Effect of Sowing Date on Growth，Yield and Quality of Summer Maize

In order to find out suitable sowing date of maize in plain area of northern Henan Province, Zhengdan 958, a large local cultivar, was selected as tested strain．Effects of delayed sowing date of summer maize on meteorological conditions, leaf area index, photosynthetic characteristics, yield formation and grain quality of maize growth and development under conditions of four sowing dates（May 31, June 10, June 20 and June 30）were compared and studied, so as to provide reference and guidance for high-quality and high-yield maize．Results showed that, with delay of sowing date, incidences of high temperature and continuous rain during flowering period decreased, leaf area index and photosynthetic potential showed an increasing trend first but then decreasing, and leaf area index and photosynthetic potential were larger in B₃ treatment．Maize yield was not very different among B₁, B₂ and B₃ treatments, and decrease in yield was extremely significant in B₄ treatment compared with other sowing periods．B₃ treated maize had higher contents of amino acids, proteins, starch, etc．in order to ensure sufficient photosynthetic efficiency, achieve higher yield and superior grain quality of maize, the latest sowing date of Zhengdan 958 could be postponed until 20 June．