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ASSAM

Geographical position and climate

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Assam one of the state of the north-east India, is situated between 24 and 28 16’ latitudes and
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89 4’ and 96 0’ longitudes. The state has three distinct physiographic units the plain, the plateau
and the hills. The Brahmaputra and the Barak river valleys accounting for 80.8% of total
geographic area are the two priority units for agricultural development in the plains. The Assam
plateau covering the districts of KarbiAnglong and Dima Hasao seperates both the valleys. On
the basis of variation in physiography, climate, soil, farming systems, crop and cropping system
and hydrology, the state of Assam has been classified into six agro-climatic zones under the
National Agricultural Research Project. The climate of Assam is humid subtropical in nature
with warm-humid summer and cool dry winter. Assam at present consists of three hill districts
and thirty plain districts.The climate of the hills is generally salubrious while that of the plains is
comparatively warm in summer but cool in winter.Assam experiences the predominant influence
of the south west tropical monsoon which is normally active from April to October with
occasional winter showers. The annual average rainfall of the state varies between 1600and 3569
mm. The average rainfall for the state as a whole is about 2900mm with maximum precipitation
during June and July. The average temperature in the state varies from 4 to 19°C during the
winter and 26 to 37°C during the summer accompanied by high humidity.

Soils

The major portion of soils of Assam belong to Inceptisols (49.3%) followed by (Entisols 32.3%),
Alfisols (12.3%) and Ultisols (6.1%). The diversified geological conditions, topographical
characteristics, climatic situations and vegetation types have favour the formation of different
types of soil in the state. The most typical characteristics of Assam soil is its acidity. Major parts
of soils of Assam are acidic in nature having pH ranges from 4.2-5.8. The soils of flood plains
have slightly high pH(6.0-6.5). One stricking point is that the soils of hill zone and the area
bordering or adjacent to this zone have higher pH ranging from 6.0-7.1. The organic matter
content of these soils is generally high, while the same in majority of soils ofAssam is medium to
high. The available nitrogen in soil has been rated as low to medium in Upper Brahmaputra
Valley Zone (UBVZ), North Bank plain Zone(NBPZ) and Lower Brahmaputra Valley Zone
(LBVZ), whereas it is medium in the hill zone. The status of P 2O 5is low inUBVZ, NBPZ and
LBVZ medium to high in Barak Valley (BV), low in Hill Zone and medium in Central
Brahmaputra Valley zone (CBVZ). The K 2Ostatus in the soil is low to medium in UBVZ, NBPZ
and LBVZ, medium in Central Brahmaputra Valley zone (CBVZ) and Barak Valley zone (BV)
and low in hill zone. The deficiency of secondary and micronutrients in soils of the state is on
rise because of enhanced area under intensive agriculture. Data collected during delineation
programme under AICRP- MSPE, Assam revealed about 17.1, 22.0 and 29.7% deficiency in
sulphur, zinc and boron, respectively.

Crops and cropping systems

Assam accounts for a fairly significant share of the country’s acreage and output of many crops.
Notably are rice, rapeseed and mustard, black gram, green gram, lentil, jute, sugarcane, tea,