Effects of Nitrogen Application Level on Endogenous Hormones, Yield and Quality of Tartary Buckwheat

  Objective  Effects of varied levels of nitrogen fertilization on the endogenous hormones, yield and quality of tartary buckwheat were studied.

  Method  The tarary buckwheat variety of Qianku 6 (QK6) plants were treated with different nitrogen applications (i.e., CK of blank control, LN at 50 kg·hm^-2, LN at 100 kg·hm^-2, and HN at 150 kg·hm^-2). Conditions of the rhizosphere soil as well as the root morphology, endogenous hormones in leaves, and grain yield and quality of the buckwheat plants were monitored for analysis.

  Result  Increased nitrogen raised the contents of available nitrogen, phosphorus, and potassium in the rhizosphere soil initially and followed by a decline. The length, surface area and volume of the roots showed a similar trend that peaked under MN and minimalized under CK. But little effect was observed on root diameter. ACC, IAA, Z+ZR and polyamine had the same trend of increasing and declining, but ABA the opposite. The plant height, main stem count, grain weight and count per plant, 1000-grain weight and grain yield of QK6 also increased initially and decreased later, but no significant effect on the number of main stem nodes. Again, the contents of protein, total dietary fiber, rutin, quercetin and kaempferol of the plants increased at first and then decreased with increasing nitrogen. The highest content of flavonoids was found in the grains of the plants treated under CK and the lowest in those under HN.

  Conclusion  The nitrogen application at a rate of 100 kg·hm^-2 appeared appropriate for QK6 cultivation rendering a maximized fertilization benefit. Excessive or insufficient application on nitrogen would lead to a reduction on the grain yield and quality of buckwheat plants.