Abstract
Irrigation is of major importance in many countries. It is important in terms of agricultural production and food supply, the incomes of rural people, public investment for rural development, and often recurrent public expenditures for the agricultural sector. Nigeria’s irrigation system is confronted with many challenges which included a widening gap between demand for food and domestic supply as a result of population growth and changing patterns of consumption. The evaluation study was carried out at the Itoikin Irrigation Scheme using performance indices. The site is one of the irrigation projects under the Ogun-Osun River Basin Development Authority (O-ORBDA) located in the Epe Local Government Area of Lagos State. The potency and vulnerability of Itoikin Irrigation Scheme were evaluated. The physico-chemical properties of soil, soil and water inventory were used to carryout the evaluation. Soil samples were collected at different depth and taken to the laboratory for measurement and Analysis. Soil and water inventory, Crop water requirement and evapotranspiration, Irrigation scheduling for maize and rice at the scheme and Analysis of moisture content were assessed. The range of electrical conductivity (EC) is measured and the values range from 102.8 ms cm-1 to 308 ms cm-1. The lowest electrical conductivity is 102.8 ms cm-1 at F4, depth 30-45 cm while the highest is 308 ms cm-1 at F3, depth 15-30 cm. The hydraulic conductivity (k) ranges from 3.75 × 10-4 to 8.99 × 10-4 cm s-1. The lowest of the hydraulic conductivity was in F3 at depth of 25-50 cm in silt clay loam, while the highest was in F2 at depth of 25-50, in silt clay. The (EC) is too high and needs to be reduced. Root development will not pose as a problem as the bulk density will not restrict the development of the root, while the soil pH will allow the cultivation of maize, rice and vegetables. The minimum temperature ranged between 21.8ºC and 24.1ºC while the maximum temperature ranged from 28.2ºC to 33.2ºC. The average minimum and maximum temperatures are 22.8ºC and 30.8ºC respectively. The highest humidity was recorded on June (100%). The wind speed ranged between 156 km day and 207 km day and the values does not pose any adverse effect on the productivity of the crops. The evapotranspiration (ET) ranged between 2.5 mm day-1 and 4.22 mm day-1 with an average of 3.44 mm day-1. High values of evapotranspiration (ET) recorded in the months of February, March and April indicates that more water is loss during this period. The (ETcrop) and crop water requirement for maize at the scheme varied from 1.36 to 6.35 mm day-1 and 5.1 to 63.5 mm dec-1 respectively. The total amount of water consumed by the crop is 398.2 mm dec-1, while the effective rainfall was 212.2 mm dec-1 during the farming season. The total evapotranspiration is 494 mm dec-1. The crop evapotranspiration (ETcrop) and crop water requirement for rice at the scheme varied from 0.35 to 4.30 mm day-1 and 1.0 to 47.1 mm dec-1 respectively. The total amount of water consumed by the crop is 494.3 mm dec-1, while the effective rainfall was 250.3 mm dec-1 during the farming season. The total evapotranspiration is 491.9 mm dec-1. The soil moisture contents were investigated to the depth of 45 cm. The minimum and maximum values are 20.6 mm and 34.66 mm on plot 6 were recorded. Down the profile, there is an increasing trend which posed the water at the scheme to be lost by deep percolation than runoff and evaporations.