Determination of optimum inter-row and intra-row spacing in some hybrid maize (Zea mays L.) varieties under Kirkuk conditions

This study was carried out during the spring season of 2022 at the Yaychee, Kirkuk Governorate, Iraq, to determine the optimum inter-row (50 and 70 cm) and intra-row (10, 15, and 20 cm) spacing in some hybrids of maize (V1: Sagunto, V2: Konsens, V3: Cadiz, V4: ZP 684, V5: Ronaldinio, and V6: Kilomeris). "A randomized complete block design (RCBD) was used to design the field experiment layout in a split-split plot with three replications. The earlier tasseling and silking dates were obtained by sowing on inter-row at 70 cm spacing. In addition, increasing the space between lines from 50 to 70 cm significantly increased ear leaf area, plant height, number of ears per plant, ear length, number of grains per row, number of rows per ear, weight, number of grains per ear, 1000-grain weight, biological yield, crude protein, and oil contents. On the other hand, the highest grain yield ha-1 and harvest index were obtained by sowing maize on 50 cm inter-row spacing. Increase in the inter-plant distance from 10 to 15 or 20 cm caused about 50% decrease in the number of male and female flowers. The plant height, number of ears per plant, highest values of ear leaf area, number of rows per ear, ear length and diameter, number of grains per row, ear weight, and number of grains per ear, 1000-grain weight, crude protein, and oil contents were produced from sowing maize with 20 cm intra-row spacing. Increasing the plant spacing from 10 to 15 and 20 cm resulted in a significant reduction in the grain yield. Although the highest biological yield per ha was produced" from sowing maize with 10 cm intra-row spacing, the harvest index was produced with 15 cm intra-row spacing.