The demand for food security and fresh water due to global warming causes an elevated requirement for food production and water efficiency in the North China Plain (NCP). To establish the optimal summer maize (Zea mays L.) planting schedule, a study was conducted to understand the effects of different straw mulching conditions and plant density on grain yield (GY) and water use efficiency (WUE). During 2012 and 2013 summer maize growing seasons, experiments were conducted with two different mulching treatments, i.e., 0.6 kg m-2 straw mulching (M)and non-mulching (N), and three plant density conditions, i.e., 10.0 plants m-2 (1, high plant density), 7.5 plants m-2 (2, medium plant density), and 5.5 plants m-2 (3, low plant density). The six treatment combinations were: 10.0 plants m-2 density without straw mulching (N1), 10.0 plants m-2 density with 0.6 kg m-2 straw mulching (M1), 7.5plants m-2 density without straw mulching (N2), 7.5 plants m-2 density with 0.6 kg m-2 straw mulching (M2), 5.5 plants m-2 density without straw mulching (N3), and 5.5 plants m-2 density with 0.6 kg m-2 straw mulching (M3). The results showed medium and high plant density treatments had a significant increase in spike number compared tothe low plant density treatment. Straw mulching significantly improved both the GY and WUE of summer maize under low and medium plant density treatments in both dry and normal rainfall years. M2 treatment achieved the highest GY and showed the greatest improvement in WUE of 35.4% over the non-mulching treatment across the three plant densities, and so it will be promoted as an agricultural practice in the NC
