Effects of irrigation on summer maize and yield difference between summer maize cultivars

Field experiments were conducted at Luancheng Agro-Eco Experimental Station (37°53′N, 114°40′E; 50 m above sea level) of the Chinese Academy of Sciences. The same cultivar Zhengdan 958 was used during 2008 to 2016 summer maize growing seasons. Two water levels were tested. One test involved a deficit irrigation (DI) treatment with a single irrigation event at sowing for normal germination.The full irrigation (FI) treatment was conducted based on the seasonal rainfall and associated management of soil water content. From two to four irrigations were applied annually. Soil water content was managed to maintain average soil water content over 65% of field capacity for the top 1-m soil profile during the growing season. For each irrigation, 70 mm of water was applied to each plot by surface irrigation using a low-pressure tube water transportation system with a flow meter to record the irrigation applied. Due to a breakdown of the irrigation system in 2015, only DI was performed that year, and FI was not applied. Another experiment was conducted during the 2010 to 2016 period with different cultivars that were recently certified to study the yield difference between cultivars. Eight cultivars were used in 2010 to 2012 seasons, and 16 cultivars used in 2013 to 2016 seasons, respectively. Soil volumetric water contents (v/v) were monitored using the neutron meter (503 DR, CPN International Inc., USA) with access tubes installed in the center of the plots. Leaf angle (°) is the sharp angle between leaf and stem. Measurements of leaf angle were performed on 9 plants of each summer maize cultivar that were selected at silking stage. The leaf angles of 12 leaves from upper to lower positions on the maize plant were measured using a protractor.