Effect of Nitrogen Fertilizer Rates and Plant Density on Straw, Fiber Yield and Anatomical Manifestations of Some Flax Cultivars

Two field experiments were carried out at the Experimental Farm at Gemmeiza Agriculture Research Station, Agricultural Research Center, Egypt, during two successive winter growing seasons of 2018/2019 and 2019/2020 to study the response of three flax cultivars, i.e. Sakha 3, Giza 11 and Giza 12 to three nitrogen fertilizer rates (30, 50 and 70 kg N/fed) and three plant densities (1500, 2000 and 2500 seeds/m²) and their effect on straw and fiber yield and its related traits as well as anatomical manifestations for flax stem at middle region. The experimental design was laid out using split-split plot design in four replications. Flax cultivars were distributed in the main plots, whereas nitrogen fertilizer rates were arranged at random in sub-plots and plant densities treatments were assigned at random in sub-sub plots. The sub-sub plot area was 9 m². Sakha 3 cultivar significantly produced the maximum total plant height, technical stem length, total fiber percentage, fiber yield/plant, fiber yield/fed, fiber length and fiber fineness in both seasons. Meanwhile, the highest No. of basal branches/plant, straw yield/plant and straw yield/fed in both seasons were recorded with Giza 12 cultivar. Meanwhile, Giza 11 cultivar gave the thickness stem diameter in both seasons. Increasing nitrogen fertilizer rates from 30 to 70 kg N/fed caused significant increases in all straw and fiber yield and its related traits of flax, except fiber fineness was significantly decreased with increasing nitrogen rates in both seasons. Increasing plant densities from 1500 to 2500 seeds/m² caused markedly increment in total plant height, technical stem length, straw yield/fed, total fiber percentage, fiber yield/fed, fiber length and fiber fineness during both seasons. On the other hand, No. of basal branches/plant, stem diameter, straw yield/plant and fiber yield/plant were significantly decreased by increasing plant densities during both seasons. The first order interactions between treatments Sakha 3 X 70 kg N/fed, Sakha 3 X 2500 seeds/m² and 70 kg N/fed X 2500 seeds/m² as well as the second order interaction between treatments Sakha 3 X 70 kg N/fed X 2500 seeds/m² were significantly recorded the highest total plant height, technical stem length, fiber yield/fed and fiber length as compared with the others interactions in both seasons. While, the maximum fiber yield/fed were recorded from the first order interactions between treatments Sakha 3 X 70 kg N/fed, Sakha 3 X 2500 seeds/m² and 70 kg N/fed X 2500 seeds/m² as well as the second order interaction between treatments Sakha 3 X 70 kg N/fed X 2500 seeds/m². Data illustrated an increase in each of total cross section area, cortex area, fiber area, xylem area, fiber index per plant, cortex % and xylem % in all flax cultivars under study (Sakha 3, Giza 11 and Giza 12) as affected by fertilized flax plants with 70 kg N/fed and plant density at 1500 seeds/m². It could be concluded that Sakha 3 cultivar and fertilizing by 70 kg N/fed with plant density of 2500 seeds/m² to maximizing fiber yield/fed and quality.