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 Changing Soil Fertility Management in Bhutan: Effects on
Practices, Nutrient Status and Sustainability*
Chencho Norbu* and Christopher Floyd
Abstract
This paper is the results of a Soil Fertility Management (SFM)
survey conducted in 1999 to determine the status and trends
in soil fertility management and associated soil conditions in
Bhutan in the face socio-economic development of the last
four decades. While the traditional SFM systems based on the
use of animal manures still dominate, the ability to maintain
and sustain these indigenous systems is being undermined
by socio-economic factors. Households have been increasingly
depending on fertilizer, especially urea, to increase soil
fertility and maintain crop yields, and this trend is predicted
to continue. Generally, soil nutrient status is poor. The major
concerns are a low pH and nitrogen, phosphate status and
unbalanced base nutrition. Since sustainable development is
a key government development objective, the survey results
were examined to determine the sustainability of existing
SFM practices and soil use for crop production. In most
situations sustainability is being maintained, but the
assessment of SFM and crop production questions
sustainability in some areas. Lack of sustainability is a
concern on both wetland and dryland soils and among
households identified as being less able to manage soil
fertility. This paper has identified implications for policy,
research and extension.
* The paper was presented in Annual Meetings of Soil Science
Society of America, American Society of Agronomy and Crop Science
Society of America, Charlotte, NC, USA. Oct 21-25, 2001.
+ Director, National Soil Service Centre, Ministry of Agriculture,
Bhutan
49
 Journal of Bhutan Studies
Introduction
Farming is fundamental to the Bhutanese economy. Some
80% of households depend on agriculture for their livelihood
and the share of agriculture to GDP is 37%.
Characteristically, farming households are small with a mean
farm size of less than a hectare. Wetland (irrigated paddy
fields) is preferred and rice is cultivated up to 2,600 mask
Winter cropping of wetland is restricted by low winter
temperatures at higher altitudes and lack of irrigation at
lower altitudes. Winter cropping is largest at middle altitudes.
While only a small proportion is covered here, the double-
cropped area is increasing. Maize is the predominant crop on
dryland and at higher altitude (above 2,500 masl) wheat
and/ or buckwheat are the main staples. Although
subsistence cropping predominates, mandarin oranges at
lower altitudes and apples at higher altitudes are the major
cash crops, making an important contribution to GDP. Other
important cash crops are potato, cardamom, ginger and chili.
As in any other farming system, soil fertility is fundamental to
the productivity and sustainability of farming in Bhutan.
Traditionally, soil fertility management (SFM) has been based
predominantly on the use of animal manures through either
tethering of animals in fields or the use of farmyard-manure
(FYM). The traditional labour intensive SFM systems are
based on the integrated use of the forest as a source of fodder
and leaf litter, livestock for dung, and crops as supply of crop
residues. The use of chemical fertilizers has increased
substantially parallel to the socio-economic development of
the past 40 years. Absolute levels of chemical fertilizer use are
low compared to a global level, but households are
increasingly relying on these fertilizers.
The objective of this paper is to provide an overview of the
status, trends and sustainability of soil fertility management
and associated soil conditions in Bhutan against the social
and economic transformation. Following a brief description of
50
 Changing Soil Fertility Management in Bhutan: Effects on
Practices, Nutrient Status and Sustainability
the data sources, three main issues are examined namely,
trends in SFM practices, soil fertility status and its
sustainability. The paper concludes by identifying the
implications for policy, research and extension with respect to
soil fertility and its management in Bhutan.
Two principal sources were used for this survey: a national
Soil Fertility Management (SFM) survey of 1999/2000 and a
Watershed Farmyard Manure (FYM) survey of 1998/1999.
Soil Fertility Management (SFM) Survey
A total of 32 villages were selected as representative of
farming systems across Bhutan. It used qualitative data
collection methods (example PRA and focus group discussion)
at the village level to identify major SFM issues and trends in
the villages. Information provided by household interviews in
a random sample of 12 households per village formed a
quantitative data on household SFM practices, resource and
perceived trends in yields and soil fertility. For a standard
nutrient descriptors, soil samples from a random selection of
(380) fields were analyzed.
Farmyard Manure (FYM) Survey
This survey was conducted amongst 23 households in a mid-
altitude watershed over one cropping year 1998/1999.
Household interviews were used to characterize each
household for socio-economic status, resource base and SFM
profile. All fields cultivated by the sample households were
monitored for a cropping year to determine rates of nutrient
application from tethering, FYM and fertilizer application by
direct measurement and nutrient analysis.
ISSUES
Soil Fertility Management (SFM) Practices
The trend in the use of the major SFM practices is
summarized in Table 1. The increasing use of fertilizers is the
most important change.  Although only 41% of households
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 Journal of Bhutan Studies
have used fertilizers, the trend is strongly positive amongst
households that have used fertilizers, and of these, 66% of
households have increased the fertilizers use.
Table 1: Percent of households reporting change in use of tethering,
FYM and fertilizers as an SFM practice
SFM
Practice
Change in SFM Practice
SFM not
used
Increased
Same
Decreased
Tethering
14
37
13
37
FYM Use
27
41
15
17
Fertilizers
27
11
3
59
Source:   SFM Survey.   379 household respondents
A complex of interrelated factors influence the changing
pattern of SFM practices in Table 1 but three major factors
are identified: fertilizer availability and effectiveness, livestock
numbers and management system and household labour
availability.
Fertilizers Availability and Effectiveness
Fertilizers have only been available in Bhutan since the early
1960s and their use has been an important part of
government agricultural development strategy to increase
yields and production. Increased use of fertilizers reflects: 1)
their increased availability as road access and distribution
systems have improved; 2) effective promotion of their use
through agricultural extension programmes; and 3) their
effectiveness, providing substantial and cost effective yield
increases.
Currently fertilizer prices are subsidized through indirect
government support to the national marketing and
distribution system.
Livestock Numbers and Management Systems
The supply of animal manures for either FYM or tethering use
is dependent on the number of livestock kept and their
management system. Data indicates that livestock numbers
52
 Changing Soil Fertility Management in Bhutan: Effects on
Practices, Nutrient Status and Sustainability
are declining. Review of livestock population and composition
over the years indicate significant decrease in total livestock
numbers and an increase in the number of cross breed
livestock at the expense of a decrease in the number of local
breed between 1986 and 1996 (MoA, 1999). This trend is
complemented by farmers moving from extensive (grazing)
through semi-extensive (tethering) to intensive (stall feeding)
systems, particularly associated with adoption of crossbreds.
Although declining livestock numbers reduce the supply of
manure, recovery of dung is greater in the more intensive
systems.
Household Labour Availability
Declining availability of household labour is an established
trend in Bhutan. In the SFM Survey, 48% of households
reported a decline in household labour availability in the last
10-15 years. A contemporary survey in the west-central
region confirms this finding, and 50% of 300 respondent
households report a decline in household labour availability
(Yeshey, 2001). The three reasons reported for labour decline
are household members leaving for marriage (30%),
government employment (26% of households), and schooling
(24%).
Declining labour availability means that the effectiveness of
labour use is an overriding factor determining household SFM
strategies. Use of FYM is labour intensive and, in the face of
declining household labour, households will move to more
intensive livestock management systems (ultimately stall
feeding) that reduce the labour required (traditionally
children) for shepherding. Fertilizer use is an extension of this
labour saving strategy; substituting cash for labour in
providing plant nutrients.
Soil Fertility Status
Soil fertility status is assessed in two ways to provide a
broader view. The first is based on the results of the analyses
of the soil samples from the SFM Survey, and the second is
53
 Journal of Bhutan Studies
based on the household perceptions of yield and soil fertility
changes in the last 10-15 years.
Soil Analytical Results
Bhutan is characterized by considerable diversity in
agricultural soils. Climatic zones range from the subtropics
from 150 masl with high annual rainfall (ca 5500 mm) in the
south to cold temperate with low rainfall (400 mm) in the
north. Geology is dominated in the north by granitic gneiss
and in the south by phyllite schist. This diversity means that
even simple stratification of the soil analysis results by soil
type and agro-ecozone is lengthy and beyond the scope of this
paper. Although any summary of soil nutrient status runs
the risk of oversimplification, the results of key soil variables
for 376 samples taken from the SFM Survey are summarized
in Figure 1 to provide an overview of the results and identify
the major features.
Figure 1: Soil nutrient status-rating chart for SFM Survey samples
100
SFM/AF Survey Soil Sample Ratings
._.
55 &
$aa$i,TtTjgf-
\,  C ^C'% "*"   Q   »  ^   ■»
bee "Interpretation ot soil Analyses (DsS 2001) for boundary values
,%\%%
Rating
||H Very high
I       I High
| | Moderate
ill! Low
I^Very low
54
 Changing Soil Fertility Management in Bhutan: Effects on
Practices, Nutrient Status and Sustainability
Figure 1 gives the proportion of the samples that fall into five
rating classes for each soil descriptor. The rating class
boundaries are derived from international sources and
standards and classes are designated very low to very high.
Any soil variable in which the proportion of samples classified
as low or very low exceeds 40% is considered to indicate a
potential soil fertility problem.
The main features ofthe results given in Figure 1 are:
■ Although nearly half of all samples had low or very low
pH (i.e. pH <5.5), only 15% of samples had
exchangeable aluminium levels classified as high or
very high. Except for some lowland subtropical soils,
aluminium toxity is of limited concern.
■ Total and organic carbon levels are generally adequate
although total N levels were low or very low (<0.2%) in
40% of samples. As result of the low total N levels, C:N
ratios are favourable (i.e. low or very low [< 19]).
■ For available P (Bray) and K, 50% of the samples are
rated low or very low (<5ppm P and <40ppm K). Of
these, low available P is of greatest concern as soil
parent materials are generally K rich and this is
reflected in predominantly moderate to high levels of
exchangeable K.
■ The major area of concern is base nutrition and
particularly the imbalance between exchangeable bases.
Base saturation and total exchangeable base levels are
low or very low (>70% of samples). The low to very low
exchangeable Ca and Mg levels (more than 70% of
samples) as compared to predominantly moderate to
high levels of exchangeable K are reflected by
unfavourable Mg:K and Ca:K ratios.
Trends in SFM practices are likely to exacerbate these
deficiencies. Decreasing use of FYM reduces the additions of P
55
 Journal of Bhutan Studies
and Mg and these nutrients are not usually added by the
fertilizers used. In addition, the predominant use of urea is
likely to exacerbate problems of low pH.
Household Perceptions
An average of 21% and 22% of households reported increased
soil fertility of wetland and dryland respectively in the last 10-
15 years. In contrast, for wetland 35% and for dryland 39%
of households reported SF as having declined. Household
perception of changes in the soil fertility status of their
wetland and dryland in the last 10-15 years is illustrated in
Figure 2. This perception differs significantly between
households depending on their SFM ability (p=0.009). In the
case of wetland, 49% of poor SFM ability households reported
a decline compared to 27% for good SFM ability households.
Comparable figures for dryland are 55% and 31%.
Figure 2: % of households reporting a decline in soil fertility of their
wetland and dryland by household SFM ability
CD      CD
60
50
40
30
20
10
0
\z
JZ
D Wetland
■ Dryland
Good        Medium Poor
Household SFM Ability
The main indicator used by the majority of households to
assess soil fertility is crop yield; other factors such as soil
conditions (e.g. colour, tilth and texture) and erosion hazard,
although considered, are secondary. The association between
soil fertility and yield is confirmed by the survey finding that,
on average, 39% of households report a decline in the yield of
56
 Changing Soil Fertility Management in Bhutan: Effects on
Practices, Nutrient Status and Sustainability
their main staple (Table 1). The trend in yield decline is
greatest in households with wheat and buckwheat as their
main staple; these are predominantly households living at
higher altitudes.
Table 1: Percent of households reporting specific change in yield of
their main staple crop in the last 10-15 years
Yield change in
last           10-15
years
Staple Crop
Rice
Wheat
Maize
Buckwheat
All
Staples
Increase
21
25
33
36
27
Same
43
13
32
9
35
Decrease
36
63
35
55
39
Household
count
183
24
140
22
374
Source:   SFM Survey
The association between crop yield and soil fertility is
reinforced by the reasons given by respondent households for
staple crop yield increases or decrease (Table 3). The main
reasons given for yield increase are the use of fertilizers
and/or more FYM. Conversely, soil fertility decline dominates
the reasons given for yield decrease. In the Bhutanese context
an important feature of these results is that 'soil fertility
decline' was reported as a reason for yield decrease by three
times as many households as those reporting yield decrease
due to damage by wild animals. Hitherto, crop damage by
wild animals has been widely reported and regarded as the
most important problem facing farming households.
Table 1 Reasons reported by households for yield increase or
decrease inthe household's main staple crop
Reasons    reported    by    more    than    5%    of
households for:
%of
households
Yield increase
Use of chemical fertilizers
32
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 Journal of Bhutan Studies
Use of higher yielding crop varieties
27
Application of chemical fertilizers with FYM
24
Application of FYM
22
Reporting households
99
Yield decrease
Soil fertility decline
46
Damage by wild animals
16
Use of less FYM and compost
14
Pests and diseases
12
Water shortage
9
Better crop management
8
Reporting households
142
Source:   SFM Survey
While accepting that crop yields reflects other influences
particularly weather, water availability and crop management,
these results illustrate that soil fertility is declining in a
significant proportion of agricultural land. They also
demonstrate that soil fertility and its maintenance is an
important feature affecting farming in Bhutan and that it is
stratified. Households identified as being less able to manage
soil fertility and those at higher altitudes depending dryland
staple crops appear at most risk.
Sustainability
Sustainability is a complex issue and any discussion needs to
be clear as to what defines sustainability. Here the definition
that "a system is sustainable over a defined period if outputs
do not decrease when inputs are not increased" (Monteith,
1990).
The evidence presented above of declining soil fertility and
crop yields and increasing use of fertilizers suggests that the
lack of sustainability of SFM systems in Bhutan is a major
concern. About 40% of households are reporting decline in
soil fertility and staple crop yields. Soil fertility decline is
reported as a major reason for yield decline and the main
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 Changing Soil Fertility Management in Bhutan: Effects on
Practices, Nutrient Status and Sustainability
strategy for maintaining or increasing yield is reported as the
use of chemical fertilizers (Table 3).
A complex of socio-economic factors, probably most
importantly a decrease in household labour availability and
lack of profitability of farming underlie the decline in yield
and soil fertility and in particularly undermine the
sustainability of the traditional SFM systems based on animal
manures. It is not possible to present and discuss these
socioeconomic factors in detail in this paper. The evidence
shows that a major factor involved in the (un)sustainability of
SFM systems is the increased use of chemical fertilizers and
for this reason this paper concentrates on this aspect of the
problem.
Chemical Fertilizer Use Patterns
Urea is the main fertilizer used in Bhutan. Of the 2,016
metric tonnes of chemical fertilizers used in 1999, 56% was
urea. The ratio of N:P:K in fertilizer sold in the three years to
1999 was 5.7: 1.3: 1 and indicates a serious imbalance in
nutrient use. Survey results confirm the dominance of urea
and show that, with the exception of potato, most households
use urea only (Table 4). The use of compound and phosphatic
fertilizers in potatoes is related to potato's role as a cash crop.
There is a large economic response to single super phosphate
(SSP) in potato and its use has been strongly promoted by the
extension services. On other crops farmers mostly use urea.
Table 2: Mean farmer estimated rates of fertilizer applied (kg ha-1) for
urea, suphala and single superphosphate by crop
Fertilizer applied
Crop
(Fertilizer application rate ±sem
where applied with [respondent]
number)
Rice
Wheat
Maize
Potato
Urea (0:46:0)
95+9
[80]
104+1
7
[181
164+1
5
[431
213+40
[34]
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 Journal of Bhutan Studies
Suphala (15:15:15)
64+17
[9]
133+3
3
[61
217+44
[22]
Single Superphosphate
(0:16:0)
72+43
[4]
115+2
8
[61
247+37
[24]
Source:   SFM Survey
The extent to which households are dependent on fertilizer for
yield is shown in Table 5. These substantial yield increases
using relatively low rates of fertilizer use (Table 4) illustrate
why fertilizer use is attractive to farmers.
Separate estimates suggest that in two of the main rice
producing valleys as much as 30% of the current production
of rice is due to the application of urea (SSF & PNMP
unpublished data).
Table 5: Mean farmer estimated yields with and without fertilizers
applied and percentage yield increases resulting from fertilizer use by
crop
Crop
Rice
Wheat
Maize
Potato
Yield (kg ha1) with fertilizers
5,590
±280
2,870
±880
4,408
±470
12,450
±2,000
Yield     (kg     ha1)     without
fertilizers
3,970
±210
1,790
±590
2,662
±300
7,100
±1,300
Yield     change      (%)      with
fertilizers based on farmers'
estimated yields
51
70
66
88
Farmers'     estimated    yield
change    (%)    if   unable    to
recall actual yield change
37
38
38
Overall    yield    change    (%)
mean of previous two rows
59
64
76
60
Respondents
71
17
42
25
Source:   SFM Survey
60
 Changing Soil Fertility Management in Bhutan: Effects on
Practices, Nutrient Status and Sustainability
The predominant use of urea has important implications for
the sustainability of soil use and this is illustrated below with
partial nutrient budgets from a wetland and dryland soils.
Wetland Soils
Partial nutrient budget for nitrogen, phosphorus and calcium
from 102 fields growing rice in the FYM survey are illustrated
in Figure 3, Figure 4 and Figure 5.
In the figures, fields have been sorted by increasing amount
of the nutrient applied from three sources, FYM, tethering
and fertilizers1. The lowest Y-axis gridlrne in the figures is
fixed at the amount of the nutrient removed by the estimated
mean yield of a rice crop amongst the surveyed households.
The amount of nutrient removed by the estimated mean yield
rice crop is about 46 kg N ha1; 13 kg P ha1; 69 kg K ha1;
and 18 kg Ca ha1. The other Y-axis gridlines are multiples of
this nutrient removal.
1 Nutrient recovery assumed as 80% from organic sources and 50%
from inorganic fertilizers.
 Journal of Bhutan Studies
Nitrogen adjusted for source applied to rice fields
16   21   26   31   36   41   46   SI   56   61   66   71   76
■ FYM BTethering ■Fertiliser!
91        96       101
Field
Figure 3 Partial nitrogen budget for rice fields in the Lingmutey Chhu watershed
1998-99
P kg/hi
Phosphorus adjusted for source applied to rice fields
Figure 4 Partial   phosphorus   budget   for   rice   fields   in   the   Lingmutey   Chhu
watershed 1998-99
62
 Changing Soil Fertility Management in Bhutan: Effects on
Practices, Nutrient Status and Sustainability
Calcium adjusted for source applied to rice fields
91 96        101
|TYM n Tethering ■Fertilisers |
Figure 5 Partial calcium budget for rice fields in the Lingmutey Chhu watershed
1998-99
The main results and issues that emerge from the partial
budgets results are;
■ More than 50% of fields are receiving less N and P than
is removed by a rice crop of estimated mean yield. This
proportion is 78% for N and 92% for P.
■ The proportion of fields not receiving N, P and Ca from
nutrient management is between 20% and 40% the
situation is worst for P and Ca because these nutrients
are not being supplied in fertilizers.
■ As a result of the Ca needed to neutralize the urea
applied as fertilizer, an effective negative application of
Ca is occurring in 29% of rice fields. Thus 40% of the
fields are effectively receiving no, or a negative
application of, Ca.
Continuation of this management regime will mean that it will
be difficult to increase rice yields without the risk of depleting
soil nutrient stocks, particularly of P and Ca. P and Ca are of
greatest concern; FYM derived from cattle is a poor source of
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 Journal of Bhutan Studies
P and Ca is not being provided in fertilizers and liming is not
an established practice in the area.
Dryland Soils
Comparable partial budget information is not available for
dryland soils. However, data from the SFM Survey for dryland
fields (Table 6) relating household perceptions of SF changes
to whether chemical fertilizers are applied to those fields
demonstrate a significant (P<0.001) association between
perceived SF change and fertilizer use. Where SF is perceived
as having remained the same or has decreased, fertilizer is
not used on most fields (71% and 89%). Where SF is
perceived to have increased, fertilizers are used on most fields
(58%).
As the rate of urea applied is higher on maize crops than rice
crops (Table 2) it is assumed that the partial nutrient budgets
for dryland fields would be comparable to those illustrated
here for wetland. FYM survey results show that FYM
application rates to rice (7,800 ±700 kg FYM ha1) and maize
(8,100 ±1,700 kg FYM ha1) are similar.
Table 5 : Perceived changes in soil fertility on dryland versus fertilizer
use (% of fields)
Fertilizers used on field
Perceived soil fertility change
Increased
Same
Decreased
No
42
71
89
Yes
58
29
11
Respondents
55
62
71
Source:   SFM Survey
IMPLICATIONS
This paper identifies implications of soil fertility management
in Bhutan at a policy, research and extension level.
Policy
1. Improving SFM will depend substantially on improvements
to the productivity and profitability of the farming system.
64
 Changing Soil Fertility Management in Bhutan: Effects on
Practices, Nutrient Status and Sustainability
The more productive and profitable farming is the greater the
incentive to invest. In particular, improvements needed are
those that are compatible with improved FYM and fertilizer
management and use and those that increase returns to
labour. Here improvements in infrastructure and markets are
important, especially if these are likely to stimulate intensive
livestock production.
2. Given the large and negative impacts of unbalanced use it
is important that fertilizer prices are not subsidized and so do
not undervalue the traditional and more soil friendly methods
based on FYM use. At the same time further liberalization of
fertilizer distribution systems is needed to provide widespread
and improved access to this important SFM input.
Research
3. The most important research implication arising is the
issue of sustainable soil fertility management on both wetland
and dryland.
Nutrient budgets for rice in the FYM survey indicate that P
and Ca are priorities but, given the low exchangeable Mg
against rich K soils, poor and unbalanced base nutrition
identified in the soil sample results, Mg nutrition also needs
consideration.
4. More information is needed for maize production on
dryland. Here use of urea is widespread but negative effects
may be being offset by the general higher rates of FYM
application on maize than on rice.
5. There is a need to examine the importance of poor and
unbalanced base nutrition in improving productivity of the
main high value crops of apples and mandarin. These crops
are major contributors to agricultural domestic product and
improved soil fertility and so increased use of fertilizers need
to be an important component of strategies aimed at
increasing production and productivity.
65
 Journal of Bhutan Studies
6. Addressing the other important but general constraints
with respect to FYM use requires farmer relevant options to
increase the supply of FYM and to reduce its labour
requirements. In this respect, on-farm fodder crops are the
priority.
Extension
7. The priority for extension is to work with farmers to
address unbalanced fertilizer use. Fertilizer use is the single
most important change in SFM that has occurred in the last
10-15 years and farmers lack the understanding of simple
principles of crop nutrition to be able to make informed
decisions on fertilizer use.
8. The other priority for extension is to promote on-farm
fodder crops to increase the supply of FYM and to reduce its
labour requirements by facilitating more intensive livestock
management systems.
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 Changing Soil Fertility Management in Bhutan: Effects on
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