Impact of the sowing date on grain yield, yield components and physiological growth indices of six grain maize cultivars in Iran

In order to investigate the impact of the sowing date on yield, yield components and physiological growth indices of grain maize (Zea mays L.) cultivars, a field experiment was conducted at the Faculty of Agriculture of the University of Lorestan in 2011 as a randomized complete block design with factorial arrangement of treatments and three replications. Treatments consisted of two sowing dates (21st May and 13th June) and six maize cultivars, namely T.V.C.767 and S.C.704 from a late maturing group, cultivars T N.S640 and Maxima from a mid maturing group, and cultivars Koppany and D.C.370 from early maturing group. Results indicated that the main effects of the experimental factors were statistically significant in terms of 1000-kernel weight, number of kernels per ear, number of kernels per row, number of rows per ear and harvest index. The interaction between sowing date and cultivar was only significant in the case of biological and grain yields, ear length and plant height. In the first sowing date the highest and lowest grain yields belonged to cultivars S.C.704 and D.C370 (12.7 and 7.5 t ha-1, respectively). In the second sowing date, N.S.640 from mid maturing group was ranked first in this regard (13.37 t ha-1). Higher grain yield in S.C704 and N.S640 compared to other cultivars, could be attributed to their higher leaf area index, leaf area index duration and crop growth rate. In total, planting late maturing group cultivars is not recommended for the second sowing date.