Effect of Stream Sizes and Furrow Geometry on Furrow Irrigation Erosion in Samaru, Northern Nigeria

Furrow irrigation is one the most widely used means of water application to crops in Samaru and environs. Erosion created by furrow irrigation is threatening the sustainability of furrow irrigation in Samaru. The continuous loss of soil rich in plant nutrients depresses the productive capacity of soils. This study explored the effects of three irrigation stream sizes (2.5, 1.5 and 0.5 l/s) two furrow lengths (90 and 45 m) and two furrow widths (0.75 and 0.9 m) on furrow irrigation-induced erosion. Measurements of runoffs and sediment concentrations in furrows during irrigation events were made in the dry irrigation seasons of 2009/2010 (trial 1) and 2010/2011 (trial 2) on an area of 0.36 and 0.2 ha respectively. Soil erosion in each furrow was computed from the runoff, sediment concentrations and the furrow wetted area. Wooden profilometers were used to examine the dynamics of soil erosion along the furrows. The variations in soil erosion among the treatments were significant at P<0.001. The application of 2.5 l/s stream size induced the highest soil erosion of 0.4697 t/ha/season and runoff volume of 104.47 l/season. The use of 45 m-long furrow length resulted into the highest soil erosion of 0.4986 t/ha/season. And soil erosion of 0.4700 t/ha/season was recorded in 0.75 m-wide furrows. The results evidently showed that stream size was principally responsible for the erosion losses during furrow irrigation. Short furrows that limit redistribution of eroded soil particles, were more prone to erosion than long furrows. The result also pointed that increasing furrow width from 0.75 m could be a means of limiting furrow irrigation erosion. The in- field soil erosion measurements showed that bulk of the soil erosion occurred from the head end of the furrows and deposited on the lower portions of the furrows.