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Nutrient flow from the forest
Life source for traditional
Bhutanese agriculture
Walter Roder, Karma Dorji, and Georg Gratzer

Tibet
West Bengal Assam

Steep slopes
High rainfall
Poor parent material
High erosion

In-organic fertilizers
N 3.3 kg/ha
P 0.7 kg/ha
K 0.5 kg/ha

How is this possible?

Objectives of presentation
describe methods used for gathering and
transfer of nutrients
describe nutrient sources
describe techniques applied to enhance
nutrient flow and availability

Materials and methods
Published data
Complementary investigations
Litter raking area
Tree species used for litter raking
Nutrient content of materials collected form the
forest
Nutrient content of cattle manure

Cut and carry, weed
Hay/silo
Turnip/Radish
Fodder tree
Maize straw
Rice straw
Buckwheat straw
1
Forest grazing
Grazing cropland
Ara/chang residues
Pangshing/Tsheri
Improved pasture
Common pasture
Other crop by-product
Fodder resources
0 10 20 30 40 50
Respondents (%)

Table 2: P-content in the soil, plant and manure from selected sites at elevation
of 2600-2800 m dominated by blue pine (Pinus wallichiana) 1
Site Soil Plant Manure
Avail. (P
mg/kg)
P (%) P (%)
Intensive used white
clover
11.6 0.18 0.60
Cultivated fields
7.1 0.20 0.51
Forest/permanent
grassland 1
3.9 0.10 0.34
1 The dominant herbaceous species included: Arundinella hookeri, Eragrostis nigra
and Potentila spp.

Relationship between P in plant
and P in dung
P-content dung (%)
1
0.8
0.6
0.4
0.2
0
0 0.05 0.1 0.15 0.2 0.25 0.3
P-content plant (%)

Nutrient content in manure as influenced by herd
(grazing) and date)
N (%) P (%) K (%)
Herd/location
BS-farm 1.9 0.69 0.63
Jalikhar 1.7 0.48 1.01
Tangbi 1.4 0.32 0.90
Chumey
Anova
1.5 0.29 0.79
Herd/location

Nutrients transfered
With 200-300’000
animals about
300-700 t P
1500-3500 t N
0.1-5 kg P/animal/year
0.5-25 kg N/animal/yea

Sogshing = Life
forest

Importance of sogshing in different regions of Bhutan
Parameter Area
(a/hh)
Frequency
(% hh)
Area per
crop land
(ha/ha)
Major tree species
Wet subtropics 0.015 4.9 0.01 Schima wallichii
Castanopsis indica
Foot hills 0.067 19.2 0.07 Alnus nepalensis,
Schima wallichii,
Dry valleys
High areas
Quercus grifithii
0.23 41.8 0.24 Chir pine, Quercus
grifithii, Quercus
lanata, Blue pine
0.13 21.0 0.13 Blue pine, Quercus
semecarpifolia

Nutrient content of major litter sources
Litter type N P K
Blue pine needles 0.81 0.05 0.27
Blue pine needles & fern 0.51 0.06 0.27
Fern 0.95 0.07 0.44
Chir pine needles 0.74 0.08 0.22
Oak 0.95 0.07 0.44
Oak, fern and Puya 0.99 0.07 0.70

Soil cutting
Fuel cutting/carrying
Making mounds
Burning
Spreading soil
Sowing
Guarding
Harvesting
Threshing
0 40 80 120 160
Labor days

250-500 t of topsoil
temperatures of 500 ° C
150-400 labor days ha -1

Changes in soil parameters before and after burning
Parameter Before
burning
After burning
Soil pH 6.0 6.9
Organic C (%) 3.3 0.8
Total N (%) 0.17 0.08
C:N ratio 22 11
Available P 1) (mg kg -1 ) 1.0 6.8
Available K 2) (mg kg -1 ) 34 69
1) Extraction with NH4OAc+EDTA
2) Extraction in CO2 saturated water

P and N added by blue pine biomass
Content
(%)
Quantity
(kg/ha)
Biomass - 5700
Phosphorus 0.103 6.1
Nitrogen 0.94 55

Estimated quantities of P from the forest
added to agricultural land
Source Quantity
(t/year)
Ash from fire wood 100
Cattle grazing in
400
forest
Sogshing 200
Grass fallow system 10
In-organic fertilizer 153

The traditional methods are:
Ingenious adaptation to given condition
Harmful for forest
Excellent example of organic agriculture
Labor intensive methods poorly use resources
Sustained use of local resources
Harmful for environment