Effect of delayed planting date and seeding rate on yield and its components in two winter bread wheat genotypes.

In order to study the effects of delay planting date and seeding rate on seed yield of two wheat genotypes، Zarrin and C-79-16 were planted dates (7 October، 17 October، 27 October، 6 Novamber، 16 Novamber، 26 Novamber، 5 December and 15 December) with three seeding rate (450، 550 and 650 seed/m2). Experimental design was a Strip Split plot layout based on Randomized Compelet Block Design with three replications in two years (2003 - 2005) at Agriculture Research Station of Miandoab in West Azarbayjan. Interaction effects planting date × seeding rate and planting date × genotypes × years were significant on seed yield (p < 0. 05). Grain yield was decreased from 6071 to 3753 kg/ha-1 as delay planting date from 7 October to 15 December with 450 seed/m2. But higher seeding rate (650 seed/m2) yielding more grain، especially in the last four planting dates. Regression analysis showed that delay planting date for each day of delay 7 October on with seeding rate of 450 seed/m2 decreased the grain yield by 37 kg/ha in a day. Result of this research showed that when planting date is delayed، seeding rate should be applied for increasing seed yield.