Response of seed yield and fatty acid compositions for some sunflower genotypes to plant spacing and nitrogen fertilization

A field experiment was conducted at the experiment Farm of Kafr-El-Hamam Research Station, Zagazig, Sharkia Governorate, Agricultural Research Center, Egypt during the two successive summer seasons of 2015 and 2016 to achieve the highest yield and good oil quality of three tested sunflower genotypes. In both seasons, the experiment was conducted using the split split plot design in randomized complete block design with three replicates arrangement keeping plant spaces (15, 20 and 25cm apart between hills) in main plots, nitrogen fertilization levels (15, 30 and 45Nfad.−1) in sub plots and sunflower genotypes (Giza 102, Sakha 53 and promising line of L120) in sub sub plots. Yield and quality traits were significantly influenced by plant spaces, nitrogen fertilization levels and genotypes as well as interactions in both seasons and their combined analysis. The wider plant spacing of 25cm seems to be a good compromise between the highest seed yield fad.−1 and good acid composition of oil. Gradually increasing of nitrogen fertilization level had a positive reflected on yield and desirable acid composition of oil. Sakha 53 was ranked in the first order in stem diameter, head diameter, 100-seed weight, seed weight plant−1, flowered late and hence seed yield fad.−1 as well as seed oil content whereas, Giza 102 characterized with its contained the highest proportion of oleic and linoleic unsaturated fatty acids. The highest values of head diameter, 100-seed weight, seed weight plant−1 and hence seed yield fad.−1 as well as the highest proportion of oleic and linoleic unsaturated fatty acids composition were obtained by grown sunflower cv. Sakha 53 at wider spacing of 25cm with application of nitrogen fertilization levels of 45Nfad.−1. Correlation and path analyses revealed that 100-seed weight and head diameter had the highest direct and indirect influence on seed weight plant−1, at the same time also, oleic acid content and linoleic acid content had the highest direct and indirect effect influence on seed oil content indicating their importance as selection criteria to improve yield and oil quality of sunflower.