The effect of planting date and cultivar on yield and yield components of corn in Karaj city

The aim of this study was to investigate the effects of planting date(13 May,10 June And 8 July) and corn cultivars(KSC400,KSC647 And KSC 704) on the yield and yield components in Karaj. An experiment was conducted as a split-plot design based on randomized complete blocks with four replications in the research farm of the University of Tehran. The results showed that the highest yield belonged to the second planting date (11.98 t.ha-1), the third planting date (11.56 t.ha-1), the first planting date (11.18 t.ha-1), respectively. The results revealed that in the first and third planting dates, corn grain yield was decreased due to the occurrence of the high daily temperatures in the reproductive stage. Furthermore, a coincidence of the decreasing temperatures with the grain filling period in autumn led to corn grain yield reduction. Due to the appropriateness of the reproductive stages in the second planting date, the length of seed abortion was decreased and the length and size of the ear, the weight of the ear, the number of seeds per ear, and grain yield were increased. The results revealed that the 400 cultivar (10.25 t.ha-1) in July, 647 (12.35 t.ha-1) in May and 704 (13.77 t.ha-1) in June had the highest yields in the study area. In addition, to reduce the frequency of irrigation and save water, it is recommended to cultivate medium and early maturing varieties of corn on 13 May and 8 July sowing dates, respectively.