Straw, Seed Yield and Quality of Three Linum usitatissimum L. Cultivars in Relation to Nitrogen Fertilizer Rate and Plant Density

Methodology: Two field experiments were conducted on the Experimental Farm at El-Gemmeiza Research Station, Gharbia Governorate, Agricultural Research Center, Egypt, during two successive winter seasons of 2018-19 and 2019-20. Aims: To investigate the effect of three nitrogen fertilizer rates, i.e. 30, 50 and 70 kg N feddan-1 [one feddan (fed) = 4200 m2] and three plant densities, i.e. 1500, 2000 and 2500 seeds m-2 on flax (Linum usitatissimum L.) yield and its quality of three cultivars of flax, i.e. Sakha 3, Giza 11 and Giza 12. Results: Results in combined analysis of the two seasons showed that Sakha 3 cultivar significantly produced the maximum total plant height, technical stem length, upper branching zone length, No. of seeds capsule-1, total fiber percentage, fiber yield plant-1, fiber yield fed-1, fiber length and fiber fineness. Meanwhile, the highest No. of basal branches plant-1, straw yield plant-1, straw yield fed-1 and seed oil content were recorded with Giza 12 cultivar. While, Giza 11 cultivar gave the maximum stem diameter, No. of upper branches plant-1, No. of capsules plant-1, No. of seeds plant-1, seed index, seed yield plant-1, seed yield fed-1, harvest index, oil yield plant-1 and oil yield fed-1. Increasing nitrogen fertilizer rates from 30 up to 70 kg N fed-1 caused significant increases in almost straw, fiber, seed and oil yields and its related traits of flax, on the other hand, fiber fineness which significantly decreased with increasing nitrogen rates. Flax plants growing at 1500 seeds m-2 markedly gave the greatest No. of basal branches plant-1, stem diameter, straw yield plant-1, upper branching zone length, No. of upper branches plant-1, No. of capsules plant-1, No. of seeds plant-1, seed yield plant-1, harvest index, oil yield plant-1 and fiber yield plant-1. Meanwhile, the maximum total plant height, technical stem length, straw yield fed-1, seed yield fed-1, oil yield fed-1, total fiber percentage, fiber yield fed-1, fiber length and fiber fineness were obtained from flax planting at 2500 seeds m-2. The maximum fiber yield were recorded from the interactions among treatments Sakha 3 X 70 kg N fed-1, Sakha 3 X 2500 seeds m-2, 70 kg N fed-1 X 2500 seeds m-2 and Sakha 3 X 70 kg N fed-1 X 2500 seeds m-2. Meanwhile, the maximum seed and oil yields fed-1 were recorded from the interactions between treatments Giza 11 X 70 kg N fed-1, Giza 11 X 2500 seeds m-2, 70 kg N fed-1 X 2500 seeds m-2 and Giza 11 X 70 kg N fed-1 X 2500 seeds m-2. Generally, it could be concluded that Sakha 3 cultivar under soil fertilized by 70 kg N fed-1 with plant density of 2500 seeds m-2 to maximizing fiber yield fed-1, while Giza 11 cultivar with the same rates of nitrogen and plant density to maximizing seed and oil yields fed-1.