Response of some flax (Linum usitatissimum L.) genotypes to different soil application levels of humic acid

Two field trials were established during 2021/2022 and 2022/2023 seasons at the Experimental Farm of Sakha Agricultural Research Station, Egypt, to evaluate the response of some flax genotypes (Strain 651, Sakha 3, Sakha 5 and Giza 12) to different fertilization levels of humic acid (HA) (0, 1000, 1500 and 2000 g/fed[1]) as a soil application. Split-plot design was used for the experiment with four replicates. The main-plots were assigned to the four fertilization levels of HA and the sub-plots were allocated to the four flax genotypes. The results pointed out that using 2000 g/fed of HA treatment significantly attained the highest values of all studied characters followed by 1500, 1000 and 0 g/fed during both seasons. The results also, referred that S.651 was significantly superior to the rest of the other genotypes in technical length, fiber length, fiber percentage and fiber yield/fed within both seasons. Giza 12 recorded significantly the most beneficial results for stem diameter, straw yield/plant, straw yield/fed, fruiting zone length, seed index and seed yield/plant in both seasons. Also, Sakha 5 significantly surpassed the other genotypes in number of capsules /plant, seed yield/fed, oil percentage and oil yield/fed in the 1st and 2nd seasons. Thus, this research recommended the use of 2000 g/fed of HA with the promising strain (S.651) to obtain the highest fiber yield/fed, or with Sakha 5 to gain the highest seed and oil yield/fed in Northern Delta region of Egypt. Keywords: Flax genotypes, humic acid, straw yield, seed yield, oil yield, fiber yield [1]  fed = feddan = 4200 m