Effect of sowing date on the yield of maize (Zea mays L.) in different years

The effect of the sowing date and the vegetation period of the hybrids on the grain yield of maize and the moisture content (%) at harvest was studied in a two-factor experiment in a small-plot design, based on the data for 2001-2002. In the experiments the sowing time treatments were: early sowing date (Apr. 5) optimum sowing date (Apr. 25) and late sowing date (May 15). Ten hybrids with different vegetation periods were sown in the plots. In 2001 the hybrids were: Sprinter, DK 355, PR39KO8, DK 440, PR37M34, AW043, PR36R10, Celest, DK 537 and Florencia, and in 2002: Sprinter, Goldacco, DK 391, DK 440, PR37M81, PR37M34, LG23.93, LG23.72, Celest and DK 537. The experimental data were evaluated with analysis of variance, regression analysis and correlation analysis each year. dIn 2001 the greatest maize yields were obtained after sowing at late dates (10.178 t/ha), while there was a non-significant reduction after optimum and early sowing (9.73 and 9.679 t/ha). In 2002 there were significant differences between the maize yields obtained after sowing at late (9.235 t/ha) optimum (7.996 t/ha) and early dates (6.994 t/ha). The hybrid effect was significant at the 0.01 level of significance in 2001 and 2002. As the result of sowing date, the moisture content (%) of the yield at harvest was lowest in the early and optimum sowing date treatments, rising significantly after late sowing. A positive, moderately close correlation was found between the sowing date and the seed moisture content at harvest (R-2 was 0.545-0.818 in 2001 and 0.630-0.891 in 2002). The results of regression analysis were used to predict the effect of sowing date.