asked about it. Rice varieties are most often
characterized by crop duration (do, kang and pi mean
early, medium and long duration, respectively) and grain
size (i.e. met nyai and met noi mean large and small grain
size, respectively). Farmers were asked to distinguish
and name the different soil types in their field. For those
farmers who identified two or more soil types in their
field, they were asked to rank their soils in terms of
preference and quality and indicate what crops they
planted on each soil and why. Interviews were conducted
with farmers after planting and were conducted in the
village or in the temporary field hut constructed in the
field. In-field verification of survey data was done with
36 farmers that were involved in more detailed surveys
(see Sections 2.3 and 2.4 below). The approach used here
is similar to that used by Birmingham (2003), Habarurema and Steiner (1997) and Steiner (1998); however, in
this study, the group interviews were not used (general
cropping practices, soils information from this area and
farmer soil terminology were already available from
other project report (McAllister et al., 2001) and we did
not want to over burden farmers).
67
times, harvested area and area abandoned due to weed
damage.
In addition, nine of these farmers were asked to keep
detailed records of their labor use in their upland rice
fields. Farmers were given forms to record the type of
work they performed and the amount of time it required
each day.
2.4. Verification of farmers' knowledge of soils
Verification of farmer knowledge involved taking
crop cuts at harvest to compare crop yields and nutrient
uptake from different soils, and laboratory analysis of
soils to compare with the farmers indicators of soil
quality. This field study conducted in 2001 and 2002
involved 36 farmers (18 farmers' fields in each year)
from Hatxua, Houayluang and Pakchack villages.
Farmers in 2001 were the same as those involved in
the agronomic practices survey. Farmers were selected
that distinguished two or more soil types in their field. A
total of 94 monitoring plots were set up in each soil the
farmers had distinguished. Slope gradient was recorded
for each plot. Soil samples (0–15 cm) were collected
from all plots. Rice yield was measured in 82 plots (50
and 32 plots in 2001 and 2002, respectively). It was not
possible to harvest rice from 12 of the plots as the farmers
harvested rice before crop cuts could be taken. At rice
maturity, rice yields were measured and number of hills
was counted from two 4 to 6 m2 areas in each plot. In
addition, 10 randomly selected rice hills were sampled
from around the harvest area for determination of harvest
index, and N and P contents of grain and straw.
Soil analysis included pH (1:1 ratio of soil/water),
texture (pipette method), extractable P (Bray No. 2,
Nanjo, 1997) and total C and N contents analyzed by a
tracer mass spectrometer (Tracer MAT, Thermo Quest
Co. Ltd., Tokyo). Cation exchange capacity (CEC) was
measured after successive extraction using 1 N ammonium acetate at pH 7.0 and 10% NaCl solutions
(Thomas, 1982). Crop N and P contents were determined colorimetrically (U1100, Hitachi Seisakusho Co.
Ltd., Tokyo) after digestion in H2SO4 and H2O2.
2.3. Survey on agronomic practices
2.5. Statistical analysis
A more detailed survey, comprising 18 of the above
mentioned farmers, was conducted in three villages
(Hatxua, Houayluang and Pakchack) in 2001. Selection
of farmers was based on their choice to be involved and
limited by how many farmers the research team could
manage. This survey collected and verified (through
field visits) information in more detail on agronomic
practices, length of fallow period, number of weeding
Simple linear and multiple regression analyses are
used to identify relationships between fallow length,
measured soil properties and rice yield variables.
Analyses of variance (ANOVA) are conducted to test
whether local description of soil quality is related to
scientifically measured chemical and physical properties, and crop (upland rice) productivity.
68
K. Saito et al. / Geoderma 136 (2006) 64–74
3. Results
3.1. Upland rice in slash-and-burn systems
Labor input for weeding accounted for approximately 50% of the total labor inputs and averaged 145 days
ha− 1 year− 1 (Table 1). The total labor input for the first
and second weeding, conducted in the first 2 months of
rice growing season, accounted for 77% (107 days ha− 1
year− 1) of all of weeding labor input, indicating that two
persons have to weed continuously during the first
2 months (average field sizes are about 1 ha for
glutinous rice as shown in Table 2). These results
confirm those of Roder et al. (1997), who reported that
upland farmers considered weeds as the largest
constraint to upland rice production and low labor
productivity. Five of the 18 farmers surveyed in 2001
could not harvest upland rice in part of their fields (10%
to 44%) due to the inability to control weeds.
Loum and Khamu farmers prefer glutinous rice and
97% of households surveyed planted glutinous rice
(Table 2). The 3% that did not plant glutinous rice had
lowland rice fields (15%) or preferred to eat nonglutinous rice. Non-glutinous rice was planted only by
18% of farmers and was used for household consumption, noodle making or as a cash crop.
The average number of glutinous rice varieties planted
per household planting glutinous rice was 2.1 and ranged
from one to five. This is in alignment with that reported by
Appa Rao et al. (2002b) who collected rice varieties from
all over Laos. Thirty-five names of local glutinous rice
varieties were identified in this survey and there were no
improved varieties. The high diversity of rice varieties is
common in Laos and is described in detail by Appa Rao et
al. (2002a,b). Farmers plant several varieties for a number
Table 1
Labor requirement for upland rice farmsa
Activity
Day ha−1
(range)
Slashing
Burning
Second burning
Planting
Total weeding
1st weeding
2nd weeding
3rd weeding
4th weeding
Harvesting/threshing/
transport
Total
39 (12–80)
1 (0–2)
15 (0–67)
14 (10–19)
145 (90–252)
60 (35–94)
47 (23–83)
30 (0–67)
8 (0–30)
64 (28–122)
14
b1
5
5
52
22
17
11
3
23
278 (149–455)
100
a
Percent of total labor
requirement
Data was obtained by interview with nine farmers in this study.
Table 2
Household planting crops and area planteda and crops planted
associated with farmers' evaluation of soilb in this study
Glutinous rice
Non-glutinous rice
Job's tears
Sesame
Peanut
Household
planting
(%)c
Area
planted
(ha/hhd)
Respondents (%)b
Good soil
Poor soil
97
18
63
39
14
1.00e
0.23
0.20
0.09
0.02
59
31
10
9
32
41
69
90
91
68
a
Data from survey, n = 233 households.
Data from survey, n = 138 households. For farmers that
distinguished two soil types, first one and the other were defined to
be good and poor soil, respectively. When farmers distinguished three
or four soil types, first one and the others were defined to be good and
poor soils, respectively.
c
Percent of households who planted each crop in total of households
interviewed.
d
hh = household. Data of area planted was calculated from
household who planted each crop.
e
Area of crops planted was calculated by weight of seeds planted
and the seeding rates (rice, 60 kg/ha; Job's tears, 25 kg/ha; sesame,
12 kg/ha; peanut, 60 kg/ha).
b
of reasons including staggering labor requirements for
harvest, spreading risk and securing grain for periods
when households have a deficit (Roder et al., 1996; Appa
Rao et al., 2002a). A combination of early and late
duration varieties was most popular with farmers who
planted two varieties, while late varieties were most
popular with farmers who planted only one variety. The
percentage of area planted to early, medium and late
glutinous varieties was 33%, 13% and 55%, respectively.
Early duration varieties are important for an early harvest
to ensure food security during rice deficit periods that
averaged 4 months year− 1 (Roder et al., 1996)m but
farmers prefer late duration varieties, as most farmers
believe that late duration varieties of glutinous rice can
produce higher yields than early duration varieties.
Loum and Khamu farmers differentiate between
small and large grain size glutinous rice varieties (some
also mentioned medium grain size) (Table 3). The
percentage of farmers that plant both large and small
grain size glutinous varieties was 53%. Farmers in this
study generally prefer to eat large grain varieties to small
grain ones (Songyikhangsuthor et al., 2002). Furthermore, farmers report that milling recovery of large grain
size varieties is also better.
3.2. Other major crops
After upland rice, the most popular crop was Job's tears
(Coix lacryma-jobi L.), followed by sesame (Sesamum
K. Saito et al. / Geoderma 136 (2006) 64–74
indicum L.) and peanut (Arachis hypogaea L.) (Table 2).
These crops were planted primarily as cash crops. Of
these, 63%, 39% and 14% of the farmers planted Job's
tears, sesame and peanut, respectively. Maize (Zea mays
L.) and cassava (Manihot esculenta Crantz) were planted
by less than 5% of households and are generally grown
more by Hmong farmers (the other major ethnic group in
this region) for animal feed or as a cash crop. For the
purposes of this paper, maize and cassava are not
discussed further.
For those farmers planting Job's tears, sesame and
peanut, the average amount of seed planted per farmer
was 7.3, 1.0 and 0.5 kg, respectively (approximately
equal to 0.20, 0.09 and 0.02 ha, respectively). Compared
with the area planted to glutinous rice (1.0 ha), the area
of these crops was small.
3.3. Farmers' description of soils
When asked to identify different soil types in their
fields, 59% of farmers identified two or more soils. Of
the 138 farmers who distinguished at least two soil
types, 78%, 21% and 1% of farmers distinguished two,
three and four soils, respectively. There were no
common names of soil types in this area but farmers
Table 3
Household planting glutinous rice varieties divided into three
categories—duration, grain size and name, and area planteda and
glutinous rice varieties planted associated with farmers' evaluation of
soilb in this study
Household Area
planted
planting
(ha/hhd)
(%)c
Duration
Early (Do)
Medium (Kang)
Late (Pi)
Grain sizef
Large
Small
a
Respondents (%)b
Good soil Poor soil
70
27
77
0.46e
0.46
0.70
79
69
42
21
31
58
80
70
0.70
0.61
79
29
21
71
Data from survey, n = 233 households.
Data from survey, n = 138 households. For farmers that
distinguished two soil types, first one and the other were defined to
be good and poor soil, respectively. When farmers distinguished three
or four soil types, first one and the others were defined to be good and
poor soils, respectively.
c
Percent of households who planted each glutinous variety in total
of households interviewed.
d
hh = household. Data of area planted was calculated from
household who planted each glutinous rice variety.
e
Area of glutinous rice varieties planted was calculated by weight of
seeds planted (60 kg = 1 ha).
f
Except for medium size or other type grain, because of few
respondents.
b
69
Table 4
Soil descriptors associated with ranking by individual farmersa
Soil descriptor
Translation
Respondents (%)b
Good soil
Din dam
Black soil
65
Din sot, Bo mi mak hin Not stony, pure soil
16
Din pui
loamy soil, not compact, 8
loose soil
Din ki mon, Din poi
Powdered soil
4
Din neo
Cray, sticky soil
4
Fai mai dee
Good burning
4
Din dak sai
Sandy soil with clay
4
Poor soil
Din deng
Mak hin, Hin rai
Nya rai, mi nya kaw
Din kene, Din nene
Din luang
Din kao
Fai mai bo dee
Mi hak mai
Din ki sai
Red soil
50
Stony
49
Weeds
12
Hard, compact soil
9
Yellow soil
7
White soil
7
Bad burning
7
Tree roots were infested 6
in the soil
Sandy
4
a
Data from survey, n = 138 households.
Sum N 100% because some respondents gave more than two
descriptors. For farmers that distinguished two soil types, first one and
the other were defined to be good and poor soil, respectively. When
farmers distinguished three or four soil types, first one and the others
were defined to be good and poor soils, respectively.
b
distinguished soil types by color, stoniness, texture,
weediness and quality of burning. Farmers gave one to
four descriptors for each soil type. For example, din
dam (one descriptor; means black soil) and din deng
mak hin din pui (three descriptors; means red, stony,
loamy soil).
Descriptors of soils used by Loum and Khamu
farmers, and men and women were similar (data not
shown). Therefore, the data was combined for analysis
(Table 4). The most popular descriptor of good soil was
black color. Farmers mentioned that black soils were
fertile, had a high water-holding capacity, were
inhabited by earthworms (as evidenced by the presence
of earthworm castings) and produced high rice yields.
Red, white and yellow soils were mostly commonly
used to describe poor soil. Farmers thought that these
soils had poor fertility, tended to dry up quickly and
produced lower yields. The presence of stones was also
a descriptor of poor soil. Stony soils were difficult to
weed and produced low yields. Farmers preferred loamy
and clayey soils to sandy ones because loamy and clayey
soils had a higher water-holding capacity. Interestingly,
when farmers were asked how to distinguish soil
types, some farmers mentioned the occurrence of
70
K. Saito et al. / Geoderma 136 (2006) 64–74
weeds (especially Imperata cylindrica L. and Mimosa
invisa Mart. ex Colla) to describe poor soils and other
farmers mentioned quality of burning, thinking that
good soils resulted from a good burn which provided
fertilizer from the ash and reduced weeds.
because they produced more leaves than grain and was
likely to lodge, and that late duration varieties grow
better than early duration varieties on poor soil due to its
longer growing period. However, some farmers also
noted that late duration varieties could not grow on poor
soils that dry up quickly at the end of the season.
3.4. Soil properties in relation to cropping practices
3.5. Soil properties in relation to upland rice yields
In discussing with farmers their choice of crops on
different soils, we focused on farmers that distinguished
at least two soil types on their fields, as these farmers
clearly had a choice to make as to what crops to plant in
their soils. In general, glutinous rice was planted on
good soils, while most other crops were planted on poor
soils (Table 2). This was observed in both Loum and
Khamu farmers, and both men and women (data not
shown). When asked why, farmers reported that Job's
tears and sesame grow better than rice on poor soils.
Some farmers also reported that when Job's tears and
sesame are planted in good soil, they produce more
leaves relative to grain.
Focusing only on rice varieties being planted on
different soils, farmers tended to plant early duration and
large grain glutinous varieties on good soils, while late
duration and small grain varieties were planted on poor
soils (Table 3). Many farmers reported that early
duration and large grain varieties could not grow well
on poor soil. Furthermore, they reported that late
duration varieties produced low yields on good soil
High variation in soil properties, with the exception
of pH, was observed among the plots for both 2001 and
2002 data set (data not shown). Data from 2001 and
2002 was combined and shown in Table 5. Most soils
were of medium to fine texture with more than 30%
clay, which is consistent with the previous observations
in uplands of northern Laos (Roder et al., 1995a,b) and
northern Thailand (Funakawa et al., 1997a,b). Total C
content was strongly correlated with total N and showed
some association with clay content. High variation was
also observed for upland rice yields, total biomass, total
N uptake and total P uptake (Table 5).
There was no relationship between fallow period and
measured soil properties or rice yields (data not shown),
similar to reports of Roder et al. (1995a). However, in a
more rigorous on-station study in northern Laos, Saito
(2005) showed that shorter fallows resulted in lower
total N, available N, extractable P and rice yields. Poor
relationship between fallow and rice yields in this
current study is probably because the variability in soil
Table 5
Relationship (correlation coefficients) between various soil parameters and yield variables of upland rice (2001 and 2002, n = 82)
Range (CVa)
Soil parameters
pH
Total N (mg g− 1)
Total C (mg g− 1)
Extractable P (mg kg− 1)
CEC (meq 100 mg− 1)
Sand (%)
Silt (%)
Clay (%)
Slope (%)
Rice yield variables
Rice yield (t ha− 1)
Total biomass (t ha− 1)
Total N uptake (kg ha− 1)
Total P uptake (kg ha− 1)
HI
5.0–6.8 (5)
1.7–3.2 (15)
13–42 (21)
1.5–42 (93)
7.3–37 (27)
14–55 (27)
9–51 (25)
12–55 (20)
8–64 (37)
0.67–2.8 (29)
1.5–7.5 (33)
11–52 (33)
1.8–13 (36)
0.24–0.49 (14)
a
Coefficient of variation (%).
* Significant at the 0.05 level.
** Significant at the 0.01 level.
Correlation coefficients
Rice yield
Total biomass
Total N uptake
Total P uptake
Soil total C
0.23⁎
0.25⁎
0.24⁎
ns
0.23⁎
− 0.30⁎⁎
ns
0.28⁎
− 0.25⁎
0.29⁎⁎
0.21⁎
0.30⁎⁎
ns
0.25⁎
− 0.30⁎⁎
ns
0.34⁎⁎
ns
0.21⁎
0.26⁎
0.27⁎
ns
ns
− 0.34⁎⁎
ns
0.35⁎⁎
ns
0.35⁎⁎
ns
ns
0.45⁎⁎
0.28⁎
− 0.28⁎
ns
0.26⁎
ns
0.27⁎
0.79⁎⁎
–
ns
ns
− 0.35⁎⁎
ns
0.33⁎⁎
− 0.27⁎
–
0.87⁎⁎
0.81⁎⁎
0.56⁎⁎
ns
0.87⁎⁎
–
0.82⁎⁎
0.60⁎⁎
− 0.42⁎⁎
0.81⁎⁎
0.82⁎⁎
–
0.58⁎⁎
− 0.23⁎
0.56⁎⁎
0.60⁎⁎
0.58⁎⁎
–
ns
0.24⁎
0.30⁎⁎
0.27⁎
ns
ns
K. Saito et al. / Geoderma 136 (2006) 64–74
Table 6
Soil properties and rice yield variables classified by soil color
Black Red
soil
soil
Other soil
PR N F LSD
(white/yellow)
(0.05)
Soil properties
pH
Total N (mg g− 1)
Total C (mg g− 1)
Extractable
P (mg kg− 1)
CEC
(meq 100 mg− 1)
Sand (%)
Silt (%)
Clay (%)
n = 48
6.3 aa
2.4 a
28 a
8.5
n = 32
6.1 b
2.2 b
24 b
6.1
n=6
6.1 ab
2.2 ab
26 ab
6.1
0.05
0.02
0.02
0.32
24 a
20 b
22 ab
0.04 3.4
31
30
40
33
32
36
32
32
36
0.74 ns
0.57 ns
0.13 ns
Rice yield
variables
Rice yield (t ha− 1)
Total biomass
(t ha− 1)
Total N uptake
(kg ha− 1)
Total P uptake
(kg ha− 1)
n = 45 n = 24
n=6
1.9 a
4.3 a
1.6 b
3.6 b
1.2 c
2.7 c
b0.01 0.26
b0.01 0.68
28 a
26 a
19 b
0.05 4.9
7.3 a
6.0 ab
4.9 b
0.03 1.39
0.16
0.18
3.1
ns
a
Values on a row followed by the same letter are not significantly
different at 5% level based on mean separation by LSD.
properties, crop management and rice varieties between
farmers are too large. Also, since total soil C changes
very slowly with time, a more labile C pool may be more
sensitive to changes in fallow period. Using multiple
71
regression, the relationship between rice yield and soil
properties was poor and resulted in R2 values of 0.23 or
lower for data sets from 2001 and/or 2002. Therefore,
only the results of simple correlation analysis of the
combined data set from 2001 and 2002 (n = 82) are
discussed. Rice yields were positively but weakly
related to pH, total N, total C, CEC and clay contents
negatively related to sand content and slope gradient
(Table 5). Similarly, Roder et al. (1995a) also reported
from one study that soil organic matter was associated
with rice yield (r = 0.42), while in another study
comparing high and low yielding areas in 55 fields,
pH, total N, total C, extractable P and CEC were
significantly higher in the high yielding areas. Unlike
George et al. (2001), extractable P measurements in this
study were not correlated with rice yield, but there was a
significant relationship with total P uptake.
3.6. Comparison of farmers' description of soil quality
with laboratory analysis and rice yields
When farmers' descriptors of soil quality were
compared to chemical and physical analysis of the
soils, soils described as black in color had higher pH,
total N, total C and CEC levels than the other soils
(Table 6). Furthermore, the mean upland rice yield from
these black soils was significantly higher than that from
other soils. Sandy soil (Din ki sai), described by farmers
as poor, had the lowest pH, total C, total N, extractable P
Table 7
Soil properties and rice yield variables classified by texture
Din neo
Din pui (loamy soil, Din ki mon,
Din kene, din nene Din ki sai Din dak sai PR N F LSD (0.05)
(clayey,
not compact,
Din poi
(hard, compact soil) (sandy soil) (sandy soil
sticky soil) loose soil)
(powdered soil)
with clay)
Soil properties
pH
Total N (mg g− 1)
Total C (mg g− 1)
Extractable P
(mg kg− 1)
CEC (meq 100mg− 1)
Sand (%)
Silt (%)
Clay (%)
Rice yield variables
Rice yield (t ha− 1)
Total biomass (t ha− 1)
Total N uptake
(kg ha− 1)
Total P uptake
(kg ha− 1)
a
n = 10
6.2 aba
2.2 ab
26 a
5.1 b
n=9
6.2 ab
2.4 a
29 a
15.3 a
n=8
6.3 a
2.3 ab
28 a
10.1 ab
n=5
6.1 ab
2.1 b
25 a
6.7 b
n=3
5.3 c
1.9 b
16 b
3.2 b
n=2
5.9 b
2.1 b
20 b
3.0 b
b0.01
0.03
b0.01
0.03
25
30
30 b
41
23
26
37 a
37
30
33
28 b
39
23
37
24 b
40
12
40
29 b
31
23
42
29 b
32
0.24
0.07
0.03
0.22
n=8
1.8
4.0
29 ab
n=9
2.0
4.1
32 a
n=8
1.5
3.2
23 ab
n=4
1.8
4.0
30 ab
n=3
1.2
2.6
15 c
n=2
1.6
3.7
22 bc
0.13 ns
0.34 ns
0.03 8.9
6.5
7.2
7.1
5.6
3.4
7.0
0.15 ns
Values on a row followed by the same letter are not significantly different at 5% level based on mean separation by LSD.
0.36
0.30
4.9
8.12
ns
ns
8.4
ns
72
K. Saito et al. / Geoderma 136 (2006) 64–74
and CEC, had high sand content, and tended to have
lower total N uptake and rice yields (Table 7). Clayey
soils (Din neo) had higher clay contents (P = 0.22) and
rice yields from clayey and loamy soils tended to be
higher than from sandy soils (P = 0.13). Stony soils
showed no difference in soil properties and rice yield
variables from other soils (data not shown).
4. Discussion
Farmers surveyed in this study are knowledgeable of
their soils and take a holistic view of soil quality.
Barrera-Bassols and Zinck (1998, 2003), based on
survey results from 25 countries in Africa, America and
Asia, reported that color and texture were the most
commonly recognized descriptors of soil in most
cultures. The use of color as a major descriptor of
soils by different ethnic groups is further confirmed in
Laos (Lao Swedish Upland Agriculture and Forestry
Research Program, 2003). Farmers preferred black soils
to red, white and yellow soils, and preferred clayey or
loamy soils to sandy or stony soils. Similar findings
have been reported by Fujisaka (1991) from northern
Laos and Barrera-Bassols and Zinck (1998, 2003).
While the farmers in this study also used color and
texture to describe soils, they also used the occurrence of
weeds and stones and the quality of burning (Table 4).
There was good correlation between farmers' knowledge of soils and the soil chemical and physical
properties (except stoniness) as others have found
(Hirai et al., 2000; Birmingham, 2003; Gray and Morant,
2003; Hirai et al., 2003; Sandor and Furbee, 1996;
Tamang, 1993; Shah, 1995). In general, black soils had
high organic matter and were commonly considered to
be more fertile than the other color soils, and this is
consistent with our results that black color soils had
higher pH, total N, total C and CEC levels than other
colored soils (Table 6). Some authors (Hirai et al., 2000;
Gray and Morant, 2003; Sandor and Furbee, 1996) found
that soil physical properties were more closely correlated
with farmers' soil evaluation than soil chemical
properties were, while others (Tamang, 1993; Shah,
1995; Hirai et al., 2003) found better correlation between
farmers' soil classification and soil chemical properties.
The most important constraint to upland rice cultivation is weeds (Roder et al., 1997) and weeds are frequently
mentioned as the main reason for farmers to move to a
new field in Laos and elsewhere (i.e. Nye and Greenland,
1960; Sanchez, 1976). De Rouw (1994) reported that fire
destroyed buried seeds and vegetative parts of forest
plants resulting in less weed pressure during the cropping
season. Therefore, it is understandable that farmers
distinguish soils by considering the ease of weed control
and burn quality. Such descriptions of soils were also
found in Burkina Faso and Latin America, by Gray and
Morant (2003) and Barrios and Trejo (2003), respectively,
where farmers considered the presence of many weeds as
an indicator of soil fertility. Similarly, Hirai et al. (2003)
reported that the Karen of northern Thailand are able to
evaluate land productivity by using weed species as
indicator plants. Farmers' perceptions of stony soils in this
study did not relate well to productivity or soil chemical
properties. This contradiction reflects that other concerns
are more important for farmers in terms of agronomic
practices, especially weeding. Weeds are the biggest
constraint to upland rice production and farmers noted
that weeding was most difficult in stony soils.
Farmers' knowledge of soils directly affected both the
crops and the upland rice varieties they planted. Farmers
preferred to plant Job's tears, sesame or late duration and
small grain glutinous rice varieties on poor soils and early
duration and large grain rice varieties on good soils.
Similarly, Fujisaka et al. (1996) reported that farmers
adapted to micro-local soil conditions using a range of
adapted crop associations, based on their acquired
knowledge. Habarurema and Steiner (1997) and Steiner
(1998) showed that farmers planted their crops according
to soil type (plant the demanding crops on the best soils
and less demanding crops on less fertile soils), but, in
practice, the availability of certain soils is limited and
farmers were forced to make a second best choice. This is
perhaps reflected Tables 2 and 3 in this study which shows
broad agreement between farmers as to the best combinations but since some farmers do no have a certain soil an
alternate choice needed to be made. In contrast, Gray and
Morant (2003) observed that farmers differed in their
choice of crops to plant on a soil type, reflecting the many
dimensions of soil fertility from the farmers' perspective.
Despite farmers preference for large grain size
glutinous rice varieties (Songyikhangsuthor et al.,
2002), a high percentage of small grain varieties is
still grown (Table 3). Most farmers believe that small
grain glutinous rice varieties grow well on poor soils.
Therefore, the high percentage of area planted to small
grain varieties may be their environmental adaptation to
the current upland conditions where shortened fallows
have resulted in declining rice yields (Asian Development Bank, 2001; Trosch, 2003; Saito, 2005). However,
information on such adaptation to change is limited not
only in Laos but also in the other countries and further
research is needed in this area.
The lack of difference between the two ethnic groups
may reflect the close proximity in which they live (Fig. 1)
and the subsequent sharing of information. To study this
K. Saito et al. / Geoderma 136 (2006) 64–74
in more detail, it would be beneficial to study different
ethnic groups in more isolated environments. Indeed,
others have reported differences in how Lao Loum,
Khamu and Hmong farmers name and classify soils (Lao
Swedish Upland Agriculture and Forestry Research
Program, 2003); however, it is not clear from their report
if farmers of different ethnic groups manage their soils
differently. Given that there were no measurable
differences between ethnic groups in our study, it is not
surprising that gender differences related to soil
preference and knowledge were also not detected. One
may expect gender differences to be observed, for
example, if women are more involved with weeding or
the growing cash crops. Again, this requires additional
investigation using a purpose driven selection and
disaggregation of informants.
5. Conclusion
Our study reveals that farmers are knowledgeable of
their soils and their knowledge correlates well with
scientific understanding of soils. They use this knowledge to establish cropping systems that are adapted to
their upland conditions. The most popular criterion used
for descriptors of soil types was color and scientific
investigations correlated best with farmers' perceptions
of soil types classified by color rather than texture. Thus,
soil color described by farmers will be more useful tool
for researchers and extension workers to effectively
dialog and work with farmers to understand their natural
resources better and develop improved crop production
systems. Further research is needed on establishing the
methodology of using such knowledge of soils effectively with farmers. Such methods may be applied when
using participatory approaches as proposed by Barrios et
al. (2000) and Steiner (1998). For example, Barrios et al.
(2000) provided a guide for decision making in natural
resource management using farmers' knowledge. Steiner
(1998) suggested that research and extension staff can
provide a range of cultivars and flexible soil management recommendations while relying on farmers' site
specific knowledge. This would not only assist farmers
in making optimum use of their natural recourses but
would also help create an atmosphere of trust.
Acknowledgements
The research was partly funded by the Swiss Agency
for Development and Cooperation (SDC) and “Global
Environment Research Fund”, The Ministry of the
Environment, Government of Japan (Project S2-3b).
The authors would like to gratefully acknowledge the
73
support and help they received from the staff of the
District Agricultural and Forestry Office in Pak Ou
district.
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