Land Use and Soil
State of Environment Report of Tripura for the year of 2002

1.0 Land and Land use

The State of Tripura with 1.05 million hectare of land area (10,491.6 sq. km) has nearly 58% of total under forest area (0.61 mha), followed by agriculture (0.28 mha). Of the total land resource biomass producing area has been calculated at 0.92 mha, the remaining 0.13 mha being demarcated as non-biomass producing land. The resources therefore show a significant 87.62% as productive biomass generating area. Of the 0.92 mha, forest land or common land occupy 0.61 mha and private land occupies 0.31 mha (Table-1 & Fig. 1).

The land resources apart, the present land use profile of the State shows that forest with 0.61 mha and net area sown is 0.28 mha; the area not available for cultivation is put at 0.13 mha (non agricultural uses). Land under miscellaneous tree crop is estimated at 0.027 mha, cultivable wasteland at 0.001 mha and fallow land at 0.005 mha, including old fallow and current fallow (Table-2 & Fig.2).

Table-1 : Land use pattern in Tripura

Sl. No.

Land Use Pattern

Area (mha)

1.

Geographical area

1.05

2.

Land utilisation

1.05

3.

Biomass producing area

0.92

4.

Non-Biomass producing area

0.13

5.

Biomass producing common land/Forest area

0.61

6.

Biomass producing Private land

0.31

7.

Percentage of Biomass producing common land

58.09%

8.

Percentage of Biomass producing land

87.62%

         [Source: Land use Statistics for 1994-96, Ministry of Agriculture, 1998]

 


    
Table – 2 : Land use (mha)

Sl. No.

Land use pattern

Area

1.       

Total land

1.05

2.       

Forest area

0.61

3.       

Agricultural area

0.28

4.       

Other

0.13

5.      

Miscellaneous crop

0.027

6.      

Cultivable wasteland 

0.001

7.       

Fallow land

Old

0.001

Current

0.004

Total

0.005

  [Source: Source: Land use Statistics for 1994-96, Ministry of Agriculture, 1998]

 


 

1.1 Soil

The soil types of Tripura can be classified under five major groups, of which Red loam and sandy loam soil occupies 43.07 percent of the total area followed by Reddish yellow brown sandy soils (33.06%), the other three groups occupy less than 10 percent each (Table-3 & Fig-3).

Table-3 : Soil of Tripura  

S. No.

Soil Group

Area

Soil taxonomic unit

Sq. km

Percent

1.

Reddish yellow brown sandy soils

3,468

33.06

(a)    Ultic Hapludalfs

(b)    Udic Ustochrepts

(c)    Typic Udorthents

2.

Red loam and sandy loam soils

4,514

43.07

(a)    Ultic HaplustaIfs

(b)    Typic/Ultic Hapludalfs

(c)    Typic PaleudaIfs

(d)    Typic Ustochrepts

(e)    Typic Drystochrepts

(f)     Udic Ustochrepts

(g)    Typic U.stochrepts

 

3.

 

Older alluvial soils

 

1,019

 

9.71

 

(a)    Typic OchraquaJfs

(b)    Typic Haplaquepts

4. Younger alluvial soils 980 9.34

(a)    Typic Udifluvents

 

5.

 

Lateritic soils

 

510

 

4.86

 

(a)    Typic Palehumults

(b)    Typic Plinthustults

(c)    Typic Plinthudults

(d)    Typic Paleudults

 

 

10,491 100.00    

   [Source : Based on LANDSAT imagery data (1986) and the Atlas of Agricultural  Resources of India (Das Gupta 1980).]

 


 

The annual average rainfall being fairly high (2000-3000 millimeters), the process of chemical weathering and rapid erosion of the soils and bed rocks appear significant.

The occurrence of different soil groups can be correlated with topographical variations, land slope, climate, vegetation cover and present rock material. Dutta et.al. (1982) provided a detailed document of Soil of North Eastern Region including Tripura and showed the association of variable taxonomic units under each of the soil group, ranging between one to seven (Table-4).

1.2 Reddish Yellow Brown sandy Soil

This soil type covers nearly one third of the total geographical area of the State, mostly distributed along north south axis. Poor in nutrient, the sandy soil due to leaching under heavy rainfall, the soil type shows a resilience process through utilization of ground biomass of leaf litters. Tropical evergreen forest of Tripura largely grow in sandy soil but clear felling of trees in the hill forest can cause serious erosion problem to these soil resources.

The reddish yellow brown sandy soil consist of seven soil series.

Table-4 : Reddish Yellow Brown Sandy soil

Sl. No.

Series

Characteristics

1.

Chhnraipara Series

Deep dark grayish brown, in steep hill slope, often eroded, affected by Jhum

2.

Ramdurgabari Series

Sandy loam to loam, in hill slopes, variably eroded, affected by Jhum

3.

Belbari Series

Moderately drained in hill slope, sandy loam to clay loam support thin forest.

4.

Radhamani Series

Very deep, in very steep hill slope, sandy loam to loam, severely eroded, thin vegetation cover.

5.

Dhumachara Series

Dark brown, deep, well drained, in steep slope, sandy clay loam, support shrubs and grasses.

6.

Naraifung Series

Deep, dark brown, moderately well drained, in moderate to steep slope, sandy loam, subsoil ferruginous, under dense forest.

7.

Sankoma Series

Light textured, dark grayish brown to dark brown, moderately drained, in strongly sloping or steep slopes; subsoil clay loam; moderately to severely erosion prone, covered by thin vegetation.

 [Source: Digar et.al. 1982]

 1.3 Red Loam and sandy Loam

About 43-45 percent of total geographical area of Tripura is covered by the red loam and sandy loam soils. Such soil is normally associated with forest ecosystem and is rich in nutrient. In heavy rain fall area, such soil is prone to heavy erosion, specially in slope areas. Due to possible impact of deep ploughing, arable farming in red loam and sandy loam soil is not recommended specially without strict regime of soil conservation. Long cycle of Jhum cultivation is a better way of crop production in such soil zone. It is recommended also for plantation crop with adequate scope for ground cover, specially, rubber, tea, coffee and pineapple. In case of conversion of forest in such soil zone, adequate soil conservation measure is recommended. At least 14 different soil series have been identified by National Bureau of Soil Survey and Land Use Planning in red loam and sandy loam soil of Tripura. (Table-5)

 Table-5 : Red Loam and Sandy Loam Soil

 

Sl. No.

Series

Characteristics

1.       

Tuikarma Series

Dark to dark brown, deep, moderately well drained, in steep slope, with clay loam sub-soil, eroded, under thin forest cover.

2.       

Chandrajaipara Series

Fine loamy soil, dark grayish brown, very deep, well drained, with clay loam sub-soil severely eroded, under forest.

3.       

Hazapara Series

Coarse loamy soil, dark grayish brown, eroded, well drained, under forest.

4.       

Jainarayanpur Series

Fine loamy soil, dark brown, in steep slopes, very deep, with clay loam sub-soil severely eroded.

5.       

Khowai Series

Fine loamy, dark grayish brown, deep well drained, sandy clay subsoil, under shrubs and grasses.

6.       

Monguabari Series

Fine loamy, dark grayish brown, in moderate slope, with clay subsoil, under shrubs and grasses.

7.       

Jhukharaipara Series

Fine loamy, dark grey, very deep, well drained, with clay loamy subsoil, under erosion.

8.       

Kathalbagan Series

Fine loamy, dark grayish brown, moderately well drained, in very steep hill slope, under forest and Jhum.

9.       

Mahamunipara Series

Very dark grayish brown, very deep, in moderately steep to very steep slope, erosion prone, under moderate forest cover

10.   

Kathalia Series

Brown to dark brown on very steep slope, under the forest and plantation crop and Jhum.

11.       

Jagatramchara Series

Very deep, very dark, on gentle to steep slope with clay loam to clay subsoil, under plantation crop and Jhum.

12.       

Ambagan Series

Moderately well drained, on moderate slope, subsoil clay loam, under orchard.

13.       

Paglachara Series

Very deep, dark yellow brown on steep to very steep middle hill slopes, under moderately dense forest and Jhum.

14.       

Gongrai Series

Very deep, dark brown, well drained erosion prone, under forest and Jhum.

[Source: NBSSLUP]

1.4 Older Alluvial Soil

About 10 percent of the State is covered by older alluvial soil. Normally located in river terraces and high plains, the soil is rich in organic nutrient and suitable for arable farming. Much of older soil however remains under tropical forest cover. Due to possibility of gully erosion in uplands, slopes and river terraces, older alluvial soil need special soil conservation measures.

At least five distinct series are recognised under older alluvial soil (Table-6) 

Table-6 : Older Alluvial Soil

 

Sl. No.

Series

Characteristics

1.       

Bakuri Series

In very gently sloping river valley, moderately well drained, covered by grasses and shrubs.

2.       

Tuikthang Series

Fine loamy soil, dark grey, very deep, moderately drained on developing valley land, usually under Paddy cultivation.

3.       

Kalachara Series

Fine loamy soil, ill drained, very deep, in leveled river valley, with silty loam or clay loam subsoil, usually under paddy cultivation.

4.       

Gangasardarbari Series

Fine loamy soil, very deep, greyish brown, well drained, on gently sloping land; subsoil heavy clay loam; partly eroded, covered by bushes, occasionally by paddy cultivation.

5.       

Lalpumbari Series

Fine loamy soil, very deep, dark grey, moderately drained, on gently sloping valley, slightly eroded, under bushes.

[Source: NBSSLUP]

1.5 Younger Alluvial Soil

About 9 percent of the State of Tripura is covered by younger alluvial soil, confined to the flood plains of river (e.g. Khowai, Haora, Gumti and Muhari, etc.). This composed of clay loam and loam and is extremely rich and fertile due to impact of annual flooding. While assured cultivation of Jute and Paddy in such soil regime is known, the danger of erosion by lateral cutting and bank collapse has to be kept under consideration to avoid wash-down to Bangladesh plains from the State of Tripura. River training work was recommended in the earlier “State of Environment Report in Tripura” (1989) in such soil zone.

1.6 Lateritic Soil

 Along the western boundary, moorish upland with lateritic soil can be recognised. Approximately 5 percent of the total land in Tripura can be classified under “lateritic soil”. Coarse in texture and very poor in nutrients, this soil type can support scrubland and wild bushes. No arable farming or agroforestry can be undertaken in this soil condition in view of nutrient material being washed down from bedrock to lower horizon.

1.2 Soil and Optimising Land Use

The National Bureau of Soil and land Use Planning published the results of detailed study on the issue of optimising land use based on soil features (1997) along with two maps. The finding of NBSSLUP showed some vital features.

Four major land classes and seven subclasses could be identified in the state. About 19% of the area belong to class-2 and form the main food grain producing area in the south and west. Drainage is by and large the major limitations for irrigation. Both surface and subsurface drainage is restricted due to (i) very high ground water table either due to depression or other reservoirs, (ii) poor infiltration rate of soil due to high percentage of clay, silt or both. About 12% of land is grouped under class-3, which is composed of very narrow interhill valley; more than 20% land belong to class-4 where topography is major limiting factor for appropriate use, but can be made suitable for the tree crops, plantation crops, horticulture crops and spices.

The issues of soil erosion and soil under flooding also come under serious concern of environmental conservation. In the State of Tripura, soil erosion factors have been grouped under 8 class categories (Table-7 & Fig.,-4). The maximum area come under class 2-2 in the middle level of erosion (26.2%), while insignificant erosion is noted in class 1-0 (19.0%) and highest level of erosion in noted in class 4-3 (10.4%)

Table-7 : Soil Erosion in Tripura

Class

Area in ha.

Percentage

4-3

109730

10.4

3-4

39588

3.8

3-3

10804

1.0

3-2

169630

16.2

2-2

274360

26.2

2-1

206278

19.7

1-1

33986

3.2

1-0

199384

19.0

Water bodies

5047

0.5

Total

1048807

100.00

 


[Source : NBSSLUP, 1997]

  Major causes for erosion are recorded as (i) erosion under water; 25% of Tripura fall under severe to very severe erosion class classification due to removal of vegetation cover. Maximum area falls under moderate erosion.Soil under different flooding condition also limit appropriate use of this vital natural resource base. Fortunately nearly 80% of the area show nil to slight erosion, while 20% of the area show moderate to severe erosion due to flooding of which 4.4% or 45000.8 ha of land show most severe erosion (Table-8 & Fig.-5).

Table-8 : Soil under different flooding classes

 

Class

Area (‘000 ha.)

Percentage

Severe

45.8

4.4

Moderate- Severe

41.8

4.0

Moderate

37.9

3.6

Moderate-Slight

72.9

7.0

Slight

11.3

1.1

Slight-Nil

1.5

0.1

Nil

732.6

69.8

Nil-Slight

100.0

9.5

Water-bodies

5.4

0.5

 


[Source: NBSSLUP, 1997]

With regard to soil degradation, four different class categories were used (slight/moderate/strong/extensive) but extensive degradation has never been noted. The causes for degradation are attributed to water erosion, chemical deterioration, and physical deterioration. Only 113,000 ha. of soil is put under stable terrain under natural condition. Total soil area under “strong” degradation come to 508000 ha or little less than 50 percent of the total geographical area of the state.

1.3Physiochemical Characteristics and Nutritional Status of Soil

Land degradation in Tripura is mainly caused by shifting cultivation, large-scale deforestation, and improper land use. An ICAR report shows a gradual decline in soil pH, organic carbon, clay ratio, available NPK and exchangeable Ca and Mg in shifting cultivation site within a three year cycle (M. Datta et.al. 1995). On the other hand, terraced agricultural land produced an appreciable rise in available NPK but fall in exchangeable acidity and available Fe and Mn contents.  In the agro-forestry system, rhizosphere soil under the cover of some tree species indicate rise in soil pH, organic carbon, water holding capacity, available NPK and exchangeable Ca and Mg, but an inconsistent change in available Fe and Mn was noted. Table -9 Show some physico-chemical properties and nutritional status of soil in different land use system.

Table-9 : Physico-chemical properties and nutritional status of soil

Site

pH

O. Carbon (%)

Max. Water holding capacity (kg/kg)

N

(kg/ha)

P

(kg/ha)

K

(kg/ha)

A.

Shifting Cultivation Site

Peripheral upland

4.5

0.87

0.35

241.4

2.0

87.6

Midland

4.5

0.69

0.36

239.2

1.7

101.4

Lowland

4.9

0.84

0.39

329.3

3.8

100.0

B.

Agricultural Land use Site

Peripheral table land

4.4

0.90

0.41

372.5

7.7

161.0

Terraced Midland

4.7

0.70

0.39

308.6

2.9

73.9

Terraced Lowland

4.2

0.87

0.39

337.4

4.5

111.0

C.

Horticultural Land use Site

Halfmoon Terraced Lowland

5.6

0.67

0.39

436.6

4.9

175.7

Halfmoon Terraced Midland

4.9

0.66

0.40

384.5

5.3

146.7

Halfmoon Terraced Lowland

5.7

0.69

0.42

411.8

4.8

133.0

[Modified from M. Datta el.al. 1995]

1.4Soil Conservation

The State Soil Conservation Department linked with Horticulture Department have undertaken two major programme - heads viz. “Watershed Development Project in Shifting Cultivation Area”, “National Watershed Development project in Rain-fed area” since 9th Five Year Plan.  Under these two thrust areas (as per the information provided by the authorities), selected area-based projects have been undertaken (Table-10).

Table-10 : Soil Conservation Projects

A.

Watershed  Development Project in Shifting Cultivation Area

 

No. of Projects

South (ha)

North (ha)

 

Dhalai (ha)

 

West (ha)

 

Total (ha)

 

 

Target

Achievement

Target

Achievement

Target

Achievement

Target

Achievement

Target

Achievement

14

8478

4578

4176

2490

3457

1728

NA

NA

16111

8796

B.

National Watershed  Development Project in Rainfed Area

 

No. of Projects

 

Total Area

Total Allocation

 

 

Target

 

Allocation

Target

 

Allocation

46

48936

23000

1800

957.08

It is apparent that the programmes have so far achieved nearly 50% of the targeted area since 1997-98 (for B) and 1998-99 (for A); as programmes are scheduled to be completed by March 31, 2002, the targeted coverage of soil conservation work would be hard to complete. More strategic planning, timely release of fund and monitoring of field based work -progress will be essential for conservation of soil resources of the State. It is noted that the Soil Conservation Department has no programme on the affected Forest area, and as such soil conservation work in the upper catchment area remains largely unattended. The State Forest Department has no separate programme for soil conservation (normally Forest and Soil Conservation works are linked up in other Indian states). A review of current soil conservation works and required support to the cartographic system appears essential for protecting this vital resource base. In order to build capacity, training in the use of Remote Sensing data, (also lacking in the present set up) is strongly recommended during early phase of 10th Five Year Plan.

 
top