MORPHOMETRY, SOIL ERODIBILITY AND PRODUCTIVITY POTENTIAL OF A TRANSECT OF MORIDHAL RIVER BASIN IN DHEMAJI DISTRICT OF ASSAM

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dc.contributor.advisorDeka, Bipul
dc.contributor.authorBharteey, Prem Kumar
dc.date.accessioned2021-01-06T08:04:38Z
dc.date.available2021-01-06T08:04:38Z
dc.date.issued2020-08
dc.description.abstractThe present investigation was carried out to study the morphometry, soil erodibility and productivity potential of Moridhal river basin in Dhemaji district of Assam. The Moridhal watershed, encompassing 30,730 ha geographical area, is situated between 94052 E to 94069 E longitude and 27038 N to 27064 N latitude. Based on total variation in satellite data (Resourcesat-2, LISS-4), four distinct physiographic units of the Moridhal watershed were delineated which includes: upper piedmont plain (1,844 ha), lower piedmont plain (2,391 ha), alluvial plain (9,888 ha) and flood plain (16,607 ha). The stream order map of the Moridhal river basin was prepared by on screen digitization using Q GIS software and the morphometric parameters were evaluated through measurement of linear, areal and relief aspects. The drainage streams were delineated up to 4th order with stream numbers of 36, 14, 5 and 1, for I, II, III and IV order, respectively. The mean bifurcation ratio and Rho coefficient for the Moridhal watershed was computed to be 2.22 and 0.41, respectively. The computed value of aerial aspects like elongation ratio, circulatory ratio, form factor ratio and shape factor revealed elongated shape of the watershed area. The studied relief aspects include parameters like basin relief, relief ratio, ruggedness number, and relative relief. The calculated value of ruggedness number (0.03) and relative relief (0.055 per cent) indicated higher infiltration and lower runoff in the studied area. GPS based surface and core soil samples representing different physiographic units were collected and analyzed for various physico-chemical properties. The texture of the studied soils varied from loamy sand to clay, sandy loam being dominant. There was an increasing trend of very fine sand and silt content from upper piedmont plain to floodplain. The bulk density and particle density of studied soils varied from 1.10 to 1.67 Mg m-3 and 2.16 to 2.74 Mg m-3, respectively. The value of porosity, water holding capacity and hydraulic conductivity of the studied soils ranged from 24.99 to 54.68 per cent, 19.88 to 63.12 per cent, and 0.11 to 6.54 cm hr-1respectively. Field capacity and available water content showed significant positive correlation with clay content and porosity, while permanent wilting point exhibited significant positive correlation with sand content. The pH of the soils was extremely acidic (4.2) to slightly acidic (6.3). The electrical conductivity in the studied soils varied from 0.01 to 0.16 dS m-1 which was almost negligible. The cation exchange capacity of the studied soils varied from 3.88 to 19.40 cmol (p+) kg-1 with a mean value of 9.69 cmol (p+) kg-1. Amongst the exchangeable cations, Ca++ was found to be the dominant in the studied soils followed by exchangeable Mg++, K+ and Na+. The exchange capacity of clay and apparent CEC showed wide variation in the studied area. The base saturation varied from 33 to 83 per cent and the organic matter content was medium to high (range 5.50 to 29.60 g kg-1). The available N, available P2O5 and available K2O content varied from low to high with a range between 137.98 to 570.75 kg ha-1, 18.47 to 67.20 kg ha-1 and 37.23 to 549.16 kg ha-1, respectively. The nutrient index for available N, P2O5 and K2O were found to be 1.88 (Medium), 2.15 (Medium) and 1.32 (Low). The principal factor analysis, which was carried out using 35 characters, could explain 71.20 per cent of the total variance with the seven number of extracted eigen values. There was an increasing trend of macroaggregate from upper piedmont plain (mean 24.9 per cent) to flood plain soils (mean 47.4 per cent). The microaggregate in the studied soils varied from 17.8 to 89.8 per cent and the mean weight diameter ranged between 1.00 to 2.74 mm. The erodibility of the studied soils was assessed by computing various erodibility indices like clay ratio, silt clay ratio, modified clay ratio, dispersion ratio, erosion ratio and erosion index. The mean value of clay ratio, silt/clay ratio and modified clay ratio were found to be 4.02, 1.35 and 3.63, respectively. The dispersion ratio of the soils varied from 0.06 to 1.18 with a mean value of 0.19. It was observed that 48.82 per cent of the total studied soil samples had dispersion ratio values above 0.15 which may be considered as erodible. The erosion ratio and erosion index of studied soils varied from varied from 0.01 to 0.55 and 0.03 to 0.71, respectively. It was observed that almost all the studied physico-chemical properties influenced the erodibility indices to a great extent. The soil loss varied from very slight to very severe (range 0.87-67.77 t ha-1 yr-1) with a mean value of 16.19 t ha-1 yr-1. A significant positive correlation of soil loss was noticed with very fine sand (r = 0.229**), silt (r = 0.212**), microaggregate (r = 0.351**) and relief (r = 0.711**). The studied soils exhibited a decreasing trend of soil loss from upper piedmont plain towards flood plain. The productivity indexes of the studied soils varied from 12.13 to 62.14 with a mean value of 35.22. The potentiality index and coefficient of improvement values of studied soils varied from 41.04 to 90.25 and 1.11 to 4.69, respectively. Soil site suitability criteria for crops viz., Sali rice, Ahu rice, Boro rice, wheat, mustard/rapeseed, sesame, pea, potato, onion and coconut were evaluated. The study revealed that the soils were permanently unsuitable (N1) to moderately suitable (S2) for Sali rice, Ahu rice, Boro rice, wheat, pea, mustard/rapeseed, sesame, potato, onion and coconut. Major constraints identified in the watershed lies in acidity, organic carbon, texture, flooding, drainage and low precipitation in early growth stage during rabi season. GIS based maps for various themes like pH, organic matter, available N, available P2O5, available K2O along with soil loss, productivity, potentiality, and soil-site suitability for studied crops were also prepared to depict the spatial distribution under different classes.en_US
dc.identifier.urihttps://krishikosh.egranth.ac.in/handle/1/5810159272
dc.language.isoEnglishen_US
dc.publisherAAU, Jorhaten_US
dc.subSoil Sciencesen_US
dc.themeMORPHOMETRY, SOIL ERODIBILITY AND PRODUCTIVITY POTENTIAL OF A TRANSECT OF MORIDHAL RIVER BASIN IN DHEMAJI DISTRICT OF ASSAMen_US
dc.these.typePh.Den_US
dc.titleMORPHOMETRY, SOIL ERODIBILITY AND PRODUCTIVITY POTENTIAL OF A TRANSECT OF MORIDHAL RIVER BASIN IN DHEMAJI DISTRICT OF ASSAMen_US
dc.typeThesisen_US
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