This study investigated the water use efficiency and yield for the production of green ears of corn subjected to irrigation with drip system and with potassium fertilizer levels in Sumé, Paraiba State, Brazil. The experimental design was a randomized design with four replications in a split plot design with six water slides (0.25 ETcp, 0.50 ETcp, 0.75 ETcp, 1.00 ETcp, 1.25 ETcp and 1.50 ETcp) and six doses of potassium (0, 20, 40, 60, 80 and 100 kg·ha^-1). The maize hybrid AG 1051 was mechanically sown on 13/01/2012 and the spikes in the green stage (doughy grains) were harvested 67 days after planting. Water consumption for producing one ton of maize cobs in the slides 132, 264, 396, 528, 660, and 792 mm of water within all treatments of potassium fertilization increased, indicating that the WUE decreases with the increasing amount of water applied via irrigation. Therefore, it was observed that the water use efficiency average was 61.76 mm·t^-1 (2.02 kg·m³), i.e. for each m³ of water used 2.02 kg of ears of corn were produced with default. The application of 680.64 mm of water and 72.14 kg·ha^-1 potassium maximized the yield of ears, resulting in the maximum yield of ears of 10.82 t·ha^-1.