MSc.

A research work has been done to characterise the soils of Koliyoor watershed using Geographic Information System (GIS) tools. In order to generate various thematic layers, cadastral maps (1:5000), toposheets (1:50000), DEM (ASTER-30m) and satellite imageries of Google earth were used. The watershed was transected and soil sample were collected. The attribute data base, formulated using the results of chemical analysis of 174 soil samples was integrated into the GIS and various thematic maps were produced.
The major outputs generated on the Koliyoor micro watershed were the rated fertility maps of Organic Carbon, Available Phosphorus, Available Potassium, Available Sulfur, Available Calcium, Available Magnesium, Available Iron, Available Manganese, Available Copper, Available Zinc, and Available Boron. Maps showing the spatial variation of Soil Reaction, Electrical Conductivity, Bulk Density, Water Holding Capacity, Slope Aspect and Slope Classes were also generated. Data of Organic Carbon content was used for rating of Available Nitrogen. Using the thematic layers of Available Nitrogen, Available Phosphorus and Available Potassium, map showing NPK status also was generated.
The samples fell into two textural classes namely, Sandy Clay Loam and Sandy Loam. Soils were acidic with an average soil reaction of 6.02. Most of the samples were in Medium Acid class and the least in Neutral class. Highest mean value (6.1) of soil reaction was recorded from the samples taken from plots of coconut based cultivation. Electrical conductivity of the soils of Koliyoor micro watershed ranged from 0.01 to 0.26 dS/m which means that only non-saline soils are there in this area.
Organic carbon content of the samples ranged from 0.1 to 1.9 % with a mean value of 0.72 %. Plots of homestead cultivation showed maximum mean status (0.82 %) of organic carbon in samples. Majority of the watershed area belongs to the Medium class of available phosphorus with a range of 3.1 to 59.1 kg/ha and mean value of 22.1 kg/ha. The samples from converted paddy fields showed highest mean value (25.5 kg/ha) of P status. In the case of potassium also, majority of the area shows medium status. It ranged from 20.16 to 481 kg/ha. The mean value was found as 196.55 kg/ha. Samples taken from converted paddy fields showed highest mean availability of potassium (210 kg/ha). Soil samples from homestead area showed lowest mean value (101.4 kg/ha).
NPK status analysis revealed that, only 0.1 ha area showed low status for all of the three nutrients. High status was shown for these nutrients by about 15.23 ha area. 200 ha area was medium in the case of combined in NPK status.
Sulfur content of the samples ranged from 8.93 to 71.4 kg/ha with a mean of 30 kg/ha. The highest average value (39.2 g/ha) was seen among the samples from homestead cultivation and lowest mean (12.1 kg/ha) was from non-agricultural area. Koliyoor watershed showed relatively higher Ca content that ranged from 75 to 900 ppm with a mean value of 337.33 ppm. Converted paddy field samples were with the highest mean value (428.5 ppm) and the lowest mean availability (301.1 ppm) was seen in the plots of coconut based cultivation. Magnesium deficiency was seen all over the area, which ranged from 12 to 167 ppm with a mean value of 49.47 ppm and mode value of 42 ppm. Converted paddy fields showed comparatively high status of available magnesium with a mean value of 91 ppm while the lowest mean status (32.8 ppm) was seen in the samples from coconut based cultivation.
Iron status in the soils ranged from 4.6 to 164 ppm with an average value of 49.62 ppm. Highest mean value (69 ppm) was seen in converted paddy fields and the lowest (41.03 ppm) from non-agricultural area. Soil samples from the study area ranged from 0.01 to 8.66 ppm in available copper content. Mean value obtained was 3.47 ppm. Samples from converted paddy fields showed highest mean value (4.1 ppm). The lowest mean value (1.1 ppm) was obtained from non-agricultural area. Koliyoor micro-watershed showed 100 % sufficiency of available manganese. Soil samples ranged from 5.5 to 95.3 ppm in manganese availability. The mean status obtained is 32 ppm. Plots of homestead cultivation showed higher availability of manganese and highest mean value of 40.01 ppm. Lowest mean value (21.33 ppm) was seen in non-agricultural area. Soil samples showed a range of 0.03 to 4.01 ppm regarding zinc availability. The average value obtained was 0.71 ppm. Among the land use types, plots of homestead cultivation showed higher zinc availability with a mean value of 1.01 ppm. The lowest mean value (0.53 ppm) was seen in the category of converted paddy fields. Soils of Koliyoor micro watershed showed an overall deficiency in Boron availability. It ranged from 0.01 to 0.66 ppm with an average value of 0.27 ppm. Coconut based cultivation showed lowest mean availability (0.22 ppm) of boron while samples from non-agricultural area showed highest mean status of 0.43 ppm.
Bulk density of the samples ranged from 1.3 to 1.7 mega gram per cubic meter with an average value of 1.4 mega gram per cubic meter. Organic matter status and texture of the soils were important in influencing the bulk density of soils. The samples showed a range of 18 to 29.8 per cent regarding water holding capacity. Average value obtained was 23.4 per cent.
The slope of Koliyoor micro watershed ranged from zero to 15 percentage forming five classes, ranging from ‘Nearly Level’ to ‘Strongly Sloping’. Within the obtained range of slope gradient, three topographical classes were identified, ranging from ‘Flat’ to ‘Rolling’ type. In Koliyoor micro watershed, the land showed 9 slope aspect classes facing the directions ranging from Flat to North-West.
The data on soil resources of Koliyoor micro watershed were integrated in a GIS environment and thematic maps on all the parameters were generated. Spatial distribution of different classes of nutrients was used for fertility characterisation of the watershed.