A Study on Effects of Planting Dates on Growth and Yield of 18 Corn Hybrids (Zea mays L.)

In this study 18 new corn varieties consist of 15 foreign early and mid-mature single cross hybrids and 3 Iranian commercial hybrids (KSC704, KSC647and DC370) were evaluated at two sowing date (5 and 20 June) based on RCBD with 3 replications at Khorasan Razavi Agricultural Research Centre, Mashhad, Iran on 2009. This study showed that among all hybrids, EXP1 (16.03 ton/ha) and OSSK617 (15.51 ton/ha) had the highest yields in early planting (5 June) and EXP1 (16.52 ton/ha) and KDC370 (16.22 ton/ha) produced the highest, yields in late planting (20 June). Results of this experiment also indicated that yield component such as 300 kernel weight, kernel no. per row, kernel depth and ear length were adversely affected in delay planting condition. Delay planting reduced 300- kernel weight, kernel no. per row, kernel depth and ear length. Results of cluster analysis using Wards’ method divided the corn hybrids into 4 different clusters (low intra-group and high extra-group similarities). From the results of cluster analysis it is recommended to make crosses among genotypes in Clus1 (ZP434, BC582 and EXP2 hybrids) and Clus4 (ZP684, SIMON and KSC647) in breeding programmes. Classifying genotypes according to their agronomic traits with sophisticated multivariate techniques could reduce the time period and expenditure for crop improvement