RELATIONSHIP BETWEEN SEED POSITION 0N THE COB, N LEVEL AND HARVESTING DATE IN MAIZE SEED QUALITY

Abstract

To investigate the effects of seed position on the cob (lower and upper third),seed harvested at physiological and one month later and 200 and 400 kg N/ha when grown in spring and fall of the next year, using seeds of maize synthetic B-106. The experiment was conducted for four seasons on the farm of Field Crop Research Station/College of Agric./Univ. of Baghdad during spring and fall of 2009 and 2010. Results showed that seeds produced in the spring and fertilized with 400 kg.ha-1 gave higher seeds.plant-1 (343 and 601)and grain yield.plant-1 (78 and 124 g.plant-1)as compared to 200 kg.N.ha-1 which gave lower grain.plant-1 (64 and 112)for both seasons, respectively. Late harvest of spring grown seeds gave higher plant leaf area (0.608 m2), crop growth rate (2.3 and 4.5 g.m-2.d-1) and plant dry matter (229 and 283 g.plant-1),that increased seed yield (78 and 120 g) as compared to early harvest which gave lower plant seed yield (69 and 108 g), both seasons, respectively. Accordingly, to produce maize seeds of high agricultural quality, we should take spring grown seeds fertilized with 400kg.N.ha-1 , and harvested one month after physiological maturity. However, to have high seed yield for industry or feed, we recommend fall grown seeds taken from lower third of ear, and fertilized with 400kg.N.ha-1. Lower third seeds grown in the fall gave plant growth rate (2.2 and 4.2 g.m-2.d-1), plant dry matter (205 and 374 g),ear seed number (322 and 601) and plant grain yield (73 and 128 g) as compared to lower plant yield of upper third seeds which gave (67 and 108 g.plant-1),for both seasons, respectively. Genetic contamination was higher in lower or upper third of ear when foreign pollinator pollens available, early or late, in the seasons,respectively.