Fertility Potential Classification of Soils in Different Landscape Units of the Northern Brahmaputra Valley Zone of Assam

The Brahmaputra valley of Assam is a part of the vast Indo-Gangetic plain and covers an area of 56,578 km2. Fifty rice-growing soils from different landscape units of the northern Brahmaputra valley zone of Assam were evaluated for their fertility potential classification. The fertility potential classification was carried out by using principal factor analysis. Altogether 27 soil properties including all major physical, chemical and erosion related parameters were used in the analysis. The principal factor analysis synthesized seven factors which explained 81% variability. Based on the calculated component scores the individual soils as well as the landscape units were graded. The soils of Dhullie (No. 32) ranked top from fertility point of view. Among the different landscape units of the studied area the old flood plain soils were found to be the most fertile. It was recommended that the characters which affect adversely on soil fertility should not be considered in evaluating fertility potential. The grading and ranking of the soils appear to be in close agreement with soil chemical analysis.