Evaluation of the effect of nitrogen fertilization and tillage on the yield and the nutritional profile of flaxseed

Details

Supervisors

Bertin, Pierre ; Larondelle, Yvan

Faculty

Faculté des bioingénieurs

Degree label

Master [120] : bioingénieur en sciences agronomiques

Abstract

Oilseed flax is not commonly grown in Belgium, despite its various advantages and its increasing demand. From an agronomic perspective, it is an interesting plant to insert in the crop rotation and it is relatively easy to grow. From a nutritional point of view, it is rich in omega-3 fatty acids, essential amino acids, dietary fibers and antioxidants such as lignans. This makes flaxseed a functional food, that is a foodstuff that prevents many chronic diseases and provides numerous health benefits. More documentation regarding agronomical practices of flax cultivation and their effects on yield as well as on the nutritional profile of the seeds is needed. The nitrogen input is believed to be an important driver determining yield and quality parameters such as oil yield, fatty acid profile, vitamin E and protein contents of flaxseed. As more and more farmers move to reduced-tillage practices, it would be interesting to determine the effect of such practices on flax yield and quality. The aim of this master’s thesis was therefore to determine the effect of nitrogen fertilization level and tillage practice on the yield of flaxseed, but also on its nutritional profile. To this end, flax was grown in a field in Vieux-Sart (Belgium) with six different levels of nitrogen and either under tillage or no-tillage conditions. After harvest, seeds were analyzed to determine oil yield, fatty acid profile, vitamin E profile and protein content. Many results were not significant, which can be partly attributed to the exceptionally dry and hot climatic conditions of spring and summer 2018 and to the high residual soil nitrogen content before the onset of the experiment. On the one hand, nitrogen fertilization level positively influenced flax height under tillage, but did not influence flax yield, contrary to what had been expected. Neither did it influence oil content, fatty acid profile, vitamin E profile or protein content. On the other hand, plant density was higher under tillage but yields were not significantly greater. This could encourage farmers to grow flax under no-tillage. Tillage had no effect on oil content or vitamin E content but significantly influenced the fatty acid profile, even though the effect was tiny. From this research, it emerges that more work about the effect of soil nitrogen on flax yield and quality is needed to properly manage nitrogen fertilization. Tillage also seems to affect different yield and quality parameters, which is of interest for improving flax nutritional potential. More studies on the effect of tillage are however needed to draw more reliable conclusions.