Variation of physiological determinants of yield in linseed in response to nitrogen fertilization

Linseed, or oilseed flax, is an important source of edible and industrial vegetable oil and is grown widely in temperate regions of the world. Understanding the factors that can affect seed yield and therefore linseed production is important in order to meet the growing demand for this crop. Nitrogen, one of the most essential nutrients for linseed, is often applied to improve yield and quality. In the present study, a 2-year field study was conducted to determine the effect of N fertilization on various aspects of linseed growth, including phenological stages, seed yield and yield components, contribution of yield components to seed yield, biomass growth rate, and nitrogen uptake rate. Three different cultivars were used (Creola, Livia, and Lirina) and three rates of N fertilization were applied (0, 40 and 80 kg ha−1). N fertilization was found to increase seed yield by an average of 37% above the control rate over the 2-year study period. Application of N affected yield components, especially the seed weight per plant, the number of capsules per plant, the number of capsules m−2, and the number of seeds per plant, which were increased by an average of 54, 62, 45, and 56% respectively compared with the control. Phenological stages (time to reach flowering, seed maturity, and seed filling period) were also affected by N fertilization and the seed filling period was increased by 10% compared with the control. Plant height was also increased with N application and cultivar height differences were also apparent. Biomass growth rate, economic growth rate, and seed growth rate were all increased with N application, but much higher increases were found in the N uptake rate, economic N rate, and seed N uptake rate. Seed yield was correlated with the yield components, seed filling period, biomass growth rate (BGR), economic growth rate (EGR), seed growth rate (SGR), and nitrogen uptake rate (NUR). In addition, NUR was negatively correlated with the economic N uptake rate (ENUR) and seed N uptake rate (SNUR). In conclusion, the present study indicates that N fertilization promotes the growth of linseed, affecting the development and increasing the BGR, EGR, SGR, and also NUR, ENUR, and SNUR. These are important physiological determinants of seed yield that can be used as additional selection criteria for yield improvements.