Source limitation, nitrogen topdressing and seed yield relationship in different cultivars of maize (Zea mays L.)

Maize has now become an important staple food. In Iran, maize in its many forms, is included as a part of the diet of many people. This experiment was done in 2010 to evaluate the effects of nitrogen topdressing on source limitation, seed yield and yield components of different cultivars of maize. The experiment was conducted at the Research Farm, Faculty of Agriculture, Islamic Azad University, Khorasgan Branch (Isfahan). It was a split plot arrangement based on a randomized complete block design with three replications. Four nitrogen topdressing levels (0, 50, 100 and 150 kg N/ha) were tested in main plots and three cultivars (DC 370, MV 524 and SC 704) were tested in sub plots. Nitrogen topdressing was done when plants had 5 to 6 leaves. Nitrogen topdressing had significant influence on number of seeds per row, number of seeds per corn, thousand seed weight, seed yield, biological yield, harvest index and source limitation. Cultivar also had a significant influence on all characteristics evaluated in this experiment and number of rows per ear was also significantly affected by cultivar. Nitrogen reduced source limitation in all cultivars significantly. There was no significant influence of nitrogen and cultivar interaction on the characteristics evaluated in the experiment. The maximum for characteristics of; number of rows per corn, number of seeds per row, number of seeds per corn, seed yield, biological yield and harvest index was related to the application of 150 kg N/ha. Although the application of 150 kg N/ha had the highest thousand seed weight, there was no significant difference between this treatment and 50 kg N/ha. SC 704 cultivar produced the maximum number of rows per corn, number of seeds per row, number of seeds per corn, seed yield and biological yield. Results were not significant in a thousand seed weight between the cultivars MV 524 an SC 704, of which the former had the maximum thousand seed weight. The maximum harvest index and source limitation was related to DC 370. Application of 150 kg nitrogen topdressing per ha and cultivar of SC 704 was determined as the most suitable for this region.