Evaluation of Sprinkler Irrigation Uniformity for Vegetable Production in Osun State

This study evaluates sprinkler irrigation uniformity and its implications for vegetable production efficiency in commercial vegetable farms in Osun State, South West Nigeria. Sprinkler irrigation is increasingly adopted by medium-scale vegetable producers in Southwest Nigeria as an alternative to surface furrow irrigation, offering potential advantages in water distribution and labour saving. However, the uniformity of water application from sprinkler systems significantly affects yield distribution and water use efficiency, and system performance under Nigerian field conditions has received limited engineering evaluation. This study measures Christiansen's uniformity coefficient, distribution uniformity, and water application efficiency for sprinkler systems installed on 10 commercial vegetable farms in Osogbo, Ede, and Ile-Ife. Catch can tests are conducted under representative operating pressures and wind conditions. Vegetable yield spatial distribution is mapped using georeferenced yield sampling across 15 measurement points per field. Regression analysis links uniformity coefficients to yield spatial variability. Findings reveal that average Christiansen's uniformity coefficient across farms is 76.5 percent, below the recommended minimum of 85 percent. Low-uniformity areas in each field show vegetable yields 31 percent lower than high-uniformity zones. Wind speeds above 2 metres per second are associated with significant uniformity reductions. The study concludes that sprinkler system performance is suboptimal on most sampled farms. It recommends system redesign with appropriate nozzle selection, operating pressure optimisation, and irrigation scheduling during low-wind periods.

Keywords: sprinkler irrigation, uniformity, vegetable production, Osun State, water application.