Chapter-3 GEOGRAPHICAL LOCATION, CLIMATE AND SOIL CHARACTERISTICS OF THE STUDY SITE

Transcription

1 Chapter-3 GEOGRAPHICAL LOCATION, CLIMATE AND SOIL CHARACTERISTICS OF THE STUDY SITE

2 Chapter-3 GEOGRAPHICAL LOCATION, CLIMATE AND SOIL CHARACTERISTICS OF THE STUDY SITE Assam, the eastern most state of the Indian sub-continent, extends from 22.19' to 28.16^ North latitude and 89.42'to 96.30' East longitude between the foot hills of the Eastern Himalayas and the Patkai and Naga ranges. Assam is bordered in the North and East by the kingdom of Bhutan and Arunachal Pradesh. Along the South lie Nagaland, Manipur and Mizoram. Meghalaya lies to her South-West, Bengal and Bangladesh to her West. Southern Assam (Barak Valley) comprising three districts, namely Cachar, Karimganj and Hailakandi, is situated between longitude 92.15''and 93.15" East and latitude 24.8" and 25.8"North, covering an area of 6,941.2 sq. km. of land. It is bounded on the North by North Cachar Hills district of Assam and Jaintia Hills district of Meghalaya, on the South by Mizoram, on the East by Manipur and by Tripura and Sylhet district of Bangladesh on the West » N.E.INDIA-^t Figure 13: Map showing geographical location of Southern Assam (Barak Valley). 61

3 Southern Assam experiences a subtropical monsoonic climate with an annual rainfall ranging between mm. The average annual rainfall of Southern Assam is over 3000mm and about 80-85% of this rainfall occurs during the months of April/May-September/October. December and January are normally the driest months. Pre-monsoon rains often accompanied by thunder and hail occur in April-May, and the monsoon arrives in early June and continues till September, although heavy rains may also occur in October. The seasonal pattern of rainfall and its variations from year to year govern the flood pulse and determine the extent and duration of inundation of the low lying rice fields by the overflowing river waters. During summer, average maximum and minimum temperature of Southern Assam is 35*'C and 26 C respectively. In winter, average maximum and minimum temperature becomes 25 C and 11 C respectively. The average relative humidity in rainy season is 94% in the morning and 75% in the evening. In Southern Assam maximum temperature and relative humidity is recorded in the months of July and August. The Southern parts of Assam (Barak Valley) are characterized by a warm and humid climate with a heavy annual rainfall. " ""Cachar *^Karimganj ^ Hailakandi Apr I I I I I I I I I I I I I May Jun Jul Aug Sep Oct Nov Figure 14: Monthwise average rainfall (mm) of the three districts of Southern Assam during last 5 years ( ). Rainfall data were collected from Meteorological Centre, Cachar College, Silchar. 62

4 ICachar n Karimganj D Hailakandi a a S <u H 40n 30 20' 5- Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec Figure 15: Monthwise average maximum and minimum temperature ( C) of the three districts of Southern Assam during last five years ( ). Data on temperature were collected from Meteorological Centre, Cachar College, Silchar. BCachar D Karimganj D Hailakandi VP 0^ s 3 'E 3 JS ' Z* Pi so lo Jan May Jun Jul Aug Sep Oct Nov Dec Figure 16: Monthwise average maximum and minimum relative humidity (%) of the three districts of Southern Assam during last five years ( ). Data on relative humidity were collected from Meteorological Centre, Cachar College, Silchar. 63

5 The topography comprises low-lying areas with numerous small hillocks strewn in between. The soil of the zone varies from alluvial to laterite soil. Texture is generally clay loam to clay. The riverine tracts are found to be of loam to sandy soil. The soil salinity of the three districts of South Assam is below 1 and the soil of the zone is very good for plant growth and development. The rice field soils have an average ph ranging from indicating the acidic nature. Table 1: Soil characteristics (mean + SD) of the rice fields of Southern Assam in autumn (A) and winter (B) cropping season. Statistical comparisons of A and B by one-way ANOVA. Soil characteristics ph Texture Sand (%) Sih (%) Clay (%) Electrical Conductivity (dsm') Water Holding Capacity (%) Organic Carbon (%) Nitrogen (%) Phosphorus (kg/ha) Potassium (kg/ha) A Autumn (ahu) season 5.3± K ± ±1.3 B Winter (sali) season 5.6± ± ± ±1.6 Rankings based on One-way ANOVA A<B (P<0.05) A>B (P< 0.05) A<B(P<0.0001) A>B (P<0.05) A<B (P<0.05) A<B(P<0.01) Source: Soil Testing Laboratory, Silchar, Govt, of Assam. : Not significant The climatic condition of Barak Valley favour rice cultivation in tropical lowlands. The Valley is characterized by heavy annual rainfall over 2500 mm, medium temperature range (15-35 C) and high relative humidity (>75%). Maximum rainfall occurs between May to August lowering the soil ph to its minimum. The temperature and relative humidity are also higher in the summer months between May to August. Among the three districts, maximum annual rainfall and relative humidity occurs in the Karimganj district whereas maximum annual temperature is found in Hailakandi district. All the three districts have a tropical warm humid climate with heavy annual rainfall. 64