RESPONSE OF DIFFERENT GENOTYPES OF SUNFLOWER TO POTASSIUM FERTILIZER

Abstract

With the aim of evaluating the genetic performance of different sunflower varieties and testing them under different levels of potassium fertilizer, and determining which varieties give a high yield under the influence of the fertilizer, a field experiment was conducted at Research Station A in the Field Crops Department - College of Agricultural Engineering Sciences - University of Baghdad - Al-Jadriya, for the spring season of 2025. The land was prepared for planting  by perpendicular plowing, harrowing and leveling according to recommendations, using an RCBD design with three replications and a split plot arrangement. The four fertilization levels (0, 100, 200 and 300 kg K ha⁻¹) represented the main plots, while the varieties (Aqmar, local, Ishaqi 1, Ishaqi 2 and Tarsan) represented the sub plots. The number of flowering days, stem diameter, leaf area, disc diameter, number of seeds disc-1, fertility percentage, dry plant weight and yield per unit area were studied. The results showed that the 100 kg K fertilizer level per ha⁻¹   superiority the highest yield amount at 5.821 tons ha⁻¹ due to its  early   flowering by a period of (71.47 days), leaf area (1.052 m²), disc diameter (23.33 cm), number of seeds (1531.5 seeds disc-1), fertility percentage (92.53%), and total dry weight (421.17 g). The results also showed significant differences between varieties, with the Tarsan variety having the highest yield per unit area at 5.071 tons ha⁻¹ due to its superior disc diameter (25.5 cm), number of seeds (1510.7 disc-1 seeds), and dry plant weight (397.89 g). The results also showed that genetic variance was higher than environmental variance for most of the studied traits. Broad-sense heritability was high for these traits at all four fertilizer levels, ranging from 0.693 for fertility percentage at 300 kg K ha⁻¹, to 0.999 for the number of disc seeds at all four fertilizer levels and for total dry weight at 100 and 200 kg K ha⁻¹. However, the genetic variance for the number of flowering days at 0 kg K ha⁻¹, fertility percentage at 100 kg K ha⁻¹, and stem diameter and leaf area at 200 kg K ha⁻¹ showed lower genetic than environmental variance, meaning that environmental variance accounted for the largest share of phenotypic variance. Consequently, the heritability broad-sense for the days number to flowering at 0 kg K ha⁻¹ was moderate, reaching 0.429. And the remaining traits were low, reaching 0.352, 0.223 and 0.146 for the three traits respectively.