GEOGRAPHIC INFORMATION SYSTEM-BASED IRRIGATION SUITABILITY EVALUATION OF LAPAI-AGAIE IRRIGATION SCHEME, NIGER STATE, NIGERIA.

Abstract

Irrigation is one of the most important inputs for an efficient and sustainable agricultural production. Many farmers are out of jobs during the dry season and prices of locally produced food are high as a result of food scarcity during this period. The objective of this study was to map potential irrigable areas based on soil physical properties and slope of the study area. To evaluate the land suitabilityfor irrigation, parametric evaluation system was applied, using soil and land characteristics. Suitability classes were defined considering the value of suitabilityindex. The overall soil suitability was estimated using the weightage of each factor(slope, soil pH, soil texture, Infiltration rate, Organic carbon, Effective soil depth, Available water capacity, Cation Exchange Capacity, exchangeable sodiumpercentage and drainage) to obtain potential irrigable sites. The ratings wereselected for different qualities. Suitability classes were defined considering thevalue of suitability index. Land suitability index was calculated based on ratings ofall factors using the equation of Rabia method of parametric evaluation system. Thedata were combined using a multi-criteria decision approach to select suitable sites for irrigation. Landsat imagery with 30m resolution was used for the overall landsuitability classification. Using an overlay tool in ArcGIS 10.1, overlay (weighted) analysis of the above factors was performed to generate thematic maps for eachfactor to develop Land Suitability maps of the study site. The GIS maps afterweighting maps of all the factors in Lapai-Agaie 1 shows 28.08 ha out of 86 ha of Lapai-Agaie 1 was marginally suitable for irrigation, 20.29 ha was moderatelysuitable and a small portion (3.6 ha) of the mapping unit was highly suitable. Marginally suitable class covered the largest area (52.46 ha out of 62 ha) of LapaiAgaie

2. Lapai-Agaie 3 which occupies 52 ha of the study site had the largest portion (44.64 ha) of the mapping unit as moderately suitable (S2), followed bymarginally suitable and a smaller portion (3.7 ha) was highly suitable. Generally,this study shows that sprinkler and drip irrigation will be preferable to surfaceirrigation since these irrigation methods were suitable for undulating slope withoutrequiring land grading and may be reliable in improving yield. The effective soildepth, slope, organic matter and available water capacity were factors that posed athreat to surface irrigation suitability in the mapping units of the study site. Landsuitability map would help in developing land use plans and formulating environmental planning policies that can enhance the development of agricultureand help in improving food insecurity in Nigeria. It was recommended that GISsystem should be adapted when evaluating the suitability of soils for irrigation.Sprinkler and drip irrigation methods will be more profitable in the study site.Organic matter application will be required to improve the organic matter content of the soil.