Study of Soil Nutrient Status of Doddavaram Microwatershed in Koyyuru Mandal of Visakhapatnam District, Andhra Pradesh, India

Aims: To asses the fertility status of the soils of Doddavaram microwatershed of Koyyuru mandal of Visakhapatnam district, Andhra Pradesh in which twenty soil profiles were studied for soil physico-chemical properties (pH, EC, OC) and soil nutrient status (N, P2O5, K2O, Zn, Cu, Fe and Mn).

Study Design: The soil profiles were selected based on the slope and its heterogeneity

Place and Duration of Study: Doddavaram microwatershed of Koyyuru mandal of Visakhapatnam district, Andhra Pradesh located in between 17° 38' 4.779" to 17° 42' 15.440" of North latitudes and 82° 10' 56.784" to 82° 15' 1.372"East longitudes

Methodology: Preliminary traverse of the entire watershed was carried out using 1:10,000 scale base map and satellite imagery. After delineating the landform on the satellite image, intensive traversing of each landform was undertaken to select the representative areas for transect study based on geology, drainage pattern, surface features, slope characteristics and land use, landforms and physiographic divisions. Transects were located across the slope at right angles to the contours and covers most of the variations observed in a landform. In each selected transect, profiles were located at closely spaced intervals to take care of any change in the land features like break in slope, erosion, gravels and stones etc . In this way totally twenty (20) soil profiles were opened and soil samples were collected and analyzed in the laboratory for soil nutrient status.

Results: The results revealed that the soils of Doddavaram microwatershed were very strongly acidic to slightly alkaline (4.58 to 7.82) in reaction, non-saline (0.02 to 0.17 dS m-1), low to high (0.10 to 0.78%) in organic carbon. Moreover, these soils were low to medium in available nitrogen (28.30 to 147.14 mg kg-1), available phosphorus (2.19 to 14.78 mg kg-1 P2O5) and available potassium (27.63 to 117.44 mg kg-1 soil). The available sulphur content in the soils varied from deficient (1.41 mg kg-1) to sufficient (20.83 mg kg-1 soil). The surface horizons of pedons 1,2,9,10,11,13,14,15,16,1718,19 and 20 were sufficient in DTPA extractable zinc, while the pedons 3,4,5,6,7,8 and 12 showed deficient levels in the surface horizons. Moreover, the zinc concentration in the sub-surface horizons was sufficient to deficient. The surface and sub-surface horizons of all the pedons in the study area of Doddavaram microwatershed were found to be sufficient in DTPA extractable copper, iron and manganese and found to be above the critical limits.

Conclusion: The analysis of macronutrients in the soils of Doddavaram microwatershed of Koyyuru mandal of Visakhapatnam district revealed that soils are low to medium in available nitrogen, phosphorus and potassium and deficient to sufficient in available sulphur. soils of the microwatershed were deficient to sufficient in available Zn and sufficient in available Fe, Cu and Mn.