Appraisal and Mapping of Soil Salinity and Sodicity Problems In Sector One of Watari Irrigation Scheme, Kano State.

Abstract

One of the main reasons for the loss of productive land in irrigated fields is the buildup of salinity in the soil. In the watari irrigation Scheme, no systematic ap- praisal and mapping have been made before within the sector. The study area was selected after a reconnaissance survey based on the farmer's complaint about the low production. Global positioning system (GPS) was used to record the coordi- nate, and delineate the boundary of the study site. The coordinates of the deline- ated boundary were Geo tagged on Google Image to obtain the image of the study site. Grids of 100 x 100m were superimposed on the Geo tagged image and were used as sampling points. A total of 234 samples were obtained from 160 ha of land for the study; within each grid, four soil samples were collected at a depth of 0 – 20cm, and mixed them into one sample from each grid. The collected sam- ples were processed and analyzed using standard laboratory procedures for salini- ty and sodicity evaluation. Standard methods were followed to measure pH, elec- trical conductivity (EC), and soluble cations. Arc GIS 10.3 was used to map out the varying degree of salinity and sodicity. The extent of the area of the classes and percentage coverage indicated that the non-saline area covers about 28.80% (46 ha) of the total land size. But 25.50% (40 ha) of the sector were slightly sa- line, moderate salinization problem within the sector occupied 34.10% (54.6 ha) of the land area. Only 11.6% (18.6 ha) of the total land size had both salinity and sodicity hazards of the sector with ECe dSm-1 and SAR values greater than 4 dSm-1 and 13, respectively. Based on the findings, the extent of soil salinity and sodicity of the study area revealed that substantial parts were consistently and continuously affected by salinity problem 71.2% (114 ha). Specific proportions of the irrigated land need special attention so as to prevent and control secondary salinization. The sodic soil should be controlled at the earliest before the soil structure is entirely destroyed since only 28.80% (46 ha) is free. The water table control by rehabilitating the subsurface drainage system seems to be the only feasible way to improve the sustainability of the scheme.