Improvement of the seed germination, growth and yield of onion plants by extremely low frequency non-uniform magnetic fields

• The magnetically treated onion seeds showed higher germination percentage.
• A pre-sowing MF treatment induced significant increases in seedling emergence and growth.
• Relative growth rates of leaves, roots and bulbs were improved in plants from treated seeds.
• A pre-sowing MF considerably improved yield and yield parameters of onion plants.
• A pre-sowing MF has potential to improve productivity of onion crop.

The effects of pre-sowing magnetic treatments on germination under laboratory conditions and emergence, growth and yield of onion (cv Red Creole) plants under field conditions were investigated. Onion seeds were exposed to 60 Hz full-wave rectified sinusoidal non-uniform magnetic fields (MFs) induced by an electromagnet at 160 mT for 15 and 20 min. Non-treated seeds were considered as controls. Plants were grown in experimental plots (2.4 m2) and were cultivated according to standard agricultural practices. During vegetative stage and bulb forming, samples were collected at regular intervals for growth rate analyses. At physiological maturity, the plants were harvested from each plot and the yield and yield parameters determined. Under laboratory conditions, the magnetically treated seeds showed a higher germination percentage than the control seeds. Significant differences were found between both treatments and the best finding was found for 160 mT for 15 min. In field experiments, the treatments led to a significant increase in seedling emergence, root length, seedling height, seedling dry weight and leaf area per plant. Also, at the vegetative stage, the leaf and root relative growth rates of plants derived from magnetically treated seeds were greater than those of the control plants. At the bulb forming stage, bulb relative growth rates from magnetically exposed seeds were greater than those of controls. At the bulb maturity stage, all magnetic treatments significantly increased mean bulb weight, bulb yield per area, number of tunics per bulb, bulb diameter and dry bulb weight in comparison to the controls. The results suggest that pre-sowing extremely low-frequency non-uniform MF treatment has the potential to improve crop productivity of onion through the enhancement of germination, seedling emergence, plant growth, bulb formation and yield.